Country report on the forestry invasive species situation in Vanuatu

Ruben Bakeo and Francis Qarani
Department of Forests, Department of Quarantine

Introduction

Invasive plant and animal species are a global concern because of their ability to interrupt biological and ecological balances and cause havoc to receiving environments. Despite the relatively long history of introduction of exotic species into the Pacific Islands, it was not until recently that efforts have been made to address them. This is true for Vanuatu, particularly with regard to invasive species that impact on forests.

This report presents the forestry invasive species situation in Vanuatu. The report begins with a general overview of forest types in the country. This is followed by a list and description of the most significant forest invasive species. Following this, mention is made of the importance and relevance accorded to forest invasive species issues in Vanuatu. The final section discusses efforts to manage and control invasive species, highlighting the key institutions or bodies involved - and the laws, policies and mechanisms employed - in addressing the threat posed by these species. No attempt is made to quantify the costs involved in management and control of these species, because of the lack of information on costs. The report concludes that increased efforts need to be made to strengthen the management and control measures required. Emphasis should be on forging an integrated approach, one also backed with much-needed external assistance.

Forest Types

Data from a forest inventory conducted from 1990 to 1993, show that around 70 percent of Vanuatu is covered by woody vegetation, half of which is closed forests with the remainder being discontinuous shrubs, secondary forest and thickets of low trees. Vanuatu has in excess of thirty forest types. These can be put into three major groups in terms of land area occupied:

• thickets - occupying more than 433 000 hectares (35 percent) of Vanuatu’s land area;

• mid-height forests totalling of 205 307 hectares (16 percent); and

• low forest covering 234 089 hectares (19 percent).

The remaining land area is mostly man-made vegetation or bare ground (more than 20 percent), grassland and scrub.

Commercially exploitable forest is estimated to be about 35 percent of forest cover, and 10 percent of the total land area is covered by primary forests. Major areas of native forests occur on the larger islands of Santo, Malekula, Erromango and Efate, with smaller areas on other islands. There is immense pressure on some timber species on the larger islands, where harvesting is concentrated. In 1998, for instance, 92 percent of logs harvested were of just two species, Endospermum medullosum (whitewood or basswood), and Antiaris toxicaria (known in Vanuatu, as milk tree). Many landowners are not keen on reforestation or afforestation and have used their logged forest lands for alternative activities like commercial agriculture. Natural regeneration is not yet a priority.

The plantation forest estate is small, with currently some 1 000 hectares planted. As part of its national forest policy (NFP) the Department of Forests (DoF) is targeting the establishment of 20 000 hectares of planted trees in the next 20 years. Many smallholders - and a few foreign investors - are actively engaged in tree planting. Negotiations are continuing with several companies, to encourage investment in commercial timber plantations. Discussions have also been held lately, about the possibility of engaging in wood-energy plantations. Among the trees encouraged for planting by the DoF are Endospermum medullosum (whitewood or basswood), Pinus caribaea (pine), Agathis macrophylla (kauri) and Santalum austro-caledonicum (sandalwood). Fruit/timber trees such as Terminalia catappa (tavoa or Indian almond) and several others are encouraged, to increase economic and other gains from forest resources. These local supply plantations are located throughout Vanuatu and range in age from12 to 25 years.

The forests of Vanuatu are less complex, in terms of biodiversity, compared with forests in larger countries. Human activities are already rapidly diminishing and altering the forest cover and biodiversity, so that the threat posed by invasive species aggravates an already very worrying situation. It is difficult to quantify the invasive-induced threat confronting Vanuatu, whether it is to forests alone or all the country’s ecosystems.

For forests and other vegetation in Vanuatu, the challenge brought about by invasive species is real and immense. The DoF, other government agencies, and regional and international entities are mobilizing resources in efforts to make sustainable management and conservation of forests a reality. However, invasive species add dimensions to the challenges of sustainable forestry. Aside from traditional forest management concerns, such as declining forest cover and imbalance between utilization and reforestation, alien species are increasingly becoming a concern, posing problems that require additional resources and even new strategies to address. Furthermore, given that some 28 percent of Vanuatu is already under man-made vegetation or bare ground, grassland and shrubs, the chances for the spread of invasive plant species into these vegetation types is greatly enhanced. This is because many invasive species tend to thrive in disturbed forests. If thickets, which already occupy more than 35 percent of land area, are also considered as prone to domination by invasive plants like Miremia peltata (big lif rop), then invasive species are indeed worthy of serious attention nationally.

