Pheromone release and perception, and fertility of insecticide-exposed cotton boll weevils (Anthonomus grandis grandis)

The objective of this work was to evaluate the effects of sublethal exposure to the insecticides malathion and beta-cyfluthrin on the pheromone perception and emission by the cotton boll weevil ( Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae)). The potential impact of such sublethal exposure on this species population growth was also determined using fertility table parameters. Males and females were exposed to malathion at 10% of the label rate for 1 min, and to beta-cyfluthrin either at the full or 20% label rate also for 1 min. The response of insects exposed and non-exposed to pesticides to their aggregation pheromone (grandlure) was evaluated in Y-tube olfactometer and the pheromone production was evaluated. In order to evaluate the possible reproductive effects, the couples remained individualized for 48 hours and the females were subsequently evaluated until their death. The treatments were: 1) insecticide-exposed male and female; 2) exposed male; 3) exposed female; and 4) non-exposed males and females. Insects exposed to both insecticides did not show a response to their aggregation pheromone during the first 24 hours after the exposition. However, insecticide-exposed males did not have their pheromone production affected compared to non-exposed males. Sublethal insecticide exposure compromised the net reproductive rate (Ro) compromising the intrinsic rate of population growth (rm) of the cotton boll weevil.