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Management of Invasive Alien Species in Thailand
Napompeth Banpot
National Biological Control Research Center, Kasetsart University
P.O. Box 9-25, Chatuchak, Bangkok 10900, Thailand, 2004-07-01


Thailand has its share of damages caused by invasive alien species (IAS) which are of undesirable nature but have also gained economic importance as beneficial exotic and alien cultivated species. An inventory of IAS in Thailand conducted by the Thailand CBC Subcommittee Working Group on Alien Species under the then Ministry of Science, Technology and Environment revealed over 1,500 alien species of animal, plant and microorganism origins, including both invasive and beneficial species. Over 23 invasive insect species of economic and agricultural importance have been identified. In addition, more than 39 insect species of exotic origin have been introduced for biological control purposes in the country from 1963 to the present, of which 19 parasitoids and predators were for insect pests of agricultural importance, and 20 species were for biological control of terrestrial and aquatic weeds. Two strayed natural enemies, one each of Siam weed and lantana, were also detected naturally in Thailand. The overall management strategies for these invasive insect species are the adoption of integrated pest management (IPM) approach, ranging from "no action", "single-component control tactics", and to "integrated pest control".


Biological invasions are nothing new as far as the evolutionary process is concerned. Such invasions are characteristic of all living organisms and have occurred since the origin of animal and plant species and long before human existence on this planet. Biological invasions by plants, animals, and microorganisms are as equally ancient as human civilization, and are ongoing chronologically indistinguishable by man. However, biological invasions have lately become one of the major global issues of concern since June 1992 soon after the UNCED's Earth Summit held in Rio de Janeiro, Brazil. Among some of the important events that happened after that was the adoption of the Convention on Biological Diversity (CBD) which, after the required number of ratification by the signatories, was entered into force since December 1993.

Prior to the Earth Summit and during the period 1982 and 1988, the Scientific Committee on Problems of the Environment (SCOPE) engaged a large number of scientists in an effort to document the nature of the invasive species "problem" which has resulted in a book entitled "Biological Invasions: A Global Perspective" by Drake et al. (1989) (Mooney 2000). CBD Article 8h states that each Contracting Party shall, as far as possible and appropriate "present the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species."

In 1996, the concern that globalization was having negative consequences on the environment led the United Nations and the Government of Norway to convene the first international meeting on invasive alien species (IAS) in Trondheim, Norway. Participants in the "Trondheim Conference" concluded that IAS had become one of the most significant threats to biodiversity worldwide and recommended that a global strategy and mechanism to address the problem be created immediately. As a result in 1997, the Global Invasive Species Program (GISP) was established by SCOPE, IUCN (The World Conservation Union) and CABI (Commonwealth Agricultural Bureau International), and the UNEP (United Nations Environment Programme) presented the GISP project to the CBD parties and other participants at the Fourth Meeting of the Conference of the Parties (COP-4) in Bratislava, Slovak Republic in May 1998. GISP thus became a global network of scientists, lawyers, policy specialists, economists, managers, and environmentalists, supported by governments and foundations, and coordinated by IUCN, CABI, SCOPE and others. The GISP objectives are to assemble and make available best practices for the prevention and management of IAS and to stimulate the development of new tools in science, policy, information and education for addressing IAS problems (GISP, no date).

Thailand is as much concerned with IAS as other countries are. Canals, rivers, and water reservoirs all over the country are clogged and extensively infested with water hyacinth and some other exotic weed species. The Water Hyacinth Control Act was promulgated in 1913 in order to prevent further spread of water hyacinth which was introduced as an ornamental plant intentionally from Java, Indonesia in 1901. The country landscape is readily identifiable with exotic plant species, some of which are invasive while many others are of economic benefit to the country. Following the "Trondheim Conference" in 1996, the Thailand CBD Subcommittee Working Group on Alien Species was formulated and created in January 1997. In addition to compiling information and preparing an inventory of the non-indigenous species of organisms of animal, plant and microorganism origins found in the country, the main task of the working group is to provide consultation on the formulation of measures to prevent and control loss of biodiversity derived from and caused by the spread of IAS. The working group has also prepared the "Guidelines for the Regulation and Prevention of Biodiversity Loss due to Biological Invasions" as one of the practices for the prevention and management of IAS in the country, based essentially on the IUCN Guidelines for the Prevention of Biodiversity Loss Caused by Alien Invasive Species (IUCN 2000), Plant Quarantine Act 1964 amended in 1999, and the country's local encounter and experience on IAS problems (OEPP 2002).

