ARS Licenses Purple Bacteria to Battle Crop
Pests By Sharon
Durham December 13, 2007
A bacterium discovered by Agricultural Research Service (ARS) scientists that is toxic to Colorado
potato beetle larvae also was found in preliminary studies to be toxic in
varying degrees to gypsy moth, small hive beetle and tobacco hornworm. Now, ARS
has licensed the technology to
Innovations, Inc., of Davis, Calif., and
Natural Industries, Inc., of
ARS is the U.S. Department of
Agriculture's chief scientific research agency.
D. Shropshire-Mitchell, entomologist
Blackburn, and molecular biologist
Gundersen-Rindal, all at the
Invasive Insect Biocontrol and Behavior Laboratory in Beltsville, Md.,
found a new bacterial species called Chromobacterium subtsugae. The
group then found that the bacterium displayed toxicity to immature Colorado
potato beetles. Additional studies will be conducted to determine potential
toxicity to non-target insects.
Soil rich in decomposed hemlock leaves and collected from the Catoctin
Mountain region in central Maryland was the source of the C. subtsugae.
The team isolated the microbe by suspending samples of forest soil in water and
then plating it directly on growth medium. The unusual purple colonies were
then tested in a project to develop a more efficient way to test for toxicity
in Colorado potato beetle.
Other insects were also affected. While tobacco hornworm and gypsy
moth weren't killed by the bacteria, their weights were drastically reduced.
Weights of tobacco hornworms that were fed the bacteria-laced diet were 24
milligrams, compared to 119 milligrams for insects that didn't eat the
bacteria. Gypsy moths that ate the bacteria weighed 40 percent less than gypsy
moths that weren't exposed.
In previous studies conducted by Martin, C. subtsugae also was
found to be toxic, in varying degrees, to western corn rootworm, southern corn
rootworm, white flies, and diamondback moth. In July 2007, a patent was granted
for use of the bacterium as a biocontrol agent against those pests.