COUNTRY REPORTS

BURUNDI
LEUCAENA PSYLLID IN BURUNDI

by

Ndayiragije Pascal and Kaboneka Salvator
ISABU, B.P. 795, Bujumbura
Burundi

The first species of the genus Leucaena to be introduced into Burundi was L. leucocephala from Yangambi, Zaire in 1933. At that time, its use was limited to providing shade to coffee plantations.

During the early 1980s, leucaenas, primarily, L. leucocephala, met the interest of forage management scientists as a high quality fodder for livestock. Thereafter, along with Calliandra calothyrsus and Gliricidia sepium, L. leucocephala has been successfully tested in the plains of Imbo, in the west and in Moso in the east and to some degree in the Central Plateau.

L. diversiflora was tested in the higher altitude zones which are also characterized by a high acid soil (pH = 4-5) and aluminum toxicity. This species, together with C. calothyrsus are good alternatives to L. leucocephala in the highlands of Burundi (> 1 500 m in altitude). They are used in contour plantings for soil conservation, fodder and fuel wood production. In urban areas, L. leucocephala is used in hedges.

Estimates of the area planted with L. leucocephala or of other so called agroforestry species are not available for Burundi. Therefore, it is difficult to estimate the economic or social impacts of pests and diseases in these plantings.

Until very recently, very little was known on potential pests and diseases of agroforestry species in Burundi. However, the leucaena psyllid, Heteropsylla cubana, was reported in the country in 1992. It was presumably introduced from Tanzania although this information has to be checked.

Among different leucaena psyllid pest management tactics being tested worldwide (biological, cultural, genetic, regulatory and chemical), only cultural methods are being evaluated in Burundi. However, biological control is a major component of ISABU. A unit for rearing natural enemies of cassava mealybug is located at ISABU headquarters in Bujumbura. This research program covers all pest management problems.

MOZAMBIQUE  

PRELIMINARY OBSERVATIONS ON LEUCAENA DEVELOPMENT IN MOZAMBIQUE

by

Carla Eunice da Silva Ruas
Forest Project for Afforestation of Maputo Province
Ministry of Agriculture, National Directorate of Forest and Wildlife
Mozambican Heroes' Square, Maputo, Mozambique

and

Romana Maria da Trindade Mário Rombe 
Forestry Department, Faculty of Agronomy and Forest Engineering
Eduardo Mondlane University 
P.O.Box 257, Maputo, Mozambique

ABSTRACT

In Mozambique, Leucaena spp. planted areas spread quickly such as in other regions of the tropics. The species has mainly been used for fodder and fuel wood. At the moment, approximately 0.05 % of the country total area comprises artificial plantations. Of this, less than 1,000 hectares are leucaena stands. This genus was recently introduced in the country.

Major plantations occur in Maputo, Gaza, Manica, Nampula and Cabo Delgado Provinces using Leucaena leucocephala K-28, K-8, Malawi and local provenances. There is a lack of information regarding leucaena plantations in the country because of the poor coordination between the different institutions involved in promoting leucaena utilization and its increased benefits for farmers. Some trials in Maputo and Cabo Delgado Provinces have been conducted by the Ministry of Agriculture in order to develop techniques in agroforestry systems. In Cabo Delgado the best provenance was L. leucocephala Philippines and in Maputo L. leucocephala K-28 in terms of growth and survival rate. L. diversifolia gave the poorest results in survival rate. Data of parameters such as density and leucaena interaction with agricultural crops are still to be collected and analyzed.

For the first time, leucaena insect pests were observed in 1993 attacking seedlings in nurseries as well as plants under field conditions in Nampula and Cabo Delgado Provinces in the northern part of the country. The pests are psyllids and locusts. Samples of the psyllid were sent to the International Institute of Entomology, UK, for identification. The only leucaena psyllid control has been the destruction of the infested plants because experience on other means of control is lacking.

* * * * *

INTRODUCTION

GENERAL INFORMATION

Mozambique is located in southern Africa between 10° 27' and 26° 56' latitude south, 30° 12'and 40° 51' longitude east extending from Tanzania in the north to South Africa, Natal in the south. It is also bordered by Malawi, Zambia, Zimbabwe and Swaziland in the west and Indian Ocean in the east. It covers an area of approximately 799,379 km² and a coastal line of 1,965 km (Empresa Moderna 1962).

The country comprises three geographic regions: the coastal belt up to 200 m of altitude covering 44% of the total area, the region of plateau varying from 200 to 400 m high which represents 43% of total surface and mountains zone more than 1000 m high covering the remaining 13% of the country area.

The climate is tropical and subtropical varying from arid to semi-arid, dry areas to sub- humid and humid regions. There are two main seasons in the year, the wet and dry season. Wet season occurs from November to April. However, some rains may fall during the dry season. In the wet and hot season, precipitation may reach 2348 mm per year observed in high altitudes above 1000 m of the sea level and average temperature 26.7°- 29.4° C. Cooler temperatures are observed in the interior uplands. Annual temperature in average varies from 18° to 26°C. Average potential evapo-transpiration varies from 1,114 mm to 2,016 mm.

According to White (1983), three broad phytogeographic regions can be identified for Mozambique namely: the Zambezian Regional Centre of Endemism, the Inhambane Regional Mosaic and the Tongoland-Pondoland Regional Mosaic. Seven broad vegetation types have been identified: miombo woodlands, the largest community with Brachystegia spp. and Julbernadia globiflora; montane woodland with Colophospermum mopane, undifferentiated woodland, Afromontane elements, coastal mosaics on the coast, halophytic vegetation and swamp vegetation (Bandeira et al in press).

The last statistical information indicates that there are more than 12,61 5,200 inhabitants in the country (Pililão 1989). Approximately 80%-90% of the population are engaged in agriculture and depend directly from this economic sector (Europa Publications Limited, 1985). However, most of the systems used comprise shifting agriculture, with negative effects to the forest cover. On the other hand, because of the recent civil war, people living in rural areas left to concentrate around towns, putting high pressure on natural forests for firewood and construction.

In terms of land use, approximately 50% of the country area is covered with natural forests. Artificial forests (plantations) comprise a small area; 0.05% of the total area. Grasslands comprise 40.33% of the land area, agriculture 6.94% and mangroves 0.57%. The remaining land is composed of dunes, water and undescribed areas (DNFFB 1992).

The primary crops produced are maize, rice (paddy), sorghum, sugar cane, ground nuts, peas, sunflower for seeds, cotton, copra, tea, bananas and sisal. Livestock production is the second most important activity in the agricultural sector producing mainly cattle, sheep, goats and pigs.

Forestry has developed in some regions of the country such as Sofala, Manica and Maputo Provinces, with afforestation programmes using the trees of the genera Eucalyptus and Pinus for sawn timber, construction timber, railroad sleepers, fuel wood, sawlogs, logs for other purposes.

Traditional agroforestry is a practice which is found in all rural areas. Extension programmes conducted by the Ministry of Agriculture have recently been developed in order to provide farmers with skills and techniques which may help them improving their incomes from agroforestry practice. In this context, leucaena was recently introduced in the country for multiple purposes and leucaena plantation areas are spreading quickly in the country.

EXPERIENCE WITH LEUCAENA

HISTORICAL BACKGROUND

Leucaena plantations were first established in the country in 1977 comprising small stands. This was done by foreign staff of the Ministry of Agriculture working in projects of afforestation.

Since 1986 the Ministry of Agriculture, through its Provincal Offices, has been setting up trials to test leucaena performance, most of them aiming at creating adequate agroforestry systems because of leucaena potential for nitrogen fixation. The trials were initiated as follows: Cabo Delgado Province in 1985 and 1987; Maputo, Gaza, Nampula and Manica Provinces in 1985 and 1989. In Mozambique the tree is mainly used for fuel wood, fodder and soil fertilization. In total, the planted area with leucaena in Mozambique is less than 1,000 ha. The largest plantation areas are located in Maputo Province which comprise approximately 50% of the total planted area.

In Nampula as well as in Manica Province, plantations with Leucaena leucocephala in agroforestry areas have been slowed down. The reasons for this are that the species in both Provinces has been regarded as a serious competitor with other crops, particularly maize and in Nampula Province due to attacks of pests. Local conditions may explain the strong natural regeneration of the species and it is believed that the huge amount of water from the rains in Nampula and Manica carries the seeds long distances where they easily germinate and propagate. On the other hand, lacking experience in resource management as well as better cultural practices leads to an inadequate resource utilization. In these cases, alternative approaches to help farmers with leucaena stand management could include the dissemination of varieties not producing seeds.

SPECIES AND PROVENANCE PERFORMANCE

Data on leucaena behaviour in Mozambique are scarce. As examples of our experience in this matter, the present report presents observations made during three trials, one of them established in the north and the others in the south of the country.

LEUCAENA SPECIES AND PROVENANCES TRIAL IN MAPUTO - A trial was conducted in Maputo to assess Leucaena spp and provenances. These tests included assessment of survival, growth and stem quality. The trial was established in January 1986 near the Faculty of Agronomy, Eduardo Mondlane University.

Nine provenances of L. leucocephala and one of L. diversifolia were tested. The experiment was set up in three blocks (replicates) in a completely randomized blocks design. The block size used was 1 m x 1 m. Plots were rectangular in shape. Approximately 1/3 of the trial was destroyed as a result of influences of eucalypts and illegal farms.

Measurements on survival and growth in height were made. Every tree present in the plots were measured. Stem quality was assessed using subjective scales varying from 1 to 3 where 3 corresponds to the shrubby type. Data were collected in April 1988.

The initial number of plants per plot was 18 and a plot which had lost more than a half of the trees was not included in the analyses. A treatment with two or more plots not included was regarded as lost. ANOVA was used to test variance differences in growth and survival. Stem quality values were subjected to chi square analysis for associations.

No significant differences were found for height growth at the 5% level of significance. Tables 1 - 4 present data for total survival, height, an ANOVA table for growth in height and average values found for stem quality. Stem quality varies with provenance at the 5% level of significance. From the results, it was concluded that in terms of survival, the provenances, K-28, 1364/84 of L. leucocephala are the best and L. diversifolia presented the lowest survival rate with less than 50% for Maputo conditions. Provenance PIC 90861 and Peru of L. leucocephala showed intermediate survival.

For stem quality, L. leucocephala provenances K-27, PIC 90861 and K-28 presented more regular stems i.e. with fewer branches. L. leucocephala provenance Cunningham was the provenance with more shrubby characteristics. Provenances 1237/84 and K8 were the intermediate. X² was 37.00.

TABLE 1

TWO YEAR SURVIVAL RATE (%) BY LEUCAENA SPECIES AND PROVENANCE
MAPUTO, MOZAMBIQUE

TABLE 2

TWO YEAR TOTAL HEIGHT (METERS) OF L. LEUCOCEPHALA PROVENANCES
MAPUTO, MOZAMBIQUE

TABLE 3

ANOVA FOR TOTAL HEIGHT, LEUCAENA TRIALS 
MAPUTO, MOZAMBIQUE

TABLE 4

VALUES (UNITS) OBTAINED FOR L. LEUCOCEPHALA STEM QUALITY 
MAPUTO, MOZAMBIQUE

PROVENANCE TRIAL IN CABO DELGADO PROVINCE - The objectives of this trial were to integrate wood production with the traditional agricultural crops in an appropriate agroforestry system, to find the most adequate tree species and provenances which would not compete with traditional crops but contribute to nitrogen fixation.

The experiment was established in Pemba Province at latitude 12° 58' south. The climate is tropical with mean temperatures varying from 26 to 30° C over the year. Annual precipitation is between 600-1000 mm, mainly occurring during the rainy season (Svensson, 1987).

The provenances used in the study were Malawi, Nampula and Philippines. The same author states that the Philippines provenance was the largest giving also the best survival rate. The Malawi provenance showed the poorest development.

AGROFORESTRY SYSTEM TRIAL IN MATOLA, MAPUTO PROVINCE - This experiment was established in  1989 at the Matola field station, Maputo Province, some 15 km from Maputo city using alley cropping system with the following objectives:

General objective:

-to define agroforestry techniques to be recommended by extension programmes Specific objectives:

-to assess the effect of planting density and the mutual interaction between leucaena plants with food crops.

-to provide fuel wood to the surrounding population.

-to assess biomass from the foliage and stems.

-to evaluate agricultural production in accordance with density used.

-to determine the best cultural treatments for the different densities.

-to assess the effect of leucaena plants on soil conservation and their contribution for a sustained production.

The site is characterized by having deep sandy soils with excessive drainage, reddish brown, not influenced by salts and of poor fertility. Values of water pH vary from 5.7 to 6.5 and the content in organic matter is less than 1 % (Wambeke and Eschweiler 1987).

The climate is tropical and semi-arid. Annual precipitation averages 775 mm with an evapo-transpiration rate of 1375 mm.

