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Managing invasive species: the threat to oil-palm and rubber - the Malaysian plant quarantine regulatory perspective

B.O. Asna and H.L. Ho
Crop Protection and Plant Quarantine Division, Department of Agriculture (DoA), Malaysia

Abstract: Currently, the acreage of oil-palm and rubber in Malaysia is 3.3 million hectares and 1.47 million hectares respectively. Both crops are among the country’s major agriculture exports and have contributed significantly to foreign exchange earnings. At present, Malaysia is very fortunate that the majority of dangerous pests or alien invasive species that could destroy agricultural industries are still not found in the country. These include Microcyclus ulei (P. Henn) V. Arx., the pathogen responsible for the South American Leaf Blight (SALB) disease for rubber, and fusarium wilt (Fusarium oxysporium f. sp. Elaeidis) for oil-palm. The introduction of invasive pests or diseases - whether by accident or otherwise - could spell disaster for Malaysia, which estimates total revenue from exports of rubber and rubber products to be 10 billion ringgit (US$2.6 billion) and oil-palm export earnings of 17.4 billion ringgit (US$4.6 billion). In view of the threat posed by invasive species, this paper highlights several measures that have been instituted to counter these threats. In Malaysia, the management of invasive species includes the prevention, eradication, containment and suppression of such pests. The Plant Quarantine Act 1976 and Plant Quarantine Regulations 1981 provide a legal framework to manage and prevent the introduction and occurrence of an invasive species. Plant quarantine activities provide the first line of defence in managing invasive species of plants. The effective implementation of this Act could prevent their potential introduction or their establishment. Besides plant quarantine measures, other activities conducted to assist in managing threats posed by invasive species are also highlighted. When species appear to spread widely and are permanently established, the control measures taken are aimed at reducing the pest population and reducing the effects or damage. An integrated management technology involving suitable combinations of cultural, chemical, biological, physical and mechanical methods is recommended. Research bodies - either government or private - have played important roles in helping regulatory bodies, extension agencies, individuals and the general public, in managing invasive species.


Malaysia is traditionally an agricultural country. Although Malaysia has broadened and diversified its economy through industrialization, agriculture remains an important sector. In terms of land use, agriculture takes up nearly 7 million hectares representing about 22 percent of the available land in Malaysia. The bulk of agricultural land is devoted to rubber, oil-palm and rice. At present, oil-palm, rubber, and the timber sector, form a major part of the country’s exports and contribute significantly to foreign exchange earnings.

Nevertheless, the area under rubber is on the decline, down to 1.47 million hectares since a peak in the 1980s. The decline in production has led to the closure of many processing plants, especially the smaller and less efficient ones, due to a shortage of raw materials. Thus, the import of raw materials from other producing countries is on the increase to meet the demands of local processors and rubber product manufacturers. Revenues from rubber, including downstream industries, are about 10 billion ringgit (US$2.6 billion). The area of oil-palm has increased to some 3.3 million hectares, and has export earnings of about 17.4 billion ringgit (US$4.6 billion). The industry has remained resilient in the face of many challenges and has continued to contribute significantly to the national economy.

Many factors such as insect pests, pathogens and weeds can limit the production of crops. At least 30 percent of crop losses can be attributed to pests. Owing to the increasing flow of international traffic, tourism, and demand for new germplasm and crop varieties, it is increasingly difficult for the plant quarantine system to safeguard Malaysia from the entry of exotic pests.

Invasive species of rubber and oil-palm in Malaysia

Malaysia is fortunate in that the majority of invasive species affecting both rubber and oil-palm plantations, such as Microcyclus ulei (P. Henn) V. Arx., the pathogen responsible for the South American leaf blight (SALB) disease for rubber and the fusarium wilt Fusarium oxysporium f. sp. Elaeidis for oil-palm, have never become established. An overview of the most important pests and diseases for rubber and oil-palm is given in Table 1. Examples of invasive weed species affecting oil-palm and rubber in Malaysia are listed in Appendix 1 of this paper.

Table 1: Major pests and invasive species to oil-palm and rubber not yet recorded in Malaysia

Scientific Name

Common Name


Fusarium oxysporium f. sp. Elaeidis

Fusarium wilt

Cecospora elaiedis

Cercospora leaf spot

Rhadinaphelenchus cocophilus

Red ring disease

Phytomanas staheli

Sudden wilt

Rhynchophorus palmarum

Palm weevil

Leptopharsa gibbicarina

Lace bug


Microcyclus ulei (P. Henn) V. Arx

South American Leaf Blight

Thanatephorus cucumeris

Target leaf spot

Phyllachora huberi or Catacauma huberi

Black crust/Black scab

Erinnyis ello

Sphinx moth

Leptopharsa hevea

Lace bug

The first major economic impact of SALB was experienced when it destroyed two of the earliest large rubber plantations at Belterra and Fordland in Brazil in the 1930s (Holiday, 1970 and Hilton, 1955). A plantation established in 1935 by Goodyear, in Panama, was completely destroyed by SALB by 1940 (Holiday, 1970). Since then SALB has remained as a major obstacle to a viable natural rubber industry in South America. The introduction of this invasive pathogen would spell disaster for the plantation industry in Malaysia. The industry employs an estimated 40 000 workers and any factor that poses a threat will create social problems. Therefore, the role of plant quarantine is important in order to manage and prevent the entry of alien species and diseases by regulating the import of agricultural commodities.

Plant quarantine legislation in Malaysia

In most countries, plant quarantine is the first line of defence against the introduction of exotic or invasive pests and diseases, by regulating the flow of plant materials. The Plant Quarantine Act 1976 and the Plant Quarantine Regulations 1981 came into force in 1976 and 1981 respectively and are implemented by the Department of Agriculture (DoA). The Act provides a broad legislative framework for the Director of Agriculture and his appointed officers to destroy, remove or treat plants or pests that affect the agriculture of the country. In addition, there are provisions under the Act that provide Plant Quarantine Officers and Inspectors with the authority to isolate, manage, contain and eradicate any dangerous or exotic pests, as deemed necessary. The Act also provides adequate provisions to call upon relevant bodies or organizations in the country to collaborate and to enforce any action to eradicate or control pests and diseases. The Act prohibits the import and possession of noxious plants and pests.

The DoA has jurisdiction over the import of plant species, plant products, growing media/rooting compost, beneficial organisms, plant pests and carriers of plant pests. Under the regulations, special emphasis is given to procedures for the import of plants from the American tropics and the West African cocoa region, where serious pests of rubber, oil-palm and cocoa occur. In addition, under the Plant Quarantine Regulations 1981 oil-palm and rubber are classified as restricted materials.

The export of plants is controlled under the Customs Order (Prohibition of Exports) 1988. Any export of plants requires an export license issued by DoA. These regulations assist in managing and preventing the movement of plants or pests of an invasive nature into other countries.

Plant quarantine regulatory measures against invasive species of rubber and oil-palm in Malaysia

Malaysia has established stringent plant quarantine measures and procedures to prevent the introduction of dangerous pests or invasive species of oil-palm and rubber. These measures and procedures are discussed below.

1. Restrictions on the importation of planting materials

The Plant Quarantine Regulations have provisions to restrict the import of planting materials and agricultural products. The import of any rubber or oil-palm planting materials is prohibited EXCEPT:

For consignments imported under refrigerated conditions, for example fresh fruit and vegetables, specific treatment of the consignment is required, regardless of the length of the journey to Malaysia. The treatment is as follows:

a) Air/flight:

b) Vessels:

For the import of agricultural goods (in dry and unrefrigerated condition) by vessels from South American tropical countries where SALB is present, the following treatment is required:

If the import of the consignments does not comply with the conditions stipulated above, the consignment will either be refused entry or disposed off.

