DEET Repels Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) Adults in Laboratory Bioassays1

Abstract

The potential of least-toxic compounds to repel adults of the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was explored. Bioassays in olfactometers and Petri dishes were designed to test the hypothesis that DEET (N, N-diethyl-3-methylbenzamide) can effectively repel H. axyridis adults. A bioassay in a y-tube olfactometer indicated that beetles spent significantly less time in the test arm (DEET; 10, 100, and 1,000 μg) than in the control arm (hexane blank) within a 10-min time frame. A bioassay in a 3-neck bulb-tube olfactometer indicated that significantly more beetles avoided the test arm (DEET, 142 μg) than the control arm (hexane blank) within a 40-min time frame. A bioassay in a Petri dish revealed that significantly more beetles avoided filter paper disks treated with DEET (0.1 and 1.0 mg/cm2; aged for 1 d or 5 d) than acetone (the control) within a 60-min time frame. Finally, another bioassay in a Petri dish revealed that significantly more beetles avoided filter paper strips coated with DEET/paraffin (1% or 9% mixture, aged for 1 d or 23 d) than camphor/paraffin (0.1, 1 and 9% mixtures, aged for 1 d or 23 d), or paraffin alone (the control). This investigation suggests that DEET has good potential for repelling H. axyridis adults and should be field-tested on urban structures.