Seeds of Leucaena leucocephala from Marracuene field, Maputo Province were obtained. The soil was mechanically prepared to remove old eucalypts and Tectona grandis which comprised a previous plantation in the area. The experiment was established in a split plot design with two replicates, three main treatments (spacing between rows of 2, 4 and 8 m) and four sub-treatments (planting spacing within rows of 0.5, 1, 2 and 3 m). Rows were oriented in an east-west direction. The plots were rectangular and the experiment occupied an area of 0.86 hectares with 2552 plants planted in February 1989. Food crops tested in the experiment were peas, ground nuts and maize.

Measurements were taken to assess plant height and diameter before cutting the plants for biomass calculations in 1993.

The raw material was weighted to determine the biomass of the foliage and woody biomass after cutting. This was done from September 1993 to March 1994. In Block II the best shoot was left standing in opposite to Block I where all shoots were cut. Products obtained from food crops were also weighted; seeds in the case of peas and groundnuts and the entire head per shoot in the case of maize.

Table 5 gives the average production in terms of leucaena biomass for the foliage and stems.

TABLE   5

LEUCAENA FOLIAGE AND STEM BIOMASS (in Kg) 
MATOLA LEUCAENA TRIAL - 1993/94

Survival rate was 87.4 % in Block I and 73.9% in Block II was 73.9%.  Mean height was 5.3 m in both blocks.   Mean diameter was 3.9 cm in block I and 3.3 cm in block II.

Comparing the results with the objectives, it is observed that these were not fully achieved because of the way the experiment was conducted. From the existing data only leucaena biomass production can be assessed. The trial did not give data concerning information on the mutual interaction between leucaena and food crops. Monitoring and records of information regarding every interventions should be undertaken to allow following development and analyses of leucaena behaviour.

PESTS OF LEUCAENA

Very few studies have been conducted in Mozambique on forest or agroforestry pests particularly those concerned with leucaena. Therefore, this is the first compilation of pest incidence on leucaena in the country. Their geographic distribution although still a preliminary study, may provide important information when plant protection programmes are undertaken on a regional basis.

Questionnaires were sent to the staff of various Provincial Directorates of Agriculture to determine presence or absence of insect pests of leucaena, descriptions of the pest, portion of plant attacked, period (month) of highest damage, stage of insect present and type of damage caused as a consequence of feeding.

Information related to cultural practices, such as crops used for intercropping with leucaena plants, density of planting were also requested.

As a result, the appearance of small winged insects, whitish on the back and yellowish on the front were observed and reported in 1993. These psyllids lay orange eggs on young leaves of leucaena (Alberto, personal communication). Larvae and nymphs live on young shoots. The project of forest extension in Nampula Province supported by the Ministry of Agriculture is at the moment studying the seasonal history of the pest, particularly the season of higher incidence and levels of infestation.

The foliage and shoots are the first attacked parts of the plant. Then the plant wilts and dies.

The pest occurs in Cabo Delgado and Nampula Provinces. In Cabo Delgado, it was observed attacking seedlings in a private nursery with 900 plants, located at Chiure District, approximately 140 km far from Pemba and 40 km from the bridge at the Chiure River, the frontier with Nampula Province. The plants were 6 months old measuring 50 80 cm in height (Moisés, personal communication). In Nampula Province, the localities already attacked by the pest are Rapale (Nampula District), Nampula town and Nacavala (Meconta District). The impact is however felt all over the Province (Alberto, personal communication).

Adult psyllids were collected and sent to the International Institute of Entomology (IIE) in the United Kingdom for identification. To date identification of the pest is still awaited.

Other pests attacking forest trees, particularly leucaena plants are locusts in Mieze, Cabo Delgado Province. The locusts feed on the very young shoots. The injuries weakens the shoots which finally fall down (Svensson, 1987). In addition, the same author reports that the damage may seldom be noticeable but every shoot that falls off reduces height by five to 10 cm.

At the moment no chemical approach has been used to fight leucaena psyllid. Cultural practices, particularly the destruction of infested plants seems to be the most important means of controlling the pest in the country by individual farmers. In the worst cases, farmers are giving up planting leucaena. Experience is lacking even at the government level in terms of alternative control methods for the psyllid, for example effective natural enemies or resistant leucaena provenances or varieties.

From this report, it can be observed that information concerning leucaena performance in Mozambique is limited. This may due to the fact that some non-government organizations which give support in programmes of leucaena dissemination in the country directly to farmers. Institutional coordination is poor between these organizations and the central government. Therefore information which covers the entire country is difficult to acquire.

LITERATURE CITED

Bandeira, S.O., J.C. Hatton, P. Munisse and S. Izidine. The ecology and Conservation Status of Plant Resources in Mozambique. 19 p.(in press)

DNFFB, 1992.    Forest inventory. Ministry of Agriculture. Maputo. Internal Report. Empresa Moderna, 1962.  Atlas de Moçambique. Lourenço Marques.

Europa Publications Limited, 1985. Africa South of the Sahara 1986. England, Staples Printers Rochester Limited.

Pililão, F., 1989. Moçambique. Evolução da toponimia e da divisão territorial  1974- 1987. Universidade Eduardo Mondlane, Maputo, 128pp.

Svensson, J. 1987. Afforestation of clayey soils in Northern Mozambique. Swedish University of Agricultural Sciences, Uppsala, 27 pp.

Wambeke, J. Van and J.A. Eschweiler, 1987. Os solos da Area "Mata da Matola", Matola província de Maputo. Nota Técnica do Instituto Nacional de Investigação Agronómica Série Terra e Agua, 54.

White, 1983.  The vegetation of Africa. UNESCO, Switzerland.

KENYA  

THE STATUS OF LEUCAENA PSYLLID IN KENYA

by

Mercy Gichora and Jeff Odera
Kenya Forestry Research Institute,
P.O. Box 20412, Nairobi, Kenya.

INTRODUCTION

The genus Leucaena is the host of Heteropsylla cubana Crawford (Homoptera: Psyllidae), commonly referred to as the leucaena psyllid. This genus comprises 13 species of which the most commonly planted is the Leucaena leucocephala (de Wit). The trees in this genus are described as ideal for agroforestry because of their multiple uses (Brewbaker 1989). For this reason, leucaena trees have found their way into many research trials and have been cultivated the world over, especially where soils are poor, and in needy communities where timber, fodder and fuel wood are in short supply.

THE TREE

In Kenya, leucaenas have attracted a lot of scientific attention and many agroforestry research trials incorporating them are found on-station in research institutes. Agroforestry technology development has reached a stage whereby many agroforestry packages have also found their way to the farm as on-farm trials involving participating farmers. In some cases, farmers have fully adopted agroforestry practices that revolve around the use of Leucaena spp.

At the Maseno Agroforestry Research Centre in Western Kenya, for example, collaborative work carried out by the Kenya Forestry Research Centre (KEFRI), the Kenya Agricultural Research Centre (KARI) and the International Centre for Research in Agroforestry (ICRAF) includes the selection and grading of superior trees of Leucaena leucocephala (Otieno et al., 1992). General multipurpose tree and shrub species screening trials have been conducted with various Leucaenas from various provenances for biomass and associated crop yields. Such leucaenas include Leucaena leucocephala from Taiwan, L. leucocephala K8 and K29 from Baobab Farm, Kenya, other Kenyan L. leucocephala provenances such as Yimbo and Kibwezi; L. leucocephala K636 from Mexico, L. leucocephala 14198 from ILCA, Leucaena collinsii from Kibwezi, Kenya; L. diversifolia K156 from Mexico, L. diversifolia 14193, L. revoluta 14201 and L. paniculata 14203 from ILCA. These on- station experiments compared leucaena performance with other tree species but no clear relationship was found to exist between tree biomass yields of different species and crop yields. The highest annual biomass yielding tree species was Gliricidia sepium. Leucaena hybrid performance has also been tested for nitrogen fixation with Leucaena hybrid (K x 1a), (K x 1), (K x 3d) and (K x 3c).

Leucaenas have also been among the MPT species screened in alley cropping trials aimed at maintaining and improving soil fertility and in fodder production trials.

On-farm experiments have involved farmers in designing tree planting trials, on-farm feeding trials, testing of hedge-row intercropping and a survey of mycorrhizal and rhizobial inoculum potential for agroforestry among others.

Experiments with similar objectives are going on in other research centres in Kenya. In the central part of the country, for example, we find Embu where agroforestry technologies are geared towards coffee-based land use systems. Training activities are also conducted to enable local forestry and agricultural institutions to carry out their own agroforestry research which seek solutions to local problems. Leucaena leucocephala is one of six species in one screening trial being evaluated for the potential of selected MPTs for production of green manure. This species is also incorporated in hedgerow intercropping for soil fertility.

Similarly at Muguga, the KEFRI Agroforestry Programme conducts several research experiments in which leucaenas are incorporated. These include integrated soil fertility management and supplementary livestock feed with L. leucocephala and Calliandra calothyrsus. Multi-storey boundary planting experiments incorporate L. leucocephala and L. diversifolia as the lower storey tree/shrub species. Multi-purpose tree fodder production in tree-grass combinations on contour bands have Leucaena K28 and L. leucocephala intercropped with napier grass in feed gardens intended to intensify fodder production for cut-and-carry mode of livestock feeding. These experiments are not only taking place on- station but also going on in the neighbourhood where participating farmers were issued with 1400 L. leucocephala and 200 L. diversifolia seedlings for planting out in 1991. No more seedlings were issued thereafter. In the future, more agroforestry activities are planned which will include the substitution of dairy meal concentrate in the diet of lactating cows with dried L. leucocephala forage. Further Agroforestry research activities are planned for Kuja River in Western Kenya where agroforestry technologies relevant to rural farmers in that part of the country will be tested for boundary planting, fodder banks, river bank stabilization, woodlots, alley-farming, home gardens and enrichment planting. By March, 1994, 300 seedlings each of L. leucocephala and L. diversifolia had been planted in a nursery which is to support this work.

This is by no means an exhaustive analysis of the work currently involving leucaena in Kenya. Much more work is being undertaken by research institutes such as KARI, ILCA and ICRAF which cannot be fully covered in this report. Non-Governmental Organizations (NGOs) as well as government departments in various Ministries are also involved in agroforestry extension activities at the grass-root level which only a very intensive country-wide survey can reveal.

Suffice it to say that at the Kenya Coast Province, KARI is leading the way in agroforestry research at the Mtwapa Regional Research Centre in Kilifi District. Both on-station and on- farm research incorporating the use of Leucaena in various ways is under way. Some rhizobial inoculation trials with L. leucocephala are on the ground at the KEFRI Coast Research Station at Gede.

THE PEST

The earliest known report of the arrival of the leucaena psyllid in Kenya was that by a KEFRI scientist dated 30 July, 1992. Insect specimens of then unconfirmed identity but highly suspected to be the leucaena psyllid were collected by a KEFRI pathologist who was on routine pest and disease surveillance on one on-farm agroforestry trial in Bahari, Tenzo Location, Kilifi District, Coast Province (Njuguna, pers. comm.). Leucaena trees were reported as infested heavily with very active insects. Symptoms included defoliation and eventual die-back of shoots. The phenomenon was said to be present in nearly all farms in the neighbourhood but was at the time confined close to the beach.

The identity of the insects collected was finally confirmed by the International Institute of Entomology (IIE) on 18 August 1992 by a letter that simply said: "Heteropsylla cubana Crawford (Homoptera: Psyllidae), a major pest of Leucaena." This initial report was followed by several others in quick milestones of the spread marked by reports from:

Today; it is believed that leucaena psyllid has spread to all leucaena growing areas in Kenya but this has yet to be confirmed.

THE STATUS OF THE LEUCAENA PSYLLID IN KENYA - OCT, 1994

A follow-up trip was made by KEFRI entomologists in September 1992 to investigate the report of the arrival of the psyllid at the Kenya Coast. Their findings were similar to those by Reynolds and Bimbuzi (1992). These were that the infestation around Mtwapa in the North Coast was severe and that the psyllid appeared to be spreading northwards along the path of prevailing southeasterly winds from the Kenya-Tanzania border in the south. Farmers were at a loss what to do.

In September, 1 994, it was found that the situation had gone through its worst stage and that the panic among farmers had subsided. The psyllid attack was still severe in some places e.g. Mtwapa KARI station and Baobab farm, Ewe, near Iowa town. Reports from the South Coast indicated a steady recovery after initial severe attack (Dr. Gathua, pers. comm.). Farmers when interviewed expressed mixed feelings about the psyllid, sometimes regarding it as a blessing in disguise for a trees whose weed potential they had realized during their experience with Leucaena.

The people working in research centres expressed the most interest in the leucaena psyllid problem. They were concerned about having to study another tree species anew just when adequate data on the performance of leucaena in various situations, especially as supplementary feed for lactating cows, had been generated and the time appeared right for research findings to be transferred to the farmer. To such, control measures which could reverse the declining trend of the leucaenas were considered necessary. This, despite there having been a shift of emphasis from leucaenas to Gliricidia sepium as livestock fodder. It was encouraging to note at the Coast Forestry Research Station that Leucaenas inoculated with Rhizobia showed the greatest recovery after the psyllid attack, an indication that there may be many avenues of hope for the species.