2. Measures for passengers on direct flights from the American tropics and African regions

Direct flights from the American tropics and African regions have commenced in order to develop social relationships and promote trade with these regions. This will result in a tremendous increase in the movement of people and trade, which also increases the risk of introduction of dangerous pests. The most threatening disease due to these direct flights is SALB. The following measures have been implemented (for passengers on direct flights from the American tropics and Africa) to prevent the introduction of SALB:

a) Interception of passengers and baggage:

i. Plant Quarantine Declaration Card

A Plant Quarantine Declaration Card was introduced to facilitate the interception - by Immigration and Plant Quarantine Officers - of travellers from the American tropics. Passengers coming from the American tropics have to report to Plant Quarantine.

ii. In-flight announcement

Malaysian Airlines makes an in-flight announcement, requesting passengers who have been to the American tropics within the past 30 days to report to the Plant Quarantine counter on arrival.

iii. Passenger and cargo manifest

The airline provides Plant Quarantine officers with the passenger and cargo manifest in order to assist the officers in intercepting passengers and cargo from the American tropics.

iv. Notification

Malaysian citizens who intend going to the American tropical region are required to inform the DoA about their journey by filling in form PQ10. They are advised to break their journey in countries where SALB is not present, for at least three days, where their clothes can be washed. The PQ10 form helps the Plant Quarantine Inspector to intercept travellers and take necessary measures when they return to Malaysia.

v. Double tagging

Double tagging of baggage from the American tropics to assist in the interception of the baggage.

vi. Separate compartment and conveyor for baggage

Baggage from direct flights from the American tropics to Malaysia is separated using different stowage compartments and conveyors.

b) Treatment for passenger

i. Floor-mat soaked with Dettol

The shoes of the passengers arriving from the American tropics are disinfected by walking over a floor-mat soaked in a 5 percent solution of Dettol. The mat is located on the passenger loading bridge.

ii. Air tunnel

An air tunnel is used to dislodge any SALB spores potentially attached to a passenger’s body. The air tunnel is equipped with a blower, sucking devices, herpa filter and UV lights. If any spores are present they will be dislodged from the passenger’s body and sucked through a herpa filter, where the spores will be trapped. The UV lights, at the top portion of the air tunnel, are switched on after all passengers have passed through the air tunnel to kill off any spores remaining inside the air tunnel compartment.

iii. X-ray machine

An X-ray machine is installed in the green lane at Kuala Lumpur International Airport, to detect any agriculture materials that are not declared by the passenger.

iv. Treatment of baggage

Baggage arriving from the American tropics is placed under UV lighting to kill any SALB spores attached to it.

3. Pest risk analysis (PRA)

A PRA is conducted for any import of oil-palm and rubber planting materials into the country. The PRA identifies and determines the following:

The significance of this uncertainty is used in determining appropriate measures.

A technical committee consisting of the relevant government agencies, researchers and universities is established to conduct the PRA.

4. Inspection at entry point

All imports of goods are subject to primary inspection at the port of entry. If, upon inspection, the imported goods or plant materials are found to be harbouring a pest, the plant quarantine inspector may:

a) instruct the owner to treat the goods or plant materials;
b) seize and dispose off the goods or plant materials; or
c) refuse entry.

5. Post entry quarantine (PEQ) screening

Imports of plants and other regulated items that are of high risk - such as plants belonging to the Plamae and Hevea families - are subject to post entry quarantine measures including:

a) thorough examination or observation for the presence of pests - the period would be one-to-two years for perennial crops or for a particular period to allow a particular disease to express the symptoms on the plant; and

b) further treatment prior to the release of the plant materials.

The PEQ unit of the Department of Agriculture at Serdang, Malaysia conducts all post entry screening of plant materials.

Other activities implemented to manage the invasive species threat

Other activities implemented to assist in managing the threats posed by invasive species include:

1. Amendment of the plant quarantine legislation

The protection of agriculture has been, and continues to be, the primary focus of the DoA efforts to prevent invasions by non-natives species into the country. However, for the effective enforcement of these regulations, there is a need to amend the legislation to more thoroughly address invasive issues and problems. Currently, the DoA is in the process of amending the Plant Quarantine Act 1971 to adequately address invasive species issues.

2. Monitoring survey and surveillance

The Rubber Board and Oil-palm Board of Malaysia, with the assistance of DoA personnel, conducts a biannual monitoring survey for the early detection of dangerous pests.

3. Contingency plan for the eradication and control of dangerous pests

Malaysia formulated an emergency contingency plan for the eradication of SALB in 1988, in the event that SALB is detected in the country. The contingency plan identifies and delineates the roles, duties and responsibilities of all agencies and rubber plantation owners that form part of the programme. The plan recommends, inter alia, conducting detection surveys for SALB and procedures for its eradication, if detected.

4. National technical committee on alien invasive species (AIS)

A technical committee on AIS has been established in Malaysia. The committee comprises members from government related agencies. The Ministry of Agriculture (MOA) spearheads the technical committee. The committee assists in:

a) identifying national needs and priorities;

b) creating mechanisms to coordinate national programmes;

c) enhancing cooperation across sectors to improve detection, eradication and control of AIS;

d) promoting awareness of multi-sectoral threats and involves all stakeholders - including local and indigenous committees - in national strategies, decisions and action plan; and

e) collaborating regionally and internationally to tackle the growing threat.

The Department of Agriculture, under the Ministry of Agriculture, and ASEANET will be organizing a national workshop on AIS in Kuala Lumpur.

5. Training

Training is an important aspect of capacity building. There is a need for enhanced training in both knowledge and skills in identifying the causal organisms of dangerous oil-palm and rubber pests. Plant quarantine staff, pathologists and entomologists at entry point need to be trained to become competent in detecting, intercepting and identifying the pests. The Rubber Board Malaysia has provided assistance in training some of our plant quarantine staff at the entry point. However, more regular training of this nature should be carried out in future.

6. Creating awareness

There is a general lack of awareness by the public of the dangers posed by the introduction of invasive species. Creating awareness can be achieved by various means such as distribution of pamphlets, public talks, meetings, dialogue and training with regard to the importance and threats of invasive species. Two pamphlets on SALB have been produced and distributed by the Department of Agriculture to all the Embassies in the American tropics, traveling agents, airlines and the tourist authority for providing information regarding the importance and prevention of the introduction of SALB into the country.

7. Notification of participants and delegates coming from South American/West African regions

Many international and regional meetings, conferences and conventions have been hosted by Malaysia recently. A system has been established in Malaysia that any organization hosting such an event, where delegates come from the American tropics or West Africa, is required to inform the DoA of these participants. The DoA makes the necessary arrangements to brief the organizers and participants on threats and impacts of a potential introduction of AIS.

8. Research

Research institutions of government-related agencies such as the Rubber Board Malaysia and Universities conduct a research and development programme in collaboration with the DoA, with a focus on prevention and control of invasive species. Research has been conducted on screening techniques at airports and the monitoring and identification of spores trapped in the air tunnel. Both government and private research organizations play an important role in helping regulatory bodies and the general public in managing invasive species.


The plant quarantine law and regulations need constant review and amendment in order to ensure that the issue of invasive species is properly addressed. Emphasis will also need to be given to increase capacity building and human resource development in order to develop a work force of highly trained, specialized, motivated and visionary personnel, and in enhancing the efficiency and quality of plant quarantine services in prohibiting and limiting the entry of invasive species into the country.

In addition, international, regional and national cooperation and coordination efforts are of paramount importance to minimize the impact of invasive species, as well as detecting, controlling and eradicating invasive species that are pests to agriculture and wild flora.


