A.S. AI-Hazmi
Introduction
Nematology in Saudi Arabia
Nematological problems
Control measures
Infrastructure and training
Support for nematology
Conclusions and recommendations
Bibliography
The Kingdom of Saudi Arabia covers a large area of about 2 000 000 km2, which is about 80 percent of the total area of the Arabian peninsula. The country lies between 15.2° and 32.6° north and 34.1° and 55.5° east and the climate is generally mild in the winter and dry and hot in the summer. Rainfall occurs in the winter but never exceeds 100 mm per year in most regions except for the southwestern mountains of Asir, where it rains more often in the summer. Irrigation is mainly carried out from tube-wells, but in the Hofuf region water is derived from natural springs. Dams have been built in many areas for water conservation and aquifer recharge.
To reduce dependence on oil exports as the main source of income and to produce more food for the increasing population with a high standard of living, Saudi Arabia has been making intensive efforts through its five-year development plans to develop the agricultural sector. The country is witnessing an unprecedented exploitation of its agricultural potential. As a result of government encouragement and financial aid, cultivated land has dramatically increased from about 435 000 ha in 1980 to more than 1.5 million ha in 1990. Sophisticated technology and modern machinery were introduced, new crops and varieties were cultivated, the greenhouse industry and large agricultural projects were established, and two more colleges of agriculture were opened. Self-sufficiency and even export of some products such as wheat, dates, watermelon, poultry and fresh eggs and milk have been achieved.
Major crops include cereals (wheat, sorghum, barley and millet), vegetables (tomato, watermelon, eggplant, potato, cucumber and onions), fruits (date-palm, citrus and grapes) and forage crops (alfalfa). These crops are cultivated over an area of nearly 1.1 million ha which represents about 81 percent of the total cultivated area. In 1990, wheat was cultivated over an area of about 744 422 ha (i.e. 55 percent of the total cultivated area), and production was about 3.5 million tonnes (Table 18).
The creation and management of a highly productive agrosystem in the desert represents an intrusion into the natural desert ecosystem and require careful evaluation to avoid unwelcome environmental consequences. The continuous transformation of the agrodesert to more intensive modem agriculture may trigger different forces in reaction to the change. One of the forces that might act is the population build-up of pests. Plant-parasitic nematodes, especially the root-knot group, have thrived in this newly created agro-ecosystem. In many instances, economic crop losses due to large infestations of Meloidogyne spp. on vegetables and in greenhouses are substantial.
Brief history
Plant nematology in Saudi Arabia is relatively young, and it is the newest among the plant protection Disciplines. Prior to 1980 the country did not have a nematologist, apart from one or two contractors who worked for the Ministry of Agriculture and Water for short periods. The few plant pathologists were busy working on fungal and bacterial diseases. Research and education in plant nematology received very little or only occasional attention. The first report of a plant-parasitic nematode appeared in 1957 when Talhouk reported the association of Meloidogyne spp., among other pests, with various crops in Eastern Province (Talhouk, 1957). During the 1960s and 1970s a few other reports of surveys appeared (Natour, 1963; Martin, 1971; Abu Yaman and Abu Blan, 1972; Abdu, 1972).
The first extensive nematode survey was conducted by Dr Eissa who was working for the Ministry of Agriculture and Water (Eissa, 1977). This was followed by a more intensive nematode survey in the Al-Kharj region (80 km southeast of Riyadh) which the author conducted for 16 months with two other colleagues on arrival from the United States early in 1981 (Al-Hazmi, Abul-Hayja and Trabuisi, 1983). In 1984, the author attempted to gather all available information about the occurrence and host range of the reported nematodes in the country to provide a host index of plant-parasitic nematodes (Al-Hazmi, 1984). The latter two surveys have actually produced some significant findings related to the distribution, host range and importance of plant-parasitic nematodes, especially the root-knot group, in cultivated fields. They also directed experimental works in subsequent years.
