Molecular identification of arthropod predators of cucumber Beetles

Cucumber beetles (Coleoptera: Chrysomelidae) are abundant and damaging pests in cucurbits.  They can drastically reduce crop yields by a combination of herbivory and transmission of the pathogen that causes bacterial wilt.  The pathogen overwinters in adult cucumber beetles; thus, to minimize the spread of bacterial wilt, cucumber beetle populations must be controlled.  Traditionally this requires significant use of synthetic pesticides.  One way in which vegetable growers can become more sustainable and economical is by lessening their reliance on pesticides through the incorporation of conservation biological control.  The aim of such practices is to reduce pest pressure by increasing the activity, abundance, and diversity of predatory natural enemies.  Our goal is to identify the guild of predatory arthropods that contribute to suppression of cucumber beetles as a first step in designing specific habitat management strategies to enhance populations of these beneficial species.  Molecular gut content analysis using DNA-based PCR was used to elucidate the importance of wolf spiders (Araneae: Lycosidae) and harvestmen (Opiliones) as predators within the cucumber beetle food web. We found that 10% of wolf spiders (n = 203) captured in cantaloupe melon fields in Ohio in August 2014 had a detectable amount of striped cucumber beetle (Acalymma vittatum) DNA within their guts.  Harvestmen exhibit a similar predation rate.  Additional predators, including ants, ground beetles, lady beetles, crickets, and centipedes, as well as wolf spiders and harvestmen, were collected in 2015 and will be analyzed using molecular gut content methods to determine their contributions to suppression of cucumber beetles.