Anwar A.I. 1999. Impact and management of selected alien and invasive weeds and insect pests: A Malaysian perspective. Paper presented at the Global Biodiversity Forum - South and Southeast Asia in Colombo, Sri Lanka, 24-26 October 1999.

Ariffin D. 1996. Major diseases of quarantine importance to oil-palm in Malaysia. Paper presented in the 12th Meeting of Joint Malaysia-Thailand Working Group, Nongkai Province, Thailand, 5-7 March 1996.

Asna B.O., Mazlan S. and Ho H. L. 2001. Plant quarantine regulation and issues in preventing invasive arthropod pests. In: Seminar on invasive arthropod pests of vegetables and economic crops Legend Hotel, Kuala Lumpur, 13-14 March 2001.

Department of Agriculture. 2001. Malaysia: Crop Hectarage Statistics 1984-2000

Department of Agriculture, Malaysia and Rubber Research Institute Malaysia. 1988. Report on contingency plan for the eradication and control of dangerous pests.

Hilton, R.N. 1955. South American leaf blight. A review of the literature relating to its depredation in South America. Its threat to the Far East and the methods available for its control. Journal Rubber Research Institute Malaysia 14: 287-337.

Ho H.L., Mazlan S. and Asna B.O. 2001. Exotic pest threat: an essential element of plant quarantine. In: MAPPs Seminar on invasive species its impact to agricultural sector, Genting Highland, Malaysia, 2001.

Holiday, P. 1970. South American Leaf Blight (Microcyclus ulei) of Hevea brasiliensis. Phyto-pathology Paper No. 12. Commonwealth Mycological Institute. 31pp.

Mat H.O and Adul Kadir A.H. 2002. Malaysia Country Report - Prevention and management of alien invasive species. In: Workshop on prevention and management of alien invasive species, May 2002, Bangkok, Thailand.

Tan M.H. 1993. Plant Quarantine Measures to Prevent the Introduction of SALB into Malaysia in relation to direct flight from the American tropics. Paper presented for Malaysia-Thailand Bilateral Meeting on SALB at Langkawi, Malaysia, 15 February 1993.

Zulkifli A. Asna B.O., Ho H.L. and Mazlan S. 1999. The current plant quarantine regulatory measures and its strategies in preventing the introduction of South American Leaf Blight of rubber (Hevea) to Malaysia. Paper presented at the 13th Meeting of the ANRPC Technical Committee on pests and diseases of Hevea. November 1999, Penang, Malaysia.

Appendix 1: List of invasive weeds in oil-palm and rubber in Malaysia.

Common Name

Scientific Name

Suspected origin


Siam weed

Eupatorium Adoratum L.

North America

Throughout Malaysia

Asystasia coromandeliana Nees

Peninsular Malaysia

Mile-a-minute weed

Mikania micrantha L.

South America

Throughout Malaysia

Goose grass

Eleusine indica


Throughout Malaysia

Creeping sensitive plant

Mimosa invisa

Tropical America

Throughout Malaysia

When good trees turn bad: the unintended spread of introduced plantation tree species in India

K.V. Sankaran, S.T. Murphy and M.A. Sreenivasan
Kerala Forest Research Institute, India
CABI Bioscience, UK Centre (Ascot), United Kingdom


Alien invasive species (AIS) have been identified as one of the greatest threats to biodiversity around the globe, second only to habitat destruction (Singh, 2001). The introduction of AIS, either intentionally or accidentally, is a by-product of increasing international trade and travel. Intentional introductions of plants are mostly for use in forestry, agriculture, fisheries, aquaculture, landscaping, etc. Accidental introductions are helped by travel and imports of various items such as wood, food, etc. In either case, alien plants with weedy characteristics can have a serious impact on the various ecosystems with a range of negative effects, e.g. competition with indigenous flora and fauna, changes in nutrient cycling and hydrology, disrupting overall economic stability of local communities, and impacting on human health. Thus, biological invasion has become one of the most challenging environmental issues faced by humanity today - a matter of global concern.

Quantitative and/or qualitative information on positive and negative impacts of AIS on our environment are rather patchy. At a global level, information is either lacking or incomplete on the alien species involved and the extent of invasion by them. It is reported that in the United States of America, direct and indirect impacts of invasive species have contributed to the decline of 46 percent of all threatened and endangered species (Anonymous, 2003). The estimated number of invasive plant species in the country is known to be around 1 400, which occupy an area of 40 million hectares. Undoubtedly, monitoring, surveillance and eradication of AIS should be a matter of huge economic concern for individual countries. For example, AIS bring about losses of more than US$137 billion in the United States of America, of which the share of invasive plants is around 10 percent of the total. The available statistics for India indicate that losses of some US$130 billion occur annually (Anonymous, 2003). Whatever the cost may be, the unintended spread of invasive species continues unabated, despite earnest efforts to manage them, especially in developing countries.

Invasions by alien species are recorded from all the seven geographical regions on the globe. As for invasive plants, a species list is available for most regions, though it is far from complete. "Toppers" in the list for the Asia-Pacific region include: Eichhornia crassipes (water hyacinth) and Salvinia molesta (aquatic weeds), Chromolaena odorata, Lantana camara, Parthenium hysterophorus, Mikania micrantha, Mimisa invisa and Ageratum conyzoides. However, there is a dearth of information on exotic trees that have become invasive after their introduction in forest plantations worldwide. This information is very essential, because these invasive trees can upset sustainable management of forest plantations and impact heavily on forest ecosystems.

A literature survey indicates that 277 tree species used in forestry worldwide are apparently invasive. Of these, 83 species are reported from Africa, 10 from Europe and 14 from Asia (Murphy and Haysom, unpublished). A majority of the invasive trees belong to Fabaceae, Pinaceae and Myrtaceae. Little information is available on why these trees were introduced in the first place, exact dates of introduction, extent of area initially planted, the spread, ecological and economic impacts, details of management, etc. With this background, an attempt has been made in this paper to examine the invasion and spread of introduced plantation tree species in India and the problems associated with these.

Exotic invasive trees in India

India is one of the mega-biodiversity countries in terms of flora and fauna because of its unique geographical position, varied climate and other factors. Of the country’s 328 million hectares, approximately 20 percent is under natural forests. Five percent of the natural forests have been declared protected areas. The country has 500 wildlife sanctuaries, 89 national parks and 13 biosphere reserves. The types of natural forests range from alpine to tropical evergreen. Forests in northeast and southwest India (Western Ghats) are very rich in biodiversity and are recognized as a biodiversity hotspot (Nayar, 1997). As in other parts of the world, a wide spectrum of plants has been introduced to India through international trade and travel. Of the total plant species recorded from India, 40 percent have been identified as being alien (Saxena, 1991). The list of alien species is increasing every year because of the large number of possible routes for alien species to enter and become established in the country. About 25 percent of the introduced species in India became invasive in a short period of time (50-100 years) (Murphy, 2001).

The main tree species introduced to India for forestry purposes include Eucalyptus (several species of which E. grandis and E. tereticornis dominate), Acacias (Acacia auriculiformis, A. mangium and A. mearnsii being the main species), Prosopis juliflora and Leucaena leucocephala. There are also several other minor species and some others introduced for non-forestry purposes. The extent of area planted under these species varies greatly between the different states and reliable data are unavailable for the whole country. Eucalypts were introduced in the late 1800s from Australia, mainly for raising pulpwood and fuelwood plantations. Eucalypus now comprises 25 percent of India’s plantation estate and is a major source of income for farmers in central and northwest India. Acacias were also introduced from Australia, and are used for reforesting disturbed lands, for timber, fuelwood, etc.

