Dallas, Texas -- Insects are probably more finicky than cats when it comes to their diets, so a Penn State insect toxicologist is targeting their taste buds in an effort to protect crops.

Dr. Christopher A. Mullin, professor of insect toxicology in Penn State's College of Agricultural Sciences, is working with corn rootworm to develop better methods of controlling this insect. Corn rootworm is the primary pest of corn in the United States. While its larva does most of the damage, this occurs beneath the ground and it is easier to target the adult beetle.

"Most pesticides are neurotoxins and must make it past all of the insect's defenses before they can effect the central nervous system," says Mullin. "Usually, hundreds of times more pesticide must be applied outside the insect so that a lethal dose can arrive at the proper location inside the insect."

To circumvent this problem, Mullin is looking at insect taste buds because they are a direct connection between the central nervous system and the outside. Insects are also specialty feeders, targeting one or two plant types as their primary food and starving if those plants are unavailable. Taste is very critical to insects.

Mullin does not know what insects perceive as taste, but he does know that chemicals considered sweet-tasting by humans are chemicals that stimulate feeding and, for the most part, chemicals that humans consider bitter-tasting put the beetles off their food.

One exception is cucurbitacin, an extremely bitter chemical found in the fruit skins and roots of squashes and other cucurbits. Adult beetles will feed on anything coated with cucurbitacin to the exclusion of other foods. Farmers currently mix ground-up squash rinds with pesticides to get the insects to ingest the pesticides.

"But purified cucurbitacins are too toxic to use and too water soluble to remain on the tiny pollen-like spheres sug
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Contact: A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
30-Mar-1998