LEUCAENA PSYLLID CONTROL

There is a joint plan of action by many institutions in Kenya which was agreed upon at a meeting held at KEFRI on 30 September,1992. This was that the most appropriate strategy to curb the leucaena psyllid problem was by integrated pest management (IPM). As such, institutions which could contribute most to the solution of this problem were identified and their roles spelled out. Today, therefore, several institutions are pursuing funds to carry out chemical screening, biological control and the use of leucaena varieties resistant to the psyllid. The work going on is commendable but institutions must be encouraged to keep their communication channels open to avoid unnecessary duplication of effort. We must further be willing to learn from the Asian experience and the wealth of experience and information generated by experts in the fight against the leucaena psyllid in Asia (Van Den Beldt and Napompeth, 1992).

NATIONAL AND INTERNATIONAL COOPERATION

The spirit of cooperation expressed on 30 September 1992 at KEFRI is mirrored today in the composition of participants in this workshop. It is our earnest hope therefore that this will be another milestone in the management of the psyllid problem both at the national, regional and international level. May the resolutions reached at this workshop pave the way forward for a lasting solution not only to this particular pest problem but also for others identified or yet to be identified as regional in nature.

ACKNOWLEDGEMENTS

Special thanks go to all who participated in interviewees and found time in their busy schedules to fill in questionnaires that have generated much of the information in this report. They include Messrs G. K. Mwaura and J. 0. Orupiny, both Foresters at the DFO's Office, Iowa; Dr. L. G. Gathua, a surgeon cum farmer/naturalist of Iowa; Dr. Rene D. Haller, Managing Director of Baobab Farm Ltd; Messrs John Juma and Mambo of GK Prison, Shimo-la-Tewa and KARI Mtwapa Regional research Centre respectively. We also owe gratitude to the Officer-in-Charge of KEFRI Coast Research Station at Gede, Mr. Njenga for a fruitful visit to the station and to the KEFRI Agroforestry Programme Head of Section, Dr. D. Nyamai who arranged for file records on KEFRI-related agroforestry research projects to be availed to us on request through Mr. Kiamba, Mr. Njuguna and others. The technical assistance rendered by Mr. Martin Karanja is hereby gratefully acknowledged. This paper was edited with the kind assistance of Callistus Ogol. Last but not least, we thank FAO who sponsored us to attend the workshop.

REFERENCES

Brewbaker, J.   L.   1989.   Leucaena:  Can  there  be  such  a  thing  as a  perfect tree? Agroforestry Today 1:4-7.

Otieno, H. J. O., B. Amadalo, A. M. Heineman and E. K. Mengich. 1992. AFRENA Project Maseno, Kenya. Progress report for the period: Jan 1991-Jan 1992. No. 55.

Reynolds L. and S. Bimbuzi. 1992. Leucaena psyllid arrives in Kenya. Agroforestry Today 4:2.

Van Den Beldt, R. J. and B. Napompeth.   1992.  Leucaena psyllid comes to Africa. Agroforestry Today 4:11-12.

MALAWI

THE STATUS OF LEUCAENA AND LEUCAENA PSYLLID IN MALAWI

by

C.Z. Chilima, G.S. Meke, L.A. Sitaubi and C. Coote
Forestry Research Institute of Malawi
Box 270, Malawi

ABSTRACT

Leucaenas, Leucaena spp. are the most widely researched, promoted and diversely used agroforestry trees grown by local farmers in Malawi. The tree grows well in most parts of the country, particularly along the Lower and Middle Shire Valleys and on the alkaline soils of the lake shore and the Bwanje Valley region. In these areas, many local farmers grow leucaena for green manure, supplementary feed for animals (especially cattle, goats and chickens), pole wood for construction and fuel wood for cooking, smoking fish and curing tobacco.

Until this year, when the leucaena psyllid, Heteropsylla cubana, was first recorded, leucaena enjoyed an environment without major pest problems in Malawi. The history, distribution and importance of leucaena in Malawi is elaborated in this report. The incidence, distribution and control options for H. cubana in Malawi are presented.

* * * * *

INTRODUCTION

Leucaenas (genus Leucaena} are native to the Mexican Yucatan Peninsula (Brewbaker 1987). The genus contains some of the most versatile trees, providing quality fuelwood, fodder, polewood, green manure, shade, erosion control and other useful products in the tropics and subtropics (Brewbaker and Sorensson 1988, Benge 1 983). As a result the tree has been widely promoted as a multipurpose tree species in agroforestry throughout Asia and Africa (Lulandala and Hall 1990).

Impetus on planting of leucaena in Malawi occurred mostly between 1973 and 1980, when an FAO sponsored livestock project became active (Khonje 1989). Since then, leucaenas have been tested extensively for their capacity to produce fuelwood, fodder and for soil protection by the Department of Agriculture (DAR), the Forest Research Institute of Malawi (FRIM), the University of Malawi (Bunda College) and the International Centre for Agroforestry (ICRAF, Makoka).

Leucaena, especially the Hawaiian Giant K-8 variety of L. leucocephala, has been vigorously promoted throughout the country. Many smallholder farms now plant and use this tree in their farming systems. Unfortunately, the tree is now under severe attack by the leucaena psyllid, Heteropsylla cubana, which was first reported from Malawi from Dedza and Zomba during the beginning of 1994 (Chirwa et al, unpublished).

With reference to various studies and surveys conducted in the country, we present a brief country status report of leucaena and leucaena psyllid in Malawi. We also present a list of the control options that are available.

HISTORY, DISTRIBUTION AND ACCEPTANCE OF LEUCAENA BY FARMERS IN MALAWI

There are unconfirmed reports that attempts to introduce Leucaena sp in Malawi were made as early as 1891 when in Zomba, the first government botanist, Mr. Alexander Whyte, planted a couple of trees in the first Botanic Garden in central Africa (Edwards and Darwin 1983). These attempts appeared to have been unsuccessful as the trees did not establish. According to Bunderson (personal communication), the first successful planting of leucaena in Malawi was made in 1969 by the Bunda College of Agriculture as a fodder crop. At about the same period, L. leucocephala, was planted in Agriculture Development Divisions (ADDs) throughout the country and several alley cropping research trial plots were set up at Chitedze Agricultural Research Station and Bunda College of Agriculture in Lilongwe. The Land Husbandry Branch of the Ministry of Agriculture also planted L. leucocephala in contour ridges to check soil erosion in many parts of Ntcheu and along the Bwanje Valley and encouraged local farmers to try the species in their fields. In 1978, the Forestry Research Institute of Malawi (FRIM) planted L. leucocephala in different silvicultural zones covering many parts of the country. It is now reported by the Ministry of Agriculture that almost everywhere in the country, farmers grow leucaena to various degrees and for various reasons (Chimphamba, personal communication). More than 30 farmers in the Ntcheu District (Chome, personal communication) report that they grow leucaena for a variety of reasons.

USES OF LEUCAENA IN MALAWI

Interviews with farmers throughout the country revealed that the tree is grown for one or more of the following purposes (Table 1):

SOIL AND CROP YIELD IMPROVEMENT - Farmers incorporate leucaena leaves into the soil to improve the soil structure and fertility which, in turn, they find improves yield with minimal inorganic fertilizer application. This finding was confirmed by Saka and Bunderson (1988), who demonstrated in their studies that a single application of leucaena leaves as a top dressing at mid-season increases soil fertility which leads to an increase in maize yields from 2278 to 3241 kg/ha. This compares with a yield of 5440 kg/ha using nitrogen fertilizer at 100 kg/ha.

ANIMAL FEED - Local grain milling companies mix leucaena seeds with other materials to make a cheap, high quality layer and growers feed for chickens. In many parts of the country, especially in the Bwanje Valley and Lower Shire, leucaena leaves are used to feed goats and cattle, particularly during the dry seasons when grass is scarce. There are reports from the Fisheries Department that research is being carried out to improve farm fish feed by adding leucaena seed and leaf material.

SHADE AND WINDBREAK - In Mangochi, L. leucocephala, is specifically planted on exposed terraces to act as a windbreak. In the tea and coffee growing areas of Thyolo, Chiradzulu and Mulanje, leucaena is also often planted for the same purpose.

SOIL PROTECTION - Farmers plant leucaena in contour ridges to check soil erosion. This is common in hilly areas along the Bwanje Valley. Extensive research and promotion of leucaena is being carried out by the Land Husbandry Branch of the Ministry of Agriculture for use of leucaena in soil protection.

FUELWOOD AND POLEWOOD - A rural fuelwood and polewood research project conducted by FRIM concluded that leucaena is a good fuelwood and polewood species in many parts of Malawi within silvicultural zones A, B and C (Nkaonja 1985 and Ngulube 1985).

In Mangochi, leucaena is used extensively to provide quality fuelwood and stakes for smoking and drying fish. On the shores of Lake Chilwa in Zomba, local fish farmers organize themselves and plant leucaena in communal woodlots to provide stakes and quality fuel wood for drying and smoking fish. Leucaena is particularly well suited to the alkaline soils of the Lake Chilwa area where other fuel wood species do not grow well.

In some of the tobacco growing areas, leucaena also provides stakes and fuel wood for drying and curing tobacco.

TABLE 1

RESULTS OF A SURVEY ON LEUCAENA USE IN MALAWI 
(Based on 47 farmers)

THE IMPACT OF LEUCAENA PSYLLID IN MALAWI

Since its discovery in Malawi, no formal surveys have been conducted to quantify the damage that the pest is causing. However, it has been reported by the DAR that severe defoliation of leucaena is common in Ntcheu, Dedza, Lilongwe and the Lower Shire (Phombeya, personal communication) and that this is having a negative impact on livestock farming in these areas.

Damage due to leucaena psyllid along Lake Chilwa is a heavy blow to fish farming and a frustration to community forestry efforts by fishing families in the area. No other fuel wood species grows as well as leucaena in the alkaline soils of the region (Wilson personal communication).

In view of the escalating costs of inorganic fertilizers in Malawi, damage caused by leucaena psyllid is having a drastic impact on smallholder crop yields throughout the country, particularly for farmers who relied on green manure from leucaena to supplement inorganic fertilizers.

The grain and milling industry which is relying on leucaena foliage to improve the quality of animal feed is badly affected by psyllid damage.

CONTROL OPTIONS 

NATURAL RESISTANCE

Studies that are being conducted by ICRAF and DAR show that all the leucaena species and provenances that were assessed were susceptible to the psyllid with the exception of Leucaena lanceolata and L. trichoides (Maghembe et al 1994). In a separate experiment involving leucaena hybrids at Makoka, it was found that all L. leucocephala hybrids were severely attacked while L. pallida and all L. pallida x L. diversiflora hybrids were less attacked. these results indicate that there is potential for controlling psyllid damage through breeding and/or use of resistant species. While advocating natural resistance as a potential control measure, it is worth considering the beneficial characteristics expressed by the susceptible leucaenas to ensure that these are not lost.

CHEMICAL CONTROL

No studies have been conducted on the chemical control of the leucaena psyllid in Malawi. This option is not likely to be favoured, mainly due to the high cost of chemicals and spraying equipment in Malawi. This is most relevant considering that most leucaena growers are smallholder, low income farmers who are aiming at reducing the costs of farm inputs.

BIOLOGICAL CONTROL

A large number of unidentified local natural enemies, mainly coccinellids, have been observed attacking psyllids in Malawi. Unfortunately, these do not seem to be effective enough to reduce damage to the trees. There may be need therefore, to attempt biological control using natural enemies imported from elsewhere, particularly from the psyllid's areas of origin (classical biological control).

SUBSTITUTION

ICRAF and the Agroforestry Extension Service have stopped promoting leucaena as an agroforestry tree, awaiting effective pest management measures. Where leucaena is grown for fodder, it has been replaced with Sesbania sesbana and where it is being grown for soil enrichment, fuel wood and other uses, it has been replaced by Gliricidia sepium, Sena siamea and Cassia siamea. The main problem with this approach is that the large investment and effort in promoting and planting leucaena throughout the country has been lost. Also, there is a risk that any replacement for leucaena may itself eventually succumb to a new pest problem. Further, it is unlikely that any single replacement will have as many useful attributes to the farming systems of Malawi as leucaena. Farmers may therefore not easily be persuaded to take up the replacement as well as they did leucaena.

CONCLUSIONS AND RECOMMENDATIONS

The importance of leucaena in Malawi cannot be overemphasized. It is a well adapted tree in most parts of the country and local farmers have accepted it for its many uses. The leucaena psyllid is a potential limitation to further planting and use of this important tree. There is an urgent need, therefore, to institute control measures for this pest. Since the psyllid is a migratory pest and leucaena is grown throughout Africa, any control approaches are best done on a multinational basis.