Of these introduced tree species, eucalypts and Acacias have not generally shown invasiveness and they generally demand a lot of care for proper growth. Although coppicing is a common feature for Eucalyptus, regeneration and spread are unknown. Likewise, though regeneration is a characteristic feature of A. auriculiformis and A. mangium, spread has not been observed. However, invasiveness has been recorded for the other three species in the list, viz. Leucaena leucocepahala, Prosopis juliflora and Acacia mearnsii. It must be mentioned here that the available information on the extent of invasion by these species, their positive/negative impacts, methods for management etc. are purely qualitative. Quantitative data have yet to be generated. There is also no comprehensive information on the extent of area planted with these species, their ecology and how they interact with indigenous species. Let us now consider the various aspects of these three tree species in some detail.

Leucaena leucocephala - Fabaceae

Leucaena, a native of southeastern Mexico, was introduced into Asia in the 19th century. The precise dates of its introduction to India are unknown. However, it became popular in the country as a versatile tree in the 1970s. The species has now been introduced and grown across all continents except Europe and Antarctica (Anonymous, 1980). Of the three subspecies of L. leucocephala, subsp. leucocephala is the only one widely introduced outside Mexico.

Rationale for introduction

Leucaena is a hardy species that can grow on a wide range of sites and soils (except highly acidic soils). It is used for a variety of purposes such as fuelwood, charcoal, pulpwood, fodder, furniture making, soil improvement, etc. The species is also used in reforesting watersheds and slopes and reclaiming marginal, disturbed and degraded lands. These are probably the reasons for its introduction to tropical and subtropical countries. It is considered to be essentially a tropical species, requiring warm temperatures for optimum growth.

Distribution in India

The species has been planted in 21 states and two union territories in the country. Extensive areas have also been planted with Leucaena in central and northwest India.

Leucaena as an invasive species

It is an aggressive colonizer of degraded and disturbed sites and spreads naturally through seeds, which are produced in large numbers (Hughes, 1998). The species is noted to grow gregariously outside plantation boundaries and agricultural areas in northwest, central and south India. Its weedy nature is mostly reported from the states of Karnataka, Andhra Pradesh, Tamil Nadu, Punjab and Rajasthan. Invasiveness is especially noted in agricultural situations, or when it is used in land rehabilitation. Outside India, Leucaena is recorded as a weed in about 20 countries where it has been introduced, including Philippines, Sri Lanka and Vanuatu (Baguinon et al., 2003; Weerawardane and Dissanayake, 2003).


Mechanical control through slashing is widely practiced, but because the species coppices readily, slashing has not been effective. Chemical control through use of 2,4-D and other herbicides has been attempted in some states but with limited success. Biological control has been considered in Hawaii (Smith, 1985) and South Africa (Neser, 1994), but discouraged by the economic importance of the tree. However, proposals for releasing a seed-feeding bruchid in South Africa are still under consideration (Neser, 1994). Formation of inter-specific hybrids with Leucaena esculenta and L. diversifolia is an impediment for biocontrol.

Prosopis juliflora - Fabaceae

Prosopis juliflora, a native of Central and South America, is a small to medium-sized evergreen or deciduous spiny tree, with a short, crooked trunk and large crown. It is highly regarded as a fuelwood source in many tropical countries. Prosopis occurs worldwide (in 52 countries) with wide distribution in South America, Africa, South and Southeast Asia and Australia (Anonymous, 1980). The tree was introduced in India in 1880, in Ananthapur district, Andhra Pradesh State, to solve the acute fuelwood crisis.

Rationale for introduction

Prosopis is a multipurpose tree used as timber, fuelwood, charcoal, animal feed and also for reclamation of wastelands and sand dunes. It is a tough and resilient tree, adaptable to all frost-free semi-arid climatic regions (Hocking, 1993). The species will coppice, pollard and regenerate rapidly and is suited to a wide range of sites and soil types. In India, Prosopis fulfils the fuelwood needs of millions of households.

Distribution in India

It occurs in 11 states and two union territories mainly in the semi-arid zones. Widespread occurrence is reported from Tamil Nadu, Andhra Pradesh and Karnataka states. Extensive areas of wastelands in the capital, New Delhi, are occupied by Prosopis.

Prosopis as an invasive species

Prosopis grows gregariously on abandoned agricultural lands and all types of degraded and wastelands. Its weedy nature has been reported in the states of Tamil Nadu, Andhra Pradesh, Gujarat, Haryana, Karnataka and parts of Uttar Pradesh. Goats, which feed on the pods, aid in dispersal and spread. The tree has been reported as a weed from many countries including Philippines, Sri Lanka and Sudan (Baguinon et al. 2003; Weerawardane and Dissanayake, 2003). Prosopis was introduced in Sri Lanka in 1880 for land reclamation. Currently it is reported to be spreading rapidly in the coastal belts of southern and western provinces. Widespread occurrence was also found in the Bundala National Park, severely affecting the ecosystem (Weerawardane and Dissanayake, 2003).

Socio-economic relevance of the tree in India

In parts of Tamil Nadu state (Ramanathapuram district), farmers find it profitable to allow growth and colonization of Prosopis in their dry lands compared with cultivating cereals and millets (Nambi, 2000 - personal communication). The trees are allowed to grow for a few years and are then converted to charcoal, thereby contributing significantly to the socio-economic situation in the state. A similar situation was also noticed in Ananthapur district in Andhra Pradesh and Bellary in Karnataka. Apart from providing means for farmer livelihoods, Prosopis also meets demands for fuelwood.


Eradication programmes against Prosopis have been attempted in several countries through chemical and mechanical methods but proved unsuccessful. In India, use of herbicides has been attempted in the past but no information is available on control measures adopted now. Because cutting promotes regeneration, mechanical methods of control cannot be recommended. Like Leucaena, inter-specific hybridization with a closely related species, Prosopis pallida is common and it challenges attempts for biocontrol. One reliable method of control is thinning and pruning of seedlings to less dense spacing, which accelerates the self-thinning process. This will promote growth of Prosopis and increase soil fertility through nitrogen fixing and decomposition of nitrogen rich litter. It is observed that the resultant growth of the ground cover (indigenous species) discourages or reduces establishment of Prosopis seedlings.

Acacia mearnsii (black wattle) - Fabaceae

Acacia mearnsii, a native of southeastern Australia, is one of the fast-growing trees of the highland tropics, widely used as a source of tannin, fuelwood, charcoal, poles and green manure (Anonymous, 1980). It is also used for soil erosion control and soil improvement. The species was introduced in India in the early 1800s and now occupies approximately 20 000 hectares in the country.

Rationale for introduction

Its multipurpose use and ability to grow in a broad spectrum of soils and sites prompted introduction. Black wattle is mainly grown in highland areas (altitudes above 1 000 metres) in the country. Tannin industries based on the species are operated in several tropical and subtropical countries.

Distribution in India

It is grown in the states of Andhra Pradesh, Assam, Karnataka, Kerala, Maharashtra, Meghalaya, Tamil Nadu and West Bengal. The species is known to occur in 25 countries in the tropical and subtropical regions of the globe. Extensive areas under black wattle exist in Brazil (200 000 hectares), South Africa (160 000 hectares) and East Africa (30 000 hectares). In addition to these, there are unrecorded plantings in agroforestry systems in many countries.

Black wattle as an invasive species

Black wattle is an aggressive colonizer due to its hardy nature and high competitive ability (Boucher, 1980). In India, invasiveness has only been reported from the states of Kerala and Tamil Nadu, but perhaps this only means that the invasiveness has escaped attention in other areas (Von Lengerke and Blasco, 1989; Sankaran, 2002). In most parts of the Nilgiris (Tamil Nadu), where it was introduced as early as 1831, it has virtually taken over the shola forests (southern montane wet temperate forests) and grasslands (Von Lengerke and Blasco, 1989). Khan (1978) has reported that bird diversity was extremely low in A. mearnsii plantations, compared with adjacent shola forests in the Nilgiris. Noble (1967) cautioned that planting of exotics like Acacia and eucalypts in the Western Ghats will be highly detrimental to the shola forest ecosystem. Black wattle is reported as a weed in several other countries including South Africa (Adair, 2002). The spread is helped by production of large numbers of seeds, which remain viable for several years. Seed dispersal is through birds and animals.


