Scientists discover bacteria aiding Southern pine beetles


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Posted: 10/6/2008


Researchers may have found the secret to controlling a tiny insect that robs Mississippi landowners of an estimated 12 million cubic feet of pine forest each year.

Though only an eighth of an inch long, the Southern pine beetle is a big pest and difficult to contain.

Scientists at Mississippi State University's Forest and Wildlife Research Center, along with colleagues at the University of Wisconsin-Madison, Harvard and the U.S. Department of Agriculture's Forest Service, have made a breakthrough with the discovery of an antibiotic-producing bacterium.

Beetles use the bacterium to protect their food against other microbes.

Published in the refereed journal Science, the research found that adult female Southern pine beetles carry a previously unknown bacterium. The bacterium produces a unique antibiotic that is highly effective against a fungus that can attack the beetles' food source.

"The beetles have established an association with a beneficial fungus," said Cetin Yuceer, forestry assistant professor and co-investigator in the finding. "Beetles bore holes through the outer bark of Southern pines to create galleries within the inner bark and phloem. During this process, the females inoculate the galleries with this beneficial fungus, which is carried in a specialized beetle storage compartment."

The fungus colonizes the galleries and serves as an important food source for developing beetle larvae, Yuceer added.

However, an antagonistic fungus can out-compete the beneficial fungus in these galleries and disrupt Southern pine beetle larval development.

"Our findings indicate that another beneficial connection also has been established between the Southern pine beetle and the newly discovered bacterium, which produces an antibiotic that inhibits the antagonistic fungus," Yuceer said.

Beetles are basically protecting their food from pathogens using a bacterium with a potent chemical inhibitor.

"Disruption of this newly identified relationship between Southern pine beetles and bacteria could be the way to control infestation of pine trees by beetles," said Jim Shepard, head of MSU's Department of Forestry.

"Southern pine beetles are extremely difficult to control, and practically no effective pest management tactics have been developed," Shepard added. Identifying beneficial associations, such as this one, could be an effective strategy in the search for new, bioactive natural products to protect plants, animals and humans.

"Perhaps some of those much-needed small molecules are waiting to be discovered in our backyard trees," Yuceer said.