TABLE 18
Cultivated area and production of major crops grown in Saudi Arabia
|
Crop |
Cultivated area (ha) |
Production (tonnes) | ||
|
|
1980/1981 |
1989/1990 |
1980/1981 |
1989/1990 |
|
Wheat |
73502 |
744 422 |
187231 |
3 463 585 |
|
Barley |
7875 |
56907 |
6011 |
361 900 |
|
Sorghum |
173432 |
153056 |
91 177 |
199908 |
|
Millet |
11757 |
8947 |
7505 |
11 940 |
|
Tomato |
12858 |
21 558 |
232 042 |
462 964 |
|
Eggplant |
2068 |
6184 |
19959 |
83385 |
|
Watermelon |
13039 |
18533 |
193352 |
460 725 |
|
Onion |
760 |
2038 |
14060 |
13554 |
|
Potato |
496 |
2298 |
6700 |
47700 |
|
Date-palm |
62230 |
67843 |
371 038 |
519765 |
|
Citrus |
4047 |
4882 |
27036 |
35233 |
|
Grapes |
4034 |
5764 |
60537 |
99799 |
|
Green fodder |
29000 |
177100 |
|
|
Source: Ministry of Agriculture and Water, statistical yearbooks.
Relative importance of plant nematology
Since 1980 plant nematology in Saudi Arabia has been growing more rapidly and gaining more importance in comparison with other traditional plant protection disciplines, especially in the fields of research and education. Officials and many growers have become more aware and concerned about the importance of plant-parasitic nematodes as major plant pests. This welcome recognition and awareness of plant nematology as a new and important discipline of plant protection has been reflected in the development of education and research programmes in plant nematology. At present, education and research in plant nematology occupy a significant and important place among those of other plant protection disciplines.
Each of the three colleges of agriculture offers a three-credit compulsory nematology course to undergraduate students majoring in plant protection. The college of agriculture at Riyadh also offers two graduate nematology courses (two plus three credits) for M.Sc. students majoring in plant pathology. It is felt that these courses offered at each level are adequate and balanced with other related disciplines. Three graduate students are now working for their Ph.D. degrees abroad.
Research in plant nematology has grown from occasional and very basic surveys into more practical and problem-solving experimental research that can reduce nematode damage and improve crop yields to the benefit of commercial and small growers. These later studies include intensive and systematic surveys of nematodes on certain important crops; cultural and chemical control; screening of resistant and tolerant varieties; host-parasite relationships; and some ecological studies. Basic research, however, is minimal. Competitive funds are provided by the King Abdul Aziz City for Science and Technology for national research projects and by the Department of Plant (or crop) Protection for small projects. During the past ten years, seven of the eight national research projects in the area of plant protection included different aspects of plant nematology. During the same period, many of the published articles in the fields of plant pathology were about plant nematodes. However, this is a long way away from accomplishing what is required. Shortage of professional nematologists is the main obstacle. In some cases, lack of trained assistants and of suitable facilities and equipment presents difficulties.
Extension and services in plant nematology are rather limited. Continuous efforts, however, by the Ministry of Agriculture and Water are being made. Awareness of nematological problems among small traditional farmers is just not sufficient.
Knowledge of nematological problems in the country is far from providing a complete picture. Probably the same situation exists in most of the developing countries. Shortage of native plant nematologists, nematode taxonomists and nematology facilities are the main factors that limit the amount of information that can be gathered on all aspects of plant nematology. Although the early general surveys and the later more extensive ones have provided important data and shed some light on the occurrence and importance of nematodes in the fields, only a fraction of the total cropped area has been sampled. Many aspects such as accurate estimates of crop losses and their impacts on farmers and socio-economics are still to be defined.
It is anticipated that the modem intensification of agriculture in the country in recent years will further increase nematological and other plant-pest problems. Continuous cropping, monoculture, greenhouse cropping, increased fertilization, continuous irrigation, light-textured soils and narrow genetic base varieties, among other components of modem agriculture, are, singly or in combination, increasing the vulnerability of crops to nematode attack. The recent significant problem caused by the cereal-cyst nematode (CCN) in many wheat fields is a good example. In the past, when traditional farming of wheat and other crops was the only available practice, CCN was not even detected. However, during the early season of 1991/92 it was found to be widespread with high infestations in many wheat fields in three major wheat-producing regions. In some fields at Hail, the population densities reached up to 67 cysts/cm3 soil. Although the initial introduction of the nematode has not been determined, probably the intensive monoculture of wheat for several years has a major role in the nematode outbreak. At present, a research proposal is being prepared to examine the effects of different cropping systems on CCN population dynamics and wheat damage.
In this review the discussion is limited to outlining briefly the nematological problems of the most important crops in the country. It should be noted that not all nematodes recorded to be associated with a given crop are necessarily pathogenic to that crop (Table 19).