Seed feeding insects have been introduced in South Africa to control seed production of black wattle, which has been successful to a large extent. However, its value as a crop has produced protests against adopting biocontrol measures. Control measures are not attempted any where in India. The state forest departments are unaware of the magnitude of the problem of A. mearnsii invasion in the different states.

Invasiveness of Acacia mearnsii - a case study from Kerala

Acacia mearnsii was introduced in to the state of Kerala in 1981, with the main intention being the conservation of natural grasslands in high altitude areas. It now occupies approximately 3 200 hectares in the Munnar and Marayur forest ranges (at altitudes 1 000 metres to 2 200 metres) in the Idukki Forest Division. The tree is used locally as fuelwood, for poles, and as a shade tree in tea plantations. Collection of bark and gum by local people is also observed.

The establishment of plantations was mostly unsuccessful because the trees failed to grow on the shallow soils in the grassland due to root coiling. However, the trees eventually invaded adjacent natural shola forests, where soil depth was greater. The spread was facilitated by seed dispersal by birds and animals like bison and deer. The collection of tree branches by local people for fuelwood purposes also contributes to seed dispersal. Thus, A. mearnsii is well established in the shola forests, suppressing natural vegetation in most of the localities where it was introduced.

Surveys carried out by the Kerala Forest Research Institute (1999-2002) indicated that black wattle has invaded deep inside shola forests at Mannavan shola (altitude 2 400 metres), Vattavada (1 800 metres), Rajamalai (2 140 metres) and Kolukkumalai (2 480 metres). The current extent of spread is estimated to be around 10 percent of the original planted area in these localities. It is expected to attain unmanageable levels in the near future causing irreversible damage to the shola forest ecosystem.

Shola forests in the Western Ghats are very rich in flora and fauna (Nair et al., 2001). They are considered ecologically unique, because they harbour many endemic species. Some of these species are thought to be endangered or threatened (Table 1). There is great concern that black wattle may cause extinction of vulnerable and critically endangered species among these if its spread to the shola forests continues at the present pace. A careful study may reveal the extent of damage that has already been done.

Table 1: Rare, endangered and threatened species in montane shola forests of Kerala, India






Justicia notha


Critically endangered


Polyalthia rufescens




Pimpinella pulneyensis


Possibly Extinct


Vanasushava pedata




Arisaema barnesii




Vernonia heynei


Critically endangered


Helichrysum perlanigerum




Anaphalis travancorica




Vernonia saligna var. nilghirensis




Impatiens elegans


Critically endangered


Impatiens anaimudica




Impatiens denisonii




Euonymus angulatus




Elaeocarpus recurvatus




Rhododendron arboreum ssp. nilagiricum




Exacum courtallense




Actinodaphne salicina




Neolitsea fischeri




Medinilla malabarica




Sonerila speciosa




Eugenia calcadensis


Critically endangered


Syzygium densiflorum




Chionanthus linocieroides




Coelogyne mossiae




Isachne fischeri




Isachne setosa




Hedyotis buxifolia




Smilax wightii




Symplocos pendula




Valeriana hookeriana



The survey revealed the spread of A. mearnsii to Eravikulam National Park (2000 metres), a protected area, which is home to the endangered mountain goat, Nilgiri tahr (Hemitraegus hylocrius), (Rice, 1984). The species is planted in areas like Kattumala, Koyyamala and Kumarikkal (all approximately 2 500 metres in altitude) close to the Park from where it may have entered Eravikulam National Park. Previous reports show that the number of endemic species and the food species for the Nilgiri tahr in the grasslands decreased with the age of black wattle plantations in these localities (Karunakaran et al., 1998). For example, while the number of endemic species was 14 in the grasslands without A. mearnsii, it was only three in the grasslands planted with the species (10-yr-old plantation). Additionally, the number of weeds was more (22 species) under A. mearnsii compared with non-planted grassland (2).

Invasion of black wattle into Eucalyptus grandis and a Pinus-Cupressus mixed plantation at Gundumalai (Munnar forest range) has also been observed. A. mearnsii virtually suppressed growth of the plantation species, overgrowing and covering the entire plantation area. Use of the species as a shade tree in tea plantations in certain areas has accelerated its spread to new localities. In summary, the biodiversity of the shola forests in Kerala is under serious threat due to the unchallenged invasion by black wattle, necessitating the urgent adoption of control measures.

What makes a plant species invasive?

This is an open question for which satisfactory answers cannot be easily found. However, a few generalizations can be made from the available evidence. Small seed mass, production of a large number of seeds palatable to animals, short interval between seed crops, availability of fertile land for easy colonization, animal dispersal of seeds, high competitive ability and short juvenile period are a few of the important factors that promote invasion. Other factors like absence of natural enemies in the introduced area, ability to regenerate easily and thrive in a wide variety of sites and soil types and faster growth rate compared with indigenous flora are also significant. Early prediction of potential invasiveness of a species may help in preventing introduction of such species, but reliable tools are yet to be developed for such predictions (Dulloo et al., 2002).

Management of alien invasive trees

A lack of awareness among foresters, policy-makers and other stakeholders of the negative impacts of alien invasives is cited as a major impediment preventing their management (Boudjelas and Saunders, 2002). However, it may be noted that in certain cases, even if the negative impacts are known, control methods are not attempted in view of the large investment already made on these trees and the socio-economic benefits. Prosopis and Leucaena are possible examples of this from the Asia-Pacific region. More generally, the development and implementation of control/management methods are defeated by a general lack of qualitative/quantitative information on invasive trees present in each country, lack of skills and experience. It could also be due to a lack of information on existing tools. Another point is that worldwide, coordinated and cooperative approaches have never been made to understand the ecology of AIS and develop methods for their management (Boudjelas and Saunders, 2002). This has made sharing of information very difficult.

Given the background of the already known enemies, let us now examine whether there are any potential species that are awaiting their turn to become invasives in India? Data indicate that there are several tree species introduced to India for forestry purposes, which are weedy elsewhere, but not yet in the Indian situation. Foremost among these is Paraserianthes falcataria (L.) Nielson, which is a native of the Moluccas, New Guinea and Solomon Islands, and has been planted widely in South India. P. falcataria is reported to be weedy in the Seychelles islands (Dulloo et al., 2003). Likewise, Swietenia macrophylla King is another species that is weedy in Philippines and Sri Lanka (Baguinon et al. 2003; Weerawardane and Dissanayake, 2003). There may be many more. Because we know the potential of these trees to become weedy, attempts need be made at the earliest possible juncture to prevent their spread. Periodic cutting and removal of these trees and rapid replanting of gaps with seedlings of indigenous species may be practiced as a first step to arrest spread.

Future needs

Efforts are primarily needed to identify all the invasive tree species present in each region. Attempts also need be made to understand the population ecology and autecology of the species and to quantify the extent of invasion and the ecological and economic impacts. To facilitate this, cooperation between countries in each geographical region is necessary. Such cooperation will pave the way for information sharing, capacity building and developing practical guidelines for managing the tree weeds. Additionally, each country needs to review existing quarantine regulations and make necessary changes, so as to prevent accidental introduction of exotics. Countries should also make arrangements for raising awareness on invasives among foresters and the common public through its agencies. It would be ideal if national forest policies contained clauses for control/management of exotic invasive species. As far as control measures are concerned, an integrated approach involving biological, chemical and mechanical methods would prove more successful than the use of any single method.


