UF review suggests new approaches needed if biological control of termites to succeed

July 20, 2011

GAINESVILLE, Fla. — It sounds like a pest control technician’s dream come true — eradicating hard-to-reach underground termite colonies by introducing small quantities of a pathogen or parasite, a practice called biological control.

But after 50 years of research, scientists have yet to deliver a successful method. Researchers’ efforts have been hindered by flawed experiments and lack of field testing, according to experts with the University of Florida’s Institute of Food and Agricultural Sciences.

Their findings appear in a review article published online this week by the journal Biological Control.

Subterranean termites account for 80 percent of the nation’s annual $4.1 billion in termite control expenses. Colonies can hold anywhere from 100,000 to 1 million of the wood-destroying insects, and miles of pencil-sized tunnels.

In past studies conducted at many institutions, researchers have experimented with fungi, bacteria, nematodes and viruses thought to be promising biological control agents, said Thomas Chouvenc, a postdoctoral associate with UF’s Fort Lauderdale Research and Education Center and the review’s lead author. In a typical study, termites in a confined space are exposed to an enemy organism, often at concentrations impossible to achieve in the wild.

“We can kill a bug in a jar, but the vast majority of these studies don’t describe any way to implement that approach in the real world,” Chouvenc said.

Distributing a pathogen or parasite in a termite colony is no easy task, said Nan-Yao Su, a UF entomology professor at the center and another author of the study. He developed a baiting system widely used to control subterranean termites.

The insects detect and avoid some fungal pathogens, and will close tunnels to confine threats. Other behaviors, such as constant grooming and removal of dead individuals, reduce the likelihood of pathogen transmission.

Among the 227 studies analyzed, many were authored by scientists who were not termite experts and probably had little understanding of the insects’ behavior, Su said.

Biological control of subterranean termites may be possible, he said, but researchers should learn from past mistakes — notably, the focus on soil-dwelling fungi as potential control agents.

“Termites have lived in the soil with those fungi for millions of years, and they have evolved a wide range of mechanisms to prevent the pathogens from spreading within the colony,” Su said. “You need something that has not co-evolved with termites.”

The key to success, Chouvenc said, might be finding a pathogen that can spread to other termites before its host dies, not after.

Both researchers say journals are often biased toward publishing studies that show positive results, meaning that scientists may not learn about unsuccessful experiments.

“We need to encourage negative reporting so we don’t replicate the same mistakes,” Su said.