By Barbara Liston
ORLANDO (Reuters) - Scientists trying to understand why destructive wood-eating termites are so resistant to efforts to exterminate them have come up with an unusually repugnant explanation.
Termites' practice of building nests out of their own feces creates a scatological force field that Florida scientists now believe is the reason biological controls have failed to stop their pestilential march all over the world.
A nine-year study concluded that termite feces act as a natural antibiotic, growing good bacteria in the subterranean nests that attack otherwise deadly pathogens, according to the findings published this month in the Proceedings of the Royal Society B.
"When they make a poop, it's not like they can throw it away and say forget about this. And over the millions of years of evolution it somehow evolved to take advantage of the poop there," said Nan-Yao Su, a University of Florida entomology professor and lead scientist and co-author of the study, along with Thomas Chouvenc, a University of Florida research associate.
Su also is the inventor of the popular Sentricon termite baiting and control system, which in 1995 became the first major alternative to liquid chemical treatments.
The findings could put an end to 50 years of failed research attempts to find a species of fungi that could kill termites when introduced into nests. Research repeatedly showed that fungi killed termites in a petri dish but not in the wild, Su said.
"Nobody was able to make it work in the field, but nobody would admit it," he said.
Su's goal was to find out why biological control never worked. His research colleagues determined that Streptomyces bacteria that are found in the nests and feed on fecal matter may be producing beneficial antimicrobial compounds that protect the termites from other potentially toxic matter.
Termites, mostly the voracious Formosans, cause $40 billion worth of damage a year worldwide, eating through wood structures particularly in Japan, China and the United States, Su said.
By the time a house is infested, the underground termite nest typically is 300 feet in diameter, hosting several million termites with a biomass weight of approximately 30 pounds, the weight of a medium-sized dog.
In one example, termites took nine months to bring down a new house in Hawaii built in the 1970s inadvertently on top of an untreated termite colony, Su said.
Further research will attempt to discover a way to bypass the protective compounds to destroy the termites, and to determine whether the findings can lead to new antibiotics for humans to replace those which have become ineffective.
(Editing by David Adams and Leslie Adler)