The authors thank Dr J.K. Sharma, Director, Kerala Forest Research Institute, India for encouragement. Dr Sankaran also wishes to thank FAO for providing financial support to participate in the Asia-Pacific Forest Invasive Species Conference held at Kunming, P.R. China during 17-22 August 2003. Thanks are also due to Dr N. Sasidharan, Scientist, Kerala Forest Research Institute and Mrs. Parkruthy Srivastava, Divisional Forest Officer, Munnar for their help.


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Murphy S.T. 2001. Alien weeds in moist forest zones of India: Population characteristics, ecology and implications for impact and management.. In: K.V. Sankaran, S.T. Murphy and H.C. Evans (eds.), Proceedings of the Workshop on Alien Weeds in Moist Tropical Zones: Banes and Benefits, Kerala Forest Research Institute, India and CABI Bioscience, U.K., 20-27.

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Acacias - are they a threat as invasive species in the wet tropics?

B. Krishnapillay, H.C. Sim and M.A.A. Razak
Asia-Pacific Association of Forestry Research Institutes
Forest Research Institute of Malaysia


An invasive alien species has been described as a species that is new to a region and that has a negative impact on the new environment, ecologically, economically or socially. Invasive species have been reported to cause large economic losses, are threats to human health and welfare, and to sustainable development. The question now being asked is, "are the Acacias that have been introduced into the wet tropical regions beginning to prove to be invasive?" This paper expounds on the pro and cons of these Acacias and tries to provide a rational answer to this issue.

In Malaysia, there are two commercial species of Acacia introduced from Aru Island and New Guinea. These are the Acacia mangium and the Acacia auriculiformis. Acacia auriculiformis was introduced as an ornamental species over a hundred years ago and is now seen growing on vacant lands and in areas uninhabitable by other tree species. It is a durable species, less susceptible to rot than Acacia mangium. Acacia mangium on the other hand, is a promising fast-growing multipurpose tree species indigenous to northern Australia (Nicholson, 1981), as well as Papua New Guinea (Jones and Tham, 1980) and the islands of eastern Indonesia (NRC, 1983). It was first introduced to Malaysia (Sabah) as a firebreak species for the Pinus caribaea stands that were established in the early sixties (Lim, 1988). The species was later found suitable for plantation establishment due to its growth performance on a wide variety of soil and habitats (Tham, 1976; Nicholson, 1981). In Malaysia, both A. mangium and A. auriculiformis are classified as exotic species.

Properties of Acacias

Basically, Acacias are legumes. They nourish the soil by introducing/fixing nutrients such as nitrates into the soil, thus making the soil rich in nitrogen. The species are hardy and can survive on very lateritic and generally poor soils, where nothing else will grow. During their growth on such poor soils, Acacias help to enrich the soils and make them suitable for growing other more sensitive trees and crops. It is because of this very special characteristic of these species that they have been introduced as plantation species in Malaysia. In terms of wood properties, the wood is of reasonable quality suitable for normal and untreated garden furniture that do not come in direct contact with the ground. The wood is also relatively easy to work with, it has good bending and nailing properties and seasons well when the correct drying schedule is provided.

Commercial potential of Acacias

There is potentially a large market for certified Acacia products. Current applications include garden articles that are much sought after in France. In Japan, Acacia wood is also sought after for furniture, joinery and laminated floors for trucks etc. IKEA, the famous Swedish company, has started to use Acacia timber from certified sources for its furniture industry. The advantage of using Acacia is that the long-term availability of the timber can be safely ensured. Currently there is enough Acacia timber available that exploiting Acacia makes good commercial sense.

Ecological appeal of Acacias

There are a number of good reasons why commercial exploitation of Acacias - whether plantation-grown or from wildings - is an environmentally friendly and beneficial effort, regardless of the source.

Each cubic meter of Acacia timber extracted helps to preserve some indigenous/native trees in their natural habitat. Furthermore, Acacia is only planted on already degraded forestlands and this eliminates the need to clear native forest for establishing forest plantations. It is an excellent and ideal species to ameliorate soils that have been badly degraded such as tin tailings, bris-soils (a sandy, unstructured, soil type with low nutrient content and poor water retention qualities) and other heavily damaged types of soils. It helps to rehabilitate alang-alang (Imperata cylindrica) infested areas. In some cases it is used as a nurse tree in planting native species that need shade in the early stages of growth. Being pioneer species, when the native species canopy grows above the Acacia trees, the Acacia automatically fades off due to the shading effects. In a nutshell, Acacia plantations help to reduce the pressure on natural forests.

Diseases in Acacias of the wet tropics

Acacia plantations in the wet tropics are relatively free of disease, when compared with Eucalyptus (Old et. al., 2000). With extensive plantations being established with mono species of Acacia, fungal pathogens can be expected to be a problem in the future. The potential diseases of Acacia can be classified under four broad groups. These can be elaborated as follows:

· Foliar diseases

These include fungal spots, blotches, tip necrosis, powdery mildews and rust fungus. The rust fungus for example has been reported to be a serious problem in the plantations of Sabah. Effective fungicides are available to control such foliar diseases.

· Stem canker disease

The most common of the stem diseases is the pink disease that is very prevalent in rubber plantations. Methods to control stem canker are well established and hence it need not be viewed as a serious problem.

· Root rots

These root diseases are regarded as a serious threat to Acacia plantations in successive rotations. Such phenomena are severe, particularly when the roots from previous plantations are not completely removed. Particularly now, with the zero burning concept, roots are not completely removed and these pass on the root rot fungi to new plantings. The most common root disease noted is white rot fungi.

· Heart rot

Heart rot in Acacia is a seriously-studied disease of tropical Acacias. Trees affected by heart rot show stem defects and wasting away of the heartwood of the Acacia tree. When this disease strikes, the recovery rate for sawntimber is greatly reduced. However, if the timber is to be used for the production of pulp, such a defect is of minimal consequence. It is now believed that by proper selection of the appropriate provenance for specific sites, the attack of heart rot can be minimized or possibly even eliminated.

It is clear that plantation forestry based on Acacias in the wet tropics will have to consider diseases as a major factor in the management of stands for sustained productivity. The areas that warrant specific studies include nursery hygiene, silviculture, site management and tree improvement to minimize disease impacts during successive rotations.

Classification of Acacias in the tropics according to the source

According to where Acacias are found in Malaysia, they can be classified into three groups:

· Afforested plantations

This includes managed large-scale plantings on previously marginal land that includes alang-alang and belukar (shrub) land. Acacia, being a legume, grows best on nitrate deficient soils. It adds nutrients and thus improves the quality of the soils, while preventing laterization.

· Reforested plantations

These include plantations raised and managed on areas cleared of original primary native forest. On such soils the first rotation crops are very healthy and vigorous due to the presence of good amounts of leaf-litter and abundance of carbon and other nutrients present in the soil.

· Feral or wild plantations

Feral or wild plantations include trees that have proliferated on marginal land along the boundaries of plantations, forest clearings, rural areas and vacant land around town. Wild strains of hybrid Acacia (mangium x auriculiformis) can also be found on the peripheral zones between the Acacia plantations and rural settlements, where A. auriculiformis is grown for its ornamental value. As it is extremely hardy and prolific, Acacia gradually diminishes the potential rejuvenation of the original biota, which it colonizes in its early stages.

Are Acacias really invasive species in the tropics?

From the foregoing, what can be deduced as to the inherent feature of Acacias? Are they invasive or non-invasive? There are always two sides to a coin and, consequently, there are both pros and cons with anything we generally work with. What is important is that we have to evaluate whether the benefits outweigh the negative aspects of the species. We need to look at the problem in the right perspective, which relates both to the economic and ecological perspectives.

