Being Exposed to Acmella Oleracea-Based Insecticide Extract Reduces Mobility and Mating Success in Prostephanus Truncatus, the Major Pest of Maize in Storages

The evaluation of sublethal effects of botanical insecticides is a key tool to develop new strategies in pest management programs, since they potentially affect insect physiology and behavior. Acmella oleracea (L.) R.K. Jansen (Asteraceae) is a medicinal food plant widely used on an industrial level and with recognized efficacy against various arthropod pests and vectors. In this study, the sublethal effects of an A. oleracea hexane extract (HE) on the mobility, mating, and behavior of Prostephanus truncatus were investigated. The concentrations that killed 10, 30 and 50% of the exposed adults were 7.01, 19.5, and 39.5 mg/mL, respectively. The walking behavioral traits, i.e., duration and number of stops, and upside down (i.e., the time spent by the beetle on its back), were significantly higher in the adults exposed to LC30 than LC10 and control ones. The highest velocity was recorded for control beetles (21.5 mm/s), followed by LC10- (20.7 mm/s) and LC30-treated ones (21.2 mm/ s). Concerning lateralization, P. truncatus males were right biased during the mating sequence. Sublethal concentrations negatively affected the mating success of LC10- and LC30-exposed males in comparison with control ones. Overall, our findings outlined that the exposure of P. truncatus adults to A. oleracea HE LC10 and LC30 deeply affected their walking and mating behavior, a fact that should be considered further when optimizing pest management tactics in storages.