An inventory of alien species in Thailand _ invasive, beneficial, and naturalized _ containing approximately 1,500 species, has been compiled and is available at An overview of alien species in Thailand was also given by Napompeth (2003) at the Regional Workshop on the "Prevention and Management of Invasive Alien Species: Forging Cooperation Throughout South and Southeast Asia" organized by the United States Government in collaboration with the Office of Environmental Policy and Planning (OEPP) and Thailand Biodiversity Center (TBC), National Science and Technology Development Agency (NSTDA) under the then Ministry of Science, Technology and Environment, on behalf of the Royal Thai Government, and the Global Invasive Species Program (GISP) in Bangkok on 14-16 August 2002 and by Napompeth, Kongsawat and Iamsupasit (2003) at the 20th Pacific Science Congress held in Bangkok on 17-21 March 2003.

Global Invasive Species in Thailand

Of the "100 of the World's Worst Invasive Alien Species," a selection from the Global Invasive Species database prepared by the Invasive Species Specialist Group (ISSG), there are 8 microorganisms, 4 aquatic plants, 32 land plants, 9 aquatic invertebrates, 17 land invertebrates (14 insects, 2 land snails, and 1 flatworm), 3 amphibians, 8 fishes, 3 birds, 2 reptiles, and 14 mammals (wild and domesticated). Of these global 100 world's worst IAS, only 38 species are present in Thailand. These are: 1 microorganism (Phytophora root rot, Phytophora cinnamomi); 1 aquatic plant (water hyacinth, Eichhornia crassipes); 13 land plants (African tulip tree, Spathodea campanulata; cogon grass or alang alang, Imperata cylindrica; giant reed, Arundo donax; hiptage, Hiptage benghalensis; Koster's curse, Clidemia hirta; lantana, Lantana camara; leucaena, Leucaena leucocephala; mile-a-minute, Mikania micrantha; mimosa or giant sensitive plant, Mimosa pigra; privet, Ligustrum robustum; Siam weed, Chromolaena odorata; wedelia, Wedelia trilobata; and yellow Himalayan raspberry, Rubus ellipticus); 1 aquatic invertebrate (golden apple snail, Pomacea canaliculata); 9 land invertebrates consisting of 7 insects (Asian tiger mosquito, Aedes albopicuts; big-headed ant, Pheidole megacephalatus; common malaria mosquito, Anopheles quadrimaculatus; Formosan subterranean termite, Coptotermes formosanus; khapra beetle, Trogoderma granarium; and sweet potato whitefly or tobacco whitefly, Bemisia tabaci), and 2 land snails (giant African snail, Achatina fulica; and rosy wolf snail, Euglandina rosea); 4 fishes (carp, Cyprinus caprio; Mozambique tilapia, Oreochromis mossambicus; walking catfish, Clarius batrachus; and Western mosquitofish, Gambusia affinis); 1 bird (Indian mynah bird, Acridotheres tristis); and 8 mammals (domestic cat, Felis catus; goat, Capra hircus; mouse, Mus musculus; nutria, Myocastor coytus; pig, Sus scrofa; rabbit, Oryctolagus cuniculus; ship rat, Rattus rattus; and small Indian mongoose, Herpestes javanicus). Of these more than 38 IAS, at least 1 microorganism, 5 land plants, 5 insects, and 1 fish totaling 12 species are supposed to be either endemic or are within the center of their origins. Some of the listed land plants such as lantana and wedelia are considered of ornamental importance. The rosy wolf snail, Euglandina rosea, native to Florida, USA, was introduced intentionally from Hawaii in 1973 for biological control of the giant African snail, Achatina fulica (Napompeth and Charernsom 1979). Two fish species, namely, carp and Mozambique tilapia were introduced as protein source while the mosquitofish, Gambusia affinis, was introduced during 1919-29 for biological control of mosquito larvae. The walking catfish, Clarius batrachus, is an endemic fish and forms a high-demand staple fish diet of the country.

