Field Evaluation of Selected Plant Volatiles and Conspecific Pheromones as Attractants for Agriotes obscurus and A. lineatus (Coleoptera: Elateridae)

SIMPLE SUMMARY: Wireworms are the larval stage of click beetles, and are serious pests of multiple field crops worldwide. Pitfall traps for collecting the adult (beetle) stage of these pests are commonly used to determine the risk of crop injury, or to remove beetles from a field before they mate or lay eggs, but such traps are only effective when baited with an attractant. These attractants are typically sex pheromones produced by female beetles and attractive to males, but two blends of plant-derived compounds attract females of some species. We evaluated the attractiveness of these compounds to male and female Agriotes obscurus and A. lineatus, species that are pests in both Europe and North America. However, both blends appeared to reduce captures, even when combined with the pheromones of these species. Similarly, combining the pheromones of these two beetles into a single lure reduced captures of both species. Our results indicate that attractants for female click beetles may be highly species-specific, and that combining pheromones of closely related species with each other or with plant volatiles can reduce trapping efficacy. The development of attractants for females of key pest species would greatly advance our ability to monitor and manage these pests. ABSTRACT: Sex pheromones are commonly used in traps to monitor populations and movements of male click beetles, but to date few attractants have been identified for females. Notable exceptions are plant-derived kairomones for female Agriotes brevis and A. ustulatus, allowing the monitoring of both males and females of these species with lures containing both pheromones and plant volatiles. The attractiveness of these plant volatiles for two congeners, A. obscurus and A. lineatus, which are agricultural pests in Europe and North America, was evaluated in the current study. Both the four-component MINIM plant-derived lure for A. brevis, and the blend of (E)-anethol and (E)-cinnamaldehyde for A. ustulatus, were not attractive to A. obscurus and A. lineatus, and instead appeared to reduce captures—both when compared to blank controls, and when blended with and compared to the sex pheromones of these species. This was most pronounced in A. obscurus, where (E)-anethol and (E)-cinnamaldehyde reduced male captures by 43 and 37%, respectively. Combining the pheromones of A. obscurus and A. lineatus reduced captures of these species by 77 and 19%, respectively, compared to these pheromones singly. This suggests that attractants for female click beetles can be highly species-specific, and that the blending of pheromones of congeneric species with each other, or with plant volatiles, can reduce captures. Further research into developing such attractants for economic species is urgently needed.