DICHLOROMETHANE ATTRACTS DIABROTICITE LARVAE IN A LABORATORY BEHAVIORAL BIOASSAY

A two-choice laboratory behavioral bioassay was used to demonstrate th at dichloromethane elicits the dose-dependent attraction of second-ins tar western and southern corn rootworms. Preliminary data suggest that second-instar banded cucumber beetles are also attracted to dichlorom ethane. An eluotropic series of 10 materials, including distilled wate r, ethanol, methanol, acetone, ethyl dichloroacetate, dichloromethane, diethyl ether, benzene, hexadecane, and hexane, was tested for attrac tion of western corn rootworm larvae. Dichloromethane was the only one attractive at all doses tested, and orthogonal comparisons revealed a quadratic trend (convex) for responses of larvae to increasing dose. Benzene and hexadecane also attracted larvae, but significantly fewer than dichloromethane, and only at three doses and one dose, respective ly. Orthogonal comparisons revealed no linear or quadratic trend for r esponses of larvae to increasing doses of either compound. Dichloromet hane is the first organic compound demonstrated to attract western cor n rootworm larvae in the absence of carbon dioxide. Carbon dioxide has previously been reported to attract western corn rootworm larvae eith er independently or when combined with other organic compounds, and th e sensitivity of our bioassay was tested by demonstrating the dose-dep endent attraction of western corn rootworm larvae to carbonated water as a carbon dioxide source. We have also demonstrated the attraction o f southern corn rootworm larvae to carbon dioxide and propose that car bon dioxide and dichloromethane behave analogously when they interact with chemoreceptor sites on larvae.