In Malawi, we believe that the use of classical biological control is the most feasible and cost effective approach to the protection of leucaena plantings. Initially, a survey must be carried out to quantify the psyllid problem. Malawi is fortunate in having had practical experiences in carrying out major biological control projects including cassava mealy bug and conifer aphids. Well trained personnel, facilities and necessary national and international linkages are in place for the country to be able to carry out a biological control programme for the leucaena psyllid and to assist other countries in the region.

ACKNOWLEDGEMENTS

We would like to express our gratitude to the United Nations, Food and Agriculture Organization and to the Government of Malawi for allowing and sponsoring our participation in this very important workshop.

We also thank members of the staff in the Ministry of Agriculture, the International Centre for Research in Agroforestry (ICRAF), the University of Malawi (Bunda College) and all those who made available their precious time to provide information on the status of leucaena and leucaena psyllid in Malawi.

LITERATURE CITED

Benge, M.D., 1983. Agroforestry systems: Contour hedgerows of woody perennials (alley cropping) reduce erosion, improve soil structure, increase crop yields and produce an abundance of fodder and fuel wood. S&T/FENR series no 12, USAID, Washington, DC, USA.

Chiyenda, S. and S. Materechera, 1989. Some results from alleycropping Leucaena leucocephala, Casia siamea and Cajanus cajan with maize at Bunda College of Agriculture. In Trees for Development in Sub-Saharan Africa. IFS, Sweden, pp 135-142.

Edwards, I. and T. Darwin, 1983. Trees, shrubs and woody climbers of Zomba Botanical Garden. Research Record 61, FRIM, Zomba.

Khonje, D.J. 1989. The potential of Leucaena leucocephala in the agroforestry system of Malawi. In Trees for Development in Sub-Saharan Africa. IFS, Sweden, pp 143- 149.

Lulandala,  L.L. and J.B. Hall, 1990. Leucaena leucocephala: potential role in rural development. Working Paper 65, ICRAF, Nairobi, Kenya.

Maghembe, J.A. and P.W. Chirwa, 1994. Annual report for the year ending September 1994. ICRAF, Makoka.

Ngulube, M.N., 1985. A summary of the 1984 trial assessment results of the IRDC funded rural development and poles research project.

Nkaonja, W.J. 1985. Fuelwood and polewood research project for the rural population of Malawi. Forest Research Record 62, FRIM, Zomba.

MAURITIUS  

THE LEUCAENA PSYLLID IN MAURITIUS

by

Teeratraj Rawanawshah
Ministry of Agriculture and Natural Resources
18 Harris Street, Port Louis, Mauritius

INTRODUCTION

Mauritius lies about 800 km East of Madagascar between longitude 57°47' and latitude 20°30'. This island, of volcanic origin, has an area of 1600 sq. km. The topography rises from sea level to peaks of 827 m. It has a tropical climate and is located in the tropical cyclonic belt. The island is swept by the southeast Trade Winds from April to October. There is no dry season on Mauritius but about 70% of the net rainfall is during the summer months from December to March. The amount of rainfall varies with altitude with the west coast having the least rainfall (1500 mm/year) and the high ground about 3600 mm/ year.

Mauritius is an agricultural island with 48% of the land under cultivation.    Food crop production amounted to 72,070 tonnes of which 10,830 tonnes is fruit products.  As of 1993, the livestock production level on the island consisted of 19 400 head of cattle, 62 000 deer, 15 000 pigs, 150 000 000 poultry and 23 000 goats and sheep.

IMPORTANCE OF LEUCAENA

Leucaena leucocephala (Lam.) de Wit, locally known as "acacia", is a leguminous tree. According to Brouard (1963) it originated from Central America and was introduced in Mauritius in 1 767 by Pierre Poivre. It is found mainly in dry lowlands near the coast where the annual precipitation is less than 1250 mm and at an elevation not greater than 375 m. The plant grows in the wild in association other plant species, namely Furcrea gigantea L. (aloe fibre plant), Haematoxylon campechianum (log wood or campeche) and Panicum maximum (Guinea grass or petite fataque).  Leucaena does not thrive well in the elevated central areas of Mauritius on account of soils and a combination of low temperatures and high humidity in winter. In Rodrigues, a dependency of Mauritius, leucaena is widespread all over the island.   It is mainly used as fodder for livestock production which is a major economic activity on the island.

The variety originally introduced is most probably the Acapulco type, now known as the Hawaiian type. Since then, other varieties have been introduced into Mauritius, namely Peru, El Salvador, Bald Hills, Hawaii, and Guatemala by the Department of Agriculture (Anon 1 963). In 1 976, Cunningham, a low-mimosine leafy type capable of superior yields of edible matter and protein, was introduced by the school of Agriculture of the University of Mauritius.

The potential of acacia for fodder has been underlined by Halais (1950). The characteristics which make acacia a suitable fodder are its high palatability, high protein content and high digestibility. It is also rich in vitamins and mineral nutrients and contains amino acids in well balanced proportions. Livestock owners have long used acacia for feeding ruminants. They gather the green fodder from the naturally occurring plants. Little is sown and cultivated as a crop. Apart from its use as fodder, it is used as windbreaks in orchards and other cultivation and in soil erosion control. There is no established agroforestry on either Mauritius or Rodrigues. Mauritius has 56 998 hectares of forest lands of which 11 125 hectares are natural reserves.

LEUCAENA PSYLLID

CURRENT STATUS

Leucaena was practically free from important pests until October 1991, when leucaena psyllid was first noted in Mauritius. In February 1992, infestations were detected on Rodrigues. Specimens collected in Mauritius and sent to the International Institute of Entomology were identified as Heteropsylla cubana Crawford by Dr D. Hollis of the National History Museum in London. Mauritius was the western most point in the distribution of leucaena psyllid at the time. Since then it has been recorded from Reunion island (Quilici 1992) and Africa (Hill 1992).

The psyllid is present throughout Mauritius and all stages of the insect are found on the young shoots of leucaena causing defoliation, wilting and dieback. On Rodrigues, the situation is very alarming because the defoliation affects livestock production considerably. Surveys have revealed the presence of a few ladybirds beetle, Exochomus sp, and a few Heteroptera, and the absence of parasitism. These predators do not exert any control due to high populations of leucaena psyllid.

POTENTIAL SOLUTIONS

The solution to the threat of leucaena psyllid is not simple. To date, no satisfactory solution has been developed. Psyllid resistant varieties may exist in its country of origin, but it will take some time for the introduction and propagation of such varieties. The most promising strategy for the short term is biological control. Chemical control of the pest is expensive and as it is difficult to treat the plants in the wild and the foliage must be pesticide-free for feeding livestock. Biological control using predators and parasitoids is very useful for immediate check of the population of the pest. Among the predators, two ladybird beetles, Olla v. nigrum Mulsant and Curinus coeruleus have been found to exert certain control in Tahiti and Hawaii respectively. More specific biological control agents are parasitoids. In its area of origin, Psyllaephagus yasaeni (Encyrtidae) and Tamarixia leucaenae (Eulophidae) may be effective in controlling the psyllid at low density and thus, may prove valuable in preventing outbreaks of the pest. None of the above predators or parasites exist in Mauritius.

The defoliation, wilting and dieback of leucaena shoots is a constraint to the development of livestock in Mauritius and specially in Rodrigues. The Ministry of Agriculture and Natural Resources in Mauritius is planning for the introduction of the above predators and parasitoids with a view to start a biological control programme.

LITERATURE CITED

Anon, 1963. Annual Report for the Department of Agriculture for the YEAR  1962. Mauritius Government Printer, Port Louis, Mauritius.

Brouard, N.R., 1963.  A history of woods and forests in Mauritius.Mauritius Government Printer, Port Louis, Mauritius.

Halais, P., 1950.        L'exploitation intensive d'une légumineuse fourragère tropicale.   Revue Agricole et Sucrière de L'lle Maurice, 29:68-75.

Hill, G., 1992.   Report of a visit to Mauritius and Reunion, 23-29

June 1992 to study infestations of the leucaena psyllid on Leucaena leucocephala. Kenya Station, International Institute of Biological Control, 6 pp.

Quilici, S., 1992.   Une nuisance potentielle récernment observée à la Reunion: Le psylle du leucaena: Heteropsylla cubana Crawford. CIRAD/IRFA, Reunion, 5 pp.

NIGERIA  

STATUS OF LEUCAENA IN NIGERIA

by

P.M. Papka
Forestry Management Evaluation and Coordinating Unit
Federal Department of Forestry
Abuja, Nigeria

I would like to first seize this opportunity to immensely thank the organizers of this workshop to find it appropriate to invite a delegate from Nigeria and also FAO, particularly Mr William Ciesla for making it possible for me to attend.

The International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria had embarked on a large scale experiment using Leucaena leucocephala for alley cropping practices, especially in the southwestern part of Nigeria. Since its introduction into the country, L. leucocephala is now used in all of the ecological zones in the country to help address the differing ecological problems and needs.

With regard to leucaena psyllid, there is no record as yet of this destructive insect in Nigeria and it is our prayer that it stays away from our borders. However, since pest outbreaks do not respect political boundaries, we find our participation in this workshop to be timely. We look forward to the workshop conclusions and recommendations, the basis of which we can use to sensitize those people who have adopted leucaena as an agroforestry species in their farming systems in Nigeria.

I believe a lot of experience and lessons will be exchanged during the course of this workshop so that we are not caught unaware of the possibility of destructive pest outbreaks. This was our experience when the Oriental scale, Aoinidiella orientalis Newstead, a serious pest of neem, Azadirachta indica, first appeared in northeastern Nigeria.

Thank you.

THE SUDAN

FOREST PESTS IN THE SUDAN: THEIR ECONOMIC IMPORTANCE AND CONTROL

by

Hashim A. El Atta 
Dean, Faculty of Forestry, University of Khartoum

and

Hassan Osman Abdel Nour
Forests National Corporation
P.O. Box 658, Khartoum, The Sudan

INTRODUCTION

The forest sector contributes some 12% to the GNP of the Sudan. Beside the indirect benefits, environmental protection and work opportunities for the rural population, fuel wood represents the most tangible benefit for the people of The Sudan derived from their forests.

In 1993, the Sudan consumed energy equal to seven million tons of oil equivalent. Of this total, 80% was in the form of wood, charcoal and other biomass, 18% as petroleum products and 2% as hydropower. The total wood consumption of the period 1983-2000 is shown in Table 1. The annual export of gum arabic ranges from between 20-40 thousand tonnes and earns some $US 50-80 million (Table 2).

INDIGENOUS FOREST PESTS IN THE SUDAN

Pests of forests and forest products in Sudan include:

Coleoptera:

Cambium borers (Primarily Buprestidae and Cerambycidae) 
Wood borers (Bostrychidae)
Seed borers (Bruchidae)

Orthoptera:

Crickets (Gryllus sp.)
Tree locust (Anacridium melanorhodon melanorhodon)
Desert locust (Schistocerca gregaria)
Mole crickets (Gryllotalpa africana)

Isoptera:

Sand termites (Psammotermes hybostoma)
Large mound-building termites (Macrotermes sp.)
Lesser mound-building/subterranean termites (Odontotermes sp.)
Ground dwelling termites (Microtermes)

TABLE 1

ESTIMATED CONSUMPTION OF WOOD PRODUCTS IN THE SUDAN, 1983 - 2000 (Production units are in millions of cubic meters of roundwood equivalents)

Source: World Bank Forest Sector Review - 1986.

TABLE 2

SUDAN EXPORTS OF GUM ARABIC

SIGNIFICANT OCCURRENCES OF FOREST PEST DAMAGE

DECLINE OF ACACIA NILOTICA:

BACKGROUND - Sunt, Acacia nilotica, is the most valuable timber producing species in northern Sudan. The contribution of A. nilotica to the total sawn timber production in northern Sudan is estimated in the range of 40-50% and it contributes to fuel wood production by 10-15%. The timber is used for railway sleepers, heavy construction, turnery, boat building, fuel wood and tanning material from the bark and pods. The tree occurs in pure, even age stands which have been artificially regenerated by direct seeding in flood plains and remnants of oxbow lakes along the Nile and its tributaries. Along the Blue Nile and its tributaries, A. nilotica plantations are managed on 20 or 30 year rotations.

Dieback of A nilotica was reported as early as the 1930s and was attributed to attack by a cambium and wood boring beetle, Sphenoptera chalcichroa arenosa (Coleoptera: Buprestidae) (Peake 1956). The dieback and mortality of A. nilotica was attributed to the larvae of the beetle which tunnels in the cambium layer of branches and gradually kills the tree.

In a study conducted in Lembwa Forest (Blue Nile), losses due to the dieback recorded following a 4 year period 30% in dbh 1 % in height growth, 54% in volume and 60% in mean annual increment (El Atta 1988).

