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Colorado Potato Beetles May Succumb to the Glow

By Sharon Durham
October 26, 2001

A glowing bacterium called Photorhabdus luminescens reduced Colorado potato beetles by 100 percent in lab studies conducted by scientists with the Agricultural Research Service, making it a prime biocontrol candidate against this pesky beetle that attacks potatoes and other crops.

While studying bacteria to combat the beetle, microbiologist Phyllis Martin at the ARS Insect Biocontrol Laboratory, Beltsville, Md., found a strain of P. luminescens that outshone the competition. She received it from entomologist Michael Blackburn. At the Beltsville lab, Blackburn is investigating some of the toxins P. luminescens produces as potential biocontrols, while Martin is looking at the whole bacteria to control the beetle.

P. luminescens has a long history of interesting roles; it was suspected of causing wounds of some Civil War combatants to glow, thus providing a curative effect against infections caused by other microbes. It appears P. luminescens causes the beetles to stop eating, though the scientists don’t know why.

The potato beetle is notorious for developing resistance to insecticides, so ARS scientists are seeking non-chemical controls as possible natural insecticides. However, bacterial testing in beetles is difficult because beetles eat only in specific conditions that include particular temperature margins present in the field.

So ARS scientists developed an artificial diet for the beetles, a tool that will help researchers study this pest insect. Colorado potato beetle larvae cause most of the plant damage, because at this stage they chew--and eat--incessantly.

Since some pest insects are showing resistance to insecticides, scientists are seeking microbes such as P. luminescens as alternatives. Scientists will conduct more tests to determine the mechanism of control and if P. luminescens can successfully be transferred from the lab to the field.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.