Cereal crops
In terms of cultivated area and production, wheat has been the most important and economic crop in the country since 1980 (Table 18). Surplus wheat grain is now exported to different countries. Barley, sorghum and millet are also important cereal crops. The latter two crops are cultivated for grain, but mainly confined to the southwestern region, especially in the area around Jizan.
Several genera or species of plant-parasitic nematodes have been recorded to be associated with wheat, including the cereal-cyst nematode, the seed-gall nematode, root-knot nematodes and lesion nematodes (Table 19). There are no available data on specific nematode problems. Recently, however, CCN (Heterodera avenae) became the most important and damaging nematode in our wheat fields. The seed-gall nematode has become unimportant in recent years, as a result of the introduction of new varieties such as Yecora Rojo, the most commonly grown variety.
Barley, sorghum and millet have received very little attention. Barley fields adjacent to the CCN-infested fields in Hail were also infested. The lesion, stunt, stem and bulb or needle nematodes were recorded on some of these crops (Table 19).
Vegetable crops
A wide range of vegetables are grown in Saudi Arabia which are very important to farmers as high-value cash crops. The major vegetable crops include tomato, cucumber, eggplant, onion, watermelon, squash and pumpkin. In recent years, large numbers of greenhouses were constructed mainly for tomato and cucumber production. Total vegetable production has increased from 756 000 tonnes in 1980 to more than 2 million tonnes in 1989. However, local demand has been increasing so rapidly that the increase of production is not enough. Only watermelon is exported to neighbouring countries.
Although many plant-parasitic nematodes have been recorded associated with most of these crops (Table 19), root-knot nematodes are by far the most important and damaging. Meloidogyne javanica, and to a lesser extent M. incognita, play a major role in limiting vegetable production, especially of tomato, cucumber, eggplant and okra. Root-knot nematodes increase rapidly to damaging levels under the country's growing conditions; susceptible crops or varieties, sandy soils, limited or unsuitable crop rotations and warm climate all favour rapid nematode development. Complete failure of production sometimes occurs especially in highly infested tomato fields or greenhouses. The root-knot nematodes on vegetables rank first in the list of nematological problems and much of the work is concentrated in this area.
TABLE 19
Major plant-parasitic nematodes associated with main crops in Saudi Arabia
|
Nematode |
Wheat |
Sorghum |
Barley |
Alfalfa |
Potato |
Tomato |
Cucumber |
Water melon |
Eggplant |
Onion |
Squash |
Date-palm |
Citrus |
Grapes |
|
Ditylenchus destructor |
|
|
|
|
+ |
|
|
|
|
|
|
|
|
|
|
D. dipsaci |
|
|
+ |
+ |
+ |
|
|
|
+ |
+ |
|
|
|
|
|
Ditylenchus spp. |
+ |
|
+ |
|
|
|
+ |
|
+ |
+ |
|
|
|
|
|
Heterodera avenae |
+ |
|
+ |
|
|
|
|
|
|
|
|
|
|
|
|
Heterodera spp.: |
|
|
|
+ |
|
|
|
|
|
|
|
|
|
|
|
Longidorus africanus |
+ |
+ |
|
+ |
+ |
+ |
+ |
|
+ |
+ |
+ |
+ |
+ |
+ |
|
Meloidogyne incognita |
|
|
|
|
+ |
+ |
+ |
+ |
+ |
|
|
+ |
|
+ |
|
M. javanica |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
|
|
|
|
|
|
Meloidogyne spp. |
+ |
|
|
|
|
|
|
|
|
|
|
+ |
+ |
|
|
Pratylenchus spp. |
+ |
+ |
+ |
+ |
+ |
|
|
|
+ |
|
+ |
+ |
+ |
+ |
|
Trichodorus spp. |
|
|
|
+ |
+ |
+ |
|
|
|
|
|
|
|
|
|
Tylenchorhynchus spp. |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
+ |
|
Tylenchulus semipenetrans |
|
|
|
|
|
|
|
|
|
|
|
+ |
+ |
|
|
Xiphinema spp. |
|
|
|
+ |
+ |
|
|
|
|
|
+ |
+ |
+ |
+ |
Note: This table does not represent a complete list of associated nematodes on a given crop; + indicates the most important nematode(s) on that crop.