By the early 1950's, the condition had affected most of the forests between Khartoum and Sennar and was estimated to have caused losses of up to 60% in the plantations along the Dinder River. The dieback was not reported south of Sennar Dam at that time. Its spread south had been cut off by complete clearing of sunt in that area to provide fuel during the dam construction (1914-1925). The forests south of the dam commence 15 km with the buffer area which was maintained clear of sunt. A legislative control measure strictly prohibited the transport of sunt wood upstream along the Blue Nile from

Sennar and from Dinder. It was believed that this action maintained the dieback status quo up to 1978 when it appeared in the Hedaibat Forest on the west bank of the Blue Nile and the Wad Behaiga Forest on the eastern bank, some 90 km south of Sennar. In 1989 it suddenly erupted reaching plague proportions. Fourteen reserves have been affected with a total area of 1191.5 feddans (500 ha) with 15% of the sunt area in the reserves being killed (Table 3).

CAUSAL FACTORS - Ciesla (1993) proposes the following working hypothesis to explain the events leading up to the occurrence of decline of A. nilotica in the Sudan:

PREDISPOSING FACTORS: Use of seed of unknown or mixed origin in the establishment of the plantations may have resulted in the establishment of certain provenances of A. nilotica in areas to which they are not suited. Annual deposits of silt during the rainy seasons gradually reduces the depth of the oxbow lakes. Consequently they hold less water and tend to dry earlier. Over time they are no

TABLE 3

AREAS KILLED BY DECLINE OF ACACIA NILOTICA IN RIVERINE FORESTS ALONG THE BLUE NILE IN 1990

* 1 Feddan = 1 Acre = 0.40 ha

Source:   Report by Sayed Yahia I. Bushara to FNC 7/1/91

longer suitable for growth of A. nilotica. Periodic droughts are a more or less regular event in the Sudan. Silt deposition and periodic drought stress affect the larger, older stands to a greater extent because there is more competition for the available moisture. Any of these factors may predispose A. nilotica to decline.

INCITING FACTORS - The most likely incitant for the current episode of decline is the massive flooding and silt deposition which occurred in 1988. Outbreaks of defoliating insect(s) and periods of drier than normal weather could also incite decline.

CONTRIBUTING FACTORS - The complex of cambium and wood boring beetles such as beetles of the families Buprestidae and Cerambycidae are considered to be contributing. These groups of insects are incapable of attacking vigourous trees but can attack and kill trees weakened by the factors discussed in the preceding two sections.

BRUCHID SEED BORERS OF ACACIA NILOTICA

BACKGROUND - Insects which bore into the seed pods of A. nilotica and destroy the seeds are the most important factor that reduces seed viability and hence germination. A preliminary investigation by Peake (1952) revealed 60% damage in stored seeds of A. nilotica in the Blue Nile State caused by Bruchidius uberatus (= B. baudoni) (Coleoptera: Bruchidae).

Recently, El Atta (1993) surveyed the occurrence and impact of seed borers on A. nilotica seeds in the Blue Nile State in two forests; Wad El Gizouli and Ed Dabkara. These are located about 1 km and 5 km, respectively, northeast of Singa. Higher rates of infestation by the larvae of the seed weevil Caryedon serratus Olivier (Coleoptera: Bruchidae) were recorded. The larvae of C. serratus bore into the seeds via small holes and feed on the embryo and the endosperm, leaving every infested seed non-viable. So far direct seeding is the only means for regenerating A. nilotica forests. Therefore infestation by seed borers present an extremely serious pest problem. Generally, the mean infestation rate was considerably higher in stored seeds (80-90%), moderate in pods on the forest floor (20%) and light in pods from the standing trees (10%). This suggests that C. serratus is a serious pest of stored seeds. All infested seeds failed to germinate. Tables 4, 5 and 6 summarise the results of field collected and stored seed survey of sunt seeds infested by C. serratus.

BIOLOGICAL INFORMATION - This insect deposits translucent oval eggs (1-2 mm long x 0.5-I mm wide) on the smooth testa of dehusked sunt seeds. The larvae penetrate the seed via the seed testa at points where they adhere to the seed and start feeding on the seed contents. The average number of eggs/female was 92.9, the mean oviposition period was 11-16 days and the mean hatch ability was 80.49% at temperatures of 35-5O C and 70% RH (El Atta 1993). Four larval instars were recorded with an average duration of 1 2.4, 10.6, 11.5 and 7.2 days respectively.

After completion of feeding, the larva emerges from the seed via 2-4 mm exit hole and spins an ovoid, papery and translucent cocoon covered entirely with short hairs. Within 10-15 days, adults start to emerge from the cocoons.

The survey revealed that Bruchidius uberatus is predominant in the field attacking pods still attached to the trees. The insect failed to infest dehusked sunt seeds.

PEST MANAGEMENT - Suggested control measures are as follows:

CULTURAL -

Dehusking of A. nilotica seeds before storage will prevent attack, especially by B. uberatus because it does not attack dehusked seeds.

CHEMICALS -

Botanical insecticides, such as neem seed kernel powder, neem seed oil, castor oil and eucalyptus oil, provided effective control against these two bruchids. They exhibited a very good ovicidal effect, larval and pupal mortality. Botanicals also caused 95% egg mortality in the two bruchids, 92.2% mortality of the immature stages of Caryedon serratus (at 2.5 and 5 ml/kg doses) and 100% mortality of the immature stages of Bruchidius uberatus. Oils extracted from Eucalyptus camaldulensis exhibited a knock down effect and caused 100% mortality of adults of both species a few minutes after fumigation even at very low doses (El Tom 1994). Considering the very high levels of efficiency in controlling both bruchids using botanical extractives and considering the safety of such materials as they exert no environmental hazards, emphasis should be directed towards the use of botanicals as possible control materials against these insect pests.

TREE LOCUST

BIOLOGICAL DATA - The tree locust or night wanderer, Anacridium melanorhodon melanorhodon (WLK) = (Orthoptera: Locustidae) is another serious pest of Sudanese forests. Description, life history and bionomics of this insect are presented by Schmutterer (1964). It occurs in northeastern, central and west Africa including the Cape Verde Islands. In the Sudan, this species has been recorded mainly from the central, northern and western areas. It is very common in Kordofan and Darfur where it may cause harm to gum trees, Acacia Senegal, heglig, Balanites aegyptiaca, and occasionally to crops such as cotton, fruit trees (eg mango, guava, citrus, date palm) and to dura (Sorghum) in the milky stage.

The adults fly in scattered swarms at night or early in the morning, hence the name "night wanderer". During the day, the swarms settle on trees, especially Acacias. One generation exists per year breeding starts during the rainy season. The female lays 1-3 egg pods, each containing 150-200 eggs. The incubation period lasts 23-65 days. The dry season is spent in the adult stage.

TABLE 4

MEAN INFESTATION RATE OF PODS OF A. NILOTICA BY
LARVAE OF C. SERRATUS, ED DABRAKA FOREST, SUDAN

TABLE 5

MEAN INFESTATION RATE OF PODS OF A. NILOTICA BY 
LARVAE OF C. SERRATUS IN WAD EL GUZOULI FOREST, SUDAN

Source: El Atta (1993)

TABLE 6

MEAN INFESTATION RATE BY LARVAE OF C. SERRATUS IN DEHUSKED 
STORED SEEDS FROM THREE STORAGE FACILITIES IN THE SUDAN

Source: El Atta (1993)

IMPACT ON GUM PRODUCTION - The tree locust is a defoliator and the impact on gum production is mainly through defoliation. Acacia Senegal trees enter a natural dormancy period prior to being tapped. For trees growing on well drained sites, this takes place towards the end of October. If swarms of the tree locust alight on the trees and defoliate them prematurely (before natural leaf fall), the trees respond by resuming their vegetative growth and produce a new generation of leaves. In so doing, they use up their stored nutrient reserves which otherwise would have been used to produce gum when tapped.

Gum tappers have learned this by experience and refrain from tapping when swarms of the locust appear. The amount of loss in gum production is proportional to the intensity of defoliation. A recent study showed that the mean total gum production was 85.6, 19.6, 9.4, 4.9 and 11 gm/tree in undamaged, hight, medium and heavily locust defoliated and heavily artificially defoliated trees respectively (Table 7). The loss in gum production was 75.9,89, 94.2, and 87.1% in light, medium and heavy locust defoliation and heavily artificially defoliated trees respectively (Table 8).

CONTROL MEASURES - Control of the tree locust is limited to ground and/or aerial chemical spraying by the Plant Protection Department of the Ministry of Agriculture, Food and Natural Resources.

TERMITES

Harris (1968) listed 38 termite species from 26 genera that were known to occur in the Sudan at the time. It seems that this listing is far from complete (Wood et al 1982). Both indigenous and exotic forest trees are subject to termite damage with the latter being more susceptible, especially new transplants and pole sized trees. Usually termite attack follows weakening of trees by stress factors such as lack of moisture stress. This is caused by drought, prolonged gaps in rainfall or irregular irrigation. Other factors include fire, pests and deep scars or wounds which expose the heartwood and allow access to the heartwood.

Low rainfall in the western Sudan for two successive years during the drought years of the early 1970's weakened exotic cypress, Cupressus lusitanica, plantations in shallow mountain soil on Jebel Marra, making them susceptible to attack by subterranean termites. In Beldong, virtually every tree had been girdled by Microtermes sudanensis and Ancistrotermes crucifer. Tunnelling had progressed into the root-collar zone. In Galol, with even less rainfall, Odontotermes sudanensis had girdled the roots (Abd El Nour 1975). Eucalyptus camaldulensis, E. citriodora and E. umbellata were also affected by the drought spells of 1984 and 1990 at the pole stage and mass mortality was quite sporadic. Even the indigenous trees which were weakened by drought were affected by termites. Mature Acacia senegal and A. nilotica along water courses had gnawed roots and the trees were toppled over by wind.

Abd El Nour (1982) stated that natural durability tests of home grown timbers showed that the greater majority of them are either not durable or only moderately so. Only the clay zone mahogany, Khaya senegalensis, has endured the test for 15 years.

Cultural practices conducive to the raising of healthy trees are resorted to as the first defense against termite attack. These include weeding, thinning, terrace maintenance and timely irrigation when applicable. However, as most plantations are rain fed with the periodic drought spells, cultural practices on their own, may not prevent tree damage by termites. Under these conditions, application of termiticides to the potting medium in the nursery or during transplanting becomes a necessity. Only chlorinated hydrocarbon insecticides have afforded long term protection. However they are considered as hazardous to the environment. Dipping and pressure pretreatments with chemical preservatives such as creosote oil and CCA have proven effective in protecting perishable timbers. For timber in use, injection of a weak diefdrin solution behind and under wooden frames has been successful, but not without concern over environmental and health hazards.

TABLE 7

GUM PRODUCTION BY A. SENEGAL (GM) BY LEVELS
 OF DEFOLIATION (1992 SEASON)

F = 107.19, P = 0.01, Source: El Bashir (1994)

TABLE 8

PERCENT LOSS IN GUM PRODUCTION BY VARIOUS
 LEVELS OF DEFOLIATION (1992 SEASON)

Source: El Bashir (1994)

LITERATURE CITED

Abd El Nour, H.O., 1975. Drought and termites: A threat to Cupressus lusitanica plantations in Jebel Marra-Sudan. Sudan Silva, 3:12-17

Abd El Nour, H.O., 1982. The protection of buildings against termites in the Sudan. Bulletin of African Insect Science. 6:9.

Ciesla, W.M., 1993. Decline and mortality of Acacia nilotica in riverine forests of the Blue Nile. FAO, Rome, Italy, GCP/SUD/047/NET, 17 pp.

El Bashir, Z.M., 1994. The impact of defoliation by the tree locust on the gum arabic production by hashab trees (Acacia Senegal (L.) Willd.) M. Sc. Thesis, Faculty of Forestry University of Khartoum, Sudan.

El Atta, H.A., 1988. Sphenoptera chalcichroa arenosa (Coleoptera: Buprestidae) associated with dieback of Acacia nilotica in the Sudan. Journal of Applied Entomology 106:350-355.

El Atta, H.A., 1993. The effect of Caryedon serratus Oiivier (Coleoptera: Bruchidae) on viability and germination of seeds of Acacia nilotica in the Sudan. Forest Ecology and Management, 57:169-177.

El Tom, T., 1994. The effect of some bruchid seed borers on the viability of seeds of Acacia sp. and Prosopis sp. and their control. M.Sc. thesis submitted to the Faculty of Forestry, University of Khartoum, Sudan.

FAO, 1960., Report to the Government of Sudan No. 1291.

Peake, F.G.G., 1952. On a Bruchid seed borer of Acacia arabica. Bulletin of Entomological Research, 43:317-324.

Peake, F.G.G., 1956. Notes on dieback in sunt. Acacia arabica and forest pests in Equatoria. Ministry of Agriculture, Sudan Government, Forestry Memoir No. 9.

Schmutterrer, H., 1969. Pests of crops in northeast and central Africa. Gustav Fischer Verlag. Stuttgart.

Sudan Forests Department Annual Report 1969/1970.