From the economic perspective, Acacia produces excellent fibres that are good for pulp and paper. Acacias are easy to establish in plantations and their rotation cycle is very short, compared with most of the native species found in the tropics. The trees, if properly nurtured, will also produce fairly good timber for furniture and other panel products. Because of its ease in establishment and quick growth cycles, long-term availability and sustainability of the species for the industry can also be assured, thus, making Acacias good candidates for plantations in the tropics.

From an ecological perspective, in the wet tropics, to date there has been no report that says that Acacias penetrate natural undisturbed forest. They have, however, been reported to colonize areas that are left vacant after very heavy disturbances such as mining and other activities, which render the soil totally unsuitable for other indigenous species. On such soil types, Acacias serve as soil erosion control species and furthermore enhance the quality of such soils by fixing nitrogen and improving the soil carbon content through shedding and accumulation of its leaf litter. It has been reported to be an excellent species to rehabilitate land overrun by alang-alang. Finally, in very open areas in the wet tropics, Acacias have been successfully used as nurse trees for the revegetation of such land with climax native species.


Therefore from the above, the following conclusions can be drawn in regard to Acacias:


Jones N. and Tham C.K. 1980. A report on the visit to some of the Acacia forest of Papua New Guinea and Queensland. FAO/UNDP-MAL/78/009. Working paper No. 2. Forest Research Centre Sepilok, Sabah. 33pp.

Lim M.S. 1988. Studies on Acacia mangium in Kemasul Forest. 1. Biomass and productivity. Journal of Tropical Ecology, 4:293-302

National Research Council. 1983. Mangium and other Acacias for the humid tropics. National Academy Press, Washington, D.C.

Nicholson D.J. 1981. The natural occurrence and conservation status of Acacia mangium Willd. Technical Note No.5. Forestry Department of Queensland. P.7

Old K.M., Lee S.S., Sharma J.K. and Yuan Z.Q. (2000). A manual of Diseases of tropical Acacias in Australia, South East Asia and India. Published by CIFOR, Bogor Indonesia. 104pp.

Tham C.K. (1976). Introduction to a plantation species, Acacia mangium. In: Proceedings of the Sixth Malaysian Forestry Conference, Sarawak Forest Department, pp.135-138

Pine wood nematode (Bursaphelenchus xylophilus) and other forest pathogens in Japan

Shigeru Kaneko
Kansai Research Center, Forestry and Forest Products Research Institute, Japan

This presentation summarizes the recent situation of some invasive forest pathogens in Japan, with particular emphasis on the notorious pine wilt disease caused by the pine wood nematode.

The pine wilt disease

The pine wilt disease, caused by the pine wood nematode (Bursaphelenchus xylophilus), is the most serious disease in Japanese pine forests. And the nematode is a typical example of an invasive pathogen.

The damage was first found in Kyushu, southern Japan in the early 20th century and quickly spread northward. At first, the cause of damage was considered to be the result of bark beetles. However, in 1971, the damage was demonstrated to be a wilt disease caused by a new pine wood nematode, which was thought to be endemic to Japan. In 1972, the Japanese pine sawyer was shown to be the vector of the nematode. In 1979, the pine wood nematode was first reported in North America, and the Americans thought, "we’ve been invaded from Japan". In 1981, the nematode was confirmed to be the same species that had already been found in North America in 1934.

At present, pine wilt is also causing serious damage to forests of China, Taiwan, and Korea. Very recently the nematode was also found in Portugal.

The nematode is widely distributed in North America, but American pines are resistant to it, so it causes no damage to American pines. The nematode is believed to have arrived in Japan in pine logs more than 100 years ago from North America. Conversely, chestnut blight invaded the United States of America from Japan more than 100 years ago, killing many American chestnut trees. However, Japanese chestnut is resistant to this pathogen.

Records over the period 1977 to 2001 show that the total amount of wood damaged by pine wilt was greatest in 1979. It was almost 2.5 million m3. Recently, it has been depressed to less than 1 million m3 a year. But this is still a severe rate of loss.

The northern limit of the distribution area of the pine wood nematode is almost exactly the same as the distribution area of its vector (the Japanese pine sawyer). Recently, the northern limit has not shifted much.

The disease cycle of the pine wilt disease is very unique. The causal nematode is carried by the Japanese pine sawyer (Monochamus alternatus) and invades pines when the sawyer feeds on new shoots of healthy pines. The pine wood nematode has several special characteristics, which impede the water conductivity of the xylem. Thus, this disease is caused by cooperative work between the nematode and the pine sawyer.

Phylogenetic comparisons among isolates of the pine wood nematode based on mtDNA have been reported by Hamaguchi et al. (2000). Bursaphelenchus mucronatus is a morphologically similar species to the pine wood nematode, but it has a very weak pathogenicity to pines. Both species belong to completely distinct groups from each other. In the pine wood nematode, B. xylophilus, three different lineages were found. This result suggests that there might be multiple invasions of the nematode from North America to Asia. Similar studies using larger samples are needed to know the exact root of the invasion of the nematode.

To date, enormous amounts of labour and money have been required for controlling this disease. However, complete control of the disease has not been achieved. The most important point in the control measure is the eradication of the source of infection. Spraying insecticide on pine forests at infection time is very effective, however the widespread application of insecticide has a large negative impact on the environment. Recently, control measures stressed the following two points:

1) concentrated control for important pine forests over a limited area; and
2) conversion of less important pine forests into other tree species.

Needle blight of Japanese cedar caused by Cercospora sequoiae:

Japanese cedar, Cryptomeria japonica, is one of the most important sources of lumber in Japan. Cedar seedlings, in central Japan, first exhibited signs of a needle blight around 1910. It has since spread throughout Japan as an epidemic disease. The causal fungus of the disease was confirmed as Cercospora sequoiae, which already had been found in the United States of America on the giant sequoia. Fortunately, appropriate control measures were established by spraying chemicals in nurseries.

Pitch canker of Ryukyu pine:

Pitch canker caused by Fusarium circinatum is known as one of most serious diseases of pines in California, southeastern United States of America and Mexico. In Japan, the pitch canker was found on Ryukyu pine in Amamioshima Island, southern Japan, in 1989, and now the disease appears in wider areas in the Ryukyu Islands. There has also been a recent Korean report (Lee et al., 1998) concerning an exotic pine. Careful monitoring of the extent of the damage is necessary because Japanese black pine is known to be susceptible to the pathogen. We are still unsure whether the disease was introduced from abroad or if it is endemic.

Examples of invasive insects to Japan:

Fall webworm (Hyphantria cunea) is a typical exotic pest that has invaded Japan from the United States of America. Since first found in 1947, widespread damage to endemic ornamental trees has occurred. Recently, beetles from Southeast Asia are causing damage to Japanese palm trees.

Threats to endemic species by some insects imported as pets:

Some insects imported as pets, mostly beetles with beautiful bodies, are causing a new problem (Makihara, 2003). Many escaped beetles attack Japanese plants, or mate with endemic species. These are a threat to genes of endemic species. A different regulation system is needed to address these problems.

Plant quarantine system in Japan:

Most of the forest products exported from Japan are wood-packing materials. The quarantine procedure for these differs, depending upon the importing country. Bonsai pines exported to the EU are first quarantined for two years at the growing site in Japan to check for rust diseases. The import of seeds, living woody plants and logs are subject to quarantine and a phytosanitary certificate issued by the exporting country is required. If any pests are found at the inspection, they are sterilized or the materials are incinerated. Completely processed lumber and wood chips are not subject to quarantine. Tree seedlings without soil, logs, and lumber can be imported from any country, except for certain tree species from some designated countries to guard against specific pests.

