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. 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.
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. We are using three-dimensional chemical modeling to create structural templates of stimulatory and antifeedant chemicals. Finding the structural similarities between chemicals that stimulate feeding or between antifeedant chemicals will allow researchers to pinpoint the physical characteristics of the molecular shape needed to stimulate the neurons in the taste buds.