One of the common phenomena in the issues of IAS is the "Conflict of Interest." Examples of such conflicts are imminent in exotic plant species. Ivy guard (Coccinia grandis, Cucurbitae), which is native to Central Africa, became naturalized in South and Southeast Asia to such an extent that it is either wild or semi-cultivated, but is considered a serious weed in Hawaii, USA. Likewise, the cluster eggplant (Solanum torvum, Solanaceae), which is probably native, wild and semi-cultivated in Thailand, became a serious weed in Papua New Guinea, Fiji, Hawaii and many Pacific Island countries.

This paper discussed issues pertaining to the management of invasive insect species of economic and agricultural importance in Thailand.

Invasive Alien Insect Species

In Thailand there is no estimate on the number of invasive alien insect species nor the number of all exotic insect species. The National Biological Control Research Center (NBCRC) of Kasetsart University could identify at least 23 plus serious insect pests of economic and agricultural importance to be IAS ( Table 1(1340)).

It is to be noted that only the sweet potato whitefly or tobacco whitefly, B. tabaci, in the 100 of the World's Worst Invasive Alien Species appeared in the list in Table 1(1340). This list is also not exhaustive and does not cover other exotic insects which may not be invasive and could have been naturalized. The degrees of invasiveness among them are also variable. Many insect IAS of recent invasions during the 1980s to 1990s such as spriraling whitefly, A. disperses; leucaena psyllid, H. cubana; and bean leafminers, Liriomyza spp. have already subsided in their devastation and economic status while those which have invaded longer have become occasional and minor pests. Few of the earlier and longer insect IAS of global importance such as the diamondback moth, P. xylostella, and mango leafhopper, A. atkinsoni, remain predominant and persistent as key pests of cruciferous crops and mango, respectively, in Thailand. Some insect IAS such as A. disperses, G. ficorum, and H. cubana have been successfully managed through introductions of specific and effective biological control agents, while biological control of P. xylostella failed successively although some of the introduced parasitoids have become established, and some species such as A. destructor, B. tabaci, I. purchasi, N. viridula and S. sacchari have been kept below economic threshold levels by endemic natural enemies.

Beneficial Invasive Insect Species

In addition to invasive insect species of economic and agricultural importance, since 1963 Thailand has introduced a total of 39 exotic insect species consisting of 19 insect species for biological control of various insect pests ( Table 2(1135)) and 20 insect species for biological control of both terrestrial and aquatic weeds ( Table 3(1321)). Additionally two exotic insect species, each known to be biological control agents of Siam weed and lantana, have been detected naturally without intentional introductions (Napompeth, 1982, 1989, 1990, 1992, 1994, 2001; Napompeth and MacDicken 1990). Ironically, these 41 exotic insect species could be considered "invasive" but "beneficial" on intentional basis because they have been utilized as biological control agents to overcome the target pest species which are invasive insect species. They are thus characteristically "beneficial invasive insect species" from the economic point of view.

As far as the insects intentionally introduced for biological control of both terrestrial and aquatic weeds are concerned, most of them are known safe agents having been earlier utilized in many instances worldwide (Julien and Griffith 1998). Each of them has been subjected to quarantine screening and host specificity test before the field releases were made. Almost all of them are phytophagous in feeding habit and the objective is to render them "invasive" on their respective and specific target weeds or host plants. This situation is also another classical case of "Conflict of Interest."

