Bacterium Curbs Several Insect Pests
Durham May 23, 2007
A bacterium discovered by Agricultural Research Service (ARS) scientists that is toxic to Colorado
potato beetle also has been found to be toxic in varying degrees to gypsy moth,
small hive beetle and tobacco hornworm.
Martin, molecular biologist
Gundersen-Rindal, and entomologist
Blackburn at the ARS
Biocontrol Laboratory, Beltsville, Md., and chemist
Buyer at the
Agricultural Systems Laboratory in Beltsville found and described the new
bacterial species, Chromobacterium suttsuga, now called
Chromobacterium subtsugae sp. nov. The group then found that the
bacterium displayed toxicity to Colorado potato beetle.
The findings are published in the May issue of the International Journal of Systematic and
Soil rich in decomposed hemlock leaves, collected from the Catoctin
Mountain region in central Maryland, was the source of the new species. 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.
Bacteria in the samples initially formed small and cream-colored colonies,
which gradually turned to light-to-dark violet from the center of the colony
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
reduced24 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
Martin and her colleagues will work to isolate the toxin from the
bacteria. Insects usually develop resistance to toxic substances, so it is
important to identify new toxins.
In previous studies conducted by Martin, Chromobacterium
subtsugae sp. nov. was also found to be toxic, in varying degrees, to
western corn rootworm, southern corn rootworm and diamondback moth.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.