Maryland mountain soil yields biological control agent

05/23/2007 02:00:00 AM

Scientists have discovered a bacterium living in soils rich in decomposed hemlock leaves is a powerful biological control of gypsy moth, small hive beetle and Colorado potato beetle.

Microbiologist Phyllis Martin, molecular biologist Dawn Gundersen-Rindal, and entomologist Michael Blackburn at the Agricultural Research Service's Insect Biocontrol Laboratory in Beltsville, Md., and chemist Jeffrey Buyer at the Sustainable Agricultural Systems Laboratory in Beltsville found and described the new bacterial species, Chromobacterium subtsugae sp. nov.

They found the bacterium in the Catoctin Mountain region in central Maryland. The team isolated the microbe by suspending samples of forest soil in water and then plating it directly on growth medium that doesn't contain glucose.

Fifty percent of small hive beetles died within five days when fed a pollen-based diet containing the bacteria, and the survivors weighed only 10 percent as much as small hive beetles that weren't exposed to the bacteria.

Tobacco hornworm and gypsy moth weren't killed by the bacteria, but their weights were drastically reduced due to feeding inhibition. Weights of tobacco hornworms that were fed the bacteria-laced diet were drastically reduced—24 milligrams for bacteria-treated insects compared to 119 milligrams for insects that didn't eat the bacteria.

Gypsy moths eating the bacteria weighed 40 percent less than gypsy moths that weren't fed the bacteria.

Martin and her colleagues will work to isolate the toxin from the bacteria. Insects typically develop resistance to toxic substances, so it is important to identify new toxins.



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