Significant forest invasive species

Invasive species that impact on the forests and related biodiversity of Vanuatu are numerous. A number of points need to be noted prior to enumerating and describing the impacts and significance of these species. First, in compiling this report, it was not possible to establish if any of the fungi and diseases that threaten sustainable forestry and biodiversity in Vanuatu are alien or indigenous. Second, it is difficult to list these species in any priority because of the variations in their impacts and the limited understanding of the extent of their impacts on forests. Third, some invasive species are yet to register observable impacts on the forests, and their distribution is yet to be ascertained.

Invasive plants

Of all invasive plants in Vanuatu, perhaps the most widely cited pest is Cordia alliodora (Ecuador laurel or salmwood). Introduced as a forestry tree to Vanuatu in the 1970s, this species has now become dominant and is considered a serious pest in locations where it was planted. Planting trials were initiated on the islands of Santo, Vanua Lava, Mota Lava, Ureparapara, Malekula, Ambae, Maewo, Pentecost, Efate, Epi and Eromango. These are the major islands of Vanuatu.

The introduction of this Central American tree is a classic example of an aid programme gone wrong, especially now that there is no lucrative market to sell the 800 hectares of stock planted. Cordia alliodora was introduced with the best intentions, but failed to live up to expectations for various reasons, probably linked to climatic differences between Central America and Vanuatu. It is becoming a nuisance as it slowly penetrates natural forests. It is a species that is multiplying at a faster rate than it is being harvested. Communities on a number of islands, particularly, Eromango and Maewo, have made formal complaints. Cordia alliodora is widely distributed meaning that if unchecked it could trigger an immense biodiversity problem.

Another invasive plant species that is common, particularly in the drier parts of certain islands, is Leucaena leucocephala (kasis). Also known as the "conflict tree", this species was widely promoted as, among other things, a leguminous (nitrogen fixating) tree, cattle feed and fuel-wood source. Leucaena leucocephala can form dense monospecific thickets and is very difficult to eradicate once established, rendering extensive areas unusable and inaccessible. This plant is very competitive, has a high rate of regeneration, and is threatening native plants in some areas.

Merremia peltata (big lif rop) is a vigorous creeping vine that may have been introduced to the islands during World War II, by the American army, for camouflage purposes. It is a real threat to forests because it strangles vegetation. Merremia peltata kills forests on sites disturbed by man, and where the canopy is naturally opened as a result of factors like dying trees and the impacts of cyclones. It is one of the most important weeds of plantation forestry and is also found in natural and semi-natural environments. This vine is one of two major species threatening natural regeneration in logged or disturbed areas. It prefers disturbed habitats and openings, including forest gaps and margins.

Probably the second most invasive creeping vine that threatens forests in Vanuatu is Mikania micrantha (also called mile-a-minute weed or American rope, and sometimes confused with Polygonum perfoliatum). This is a perennial, twining plant that is rampant and fast spreading. It grows best where fertility, organic matter, soil moisture, and humidity are all high. It damages or kills other plants by cutting out light and smothering them. The plant is believed to have been intentionally introduced by the American army during World War II. Like Merremia peltata it grows very fast in disturbed forests and natural openings. Forest regeneration is difficult where this plant is established.

A number of other invasive plants are worthy of mentioning here, even though their impacts are less apparent in Vanuatu. These include Acacia farnesiana and Coccinia grandis (ivy or scarlet gourd), which is a smothering vine that climbs over trees and forms a dense cover that completely shades and destroys the forest underneath. Another is Mimosa invisa, a giant plant covered with thorns. This is becoming a problem in Vanuatu, particularly in disturbed areas such as pasture. It moves into nearby forests, where it interferes with regeneration at the forest edges and forms dense tangles that are difficult to walk through.

Also noteworthy is Clidemia hirta (Koster's curse), which is a very serious weed of the forest understory in Vanuatu. Another nuisance species is Lantana camara, which is particularly common in pasture areas, but nevertheless interferes with the growth of more desirable trees. One of the activities that aids in the spread of Lantana camara is the movement of logging equipment in the forest. Lantana is a pioneer weed that grows in newly disturbed areas. Another plant with similar impacts is Psidium guajava (guava or kuava). Mixed with species such as Mimosa invisa this plant is a complete barrier to the natural expansion of forests. Birds and other animals disperse seeds of Psidium guajava. Its growth is vigorous, particularly in the low plains used for grazing or in other disturbed areas.

Invasive animals and insects

Invasive animal species are also upsetting the natural balance in the forests. Many have impacts that are yet to be fully understood, as far as forests or trees are concerned, although it is already clear that some are causing immense destruction to forest biodiversity. One major pest is Acridotheres tristis (Indian mynah). This bird may have been introduced in the 1970s. It is fast becoming a dominant species on many islands. Commonly seen on cattle ranches, the bird is now an agricultural pest and reduces biodiversity by competing for nesting hollows, destroying chicks and eggs, and evicting small mammals. A study of its impacts on the forest in Vanuatu could yield very interesting and discouraging results. By displacing and preying on other birds and species, Acridotheres tristis is bound to have negative impacts on the forest and biodiversity.