TANZANIA

INCIDENCE OF FOREST PESTS IN TANZANIA WITH A
 SPECIAL REFERENCE TO THE LEUCAENA PSYLLID

by

E.Z. Kisaka
Tanzania Forest Research Institute (TAFORI)
P.O. Box 10, Moshi, Tanzania

ABSTRACT

The invasion of Leucaena psyllid, Heteropsylla cubana Crawford (Homoptera: Psyllidae), an insect native to Central and South America is not the first exotic pest infestation in Tanzania. Three conifer aphids, Pineus ?boerneri Annand (Homoptera: Adelgidae), Euiachnus rileyi Williams, and Cinara cupressi (Buckton), both (Homoptera: Aphididae), have caused considerable damage to the Tanzanian forest estate. Two of these pests have reasonably well controlled. Previous experience gained from control measures of these three pests can be applied in the development of a pest management programme for the present the leucaena psyllid infestation. The importance of cooperation and collaboration at different levels is stressed.

* * * * *

PREVIOUS EXPERIENCE

Over the past years, increasing emphasis has been placed on promoting fast growing, exotic and indigenous trees species that serve a variety of uses such as timber, fodder, fuel wood, charcoal and rehabilitation of degraded lands. It was through such objectives that the three conifer aphids were accidentally introduced into eastern and southern African region.

The three conifer aphids are Pineus ?boerneri Annand (Homoptera: Adelgidae), Eulachnus rileyi Williams and Cinara cupressi (Buckton), both (Homoptera: Aphididae). These insects, which are indigenous to the temperate forests of North America and Europe, were introduced unintentionally into eastern and southern Africa where they became established on fast growing conifers which had been introduced into the region. These conifers include Pines such as Pinus patula, P. elliotii, P. caribaea, P. kesiya and cypress, Cupressus lusitanica. C. benthamini, C. torulosa and other conifers. In the absence of their natural enemies and in different environmental conditions these exotic pests have been very damaging to the conifer plantations. The aphids have moved freely to wherever suitable host plants occur and they do not recognise political boundaries. Their damaging effect has been so serious that could not escape the attention of researchers, farmers, foresters and other authorities concerned with plant/environmental protection. These three aphids represent a major threat to the future viability of conifers as a potential forest resource in eastern and southern African Region (FAO 1991).

The invasion of conifer aphids, and the spectacular destruction of conifer plantations in the eastern and southern Africa region had become such a crucial issue to the forest departments in the region that a special regional workshop; Exotic Aphid Pests of Conifers: A Crisis in African Forestry, was organized by the Kenya Forestry Research Institute, in collaboration with FAO, USDA Forest Service and the International Institute of Biological Control. This workshop was held in Muguga, Kenya 3 - 6 June, 1991. This workshop provided an opportunity for researchers and practitioners from eastern and southern Africa to come together and share their observations, experience, successes and failures. It was also a forum to seek international aid to help solve the problem technically and financially. It was through the workshop that some international aid agencies like the ODA, FAO, IDRC and IIBC were willing to help protect the conifer resource in this region. In addition to the workshop, several seminars and courses have been organised at the regional or national level to help solve this problem.

Since the conifer aphids appeared on this part of Africa, there are a number of pest management tactics that have been developed which have the potential to reduce aphid populations to tolerable levels. Each affected country in the region has been working either independently or regionally to develop effective control measures.

The knowledge gained on confronting other forest pests and the information known on the biology, ecology, life cycle and the natural enemies of the three conifer aphids could also be used to develop pest management measures for other forest pests like the present problem of the leucaena psyllid which is the theme of our workshop today. Some of the biological control programmes used against forest insects in Tanzania are shown in Table 1.

THE LEUCAENA PSYLLID

A GLOBAL PERSPECTIVE

The leucaena psyllid, Heteropsylla cubana Crawford (Homoptera: Psyllidae), is a pest of Leucaena leucocephala (Lam) de Wit, a fast-growing, nitrogen-fixing tree native to Mexico and Central America. This tree is widely grown in Tanzania at elevations ranging from 0 to 1800 meters above sea level in agroforestry systems. Leucaenas have turned out to be ideal trees for agroforestry, particularly when the fast growing single stem "giant" leucaenas were released by scientists in Hawaii and Australia (Brewbaker 1989).

Outside of their natural range, leucaenas have been growing well for many years without any major pest problems. However in 1983, the leucaena psyllid caused severe damage on Leucaena leucocephala in Florida. From then onwards, the insect has spread from Florida to the Pacific Islands, Southeast Asia, Australia and India. In 1992, H. cubana was reported in Kenya and Tanzania causing severe wilting, dieback and death to leucaena plants (Reynolds and Bimbuzi 1992).

THE TANZANIA EXPERIENCE

The presence of leucaena psyllid in Tanzania alarmed, among other institutions; the Tanzania Forest Research Institute (TAFORI) to take action. Investigations on the psyllid followed the same procedure as that of the conifer aphids which was to evaluate the

TABLE 1

FOREST INSECT OUTBREAKS AND BIOLOGICAL CONTROL MEASURES TAKEN IN TANZANIA (AFTER MASSAWE 1993)

damage and its extent. Surveys were carried out along the Coastal and Morogoro Regions. The surveys showed that the insect had spread to Morogoro where well established infestations were found at Sokoine University of Agriculture (SUA) in leucaena plantations and hedges in 1993. Further surveys showed that the insect had spread to almost all areas of Tanzania where leucaenas are planted. TAFORI issued a Technical Note (Kisaka 1993) to alert the public of this new insect pest. The note describes the insect and its damage. The public was asked to report similar damage to local plant protection officers and, when possible, to take the insect and plant samples to them or to nearby research stations.

Observations in the field indicated that not all leucaena trees were equally susceptible to the psyllid. Some trees have shown some resistance or tolerance. Furthermore, it was observed that the psyllid population fluctuates according to season. High populations occur at the beginning of the dry season and low population occur during the rainy season. In addition, there were other insect that have been observed in association with the psyllid. These were larvae of certain diptera and some wasps. The role of these insects has not been established and further observations are needed.

CONTROL MEASURES

Searches for natural enemies were done in all surveyed areas. A large number of generalist predators have been seen to prey on the psyllid. These included representatives of the families Coccinellidae, Syrphidae, Hemipteran bugs and spiders. No parasitised psyllids have been found in the field. The role of these indigenous natural enemies in controlling the psyllid has not been evaluated. In Asia, coccinellids and other parasitoids have been found to play a role in the psyllid control (Napompeth 1994).

Little has been done on the identification of the potential natural enemies of the psyllid in Tanzania. The most common and immediate method of fighting an introduced insect pest is the use of pesticides. This method has not been used to combat the psyllid on a large scale in Tanzania. Most of the leucaena plantings are mixed with food crops or are in cattle grazing areas, thus limiting the use of pesticides. In addition pesticides are expensive and not necessarily environmentally friendly. Some chemical pesticides have been used on a limited scale in areas like nurseries and hedges.

Several strategies have been developed to control this pest, particularly through breeding for plant resistance or tolerance to infestations (Austin 1993). As pointed out earlier, some individual leucaenas have shown resistance or tolerance in the field to the psyllid infestation. Breeding work is going at various agricultural research institutes on leucaena species/provenance selection and field testing of leucaenas which are promising for wood, fodder production and psyllid resistance. Initial results (Anon 1990 - 93) have indicated that L. leucocephala giant K28, K8 and L. leucocephala ex Peru are among the candidates for wood and fodder production. L. diversifolia has shown some resistance to the psyllid.

For a small farmer, low cost methods in the short term, such as biological control would be more viable than breeding for resistance which is long term and time consuming. Biopesticides have an advantage that the farmers are directly involved in the application and control. The absence of an established germ plasm source for supplying research material currently limits our breeding programmes.

FUTURE OUTLOOK

The impact of the leucaena psyllid on farmers is significant, particularly when compared to their low incomes. This threatens the future of leucaena plantings unless permanent control measures to reduce wood and fodder losses caused by the psyllid are found.

Agroforesters in Asia have information, germ plasm and biological control agents that could help us in Africa to combat this pest. A great deal of information on the psyllid has been generated (Van den Beldt and Napompeth 1993). Through international and regional cooperation, pest management tactics developed in Asia can be modified to meet African conditions.

LITERATURE CITED

Anon, 1990 - 94. Agroforestry Research Coordination Committee Meetings, Ministry of Agriculture and Livestock.

Austin, M.T., 1993. More on the leucaena psyllid. Agroforestry Today, April-June, 1993.

Brewbaker J. L., 1989. Can there be such a thing as a perfect tree? Agroforestry Today 1:4-7.

FAO, 1991. Exotic aphid pests of conifers: A crisis in African forestry. Workshop Proceedings. Muguga, Kenya 3 - 6 June 1991.

Kisaka E.Z., 1993. The Leucaena psyllid, Heteropsylla cubana. Tanzania Forestry Research Institute, Technical Note 1.

Massawe, A. 1993. A review of biological control of the important forest pests of Tanzania. Forestry Pest Management - A Newsletter for Eastern and Southern Africa. IIBC, Kenya Station, No.1, December 1993.

Napompeth, B., 1994. Leucaena psyllid in the Asia-Pacific Region: Implications for its Management in Africa. FAO, RAPA Paper 94/13.

Reynolds, L. and S. Bimbuzi, 1992. Leucaena psyllid arrives in Kenya. Agroforestry Today July-September:2.

Van Den Beldt and B. Napompeth, 1992. Leucaena psyllid comes to Africa. Agroforestry Today, July-September 4:11-12.

SOUTH AFRICA

POSSIBLE OCCURRENCE OF THE EUROPEAN WOOD WASP,
SIREX NOCTILIO (HYMENOPTERA: SIRICIDAE),
IN SOUTH AFRICA

by

G. Tribe
Plant Protection Research Institute
Rosebank, Capetown
South Africa

In April 1994, a disintegrated wood wasp, closely resembling the European wood wasp, Sirex noctilio, was found under the bark of a felled and discarded 44 year old Pinus radiata tree in the Tokai Plantation in the Cape Peninsula. The search for the distinct round exit holes of S. noctilio was extended to the remainder of the plantation and just under 5000 such exit holes were found in discarded logs. Roughly an equal number of exit holes were detected in dead standing trees in an adjacent stand of 44 year old P. radiata.

Living Sirex larvae were extracted from live P. radiata trees which were showing signs of foliar wilting. The distinctive brown resin streaks resulting from the reaction of the host tree to the wood wasp's fungal symbiont was also detected in the felled trees. When adult emergence begins in November, we will be able to confirm the wood wasp's identity.

South Africa is an exporter of pulp and timber. No Pinus lumber has been imported through Cape Town for at least eight years. We believe (but as yet have no proof) that this insect entered South Africa in rough hewn pine packing crates. Calculations indicate that this infestation has been present in the Cape Peninsula for at least one year but the number of exit holes indicate that the infestation may have been present for at least two years. The timber harvested from the Tokai Plantation is taken to a sawmill at Stellenbosch which is some 50 km away. Sirex larvae were detected in the adjacent Jonkershoek plantation in a stand of Pinus radiata roughly 40 years old during the first week of October 1994. No exit holes were found in any logs or trees. This indicates that Sirex arrived during the past season (November 1993-March 1994), long before a quarantine had been placed on the removal of timber from the Tokai plantation. Additional infestations have been detected in the La Motte Plantation at Franschhoek and at two plantations at Grabouw. These localities are within a radius of about 60 km from Cape Town where the wood wasp was first detected.

The infestation now has the potential to move into the neighbouring P. radiata plantations in the Western Cape and then to the Eastern and Southern Cape. Plantations in these areas are composed primarily of P. radiata although lesser amounts of P. pinaster and P. elliotii have also been established. This region has a heavy winter rainfall season and a summer dry season. Consequently the pines are under moisture stress during the peak period of Sirex activity.

ETHIOPIA

  LEUCAENA AND LEUCAENA PSYLLID IN ETHIOPIA

by

Tsenay Azage
Biological Control Unit 
Ministry of Agriculture 
P.O. Box 5689 (ILCA) 
Addis Ababa, Ethiopia

ABSTRACT

The genus Leucaena has its origin in Central America. From there, it was spread by humans throughout the tropics where to date over two million hectares of plantations have been established. The introduction of leucaena in Ethiopia is relatively recent. ft was probably established in 1979 for screening trials at a locality called Bako. Leucaena leucocephala is becoming popular in the rural and urban areas. Its importance in alleviating the shortage of feed, low soil fertility and lack of fuel wood is gradually increasing.

Recently, however, the coming of the leucaena psyllid, Heteropsylla cubana Crawford), to Africa, (in 1992 it reached Kenya and in 1993 it was observed in Ethiopia, at A wassa), has caused concern among researchers. The presence of the pest in Ethiopia is still not felt and its progress appears slow. Meanwhile, institutions undertaking leucaena research have been monitoring its movement but no serious psyllid threat of alarming proportion has been reported as anticipated. One may conclude that the damage caused by psyllid to leucaena plants in Ethiopia to date cannot be exaggerated, but the risk can be predicted, taking into account the economic problems the pest has caused in other countries.

