Identification of arthropod predators of cucumber beetles (Coleoptera: Chrysomelidae) in cucurbit agroecosystems

  • Graduate Student: Molly Dieterich Mabin, Department of Entomology, Ohio State University. Email: [email protected]
Faculty Advisors:
  • Mary M. Gardiner, Department of Entomology, Ohio State University. Email: [email protected]
  • Celeste Welty, Department of Entomology, Ohio State University. Email: [email protected]
Project Period: 2015 – 2017


The predatory arthropod assemblage often differs between organic and conventional agriculture, in terms of abundance and richness. However, this does not always result in increased biological control of a pest species. Effectively integrating conservation biological control into IPM systems depends on accurate identification of the guild of predators that provide pest suppression services. Molecular gut content analysis techniques enable researchers to accurately determine key predators of a pest; such studies allow for observations to be made within an un-manipulated system. The aim of this study was to identify the guild of predatory arthropods that consume striped cucumber beetle, Acalymma vittatum, using PCR-based molecular gut content analysis methods. Predatory arthropods were collected from four organic and four conventional farms located in Ohio. DNA was extracted from all samples and PCR used to amplify A. vittatum DNA, if present within the gut contents of a sample. In addition, predatory arthropods were sampled at each farm using pitfall traps. Of 1,215 predators tested for the presence of A. vittatum DNA, 139 were positive (11.4%). Approximately 40% of Coccinellidae, 14% of Opiliones and Carabidae, 6% of Lycosidae and Chilopoda, and 1% of Formicidae and Staphylinidae tested positive for A. vittatum DNA. A greater proportion of predators tested positive earlier in the growing season than later in the season. We found no effect of organic versus conventional management on the proportion of predators testing positive. Pitfall trap collections indicated that predatory arthropods are more abundant earlier in the season than later on organic farms, and that predator abundance does not change throughout the season on conventional farms. This study is the first to use molecular gut content methods to identify the guild of predators that consume A. vittatum. This identification of cucumber beetle predators is a first step toward efficient incorporation of conservation biological control practices into any cucurbit production system.

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