Another invasive pest is Achatina fulica (the giant African snail). This is a major agricultural and garden pest, but it also feeds on trees and leaves. It has been observed to feed on the bark of certain trees like Dendrocnide latifolia and tissues or shoots of young seedlings. It is also a vector (as are many snail species) of several human pathogens and parasites. It lays hundreds of eggs and multiplies at an alarming rate. In Vanuatu, droughts and prolonged dry conditions have killed large numbers of snails and slowed the extent of damage. Achatina fulica is found on a number of major islands.

In dealing with snails, Vanuatu has also become a victim of biological control gone wrong, with the introduction of Euglandina rosea (rosy wolf snail or cannibal snail). This species was introduced as a biological control agent for Achatina fulica. It has been discovered, however, that although Euglandina rosea has indeed attacked the Achatina fulica, there is worrying evidence that this cannibal snail has caused the extinction of numerous native snails in other countries. The cannibal snail prefers preying on smaller snails, especially if the shell can be swallowed whole, suggesting that a component of its feeding behaviour is dictated by calcium demands. This means Vanuatu risks losing most, if not all, of its native snail species. The impacts of this alien species on the vegetation of Vanuatu perhaps begins with the destabilizing of snail and other species populations that are important to natural systems on which healthy forests depend. Combined with Achatina fulica, invasive snails are serious forest pests in Vanuatu.

Another species of concern in Vanuatu is Wasmannia auropunctata (also known as cocoa tree-ant). Considered to be perhaps the greatest ant species threat in the Pacific, the little fire ant is blamed for reducing species diversity, reducing overall abundance of flying and tree-dwelling insects, and eliminating arachnid populations. Quarantine authorities have indicated that this species is currently confined to an island in the Banks group. Though its impacts on forests are yet to be fully understood, it is likely that Wasmannia auropunctata will alter many of the natural process that determine the kind of forest and related biodiversity of the islands. Given that invasive ants are capable of killing crabs, Vanuatu can expect Wasmannia auropunctata to be a major threat to its many crab species, including the famous Birgus latro (coconut crab), which is already heavily exploited by humans.

Given the spread of ants globally, Vanuatu also needs to be aware of the possible introduction of other ants such as Anoplolepis gracilipes (yellow crazy ant). Apart from the potential to devastate human surroundings this species is also known to decimate endemic species, rapidly degrade native communities, and alter ecosystem processes. It interferes with and preys on species of reptiles, birds and mammals both on the forest floor and canopy. This species has caused extensive canopy dieback on Christmas Island and is capable of changing the structure of forests as a result of its impacts on native species^[5]. The impact of sooty mould, which kills trees and shrubs, is increased where Anoplolepis gracilipes is established. Some claim this species is already present in Vanuatu, but local authorities refute this claim. Solenopsis invicta (red imported fire ant) is also a potential threat.

Importance and relevance of invasive species

The threats and nuisance posed by invasive species in Vanuatu have been a concern for a good number of years, perhaps beginning in the late-1970s and early-1980s. But, some invasive species were introduced to the islands much earlier. This is particularly true for a number of plant species like Merremia peltata and Mikania micrantha that now threaten forests and make sustainable forestry activities increasingly difficult. Despite the realization of the growing problem caused by invasive species, until recently, little was done to manage or control the spread of these species. It would also be correct to say that very little knowledge existed on these invasive species and the dangers they pose.

It was only during the latter part of the 1990s that invasive species were given increased attention. Though these are now gaining increasing importance in the country, one could only wish that efforts to address them had come earlier, and been backed with more technical and financial resources. Vanuatu, like many other island countries, now accords alien invasive species much greater relevance, but this relevance is very much belated. Through a number of studies, the National Biodiversity Strategy And Action Plan (NBSAP) project implemented by the Environment Unit has brought the issue of invasive species to the attention of a wider audience. The studies, among other things, noted the impacts invasive species are having on the environment at large. The results of the assessment were documented in the country’s National Biodiversity Conservation Strategy for further action (see below).

