PESTS OR PARTNERS?
AUGUST, 1996

Moths save Thai waters
Undoing a royal folly


By James Fahn reporting from BANGKOK

Few relationships are as ambiguous as that between humans and insects: sometimes they are allies, sometimes enemies.

In Thailand, no one knows that better than Banpot Napompeth, a US-trained entomologist and one of the country's leading experts on biological control. As executive director of the National Biological Control Research Center (NBCRC), during the last two decades he has overseen the importation of over 30 insects for use in controlling harmful pests and plants which have run wild.

Banpot is certainly aware of the dangers involved in importing foreign species. In fact, many of the projects he oversees are expressly designed to halt the rampant growth of plants and animals which have already found their way into Thailand and thrived at the expense of native species, and the local economy. But he believes the benefits outweigh the risks. "When people ask me about the dangers of biological control methods, I like to ask in return if they have considered the hazards of using pesticides and other chemicals," he explains. "Often, they haven't."

The most recent project carried out by the NBCRC entailed importing the water hyacinth moth (sameodes albiguttalis) to control the explosive growth of a plant which has clogged waterways and become a serious problem for both water-borne transport and dispersing flood waters.

The water hyacinth plant, native to South America, was originally brought to Thailand nearly a century ago by a royal consort, who came across it on a trip to Java and became entranced by its beautiful flower, according to Banpot. The plant was brought back to Thailand and clippings were handed out to favored friends.

When it began to grow prolifically, some of the plants were dumped in canals, from whence they have spread all over the country, and indeed the region. A few years after the plant was introduced to Thailand, a law known as the Water Hyacinth Act had to be enacted making it illegal to help propagate the water-borne weed. Nevertheless, and despite continuing efforts by the army, the navy and other authorities to clear the canals, the water hyacinth continues to run riot.

The humble moth has therefore been enlisted into the battle. It feeds on the leaves, and then lays eggs which hatch into larvae that eat the plant's innards, particularly parts vital to the plant's growth.

This moth is the third insect to be imported to Thailand by the NBCRC to control the water hyacinth. The mottled water hyacinth weevil (neochetina eichhorniae) was released in 1979 and the chevroned water hyacinth weevil (neochetina bruchi) in 1991. Both insects feed on the water hyacinth in a manner similar to the moth, and Banpot contends their release in Thailand has been successful. But he adds that the task they are charged with is simply too enormous to show quick results.

"The (mottled) weevil has become established in every release site. It has now spread all over Southeast Asia," explains Banpot. "But it hasn't contained the water hyacinth that well. Actually, it's a rather time-consuming process. The water hyacinth has been around for nearly a 100 years, and the weevil only 20. But I do believe it has been more successful than similar projects in the US. There is a much higher number of weevils per sample," he explains, picking up a rather wilted and battered- looking hyacinth plant being studied at the institute's main office on the campus of Kasetsart University in Bangkok.

Banpot pulls apart some of the shoots, displaying several weevils, which being nocturnal creatures scurry to get out of the sunlight. Then he points out some larvae buried deep in the core of the plant. "We brought the second and third predators because they feed on different types of hyacinth plants. The moth, for instance, goes after the smaller variety." He adds that these projects were also carried out at least partly for research reasons.

Like many of the insects imported by NBCRC, the water hyacinth predators originated in South America, but came to Thailand via research contacts in Florida. "Most of the weeds and plants which have infested Thailand originate in South America. If you talk about grasses, they usually come from the Mediterranean area," Banpot says. "And of course there are plants from Southeast Asia which have spread around the world and become pests elsewhere."

Although there are commercial outfits which sell insects that can be used for biocontrol, Banpot says he doesn't support them on principle. Insects, and presumably other species, should be considered part of the public domain, according to the researcher.

When biocontrol agents are first brought into Thailand, Banpot says they are run through extensive tests to make sure they only feed on the host at which they are aimed. "We run tests in quarantine with 30 different types of economic plants to see if the insects prey on them," he explains. "If there is any doubt about the results, we destroy the colony."

Asked whether he has ever been accused of bringing in harmful insects, Banpot says that just at the time the first weevil was brought in, there was an outbreak of a rice-eating weevil.

"Some non-scientists pointed the finger at us, but it was a different species. These water hyacinth weevils don't eat rice." Banpot has a kind of "insect cemetery" in his office where he preserves the original specimens of imported insects to be used as evidence in case of any future accusations.

Meticulous and self-confident by nature, Banpot's experience is useful in Thailand, where regulations are weak and outdated, and law enforcement often lax. Banpot also serves as chairman of the National Biosafety Council, but laments that he is often ignored by higher authorities.

Thailand's potential for developing biotechnology and using biocontrol is huge with its rich biodiversity and sizable pool of manpower skilled in medicine and agriculture. But of course it would take only one small mistake to create an environmental disaster.

James Fahn is the Environment Editor at The Nation, an English-language daily newspaper in Thailand.

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