Other pest species including the lesion, stunt, stem and bulb and spiral nematodes are also important in many vegetable fields (Table 19).
Potatoes
Potatoes have become an important food crop in Saudi Arabia in recent years. More than 15 varieties are grown in both autumn and spring seasons. Production has increased from 6 700 tonnes in 1980 to about 47 000 tonnes in 1989.
In a recent intensive survey of potato fields in six major potato-producing regions, 15 plant-parasitic nematode genera and species were recorded (Al-Hazmi, Ibrahim and Abdul-Razik, 1992). However, Meloidogyne javanica, M. incognita, Ditylenchus destructor and D. dipsaci were found to be the most important nematodes on potato. Very extensive damage was often observed in sandy fields that were heavily infested with Meloidogyne javanica.
Fruit-trees
Date-palms, grapes, citrus, figs and peaches constitute the major fruit-trees in Saudi Arabia. The cultivated area and production are relatively small (Table 18), except for date-palms where more than 12 million trees are widely grown and surplus production is exported every year.
Although fruit-trees have received very little attention, several genera or species of plant-parasitic nematodes have been recorded associated with their roots (Table 19). The citrus nematode is widely spread and causing considerable damage in established old orchards. The root-knot nematodes, particularly Meloidogyne incognita, are very important on grapes, figs and peaches. The dagger nematodes (Xiphinema spp.) have been frequently recorded on grapes. Date-palms were recorded as hosts of several plant-parasitic nematodes, but their importance is unknown. However, M. incognita and Pratylenchus spp. seem to be more important than other nematodes, especially on young date-palm seedlings.
Green fodder
In terms of cultivated area and production, alfalfa is the major and most important forage crop in Saudi Arabia. More than 17 genera and species of plant-parasitic nematodes were recorded associated with alfalfa but Pratylenchus penetrans and Ditylenchus dipsaci are the major nematode pathogens (Table 19).
Information on control of plant-parasitic nematodes in the country is scanty and fragmentary. The economic impacts and the side-effects of different control measures have not been thoroughly investigated or reported.
In the past, most of the cultivated land was worked by small farmers using traditional farming and pest-control practices. Multiple cropping or intercropping was commonly used, and a wide range of food crops were cultivated, often in the same field. Disease epidemics or insect outbreaks were very rare. However the shift from traditional farming to modem intensified agriculture in recent years has increased nematological and other pest problems. The introduction of planting materials that are infected (or infested) with nematodes represents an important source of inoculum. Once established, the nematodes can rapidly increase to damaging levels under favourable local conditions. Root-knot nematodes, which are key pests, have undoubtedly been causing serious crop losses in vegetable fields, and, more recently, CCN has become a potential threat in wheat fields.
Nematode management strategies are currently based on short-term goals. Several control measures are being used to varying extents. Use of a particular method, or a combination of methods, depends on many interacting factors, such as: availability of materials; economic feasibility; compatibility with farming practices; infestation levels; crop value; farm size and management; education level of grower; and government aid. The large variation in crop production techniques, that range from subsistence family farming to large-scale commercial agricultural companies, prevents the development of one control strategy that could be applicable to all situations. Small growers usually hesitate to follow certain recommended control measures, whereas commercial growers and agricultural companies will usually utilize expensive nematicides or resistant varieties.
There are two important points: first, cultural control measures are the most commonly practised control measure by growers; and, second, root-knot nematodes on high-value vegetable crops, whether in open fields or in greenhouses, are the nematode pests on which control measures are most widely used. Depending on the circumstances, the following control measures are being used to variable extents. The use of nematicides and resistant varieties, however, is rather limited among small growers because of the high costs or unavailability of these measures.
Legislative measures
The government has established more than 15 agricultural quarantine centres at international airports, sea ports and along the country's land borders. The rules and regulations are implemented and enforced through the governmental regulatory quarantine programmes. The seven regulations require that all imported planting materials must be pest-free and certified. Since large amounts of planting material are being imported it seems that a losing battle is being fought because alien nematodes will eventually be introduced and established as long as a host plant and a suitable climate are available. Imported planting materials that are infested with nematodes are still an important source of inoculum.
