Sublethal Effects of Neonicotinoid Insecticide on Calling Behavior and Pheromone Production of Tortricid Moths

In moths, sexual behavior combines female sex pheromone production and calling behavior. The normal functioning of these periodic events requires an intact nervous system. Neurotoxic insecticide residues in the agroecosystem could impact the normal functioning of pheromone communication through alteration of the nervous system. In this study we assess whether sublethal concentrations of the neonicotinoid insecticide thiacloprid, that competitively modulates nicotinic acetylcholine receptors at the dendrite, affect pheromone production and calling behavior in adults of three economically important tortricid moth pests; Cydia pomonella (L.), Grapholita molesta (Busck), and Lobesia botrana (Denis & Schiffermüller). Thiacloprid significantly reduced the amount of calling in C. pomonella females at LC_0.001 (a lethal concentration that kills only 1 in 10⁵ individuals), and altered its calling period at LC₁, and in both cases the effect was dose-dependent. In the other two species the effect was similar but started at higher LCs, and the effect was relatively small in L. botrana. Pheromone production was altered only in C. pomonella, with a reduction of the major compound, codlemone, and one minor component, starting at LC₁₀. Since sex pheromones and neonicotinoids are used together in the management of these three species, our results could have implications regarding the interaction between these two pest control methods.