Insect Ias Management Strategies

There is no single or centralized national authority responsible for the prevention and management of IAS in Thailand. This responsibility is scattered among different ministries such as the Ministry of Agriculture and Cooperatives (MOAC) in the Department of Agriculture (DOA) for cultivated, ornamental and other plants, insects, soil microorganisms, plant pathogens, and biological control agents; Department of Livestock Development (DOLD) for microorganisms and animal pathogens of livestock, veterinary and epizootic importance; Department of Fisheries (DOF) for fish, aquatic animals and aquatic plants (freshwater, brackish and marine); Royal Forest Department (RFD) for other plants, shrubs, trees, animals and wildlife, and endangered animals listed under the Convention on International Trade in Endangered Species (CITES); Ministry of Public Health (MOPH) in the Department of Medical Science (DOMS) and the Department of Disease Control (DODC) for microorganisms, animal and insect vectors of human diseases, and causal agents of epidemiological importance; and Ministry of Commerce (MOC) for the import and export of certain kinds of fauna and flora. While the plant quarantine office is under the Department of Agriculture, the animal quarantine office is under the Department of Livestock Development. Both departments supervised quarantine services in all important international land, sea, and air ports and border posts as well as domestic animal quarantine stations located at key geographical locations.

The Working Group on Alien Species, created under the National Environmental Board Subcommittee on the Convention on Biological Diversity, is not an authorized legal body. Its function is more advisory and is tasked to:

  • Compile information on the status of alien species in Thailand;
  • Compile information and conduct investigation on the biology, ecology, and impacts of alien species in Thailand;
  • Prepare guidelines and measures for the control and eradication of those alien species affecting and causing economic damage;
  • Prepare guidelines to regulate the introduction of alien species including genetically modified organisms (GMOs); and
  • Undertake any task assigned by the CBD Subcommittee.

Management of Insect Ias

A classical case on the timely management of insect IAS was witnessed in Thailand in May 2003 in Bangkok when over 500 nymphs and adults of the Madagascar hissing cockroach, Gromphadorhina sp., were confiscated from a pet shop, the shopkeeper fined, and the cockroaches incinerated by virtue of the announcement of the Ministry of Public Health. The cockroach was smuggled into the country, reared and sold as "pet" animals. It was believed to be an insect vector and an intermediate host of several medical and public health pathogenic agents.

However, such a case cannot be simply applied to other insect IAS of agricultural, veterinary, medical, and public health importance. Most of the insect IAS of economic and agricultural importance identified in the country are amenable to various integrated pest management (IPM) strategies ranging from "no action" or "no control", to single-component control employing various control tactics such as physical, mechanical, cultural, genetic, chemical, biological, microbial and legal control, to integrated pest control (IPC) under the concept of "Integrated Pest Management (IPM)" which is defined by Kogan (1998) as "a decision support system for the selection and use of pest control tactics, singly and harmoniously coordinated into a [single] management strategy, based on cost/benefit analyses that take into account the interests of and impacts on producers, society and the environment." A similar and analogous approach has been initiated by the World Health Organization (WHO) as an "Integrated Vector Management (IVM)" approach, but so far no substantial progress has been achieved.

Thus, most insect IAS should be subjected to timely surveillance and monitoring suggested in simple but practical integrated pest management practices. The development of simple "economic threshold levels (ETLs)" for pest scouting is basically essential for the growers to make and reach their decision accordingly. Those insect IAS which are amenable to biological control will be tested for their potential, either as augmentative or classical biological control. Microbial control agents such as various formulations of Bacillus thuringiensis (Bt) are gaining their acceptance and more investments are being provided to strengthen research and development (R&D) in this field of insect pest control in Thailand. Commercial planting of transgenic crops such as Bt cotton is still prohibited, awaiting the drafting and enactment of biosafety laws.