That more is being understood, said and done about invasive species in Vanuatu is not disputed. However, a number of other issues provide essential background to building on appreciation of the importance and relevance accorded to matters of invasive species. First, invasive species did not take priority (to a large extent this is still a problem) in government agencies until the late-1990s and early-2000. Second, because of the tradition of the sectoral approach employed by government agencies in the management of resources, the invasive problem, which cuts across sectors, has been more of a concern to the Vanuatu Quarantine and Inspection Service (VQIS) than others, although the work of the VQIS does not specifically address forest invasive species. Third, Vanuatu has limited resources and capacity in terms of expertise and finances, meaning the importance of invasive issues nationally is to a large extent driven by essential input from external entities. Fourth, the tendency in resource management has, for a long time, focused on the commercial value of resources. Threats to these resources, particularly as posed by invasive species and diseases, are seldom identified or addressed. This is especially true in forestry. Fifth, the understanding of invasive species by decision-makers is minimal and corresponds with seemingly limited political will given to the subject. Finally, island communities have little knowledge about invasive species. Put simply, for many years the majority of people did not know what an "invasive species" is. Many still think they are native and cause no detrimental impacts. More recently, many more communities are learning about these unwanted species.

Management and control measures

Plant Protection Act

Efforts are being made to manage and control forest invasive species. It is appropriate to note two phases or levels to this management and control regime. The first are measures implemented by the VQIS through the Plant Protection Act of 1997. This legislation provides for the exclusion and effective management of plant pests and facilitates exports of plant produce. The Act provides mechanisms to deter any entry of unwanted organisms (including invasive species) that may affect the environment and natural resources, agriculture, humans, control of pests and diseases; and for the eradication of exotic pests and diseases.

Phytosanitary measures

Imports: The VQIS only issues import permits for approved products from approved countries, after a risk analysis has been carried out on the product. This includes the pest list associated with the product, effects on the environment, effects on agriculture, and consulting stakeholders. Stakeholders usually include relevant government departments and industries. All products are approved on a no risk or minimum risk basis. Strict guidelines controlling imports of plants or plant products are currently in place because some plants that have been approved for import by relevant departments have become invasive.

Import certification: all approved imports of plants and plant products are documented with specific requirements for each country. The specific requirements are issued with the import permit when an application for a permit to import is lodged.

Border control: quarantine posts have been established on the main islands of Vanuatu to control the entry of unwanted pests and diseases as well as imports of plants and plant products. Controls on existing entry pathways have been quite effective.

Quarantine inspections: all approved imports of plant and plant products are inspected at the border. Goods that meet import requirements are released, while those that do not meet standards are either destroyed or reshipped. All illegal imports are dealt with under the Act and offenders are prosecuted.

Plant protection services

Surveying Vanuatu

Like most least-developed countries, Vanuatu has very limited plant protection resources. The isolated nature of the islands allows for very little surveying and monitoring. Most of the monitoring systems in place are for specifically targeted pests and are implemented by the Plant Protection Service of the VQIS. Regional institutions conduct the survey and documentation of general pests and plant diseases, with assistance from local counterparts. These are not carried out on a regular basis.

Monitoring

Monitoring of pests and diseases is carried out by the Plant Protection Service, with the assistance of rural communities. Monitoring of pests and diseases in the islands is expensive and, to mitigate costs, the VQIS has set up an awareness campaign under which targeted pests are documented and this information is disseminated to rural communities. Rural communities are advised to report any unusual plants, pest, and diseases to the local authorities or the quarantine office.

Control measures

Vanuatu has undertaken several control operations for specific pests and diseases, but with very little success. The control measures that Vanuatu has used include: mechanical control, chemical control and the introduction of bio-control agents. A good example of a biological control agent introduced to control Achatina fulica is the predator snail Euglandina rosea. The predator snail has become invasive and is attacking native snails. Mechanical control is usually done by farmers to control weeds. Chemical control was employed in an attempt to control Wasmannia auropunctata, but it has proven very costly. All flights and ships from Banks and Torres are sprayed and checked to prevent the further spread of Wasmannia auropunctata. Awareness-raising is also a major activity.

Eradication measures

There are currently no eradication programmes for established pests and diseases. Vanuatu needs assistance for the implementation of such programmes. This also applies to invasive species of plants that are well established in Vanuatu.

Emergency diseases and pest response

Vanuatu is very vulnerable to the effects of an introduction of diseases, pests, or invasive plants and animals. An emergency disease and pest response system is in place to complement and be part of a total detection/protection system. This system starts at the border, through routine surveillance, and carries into response activation to control and/or eradicate a disease or pest before it becomes established.

