Southern pine beetles colonize pine trees and lay eggs in galleries within the tree bark. They line these galleries with spores of a beneficial fungus and a bacterium. Inadvertently, they can also bring along parasitic mites and spores of an antagonistic (competitor) fungus. The antagonist fungus competes to colonize the tree, but carries no nutritional value for the larvae. As the beneficial bacterium spreads, it produces an antibiotic that inhibits growth of the antagonistic fungus.

Credit: Zina Deretsky, National Science Foundation

Adult southern pine beetle in flight.

Credit: Erich Vallery, USDA Forest Service Southern Research Station, Pineville, LA

Southern pine beetle larva in a gallery, another name for the place where the beetles lay their eggs. Within the gallery, which is prepared by an adult female, you can see a "lawn" of filamentous microbes. On the left is the fungus found inside the tree bark (red circle). The larva feeds on this fungus. Between the fungus and the larva is another filamentous organism, which is the bacteria (black square).

Credit: M. Cetin Yuceer, Mississippi State University

The researchers' findings are published in the Oct. 3, 2008, issue of Science magazine.

Credit: Copyright 2008 AAAS