In spite of the quarantine system, it is possible that many exotic species are still entering Japan. Examples of detection of invasive pests at import plant inspection are as follows:


As a conclusive summary of this paper, the following points need to be emphasized:


The author thanks Mr H. Makihara and E. Irei for their kind supply of pictures used in the presentation made to the conference.

Assisted natural regeneration: countering the impact of Imperata grass infestation in the Philippines

Peter Walpole
Director, Institute of Environmental Science for Social Change, Manila, Philippines

Bio-invasive species in the Philippines are most evident in old areas of reforestation and plantations, where exotic species have been introduced and from where they have spread. Of the more than 60 exotic species identified, only eight are potentially competitors and invasive species, usually only where the forest is already degraded. Two of these species in particular are noted for invading degraded forest and retarding ecological succession. However, by far the greatest invasive species of degraded forest, especially such lands when subjected by migrants to shifting cultivation and seasonal fires, is Imperata cylindrica. This grass has taken over several million hectares of the Philippine uplands. There have been multiple attempts, using various different techniques, to regain these lands and bring them into productivity. However, one less-recognized approach is Assisted Natural Regeneration (ANR). ANR has been undertaken by the government on many sites, usually as pilot efforts to improve degraded forest. ANR is also carried out by some communities in Imperata - or locally known as cogonal - lands. This paper gives an overview of Imperata grass in the Philippines and a brief account of community management by the practice of lodging cogon.

The problem of Imperata infestation is that it primarily affects the uplands. The actual or potential area infested is about 9 million hectares of scrub and cogonal lands that are subject to shifting cultivation and occasional burning, although figures are not wholly comparable and compatible. The bio-geophysical impacts of Imperata include:

These all affirm the need for a return to the natural vegetation of a more utilizable and sustainable cover.

Looking at the management of the uplands over the last 50 years, there has been little focused effort to address the spread of Imperata. Corporate forest management fed lowland migration to the uplands, expanding the social need for slash-and-burn (1960s-1980s). The government never comprehensively focused on improving grasslands, when leasing grazing rights and the extent to which government focused on Imperata through reforestation was not socially adapted and had limited impact. Tenurial rights of some 20 million people began in the 1980s, but only recently impacted on a larger area. Such community based management established tenure, but limited good practice. ANR strategies have not been sustained nor made socially responsive. Though ecological and economic concerns are integral to the response, they are not the primary factor. The problem is the socio-political-strategic programming needed with commitment and accountability from the top.

The cultural history of the Philippines helps give some indications as to how Imperata infestation might be dealt with over time. There have been significant social migrations to the uplands over the past 50 years, either from the lowlands or neighbouring islands. In many cases, logging operations left behind a substantial workforce, without a livelihood. The migrants had little means to sustain the productivity of the land, nor little reason to invest for the long-term, as they were legally viewed as squatters. Only recently has tenure been granted to many of these shifting farmers, however, support skills for managing Imperata lands are lacking.

Traditional utilization of Imperata lands varies. In many areas in Northern Luzon, photographs at the turn of the nineteenth century show less forest around villages than is present today. Old people tell of the distances they had to go to collect wood and that the elders had started planting pine trees from the forests in abandoned uma. These woodlands are now part of the integral management of the terrace system, called batangan for the Kankanay or muyong for the Ifugao. Places for livestock are carefully managed by fire to enhance regeneration, without burning into the forest. Thousands of hectares of land are traditionally managed in this way. Much of the forest in the Philippines is within the cultural zone of indigenous peoples and more attention needs to be given to the indigenous management of grasslands and thus, return to better utilization.

Traditional Imperata minimization occurs in communities where there has traditionally been a long engagement and dependence on forest ecosystems that is not quickly disregarded. Slash-and-burn among traditional people is known as kaingin. Fields may only be planted for 2-3 years to avoid intensive use and family groups collectively decide the next field in rotation. Cogon is maintained in limited areas for household purposes such as re-roofing. Although croplands are now becoming more permanent due to multiple pressures, community practices may also include abaca planting and restocking of forest rattan. Such intensive land use, along with tree species, gives new aspect in agroforestry, while sustaining a relation with the forest and prevents the incursion of Imperata.

Looking more at national level development planning, plantation zones and production concepts such as the timber corridor concept have developed. One such plan is for the Caraga region in Northern Mindanao. The impacts, however, have not been well thought out: about 50 percent of one province becomes part of the plantation, it is expected to produce approximately 400 000 cubic meters of logs per year, 56 percent of the regional total. However, with indigenous peoples constituting 30 percent of the population and 65.9 percent of land area as ancestral domain lands, land utilization and productivity impacts a large area, with the concomitant loss of social cohesion and ownership.

The land conversion costs of Imperata lands call for an investment cost for the first rotation of approximately US$700 per hectare. Site preparation is 25 percent of the cost, with seedling releasing and weeding constituting an additional 25 percent. Less investment is needed for the second rotation. There are new technical options of soil sterilants for non-crop areas and multiple applications of non-selective herbicide but they have not been used on a large scale. The result is that secondary forest is often selected for the establishment of plantations, so that an immediate return from harvesting trees can be used for investment. However, a new culture of small tree farmers with 5-10 hectares is emerging. These farmers enjoy a comparative advantage over the large-scale plantations in labour inputs, biodiversity recruitment and diversification and greater silvicultural options.

The impact of plantations on Imperata land rehabilitation is not entirely clear. They can utilize Imperata land and may arrest degradation if they focus on improved site management. They may create local work opportunities and improve social services, while contributing to the national economy, in the short-term. However, long-term nutrient availability is depleted and it is unclear as to the impact on future sustainability options and ecological services. Furthermore, the broader area land use by local people and local government is weakened.

In summing up the experiences of the last fifty years, particularly in the area of social forestry transitioning to community-based management of the Department of Environment and Natural Resources, a number of points can be made. Local communities must ensure sustainability, where the community stake is not derived from the salaries and allowances received from DENR and externally funded projects. But, benefits have not accrued from what has been planted; hence, DENR management has generally failed to introduce ANR to communities.

Plantations and the recognition of existing land uses have often been in conflict, partly because people have devised methods for utilizing areas for agriculture with some trees and areas maintained for a specific purpose. The main conflicts, with plantation establishment are: unclear land tenure for Community-based Forest Management (CBFM) and Certificates of Ancestral Domain Claimants, and a lack of community consultation during the planning process.

Assisted Natural Regeneration may be found in areas where individual communities practice resource diversity and where Certificate of Land Ownership Agreements (CLOAs) are awarded by the Department of Agrarian Reform (DAR) for sites utilizing Imperata lands. The lodging of cogon and selected weeding are seen as best practices in these areas. The cost of ANR is a small percentage of conventional reforestation techniques. What needs to be highlighted are sites that engage communities. On the whole, programmes need to embrace the importance of ANR and establish the integral management of the uplands with communities wherein ANR has a major role.

Forest land plantations are being reviewed by DENR. Action is also being undertaken regarding CBFM, including monitoring and apprehension of illegal CBFM logging activities and demanding the accountability of officials for permits. There is a call for departmental coordination in the granting of upland tenure and reassessing community resource use permits and forest protection responsibilities. There are new efforts to create awareness and skills training and a redesigning of ANR programming. Further dialogue towards process-driven and action-oriented systems is needed along with developing venues for entering markets for timbers sustainably grown on rehabilitated lands.

Important requirements are to:

Infestation is not a one-time problem to be solved, but rather a condition to be managed. The utilization of multiple adaptive management approaches can result in better and long-term strategies in effective control of Imperata and assist regeneration in a more continuous manner by giving greater security to communities.

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