Effects of the bittering agent denatonium benzoate on the success of toxic baiting of pestiferous German wasps (Vespula germanica)

Abstract

Our aim was to study the effects of the addition of varying concentrations of the bittering agent, denatonium benzoate (DB), to toxic baits used for the control of German wasps (Vespula germanica). We tested the level of detection of different concentrations of DB by wasps, and measured the overall effectiveness of freeze-dried baits containing 0.1% fipronil and DB to control local wasp activity. The addition of DB concentrations higher than 10 ppm to fresh beef baits made them less attractive to wasps compared with controls. Lyophilized toxic baits containing DB 10 ppm and fipronil 0.1% were as attractive as control baits and reduced local wasp abundance by, on average, 74%. The results for lyophilized baits containing 0.1% fipronil but lacking DB were similar (average reduction: 80%). The addition of DB to toxic baits against Vespula spp. can bring about undesirable effects on toxic baiting efficacy. In the case of V. germanica, we suggest using the lowest concentration possible (i.e. 10 ppm or lower) that may still elicit an aversive response in humans and/or non-target species.