Effect of Collection Month, Visible Light, and Air Movement on the Attraction of Male Agriotes obscurus L. (Coleoptera: Elateridae) Click Beetles to Female Sex Pheromone.

Abstract

Simple SummaryWireworms are larvae of adult click beetles and can be major pests of many crops. The larvae live for several years in the soil and are difficult to manage, so additional control methods are being investigated, including the targeting of their adult stage, click beetles. For example, sex pheromones of female beetles can be used to attract males to a substrate treated with an insecticide. We examined whether the response of male click beetles to female sex pheromone is affected by environmental and seasonal factors i.e., beetles collected from the field in different months. Using small-scale lab experiments, we found that the beetles’ response to pheromone was not affected by light, but that air movement made them move faster. Exposure to pheromone made the beetles move more, but this did not vary with collection month, although beetles collected in May moved more slowly than those collected in March and April. In the field, male beetles were attracted up to 14 m from a pheromone source, the furthest distance tested. Understanding how beetle response to pheromone varies with these factors is important for the refinement of programs aimed at their management.Elaterid female sex pheromone, while currently used for monitoring the adult life stage (click beetle), has only recently been explored as a potential management tool. Consequently, there is little understanding of how abiotic and biotic conditions influence the response of click beetles to the pheromone. We examined whether the response of male Agriotes obscurus L. (Coleoptera: Elateridae) beetles to a cellulose-based formulation of female sex pheromone (‘pheromone granules’) is influenced by air movement, presence of visible light, and month of beetle collection. In addition, we investigated the distance from which beetles were attracted to the pheromone granules. Click beetle response was determined by measuring movement parameters in free-walking arena experiments. The response to pheromone was not affected by the presence or absence of visible light. We found that beetles collected earlier in the season had increased activity and interaction with pheromone under moving air conditions, compared to beetles collected later. When controlling for storage time, we confirmed that individuals collected in May were less active than beetles collected in March and April. In the field, beetles were recaptured from up to 14 m away from a pheromone granule source, with over 50% being recovered within 4.4 h from a distance of 7 m or less. Understanding how abiotic and biotic factors affect pest response to pheromone can lead to more effective and novel uses of pheromone-based management strategies.