Forestry and environmental management and conservation acts

The second level of the management regime can be categorized as that executed by the DoF and the Environment Unit. The Forestry Act of 2001 makes provision for the protection, development and sustainable management of forests and the regulation of the forestry industry in Vanuatu. It notes as one of the principles of forestry administration the protection of the diversity of forests and forest ecosystems in Vanuatu. The Act, however, says nothing about the control or management of forest invasive species. Part VI of the Act talks about the protection of the environment, but focuses on conservation per se. One of the cited dangers to forests is fire. Alien species are not acknowledged. Furthermore, although the Act calls for rehabilitation of forests, this is not because invasive species are more likely to occur in logged areas hence interfering with forest regeneration. The only control measure recommended by the DoF for the management of Cordia alliodora is to use the plant as fuel-wood. Even at the level of the DoF, a sense of urgency in relation to invasive species has developed only recently. The Department has still to give invasive species the policy priority, strategies and resources required.

The Environmental Management and Conservation Act of 2002 provides for the conservation, sustainable development and management of the environment of Vanuatu. The Act defines foreign organisms as all stages of any life form that are not endemic to Vanuatu. However, this is almost all that the law says with regard to invasive species. The Act deals mostly with biodiversity in general and has little focus on invasive species.

Other measures and initiatives

Forest and environmental instruments

Vanuatu is party to a number of international and regional environment-related instruments and initiatives. There are also a number of other national instruments. These need not all be enumerated here. Vanuatu signed the Convention on Biological Diversity (CBD) in 1993 and therefore agrees to "try to prevent the introduction of, control or eradicate, those alien species that threaten ecosystems, habitats or species"^[6] and prepare a National Biodiversity Strategy And Action Plan (NBSAP) as noted above. An Act to ratify the CBD was also passed to effect the implementation of this convention. Nevertheless, there is a need for additional instruments to ensure that Vanuatu fully meets its obligations under the treaty.

The country’s constitution states that every person has among other fundamental duties "to protect Vanuatu and to safeguard the national wealth, resources and environment in the interests of the present and future generation"^[7]. A national conservation strategy was adopted in 1994, but this document says nothing about invasive species. A national forest policy (nfp) adopted in 1997 does not address the management of invasive species either. It acknowledges that vines compete with natural regeneration, but fails to note that two of the greatest vine threats are invasive. The code of logging practice (COLP) does not say anything about invasive species, but could be helpful in the control of invasive species because of its emphasis on limiting forest opening. The only national instrument to say anything much on unwanted species is the Prevention of the Spread of Noxious Weeds Regulation of 1966. This is, however, outdated and does not prevent the transmission of such weeds on trucks, heavy equipment and by other means. Another relevant ordinance is the Wild Bird Protection Regulation of 1962. This is unfortunately also outdated and not effectively applied. It fails to address the current need to protect wildlife, endangered species and habitats.

Vanuatu’s NBSAP is now complete and is, in many ways, the first policy and strategy document that gives high priority to the management of introduced species. The document notes the need to develop an administrative system to prevent adverse impacts of organisms that are potentially invasive, and also called for communities and implementing organizations/stakeholders to find opportunities to manage and eradicate species that are already threatening Vanuatu’s biodiversity (Environment Unit, 1999: 21-22)^[8]. A number of priorities, responsible agencies and required activities are noted. The provisions in the document are, however, inadequate, as far as the involvement and role of the DoF is concerned. In other words, the NBSAP cannot be translated into detailed activities to be implemented by the DoF. Given the immense need for knowledge about an enormous diversity of species that impact on the forests, it might perhaps be more appropriate to have policies and other instruments on the management and control of forest invasive species.

In August 2002, the first ever consultation involving a number of key groups in relation to invasive species was organized at the national level. The government institutions and stakeholders involved included the Environment Unit, government ministries including the departments of Forestry, Fisheries, Agriculture, and Attorney General, the VQIS, and a farm association. This is an integrated approach that partially stems from NBSAP research findings on invasive species. This group comprises the key institutions currently involved with invasive species management. The meeting noted a need to review existing policies/laws to identify their consistency or otherwise with respect to invasive species, so that the management and control of these species is provided for. The review should enable stakeholders to decide whether to work under existing laws or if there is a need to have a new law on invasive species. A policy on invasive species that identifies the roles of every institution or stakeholder is seen as essential. A review of these instruments is now underway. Vanuatu also benefited from a workshop on invasive species conducted by the South Pacific Regional Environment Programme (SPREP) and its partners. Given these efforts, more people are becoming aware of invasive species and their impacts.

Conclusion

The forests of Vanuatu - and the biodiversity of which they are a part - are becoming increasingly invaded and threatened by alien species. These species include both plants and animals. This scenario calls for concerted new efforts on the part of the DoF and stakeholders. Vanuatu has a number of instruments for environmental management. These are nevertheless fragmented and underdeveloped, while some are outdated - and more often than not, legislation is neither applied nor enforced (Environment Unit, 1998: 9)^[9]. The VQIS already has an elaborate pest and disease management and control system in place. The Forestry Act and NFP are generally devoid of provisions on invasive species. Consequently, the DoF has done little to address the crisis brought about as a result of the introduction of invasive species.