Cultural measures
As indicated above, cultural control measures are the most common control measures practised by growers, directed mainly to control root-knot nematodes in vegetable fields. These methods include:
Sanitation of nurseries. Nurseries for production of seedlings are usually selected on sites that were not previously infested with nematodes and other pathogens. Soil is usually ploughed and left dry between planting seasons. Other growers plant seedlings in plastic bags or tin containers filled with uninfested soil. Seedlings are frequently inspected for pests and if infested, they are treated or removed and destroyed. However, small farmers often do not pay enough attention to sanitation, and nematode-infested seedlings are sometimes bought and used.
Summer fallow. A common practice used by most growers is summer fallow. The climate in many regions of the country is characterized by a long and hot dry summer. Fallows during the summer often help growers to reduce infestation by root-knot nematodes, especially when coupled with ploughing to expose juveniles and eggs in roots and deeper soil layers to direct sunlight. Some work has been done in this area, and the results were very encouraging.
Crop rotation. Traditional crop rotations have evolved and are widely used for various reasons. Local growers usually rotate different groups of field and vegetable crops in the same field for maximum use of soil nutrients and to improve soil structure. Although some of these rotations contribute to the suppression of root-knot nematodes, in many cases they fail to give efficient or economic control. The reasons for such failure are mainly the result of poorly designed rotations, the wide host range of Meloidogyne species, the unavailability of suitable resistant or tolerant varieties, and a lack of knowledge with regard to variation of nematode populations and to the composition of Meloidogyne species present in the field. However, increasing numbers of growers are now aware of the importance and impact of specific and well-designed crop rotations in suppressing nematode populations. Managers of greenhouses, however, hesitate to follow crop rotations and they fumigate with methyl bromide instead. Similarly, commercial wheat growers do not practise crop rotations. However, the recent problem of CCN in many wheat fields will necessitate the practice of suitable crop rotations.
Incorporation of organic amendments. Most growers usually incorporate various organic amendments such as animal manure, green manure or sawdust into soil to improve its structure and to provide mineral nutrients. Although the effects of local, different manures on nematode populations have not been investigated, it is well known that incorporation of different organic amendments will influence nematodes either directly or indirectly. However, the large amount of organic matter needed for effective control limits practical application in large-scale systems.
Root destruction. Eliminating infected roots after harvest by uprooting and destruction will retard the spread of nematodes and reduce their initial populations in the next season. Growers are being encouraged to adopt and follow such a practice, but the response is not sufficient. Many of the small growers leave the stalks and roots to be removed at the beginning of the next season. This is causing great concern and efforts are being made to educate those growers to stop this practice.
Burning straw. Burning of straw immediately after harvest is commonly practised by commercial wheat growers, for different reasons. We have not yet investigated the impact of such a practice on the spread and population densities of CCN in wheat fields. However, some growers believe that it helps reduce soil-borne pathogens and insects.
Physical measures
Soil solarization. The long hot summer in most regions of the country provides ideal conditions for soil solarization. Soil solarization of moistened soil with clear plastic tarps has been recently used in some potato and vegetable fields, and proved to be very effective in suppressing populations of root-knot nematodes. The technique is becoming more acceptable among growers, especially in small vegetable fields, greenhouses and nurseries. Summer fallow and soil solarization are the most economic and promising non-chemical control measures of root-knot nematodes.
Soil steaming. Treatment with steam to disinfest soil in heated greenhouses has been recently applied by some commercial greenhouse growers. The technique, however, is not widely used because of the high operational costs.
Biological measures
Resistant varieties. The use of resistant varieties is an effective, economical and environmentally safe method of nematode control. Although there are many varieties of vegetable and field crops that are resistant to Meloidogyne spp. and other nematodes, use of resistant varieties by growers is rather limited. The unavailability and high cost of such varieties make their use difficult. However, some commercial vegetable growers and greenhouse managers often use limited numbers of tomato varieties resistant to Meloidogyne spp., but they misuse such varieties by growing them in monocultures. Moderately resistant or tolerant cultivars for Meloidogyne spp., or poor hosts such as cabbage, cauliflower, onion and garlic, are sometimes used in crop rotations. Cultivation of potato is increasing in recent years, but none of the 15 potato cultivars grown was found to be resistant to M. javanica, the most widespread and damaging nematode in our potato fields (unpublished data). The most commonly grown wheat cultivar, Yecoro Rojo, was found to be susceptible to CCN and rotations with other cultivars or crops are only minimal among wheat growers.
