Bug vs. bug: scientists use microorganisms to target destructive termites

April 11, 2002

ORLANDO, Fla., April 11 -- Government scientists are developing a new weapon against the Formosan subterranean termite, a highly destructive species that has caused millions of dollars in damage to houses and trees in the United States. Their findings were described today at the 223rd national meeting of the American Chemical Society, the world's largest scientific society. The method involves exposing the termites to their natural enemies, certain species of bacteria or fungi, which infect and kill the pests, said Maureen S. Wright, Ph.D., a research microbiologist with the U.S. Department of Agriculture's Agricultural Research Service, in New Orleans.

The development appears promising in laboratory tests and could provide an alternative or adjunct to pesticides, which might inadvertently harm the plants they are intended to protect, she said. In addition, it may benefit people who prefer not to use chemical pesticides in their home.

"Microorganisms represent an additional tool in the integrated pest management toolbox," said Wright.

According to the USDA, Formosan termite infestations have been found in 11 states: Alabama, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee and Texas.

Already, the Formosans have damaged large parts of the historic French Quarter in New Orleans, where they continue to wreak havoc on homes and many of the trees that line the city's streets.

Wright cautions that the new technology is not yet ready for marketing and continues to undergo refinement and further lab testing. Field-testing could begin as early as next spring, she said.

The Formosan termite is thought to have arrived in the continental U.S. nearly a half century ago. It is believed that the insects were first carried here as unwanted stowaways aboard wooden shipping crates carrying supplies home from the Pacific following World War II. Environmental factors here, including high humidity and moderate temperatures, allowed them to spread.

Environmental and health concerns have resulted in the removal of several chemical pesticides from the marketplace that were once effective in keeping the termites at bay.

In an effort to find an alternative, Wright and her associates turned to microorganisms, which are known to be natural pathogens of termites. The researchers screened hundreds of samples that are associated with the insects, including some that were collected from dead termites or found in the soil where they nest. Their ongoing search has produced three promising candidates so far: a bacterium (Bacillus) and two fungi (Metarhizium and Beauveria).

In laboratory tests, each candidate appeared to be highly lethal, with some strains killing 100 percent of a confined termite population within a one-week period, the researcher said. Similar methods using other microorganisms have taken up to four weeks to have the same effect and some never killed 100 percent, she said.

In addition to their potent killing power, the microorganisms offer a strategic advantage. They are self-propagating: Bacterial spores that attach to the bodies of the termites can be carried throughout their colonies, spreading to and killing the insects as the spores rejuvenate.

The researchers are currently trying to select these germs so that they poison the termites slowly. This approach gives the pathogens extra time to be distributed to more of the colonies' members by the termites themselves in an effort to destroy the entire colony, they said.

The microorganisms appear to work by literally eating away at the termites, most likely through an enzymatic degradation mechanism that breaks down their bodies, according to the researcher. Studies are ongoing to determine exactly how they work, Wright said.

If the tests prove effective, the germs could be turned into a powder or spray that could be directed at known termite infestations or possible hideouts. The microorganisms do not appear to be harmful to humans or plants, the researcher said.

This is not the first attempt to develop biological control agents for termites. Other labs are developing or refining similar techniques. However, Wright believes that her studies are producing more promising results to date.

"We still have a long way to go," she said, adding that the best weapon against these termites is probably an integrated approach involving a combination of biological control agents and chemicals.

The project is part of the USDA's Operation Full Stop, the government's multi-million dollar national program to control the Formosan subterranean termite. Known for its voracious appetite and massive colonies -- up to 10 million in a single colony -- this termite's territory continues to spread in spite of intervention efforts to stop it.

The USDA provided funding for this study.

-- Mark T. Sampson

The paper on this research, I&EC 319, will be presented at 1:40 p.m., Thursday, April 11, at the Convention Center, Room 304F, Level Three, during the symposium "Agricultural Applications in Green Chemistry: Application of Green Chemistry Principles in Agriculture."

Maureen S. Wright, Ph.D., is a research microbiologist with the USDA's Agricultural Research Service, Southern Regional Research Center, Formosan Subterranean Termite Research Unit, in New Orleans, La.

American Chemical Society

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