A common weakness in existing instruments is their lack of emphasis on new environmental issues, particularly the challenge posed by invasive species. The review of instruments that have bearing on invasive species is a step in the right direction. The DoF may have to develop its own instruments and be a leading implementing agency in addressing the invasive problem in forests.

It is recommended that - given the crosscutting and multi-sectoral nature of the problem and coupled with limited resources, expertise and capacity - an integrated approach with the assistance of regional and international bodies and governments would be the best option. Work begun by the relevant government agencies and stakeholders must be continued and backed by political will. The commitment of donors in terms of expertise and finance is a necessity and therefore called for. This is not only to aid in the development of the required management and control instruments, but also in actual ground implementation. The need for research into invasive species to scientifically describe the severity of their impacts and future threat to the forests is an activity to be considered seriously. The inclusion of forest invasive species in a revised NFP or the development of a policy entirely on invasive species has to be considered. Forest health surveillance should become an integral aspect of a new NFP because of the common problems addressed. There may be a need for an instrument that governs the introduction of plants and animals for biological control purposes. Government, through its agencies and stakeholders will, among other things, need to increasingly raise awareness about invasive species and work with communities. This is to develop a long-term, cheaper and sustainable approach to effectively addressing the impacts of invasive species on the forest resources of Vanuatu.

Forest invasive species and their impacts on afforestation in Viet Nam

Pham Quang Thu
Forest Protection Research Division, Forest Institute of Viet Nam

Introduction

Over the past few decades, there has been a steady expansion of forest plantations across the country. According to data collected during 1999 by the Ministry of Agriculture and Rural Development, it is estimated that 1 471 394 hectares of forest plantations have been established in Viet Nam, of which there are about 288 073 hectares of Acacia, 348 000 hectares of Eucalyptus, 218 056 hectares of pines, 100 000 hectares of Melaleuca and about 500 000 hectares of other exotic and native species plantations. Products from plantations play a very important role in supplying raw materials for industry and are gradually replacing forest products harvested from natural forests. Plantations are now regarded as a means to meet wood requirements without putting excess pressure on natural forests.

However, there is a fear that a catastrophic outbreak of pests and diseases may occur suddenly and that weed species may invade plantations during the rainy season, affecting tree growth and the quality of plantations. Outbreaks of diseases and insect pests occur in as much as 20 000 hectares of plantations annually.

Surveys of diseases, insect pests and weeds and their importance to the trees have been implemented several times, on different scales, by various institutions including: the Forest Science Institute of Viet Nam, the Forest Science Sub-Institute of Viet Nam, the Forest Inventory and Planning Institute and the Forest Protection Department. Table 1 lists the most important plantations species in Viet Nam.

Table 1: Tree species investigated.

Status of forest invasive species in Viet Nam

Forest invasive insect pests

The most important insect pest species are listed in alphabetically in Table 2, with an indication of the species that are affected by these insects. There are 19 main invasive insect species associated with large-scale monocultural forest plantations in Viet Nam. The most important is a species of leaf feeding caterpillar Dendrolimus punstatus, which invades plantations of Pinus merkusii and P. massoniana. Six species of insects, such as Anomis fulvida, Pteroma plagiophleps and Speiredonia retorta are considered to be important and widespread invasive species and their outbreaks occur widely in plantations. The other species are considered important invasive species and outbreaks have occurred locally in plantations.

Table 2: The major forest invasive insects

The main pathogens attacking forest plantations

The major pathogens affecting plantations in Viet Nam are listed alphabetically in Table 3. Nine main species have infected large-scale monocultural plantations in Viet Nam. Three of these species Cryptosporiopsis eucalypti, Cylindrocladium quinqueseptatum and Corticium salmonicolor are the most important exotic species affecting Eucalyptus and Acacia plantations. The other species are considered to be important species to both exotic and indigenous species plantations.

Table 3: Major pathogens to forest plantations

Invasive weeds in forest plantations

The main invasive weeds in Viet Nam are listed in Table 4. There were six main weeds, of which two species, blady grass and feather pennisetum, are very widespread and important in Acacia and Eucalyptus plantations.

