Unexpected Effects of Low Doses of a Neonicotinoid Insecticide on Behavioral Responses to Sex Pheromone in a Pest Insect

Abstract

In moths, which include many agricultural pest species, males are attracted by female-emitted sex pheromones. Although integrated pest management strategies are increasingly developed, most insect pest treatments rely on widespread use of neurotoxic chemicals, including neonicotinoid insecticides. Residual accumulation of low concentrations of these insecticides in the environment is known to be harmful to beneficial insects such as honey bees. This environmental stress probably acts as an “info-disruptor” by modifying the chemical communication system, and therefore decreases chances of reproduction in target insects that largely rely on olfactory communication. However, low doses of pollutants could on the contrary induce adaptive processes in the olfactory pathway, thus enhancing reproduction. Here we tested the effects of acute oral treatments with different low doses of the neonicotinoid clothianidin on the behavioral responses to sex pheromone in the moth Agrotis ipsilon using wind tunnel experiments. We show that low doses of clothianidin induce a biphasic effect on pheromone-guided behavior. Surprisingly, we found a hormetic-like effect, improving orientation behavior at the LD20 dose corresponding to 10 ng clothianidin. On the contrary, a negative effect, disturbing orientation behavior, was elicited by a treatment with a dose below the LD0 dose corresponding to 0.25 ng clothianidin. No clothianidin effect was observed on behavioral responses to plant odor. Our results indicate that risk assessment has to include unexpected effects of residues on the life history traits of pest insects, which could then lead to their adaptation to environmental stress.

Low doses of a neonicotinoid insecticide modify pheromone response thresholds of central but not peripheral olfactory neurons in a pest insect

“…In this study, we show that the dose-dependent modifications of pheromone-guided behaviour observed after clothianidin intoxication [17] might originate from the effect of insecticide treatments on the sensitivity of AL neurons to the sex pheromone. Indeed, single sensillum recordings and calcium imaging approaches show no significant effect of clothianidin at the used doses when compared with the corresponding solvent controls on the responses of individual ORNs and on the global input response in the AL.…”

“…For stimulation in calcium imaging and intracellular recordings, an artificial behaviourally active pheromone blend containing (Z )-7-dodecen-1-yl acetate (Z7-12:OAc), (Z )-9-tetradecen-1-yl acetate (Z9 -14:OAc) and (Z )-11-hexadecen-1-yl acetate (Z11-16:OAc) at a ratio of 4 : 1 : 4 was used [19 -21] in order to compare physiological results with the previously acquired behavioural data [17]. For single-sensillum recordings, only the major pheromone component, Z7 -12:OAc, was used, because ORNs are tuned to individual pheromone compounds.…”

The Sublethal Effects of Insecticides in Insects

“…However, there is still little information regarding the effects of sublethal dose/concentrations on insect behavior [21]. The sublethal doses of clothianidin on males of Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) presented a "biphasic effect" with increased or decreased male pherome response depending on the insecticide dosage [22]. Sublethal doses of deltamethrin on Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) antennae cause an increased male response to the sex pheromone (hormesis effect), but it did not affect the male response to the host plant.…”

Evaluation of the Efficiency of Certain Attractive Toxic Baits for the Control of the House Fly, Musca domestica (Diptera: Muscidac)

“…Previous works mentioned that LC 50 (84 Nano-gram/L) of imidacloprid to larvae of Aedes aegypti. Uragayala et al evaluated the Larvicidal effect of neonicotinoid insecticides against susceptible and resistant mosquito's strains [82][83][84][85][86][87][88][89][90][91][92][93][94][95][96].…”