Natural enemies. Few local isolates of fungal species were isolated from infected juveniles of Meloidogyne spp. or from the secondary treated municipal waste water used for irrigation. In greenhouse experiments, fungi were found to be parasitic or predatory on M. javanica (Al-Hazmi and Abdul-Razik, 1990). Nothing, however, is known about the role of these species or others in natural field soils in suppressing populations of root-knot and other nematodes. No attempt has been made to survey agricultural fields for nematode-antagonistic organisms. Incorporation of organic amendments into soil would definitely increase the activities of nematode-destroying fungi.
Chemical measures
Use of nematicides is relatively limited because of their unavailability or scarcity in local markets, high costs, requirements for special equipment and for trained personnel for the application of fumigants, and their negative side-effects that make their use sometimes difficult, especially for small growers. However, commercial growers and large agricultural companies do use both fumigant and non-fumigant nematicides mostly to control root-knot nematodes on high-value vegetable crops in fields and in greenhouses.
Use of fumigant nematicides, particularly methyl bromide, and to a lesser extent 1,3-D and metam-sodium, is confined to greenhouses and nurseries. Application rates vary depending on crop value; the potential damage; soil temperature and depth; application method; and the needs for additional control of other soil pests.
Few non-fumigant nematicides such as oxamyl, carbofuran and fenamiphos are available in local markets. They are used as pre- and post-plant treatments mostly for the control of root-knot nematodes on vegetables. Since these granular or liquid nematicides are cheaper and more suitable for use by small growers than fumigants, their use is increasing among small growers, and with crops other than vegetables, such as potato and more recently wheat, to control CCN. They are usually applied as granules or sprays, or water-mediated via drip or centre-pivot irrigation systems. Although these non-fumigants are not as effective as fumigants, they do increase yields compared with non-treated infested soils. However, their success has been restricted to short-term crops.
The available facilities and number of personnel involved in research, education and extension in plant nematology are relatively small in relation to the size of the country. However, nematological research and education activities represent appreciable commitments compared with those of other plant protection disciplines. In recent years, plant nematology has been growing very rapidly. However, more facilities and professional nematologists are needed. Extension services are officially provided by the Ministry of Agriculture and Water, but the three colleges of agriculture are also helping.
Education and training
Plant nematology is housed in the Departments of Plant (or crop) Protection in the three colleges of agriculture:
· College of Agriculture, King Saud University, Riyadh;· College of Agriculture and Food Sciences, King Faisal University, Hofuf;
· College of Agriculture and Veterinary Science, King Saud University, Gassim Branch at Buraidah.
Each college has a faculty member nematologist (Ph.D.), and one or two assistants, and offers a three-credit undergraduate nematology course, which is compulsory for students majoring in plant protection. Only the College of Agriculture at Riyadh offers M.Sc. programmes where students majoring in plant pathology have the chance to register in two advanced nematology courses (two plus three credits). At present we feel that these nematological courses at each level are adequate and balanced with other related plant protection courses. However, enrolment in both levels has been decreasing lately in spite of a greater national need for plant protectionists in general, and plant nematologists in particular. This perhaps is a reflection of reduced enrolment in agricultural sciences locally and worldwide. Scholarships for higher education in plant nematology are offered by the government, and currently three students are working for their Ph.D. degrees abroad.
The Agricultural Institute at Buraidah offers a good and practical programme in general agriculture leading to a diploma after two years of intensive training. Students are exposed to nematological problems through different related subjects. Graduate students are usually appointed by the Ministry of Agriculture and Water as extension workers.
Training programmes or workshops (two to three weeks) in plant protection, plant pathology or plant nematology are frequently held by the Ministry of Agriculture and Water or one of the three colleges of agriculture.
Research
Most of the research facilities and personnel are located within the three colleges of agriculture. Each college has a nematology research laboratory, an agricultural experiment station and a number of greenhouses and growth chambers. Two or three research assistants are usually involved, fully or partially, in nematological research activities helping the nematologist faculty member. Although relatively adequate at the present time, facilities need to be increased and improved in the near future. Research nematologists are few, and most of them are working on short-term contracts. The Ministry of Agriculture and Water has several agricultural experiment stations in various locations in the country and a National Research Centre at Riyadh. This centre has a nematology research laboratory and a number of greenhouses which are supervised by a nematologist.