Table 4: Major weeds to forest plantations

Impacts of invasive species to plantations

Acacia plantations

Acacia spp. plantations have been planted throughout the country for the production of pulp for paper and medium density fiberboard. In general, Acacia plantations are remarkably free of insect pests. Insects commonly found feeding on the foliage include several species of bagworms, curculionid beetles and some hairy caterpillars. However, outbreaks of insect pests in Acacia mangium plantations occasionally occur on a large-scale. Bagworm (Pteroma plagiophleps) (Lepidoptera, Psychidae) has caused damage to Acacia mangium in Hoa Binh and Ha Tay provinces (northern Viet Nam) in 2000 and 2001, respectively. Other leaf-eating insects, Anomis fulvida (Lepidoptera, Noctuidae) and Speiredonia retorta (Lepidoptera, Noctuidae) have infested thousands of hectares of 2-10 year-old Acacia mangium plantations in Tuyen Quang, Phu Tho, and Thai Nguyen provinces in 2001 and in 2002. In addition, Odontotermes sp., Microtermes sp. and Macrotermes sp. (Isoptera, Termitidae) killed 10-50 percent of planted saplings aged less than one year in several locations of the central highlands and mountainous areas.

Measures for controlling insect pests attacking Acacia plantations have been implemented. Chemical compounds are the main means of controlling these insect pests. The chemical control measures have been partially successful, but are expensive to implement and have a considerable negative impact on the environment. There are currently no effective measures for controlling termites.

Diseases associated with Acacia plantations were investigated at a number of locations in Viet Nam. The most important disease is the pink disease caused by the fungal pathogen Corticium salmonicolor (Aphyllophorales, Cortciaceae). This disease occurs in locations with high rainfall, of more than 1 800 mm per year, which includes most of Viet Nam. It attacks plantations aged more than three years. Disease incidence is regarded as very high in southeast Viet Nam, ranging from 10-40 percent depending on species/provenance or clones.

Stem canker associated with Acacia hybrids has shown a tendency to develop into outbreaks in the central highlands (Kon Tum province). One thousand hectares of 2-3 year-old Acacia hybrid plantations were infected by Botryosphaeria dothidae (Dothideales, Botryosphaeriaceae), with disease incidence ranging from 10-30 percent.

Heart rot disease occurs in Acacia plantations in high rainfall areas, especially in the north and southeast of Viet Nam. Pathogens were identified to be Ganoderma spp. The disease incidence with advanced decay and hollows was 20-30 percent.

There are currently no measures for controlling these diseases. It seems to be impossible to spray chemical compounds because of the high costs involved and the potential for environmental pollution. Screening for provenances or clones showing disease resistance, from progeny trials, has been implemented for several years, however, the results from this work have yet to be been published.

Weeds are considered to be very important invasive species in Acacia plantations aged less than two years. The dominant weeds are blady grass (Imperata cylindrica) and feather pennisetum (Pennisetum polystachion). These two species affected growth of plantations. Two other species Mimosa pudica and Eupatorium odoratum are distributed widely and considered to be important weed species.

Eucalyptus plantations

In Viet Nam, a few species of lepidopteran caterpillars have been found to feed on Eucalyptus leaves, although outbreaks are rare. The cerambycid borer (Aristobia approximator) (Coleoptera, Cerambycidae) caused severe damage to thousands of hectares of Eucalyptus camaldulensis and Eucalyptus tereticornis plantations in the Mekong delta. The most common insect pests are subterranean termites including Odontotermes sp., Microtermes sp. and Macrotermes sp. (Isoptera, Termitidae) that attack the roots of young transplants and kill 10-60 percent of saplings aged less than one year. Measures for controlling insect pests attacking Eucalyptus plantations have not yet been implemented. There are currently no effective measures for controlling termites.

Diseases associated with Eucalyptus plantations have been investigated throughout Viet Nam. The most important and widespread diseases have been leaf blight disease caused by the fungal pathogen Cylindrocladium quinqueseptatum and leaf spot disease caused by the fungal pathogen Cryptosporiopsis eucalypti. Disease incidence for the first disease was regarded as very high in southeast and central Viet Nam, ranging from 10-90 percent depending on species/provenance or clones.

Leaf spot disease is caused by Phaeophleospora destructans and is associated with E. urophylla and some hybrid clones. It was first found in Viet Nam in 2001. The disease incidence is 10-60 percent in Phu Tho and Gia Lai provinces. Disease incidence of the bacterial wilt disease caused by Ralstonia solanacearum Smit, associated with Eucalyptus urophylla plantations is 10-30 percent in the northern provinces.

There are currently no measures for controlling these diseases. Research on provenances or clones showing disease resistance from progeny trials continues to be implemented. The results of this work have not yet been published.

The most important weeds in Eucalyptus plantations are Imperata cylindrica and Pennisetum polystachion. These two species affect the growth of the plantations. Two other species Mimosa pudica and Eupatorium odoratum are widely distributed and considered to be important species.