*****

BACKGROUND

In the early years of their planting, leucaenas were often called "miracle trees", for their success as fast growing multipurpose, nitrogen fixing trees in the tropics. Several uses were tagged to this species, as a tree whose product was edible, as feed for livestock, fuel wood, building houses, green manure to enrich the soil, nitrogen fixing, easy to plant and rapid growth. These claims were made in the late 1960s when the first "giant" leucaena varieties were released by scientists.

Since the Spanish sailors of four centuries ago brought leucaenas from Mexico to Asia, the species spread widely in Asia and the Pacific region, then throughout Latin America, Australia and later in Africa. Today, farmers grow leucaenas on an estimated two million hectares in every tropical region of the world.

There are thirteen species in the genus Leucaena. Leucaenas vary widely in leaf and tree shape and range in size from shrubs to large trees, 5 m to 20 m in height, depending on variety. Leaves are alternate and bipinnately compound. They grow from sea level to over 2000 m elevation with rainfall between 500 and 2000 mm and soil pH of 5-8. Leucaenas fail on highly acid soils. Over 50 hybrids are now under study in Hawaii for growth, form, psyllid resistance, cold tolerance and fodder quality. The breeding programme for leucaenas could also solve problems such as mimosine, a toxic amino acid in leucaena foliage that causes hair loss and other damage in non-ruminant animals.

LEUCAENAS IN ETHIOPIA

The Institute of Agricultural Research at Bako Research Centre introduced Leucaena leucocephala as a leguminous tree to help farmers produce fuel wood, fodder and increase soil fertility. The performance of leucaena in this part of the country is promising as a source of multipurpose use to the farming community.

Early in the 1980's it was reported that Leucaena leucocephala was introduced in Ethiopia. . It was suggested that since most of the farming community lives above the 1 500 metre contour, and where large percentage of the plateau soils are acid, the conditions would not be favourable for the production of high yields from leucaena. In addition, leucaena prefers an attitudinal range between sea-level to 800 meters and high rainfall.

In spite of these constraints, Leucaena leucocephala is becoming popular in the rural and urban areas of Ethiopia, between 1500 and 1800 m. altitude. It is one of the most important multipurpose tree legumes and can relieve the shortage of dry season feeds, improve soil fertility and increase fuel wood supplies. The tree is also grown in hedgerows for amenity purposes around homesteads.

A number of institutions in Ethiopia have shown interest in including leucaena in their trials as a multipurpose species for soil improvement, fodder, fuel wood, alley cropping etc. Institutions that have been engaged in multipurpose tree/shrub screening trials and planting practices include the Institute of Agricultural Research (IAR), Forestry Research Centre (FRC), Alemaya University of Agriculture (AUA), Awassa College of Agriculture (AAU), the International Livestock Centre for Africa (ILCA), and some NGOs (Table 1). The various institutions put emphasis on research and development of certain technologies to suit their objectives. For instance, the Institute of Agricultural Research (IAR) is mainly concerned in the technology development that would enhance crop production. ILCA's interest is to overcome the shortage of livestock feed. The Forestry Research Centre has its objectives to test multipurpose species including leucaenas in the diverse climates of the country, so as to establish species suitability. The NGOs effort is primarily geared in the conservation activities through tree planting that include leucaena in area where it is suited.

Generally, the various trial sites are located between altitudes of 700 m (Melka Werer, eastern Ethiopia) to 2450 m (Dodola, southern Ethiopia). The rainfall at Melka Werer is about 400 800 mm and leucaena is tested under irrigation) and Aman (southwest Ethiopia) receives over 2000 mm.

The International Livestock Centre for Africa (ILCA), has included the Mexican highland leucaena in its initial screening. The performance of in some trial sites was severely affected by recurring browsing, as a result the species had poor growth but had shown remarkable survival rates.

TABLE 1

LEUCAENA SCREENING TRIALS IN ETHIOPIA

The status of leucaena in Ethiopia can be summarized in the following key points:

1. The introduction of leucaena in Ethiopia is comparatively recent, (perhaps the earliest introduction of leucaena was made in 1979 at a place called Bako, some 250 km west of Addis Ababa where leucaena was tried for the purpose of producing animal browse.
2. Initial establishment of leucaena is difficult because of browsing stress.
3. By and large, conditions in Ethiopia, such as high altitude and acid soils, may limit the production of leucaenas. However, there are suitable pockets where the species can be grown successfully.
4. Alley farming trials of L. leucocephala are too young to determine its importance for this use.
5. At present coordination among institutions concerned in the development of the technology of leucaena planting appears weak. This affects information exchange.

EXTENT OF DAMAGE BY LEUCAENA PSYLLID IN ETHIOPIA

In Ethiopia, psyllid threat to Leucaena leucocephala has not yet been devastating. The insect may be just arriving however. In an effort to get information on the status of leucaena psyllid, contacts were made with several institutions that have established leucaena trials/plantations.

According to Mr. Tesfaye Abebe, assistant professor of the Awassa College of Agriculture, about 273 km south of Addis Ababa, leucaena psyllid is already observed on leucaena trials on the campus and in the college plantation about five km away. The pest on leucaena plants was observed in September 1993, followed with its identification in the same year. At the moment the damage is confined to leucaena leaves with a symptom of poor growth performance, but no plants died as a result of pest injury. The intensity of psyllid damage vary from season to season, infestations become mild during the rainy season. However, the pest becomes aggressive in the dry season.

Another problem, not yet well identified, on leucaena seedlings was observed at a locality called Ginchi, situated about 90 km. west of the capital city, Addis Ababa. The incidence was observed by Mr. Adugna Zerihun, assistant professor at the Debre Zeit Agricultural Research Centre of the Alemaya University of Agriculture, in the summer of 1994. The pathology Department of the Centre has identified insects similar to aphids, viral diseases perhaps transmitted by "aphids", leaf spot caused by a fungus and the presence of flies. These agents were all attacking leucaena seedlings which were raised to be distributed to the farming community.

The Bako Agricultural Research Centre discovered a beetle that feeds on both Calliandra and Leucaena. It was named calliandra leaf beetle.

The reasons why leucaena psyllid does not appear to be spreading rapidly in Ethiopia and why such reports are scarce need some tentative explanations:

1. Leucaena planting generally, is on experimental level. Therefore continuous plantations over large areas, a condition conducive to psyllid spread do not occur in Ethiopia. Experimental plots are fragmentary so that a plot is less affected from neighbouring plants.
2. In Ethiopia, the farming community lives mostly above elevations of 1500 m. With Leucaena leucocephala performing well between 1 500 m and 1800 m, conditions may not be favourable for psyllid buildup or the damage may be minimized at higher altitudes.
3. Leucaena psyllid took less than one year to arrive in Kenya from the time it was first observed on Mauritius in 1992. That speed was not maintained in the case of psyllid appearance in Ethiopia. The ecological condition favourable for the growth of Leucaena leucocephala does not exist in the semi-arid region between Ethiopia and Kenya. This region can be thought of as a buffer zone, slowing down the spread of leucaena psyllid.

UGANDA

LEUCAENA PSYLLID 
A THREAT TO AGROFORESTRY IN AFRICA: UGANDA'S CASE

by

Dr G. Maiteki, P. Kiwuso and W. Kigenyi
Forest Research Institute 
P.O. Box 1752, Kampala, Uganda

ABSTRACT

Leucaena leucoceohala is a recently introduced tree species used in agroforestry in Uganda. Since its introduction, many farmers had adopted it for use in their farming systems. The tree has recently been attacked by the psyllid, Heteropsylla cubana, which is devastating it. Many farmers are getting discouraged from using leucaena in their agroforestry practices. The pest has virtually reached every area of Uganda where Leucaena is grown. So far Leucaena diversifolia is not attacked.

There are no control measures being implemented on the ground but the first task will be to carry out a survey and identify any local natural enemies associated with the pest.

We advocate the formation of a regional network to coordinate research on this pest including development of an integrated pest management technique.

* * * *

INTRODUCTION

Leucaena, a fast growing multipurpose tree species (MPTS) is a recently introduced agroforestry tree which has been planted in many districts in Uganda, following a concluded farm forestry project funded by DANIDA & implemented by CARE 1984-1990. Many NGO's also came in to support agroforestry practices and since then many districts have benefited. These include Kabale, Bushenyi, Mbale, Mukono, Kampala, Iganga, Tororo, Soroti, Mubende and Masaka. Although the above districts were pilot districts during the project, many other districts also adopted the use of agroforestry plantings in their farms.

Heifer International project, which is coordinated by the church of Uganda, made it a condition that for a farmer to get a heifer from them, he/she has to have a plot of fodder. Many farmers opted for leucaena. Two species were grown:

1. L. leucocephala - grown in lowland areas.
2. L. diversifolia - grown in highland areas

These MPTs are grown for the following uses:

1. Fuel wood - Leucaena has become a major source of fuelwood in many districts with low natural forest cover. Leucaena has the advantage of being fast growing and coppicing very well.
2. Fodder - The foliage of Leucaena is very nutritious and many farmers are growing Leucaena as a supplementary feed for their zero grazing to domestic animals. Many of them have reported not only increased weights of their animals but also higher milk production.
3. Organic fertilizer - Leucaena is a nitrogen fixing, leguminous plant and like most other legumes it forms symbiotic relationship with soil bacteria of the genus Rhizobium. Through this symbiotic relationship, atmospheric nitrogen is fixed and made available to plants as soil nutrients. This then acts as organic free fertilizer to crops within the field. The foliage can also be used as a mulch for nutrient recycling.
4. Re-vegetation of hillsides - Leucaenas are also grown along hillsides where they acts as windbreaks and conserve soil. In some agroforestry systems, leucaena is planted as hedgerows to control soil erosion.
5. Other uses include acting as stakes for climbing beans and yams and also for ornamentation.

CURRENT STATUS OF LEUCAENA PSYLLID IN UGANDA

DAMAGE

In Uganda, leucaena has been flourishing without any major pest problems of economic importance. This trend was reversed with the invasion of the leucaena psyllid, Heteropsylla cubana in 1992. Infestation by this pest is discouraging farmers from planting Leucaena. L. leucocephala has been observed to be most susceptible. Both the nymphs and adults feed on the tender parts of the tree causing necrosis, foliage deformation and in many cases complete defoliation. Trees have been observed to recover especially during the wet season but re-invasion often occurs.

The psyllid has been reported from all regions where L. leucocephala is growing with varying magnitudes of infestation. The amount of damage that this psyllid has caused has not yet been estimated but there is no doubt that it is substantial. In Uganda, L. diversifolia has not been affected by the psyllid.

CONTROL MEASURES

In Uganda, no control measures have been implemented on the ground but we propose to carry out a survey of resource damage and to initiate studies on seasonal abundance of the pest and local natural enemies associated with it. Many farmers have approached us for advice but we have normally discouraged them from using pesticides not only because it is uneconomical but also because their impact is temporary and ecologically undesirable.

IMPACT OF ATTACK

There is no doubt that H. cubana poses a serious threat to the development, expansion and utilization of leucaena in Uganda. In fact many farmers are no longer willing to use L. leucocephala in their agroforestry systems, and although L. diversifolia seems resistant, many farmers are sceptical about how long it will remain so.

Consequently if no control measures are put in place, many farmers are likely to abandon the use of leucaena. This will lead to a decline in the benefits which would otherwise accrue from the use of this multipurpose tree hence causing:

1. A decline in the supply of fuelwood.
2. A decline in agricultural crops due to loss of organic fertilizer which would otherwise be fixed by leucaena.
3. Increased soil erosion where the crop was being planted to stabilize soils on steep slopes.
4. Reduced supplies of nutritious livestock feed where leucaena was being grown for fodder.

RECOMMENDATIONS TO THIS FORUM

Considering the importance of the leucaena resource in the livestock, crop and forestry sectors in the subregion, a pest management programme should be developed as soon as possible. To this effect, the following recommendations are proposed.

1. A regional network should be instituted to coordinate research on the psyllid in order to reduce its current damaging trend on the leucaena resource.
2. Some donor agencies should be contacted to fund a leucaena psyllid research and development programme.
3. Biological control as a control option should be explored for management of this insect pest. Classical Biological control using natural enemies currently available in the Asia-Pacific Region such as Curinus coeruleus, Tamarixa leucaena and Psyllaephagus yaseeni should be extended to this region. Local natural enemies of the leucaena psyllid and factors regulating their abundance should also be studied.
4. Since some Leucaena sp. have shown some resistance, this field should further be explored by tree breeders.

OTHER FORESTS PESTS OF UGANDA

Apart from the psyllid in agroforestry, we in Uganda have other tree pest problems. These are in conifer plantations where three exotic aphids have attacked our conifer trees. These are:

1. The cypress aphid, Cinara cupressi, attacking cypress trees.
2. The pine needle aphid, Eulachnus rileyi, attacking pines.
3. A pine woolly aphid, Pineus spp. attacking pines.