Extension
Extension services are provided by the Ministry of Agriculture and Water. Extension agents usually with a B.Sc. in agronomy or plant protection, work in the different agricultural regions of the country. Although they were not specifically trained as extension agents in plant nematology, they are encouraged to participate in nematology training programmes and workshops. They help farmers, as best they can, to minimize their nematological problems and also interact with their superiors in the ministry and with the professional nematologists in the three colleges of agriculture.
The three colleges of agriculture also contribute to extension activities through different channels such as extension leaflets and bulletins, diagnostic services, nematode assays, control recommendations, training programmes and extension workshops. The College of Agriculture at
Riyadh, for example, has also established an agricultural extension centre and a small insect and disease clinic as community services. However, extension in plant nematology as such is far behind research and education. There is a great need for a strong and efficient extension service in plant nematology.
Cooperation among the above-mentioned institutions in education, research and extension exists through different formal and informal channels. Joint research projects, technical committees, training and workshops, exchange of information and opinions, educational programmes and use of facilities and equipment are examples of the different forms of cooperation. However, we all feel that more cooperation is needed, and great efforts are being made in this direction.
All aid programmes, whether in education, research or services, are provided by the government through different agencies and channels. No foreign financial aid has been provided. However, various forms of agricultural cooperation between national and many international institutions have been established for many years. The outcome of such cooperation is very encouraging and much appreciated. In plant nematology, scientific cooperation with institutions, societies and research centres has been established and even more cooperation is being sought.
Research funds are provided by the King Abdul Aziz City for Science and Technology (KACST). The impacts of governmental aid programmes, especially those provided by KACST, are well recognized and have resulted in strong research motivation and support in agricultural and other research programmes. Nematological research has benefited greatly from these funded research programmes. The results of such research programmes have provided a considerable amount of important information that can be implemented to the benefit of our growers and have directed future research programmes. These well-funded research programmes have also helped establish some good research facilities, purchasing specialized equipment and materials and in training graduate students and research assistants. However, the efficient implementation of results still needs more effort by extension specialists to simplify and transfer such results to the direct benefit of the growers.
Plant nematology in Saudi Arabia is very young. The first report of plant-parasitic nematodes appeared only in 1957. However, during the past decade plant nematology has been growing more rapidly than most of the other plant protection disciplines and progress has been made especially in the fields of education and research The root-knot nematodes on vegetables, the citrus nematode in established citrus orchards, and more recently the cereal-cyst nematode on wheat are the main nematological problems in the country. However, knowledge of nematological problems is far from complete. A shortage of professional nematologists and trained assistants is the main obstacle at the present time.
The main recommendations which are important for alleviating the nematological problems in the country are:
· Growers need to understand nematodes, their damage to crops, and how to manage them. There is a great need for extension nematologists and the service they provide.· Demonstration plots, simple pamphlets and bulletins, preferably with coloured illustrations, will help to speed up dissemination of information among growers.
· Nematological training programmes and workshops for extension agents and trained growers should be held more frequently.
· Nematode diagnostic and advisory services should be established.
· A national plan for strengthening and improving nematode education, research and extension programmes should be developed.
· Enrolment in nematology graduate (M.Sc.) programmes should be encouraged.
· Publication and/or translation of good textbooks and references in plant nematology are required.
· Cooperation with national and international institutions and scientific societies should be increased.
· Control of nematode introduction and spread should be a high priority.
· Only nematode-free planting materials should be used.
· Technical facilities and equipment and support programmes should be increased.
· Easy access is needed to nematode-resistant varieties, especially for control of root-knot nematodes, as well as appropriate nematicides.
· Growers should be trained in the efficient and wise use of resistant varieties and nematicides currently available.
· Efforts should be made to continue and increase identification of nematological problems, and assess the extent of plant damage they cause, including experimental work on the quantification of crop losses under local conditions.
· More efforts and extra care should be made when planning crop rotations to select and develop a management approach that prevents or suppresses the build-up of large nematode populations.
· Emphasis in research should be placed on the most locally promising and economical control measures. Under the country's climatic conditions, research on the efficacy of summer fallow, desiccation, soil solarization, cropping systems and other commonly used cultural practices on populations of the major plant-parasitic nematodes, such as Meloidogyne spp., should be emphasized and strengthened.
· There is also a great need for an integrated pest management approach. Resistant varieties, crop rotations, judicious use of pesticides and sanitary and cultural practices should also be employed.
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