The recommendations for the prevention and management of invasive alien species (IAS) developed at the South and Southeast Asia Regional Workshop on the Prevention and Management of Invasive Alien Species: Forging Cooperation Throughout South and Southeast Asia organized by the US Government, cohosted by the Royal Thai Government and held in Bangkok from August 14-16, 2002 could be appropriate for insect IAS as well. It was concluded that problems of invasive alien species (IAS) are causing significant ecological, economic, and social damages and pose ongoing threats to all countries within the region. It was recommended that the following actions related to the prevention and management of IAS be taken:

  • 1. Establish coordination mechanism and information exchange systems at national, regional, and international levels by the creation of IAS national focal points (NFPs) and through the Convention on Biological Diversity (CBD) Clearinghouse Mechanism (CHM);
  • 2. Ensure political commitment in terms of policy, legislation, enforcement, and implementation of activities to prevent and manage IAS initiated through national and regional strategies and plans;
  • 3. Initiate assessments of problems related to IAS and develop early warning and monitoring systems;
  • 4. Encourage appropriate and relevant research on IAS issues;
  • 5. Provide adequate financial and technical support from relevant national, regional, and international assistance agencies to address IAS;
  • 6. Build capacity in terms of human resource development and technology transfer to address IAS;
  • 7. Promote community participation and involvement in efforts to address IAS;
  • 8. Encourage partnership between public and private sectors in activities to address IAS;
  • 9. Promote awareness of IAS issues by convening workshops and seminars, as well as conducting publicity events and media campaigns; and
  • 10. Ensure the sustainability of IAS prevention and management activities in the region by developing long-term programs of action.


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  • Invasive Species Specialist Group (ISSG). No date. 100 of the World's Worst Invasive Alien Species. ISSG, Auckland. 12 p.
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  • Kogan, M. 1998. Integrated Pest Management: Historical Perspectives and Contemporary Development. Annual Review of Entomology 41: 243-270.
  • Mooney, H.A. 2000. Preface. The Global Invasive Species Programme (GISP), p. xiii. In: Economics of Biological Invasions. C. Perring, M. Willianson and S. Dalmazzone (eds.). Edward Elgar, Chetenham. 249 p.
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  • Napompeth, B. 1989. Biological control of insect pests and weeds in Thailand, pp. 51-68. In: Proceedings of Symposium on Biological Control of Pests in Tropical Agricultural Ecosystems. S. Sosromarsono et al. (eds.). BIOTROP Special Publication No. 36. Bogor, Indonesia.
  • Napompeth, B. 1990. Use of natural enemies to control agricultural pests in Thailand, pp. 8-29. In: The Use of Natural Enemies to Control Agricultural Pests. FFTC Book Series No. 40. Extension Bulletin No. 303. Food and Fertilizer Technology Center (FFTC), Taiwan. 32 p.
  • Napompeth, B. 1992. Brief review of biological control activities in Thailand, pp. 51-68. In: Biological Control in Southeast Asia. Y. Hirose (ed.). IOBC/SEARS. Kyushu University Press, Fukuoka, Japan.
  • Napompeth, B. 1994. Leucaena psyllid in the Asia-Pacific Region: Implications for its Management in Africa. RAPA Publication: 1994/13. FAO Regional Office for Asia and the Pacific (RAPA). FAO, Bangkok. 27 p.
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  • Napompeth, B. 2003. Thailand national profile report. A paper presented at the Regional Workshop on the Prevention and Management of IAS: Forging Cooperation throughout South and Southeast Asia, 14-16 August 2002 Bangkok. Organized by the US Government and co-hosted by the Royal Thai Government. (In press).
  • Napompeth, B. and K. Charernsom. 1979. Introduction programs for biological control in Thailand, 1973-1977. Technical Bulletin No. 1. National Biological Control Research Center, Kasetsart University, Bangkok. 11 p. (mimeographed, in Thai).
  • Napompeth, B. and K. MacDicken. (eds.). 1990. Leucaena psyllid: Problems and Management. Proceedings of an International Workshop held in Bogor, Indonesia. January 16-21, 1989. Winrock International/IDRC/NFTA, Bangkok. 208 p.
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Index of Images

Table 1 Invasive Alien Insect Species of Agricultural Importance in Thailand

Table 1 Invasive Alien Insect Species of Agricultural Importance in Thailand

Table 2 Insect Natural Enemies Introduced for Biological Control in Thailand

Table 2 Insect Natural Enemies Introduced for Biological Control in Thailand

Table 3 Insect Natural Enemies Introduced for Biological Control of Terrestrial

Table 3 Insect Natural Enemies Introduced for Biological Control of Terrestrial

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