We have opted for a classical biological control programme on a regional basis and we are collaborating closely with International institute of Biological Control IIBC against these pests.

ZAMBIA

DISTRIBUTION OF LEUCAENA, CURRENT STATUS AND IMPACT
  OF LEUCAENA PSYLLID AND SOME MANAGEMENT OPTIONS IN ZAMBIA

by

O. Shakacite
Forest Protection Officer
Regional Forestry Office
P.O. Box 510095, Chipata, Zambia

INTRODUCTION

Zambia covers a total land area of 752 972 square kilometres and has a population of 7.8 million (1990 census) with an annual growth rate of 3.8 percent. A large portion of Zambia is a plateau lying between 1000 and 1800 metres. The climate is subtropical warm and wet from November to April, and cool and dry from May to October. Average rainfall ranges from 600 mm in drier plateau mainly in the southern and eastern parts up to 1250 mm in the northern and northwestern parts of the country.

Zambia's agriculture is characterised by a distinct contrast between commercial and subsistence farming. The traditional agricultural practices has resulted in land degradation leading to poor agricultural production. The country's emphasis under the Economic Structural Adjustment Programme (SAP) is agriculture development. In view of this, a new approach to soil conservation emerged in the mid 1980s in the department of Agriculture and it was seen as an integral part offarming with full use made of biological techniques, supported where necessary by physical measures appropriate to the socioeconomic situation of the farmers.

The shortage of food and fodder is partly a result of declining agricultural production associated with declining soil fertility, caused by factors such as soil erosion and degradation and little or no use of manure and/or fertilizer as well as current erratic rainfall. The high population growth rates have also put enormous pressure on the land, thereby exacerbating the problems of food shortage and land degradation through indiscriminate extensive land clearing and poor land management. Thus, soil restorative fallows earlier used to sustain soil productivity under traditional shifting agriculture have become shorter and therefore ineffective or have disappeared from the farming systems altogether.

Within this broad perspective concern grew for the sustainability of various farming systems and the rural environment as a whole. It is in this context that interest was developed in planting trees as a normal agricultural activity and in the potential for improving productivity and environmental protection by growing trees together with crops in different combinations.

The main agroforestry tree species planted are Leucaena spp. Casuarina spp., Flemingia spp., Sesbania spp., Glirisdia sepium, Tephrosia volgerii. Cassia siamea, etc. Most of these are still under experimentation. Leucaena leucocephala is one of the most important exotic multi-purpose tree widely planted for agroforestry purposes. However, presently this tree species is threatened by the Leucaena psyllid, Heteropsylla cubana, a "jumping plant louse," family Psyllidae (FAO 1992).

DISTRIBUTION OF LEUCAENA IN ZAMBIA

Leucaena leucocephala Lam. (deWit) is an exotic, fast growing, small leguminous tree whose early plantings in Zambia dates back to the 1970's in a small farm in Lundazi, Eastern Province. During the 1980's, the tree's promotion as a multi-purpose tree species (MTPS) in agroforestry programmes was successful and the tree was widely established throughout the country except in Northern Province were failures are recorded due to acid soils in these areas. During the same period, the varieties of "giant" leucaena were advocated for agroforestry programmes and these were mainly introduced for experimentation by various research institutions within the departments of Agriculture and Forestry. The tree has been established to fulfil agroforestry needs, particularly soil improvement and stabilization, feed for animals, fuelwood, shade for agricultural crops and timber requirements.

Leucaena species were generally healthy except for minor problems such as leaf spot diseases and termite damages and these were not considered very serious.

OCCURRENCE OF THE INSECT

The Leucaena Psyllid, Heteropsylla cubana, was just recorded in Zambia in February 1994 in Eastern Zambia from International Centre for Research in Agroforestry (ICRAF) Research Plots, Msekera, Chipata. The pest is believed to have spread from Malawi where it was first reported in 1993. There was very little known about leucaena psyllid until damage infestations were recorded in Chipata. The pest has since spread to all parts of the country devastating leucaena. However, warning information and leaflets about the occurrence of the pest in Africa were received by the Division of Forestry Research as early as 1993.

Damage symptoms include stunting and deformation of new shoots and foliage. The honeydew produced by the psyllids allows growth of sooty moulds which affect plant growth (FAO, 1992). Both nymphs and adults feed on leucaena terminal shoots by sucking plant sap and repeated attacks cause wilting, defoliation and branch dieback. Although there are no reported deaths of plants so far resulting from heavy infestation, it is possible that death of damaged plants will eventually occur. The eggs are laid between leaf folds of shoots which appear yellowish in colour. There are no insect population studies done, but the leucaena psyllid appears to exhibit seasonal abundance with populations peaking during certain times of the year.

All species of Leucaena grown in Zambia are susceptible to attack by the pest but observations show species difference in susceptibility or tolerance. The greatest impact of leucaena psyllid is to the livestock industry. Many farmers in southern and eastern Zambia in dry zone areas planted leucaena for feeding dairy cattle, for fuelwood and other domestic uses. Leucaena is also widely planted in agroforestry systems such as alley cropping, shade for agricultural crops. But the total area of leucaena plantings in the country cannot be accurately estimated and there are no studies on economic impact of leucaena psyllid since the pest has just been introduced into the country. There are no

intentions of farmers abandoning the planting of leucaena species for agroforestry practices but they wish to have more resistant varieties introduced in the country or some other method of control be provided against the psyllid.

CONTROL STRATEGY

CHEMICAL CONTROL

In Zambia, when leucaena psyllid was first observed in February 1994, all species and provenance trials of leucaena at Msekera Agricultural Research Centre, Eastern Province were sprayed. As may be the case, the results were not encouraging. In general, chemical insecticides may provide an effective temporary relief from damage however they are not desirable from ecological environmental and economic stand point. They are known to eliminate predators (NFTA 1988, IDRC 1987). It is logistically unrealistic and extremely expensive, further, there are practical difficulties of spraying trees affected which are in most cases scattered hence increasing control costs. Spraying has since been discouraged and discontinued.

NATURAL CONTROL AND PLANT RESISTANCE

Some predators, such as ladybird beetles and ants, have been observed feeding on leucaena psyllid. The collections of the psyllid's natural enemies have since started and these specimens are yet to be identified. Observations have also started to determine whether there are any seasonal population changes with the insect. The psyllid population could be influenced by climatic factors such as heavy rainfall and high temperatures. Studies elsewhere have shown that certain strains of giant leucaena have been found to be resistant to feeding by leucaena psyllid. These include Leucaena pallida, L. collinsi and L. diversiflora (FAO 1992). In 1 991, prior to the discovery of the insect, a multi-locational trial was established at Msekera, Chipata, Eastern Zambia evaluating leucaena species and provenances in the Miombo ecozone of Southern Africa (Kwesiga et al 1992). The main objective of the trial is to evaluate adaptation and performance at different sites (Genetic X Environment). The seeds of twenty-five leucaena species and provenances were obtained from Oxford Forestry Institute (OFI). Among these were some of the already known tolerant and/or resistant species to the psyllid. Such varieties have potential for use in future leucaena plantings and with the recent out break of the psyllid it would be worth testing these leucaena species under local conditions.

BIOLOGICAL CONTROL

Biological control is one of the management tactics which is envisaged to be very effective against leucaena psyllid. This strategy is known to be more effective when used in conjunction with other management strategies. An integrated pest management approach (IPM) is essential in solving the psyllid problem. Since the psyllid is a recent introduction to Zambia, not much work has been done on this insect. Biological Control becomes a realistic proposition since elsewhere in particular in the leucaena's natural range in the Caribbean, Mexico and Americas as well as the Asian-Pacific region, predators and parasites of the psyllid have provided effective control (Pound and Martinez 1983, Nakahara et al 1987, Bakereetal 1993, Napompeth 1994). According to IDRC (1987) report many general predators have also been used against the psyllid although it is difficult to determine how effective they are in controlling psyllid populations. Further Villacarlos et al. (1990) and Yao et al (1990) report that entomogenous fungi can also help to control the psyllid populations particularly at damp sites.

The biological control agents of the psyllid as well as the biology of the psyllid and its parasitoids is known and agents are available in Hawaii and these, it is reported, have been introduced to other infested areas in the Asia-Pacific region (IIBC 1993). Such experiences can provide a guide for the region in solving the leucaena psyllid problem.

In view of this, the introduction and release of already known biological control agents in the region can be coordinated and collaborated through the existing framework of the IIBC Conifer Aphid Programme. This will avoid duplication of activities and possible conflict of interest, if any. However it is important that the psyllid population is monitored by participating countries wherever establishment of natural enemies is used. Further studies should be initiated to identify major and minor indigenous natural enemies of the psyllid and factors associated with its abundance.

PROPOSED RESEARCH ACTIVITIES

The following research activities are suggested:

1. Seek funding for the management of leucaena psyllid from National sources, Government agencies, Private Organizations, Non-Government Organization (NGO) and potential International sources.
2. Carry out field ecological studies to determine population trends of the pest and existing natural enemies prior to any importation, and determine the factors associated in regulating their abundance.
3. Introduction, selection and testing of leucaena species showing apparent resistance to leucaena psyllid and collect seeds for use on farm trials. If possible establish leucaena seed orchards for production of seeds of psyllid resistant varieties.
4. Seek funding from International Donors to assist in capacity building of biological control quarantine and insect rearing facilities.
5. Introduction and release of known exotic biological control agents with coordination on a regional level through the existing Conifer Aphid Programme.
6. Initiate and/or strengthen networking for research, information exchange and monitoring of the pest on leucaena species in the region and between participating countries in particular those with similar climatic factors.

LITERATURE CITED

FAO, 1992. Leucaena Psyllid threatens Africa's Leucaena Resource. FO 2/354, Food and Agriculture Organization, Forest Resources Division, Rome, Italy.

IDRC, 1987. Sustainable Agriculture News letter No. 1, Singapore, International Development Research Center.

Kwesiga, F., C.P. Simwanza, D.M. Phiri, and S.L. Mwanza, 1992. Biological control programme on the leucaena psyllid, H. cubana Crawford (Homoptera: Psyllidae), in Hawaii. Leucaena Research Reports 7:39-44.

Nitrogen Fixing Tree Association, 1 988, Leucaena psyllid, a review of the problem and its solutions, NFT Highlights, Nitrogen Fixing Tree Association, November 1988.

Napompeth, B., 1994. Leucaena Psyllid in the Asia-Pacific Region: Implications for its management in Africa. Regional Office for Asia and the Pacific (RAPS) Food and Agriculture Organization of the United Nations (FAO) Bangkok, June, 1994.

Pound, B., and L.C. Martinez, 1983. Leucaena; its cultivation and uses. London, Overseas Development Administration.

Villacarlos, L.T., R.V. Pagnilawan and R.P. Robin, 1990. Factors affecting leucaena psyllid populations in Leyte, Phillipines, in Leucaena psyllid: Problems and management, Winrock International/IDRC/NFTA/F-FRED, Bangkok, Thailand, pp 122-129.

Yao, A.L., Y.S. Hwang and W.Y. Wang., 1990. Natural enemies and biological control of Heteropsylla cubana on Leucaena leucocephala in Taiwan, in Leucaena psyllid: problems and management, Winrock International/IDRC/NFTA/F-FRED, Bangkok, Thailand, p 162.

ZIMBABWE 

STATUS OF LEUCAENA AND LEUCAENA PSYLLID IN ZIMBABWE

by

A.N. Mphuru 
Dean, Faculty of Agriculture and Natural Resources
Africa University 
P.O. Box 1320, Mutare, Zimbabwe

INTRODUCTION

Agriculture dominates the Zimbabwean economy and despite the fact that its contribution to GNP is less than 20%, it provides an income for almost 75% of the population. In most years over 95% of all food and beverages are locally produced.

Zimbabwe shows great agro-ecological diversity and five natural regions can be delineated on the basis of rainfall. The best soils occur mainly in natural regions 1,11 and 111 which, coupled with their higher and more reliable rainfall makes them the most productive rain-fed cropping zones. Most of these zones are under large scale commercial farming utilizing advanced agricultural technology. In these zones therefore, agroforestry has not been popular because of the nature of the farming activities.

Over 70% of the rural population live in communal areas, 90% of which are located in the low rainfall natural regions III, IV and V. These are substantial differences in the production systems within the communal areas and these are the areas where agroforestry is being encouraged.

AGROFORESTRY RESEARCH IN ZIMBABWE

Agroforestry research in Zimbabwe is fairly recent and is designed to develop and test technologies that will provide livestock fodder, firewood and maintain soil fertility on farms and in communal areas. The first trials were established at two sites namely Makoholi Agricultural Research Station and the Domboshava Agritex demonstration station near Harare. Makoholi is located to the southwest in a dryer region with farming systems based primarily on livestock production.

Among the multipurpose tree species which are on trial are Leucaena leucocephala. So far there is no report of the occurrence of leucaena psyllid in Zimbabwe. However, with the rapid spread of the pest one should expect it anytime.