Pine plantations

Outbreaks of the caterpillar Dendrolimus punctatus (Lepidoptera, Lasiocampidae) have occurred frequently on a large scale in Pinus merkusii and P. massoniana plantations in the whole country. Sawfly Nesodiprion biremis (Lepidoptera, Diprionidae) has caused considerable damage to Pinus kesyia and P. massoniana in the central highlands of Viet Nam. These two species have severely affected resin productivity in Viet Nam. Other shoot borer pests Dioryctria abietella (Lepidoptera, Pyralidae) and Dioryctria sylvestrella (Lepidoptera, Pyralidae) attacked Pinus merkusii, P. massoniana and P. caribaea in some northern provinces. Macrotermes sp. attacks the roots of young transplants and killed 10-30 percent saplings aged less than one year in several mountainous areas.

Chemical measures have been implemented by growers to manage these pests. However, these control measures are costly and cause significant environmental pollution.

White blister rust Cronatium sp. is associated with Pinus kesyia in Lam Dong and Gia Lai provinces. Disease incidence is rather high in young plantations in some locations. Identification of species and the implementation of control measures are yet to be done.

Impacts of weeds on Melaleuca leucadendra and M. cajuputi plantations

Mimosa pigra is quickly becoming one of the most serious species threats to Melaleuca plantations in the freshwater wetland areas of the Tram Chim National Park and U Minh Thuong Nature Reserve. At present, the U Minh Thuong Nature Reserve and Tram Chim National Park in the Cuu Long (Mekong) river delta are endangered by Mimosa. Mimosa plants were first observed at Tram Chim in 1985. By 1999, some 150 hectares were infested. A distribution map drawn up by the HCM Natural Science College in June 2000 showed an infested area of 490 hectares. The map also predicted that a further 4 600 hectares, or 60 percent of the park’s land area, is highly susceptible to Mimosa invasion. At present this species has also developed at other locations such as Tri An lake, Cat Tien Natural Park, and Hoa Binh lake.

A Mimosa control experiment showed that cutting stems, burning off, and a combination of the two, were ineffective measures to eradicate the plant from Tram Chim National Park. The experiment found that the plants resprouted quickly after cutting and that burning helped to trigger the spread and germination of Mimosa seeds. The most successful control method was cutting the Mimosa plants during the flood season. The Tram Chim wetlands are subject to between four and six months of flooding each year. The experiment cut the stems when the floodwater was about 30 cm above the soil surface. Four months after the treatment, when floodwater was still 60 to 80 cm above soil surface, none of the treated plants had resprouted and 75-90 percent of the roots had died.

Other plantations

Outbreaks of the leaf-feeding caterpillar, Fentonia sp. (Lepidoptera, Notodontidae), have occurred annually in Styrax tonkinensis plantations causing different levels of damage. In 2001, an outbreak of Fentonia sp. occurred, affecting about 2 100 hectares of 3-5 year old plantations. Chemical compounds were applied to control this insect. Outbreaks of sawfly (Shizocera sp.) (Hymenoptera, Agridae) have caused considerable damage to Manglietia glauca plantations in northern Viet Nam. Eutectona machaeralis (Lepidoptera, Pyralidae) attacked Tectona grandis plantations in several provinces, and caused considerable damage. Some insect pests such as: Culcula paterinaria (Lepidoptera, Geometridae), Arbela baibarana (Lepidoptera, Cossidae) and Erthesina fullo (Hemiptera, Pentatomidae) are important species affecting Cinnamomum cassia plantations, in some provinces. Cyrtotrachelus longimanus Fabr. (Coleoptera, Curcunionidae) feeds on young bamboo shoots of Dendrocalamus membranaceus causing considerable damage in Thanh Hoa and Hoa Binh provinces.

Conclusions and discussions

At present, the Vietnamese Government is in the process of implementing a programme for the reforestation of 5 million hectares, by the year 2010. This means that the area of forest plantations will increase rapidly in Viet Nam. Research on planting species, natural enemies, insect pests, diseases and weeds in forest plantations and policy related to forest development and forest protection must be conducted.

Outbreaks of diseases and insect pests affect as much as 20 000 hectares of plantations annually. The narrow genetic base of introduced planting stock increases the risk of pest outbreaks. No systematic research on insect pests, diseases and other forest invasive species has been conducted. Plant quarantine and avoidance of natural enemies to planting trees have not been sufficiently investigated, resulting in high costs to combat the pests.

At present, chemical control methods are the most commonly applied management techniques. Other control methods are rarely applied. Screening for disease resistance or insect pest resistant tree varieties commenced several years ago, but there are currently no published results from this.

There is a need for capacity building in the area of invasive species through on the job training. Additional extension activities are required to promote the use of IPM among farmers in Viet Nam.

There is a direct need for basic information on important insect pests, pathogens, weeds etc. This should be obtained by means of an intensive research programme.