Gut content analysis of arthropod predators of codling moth in Washington apple orchards

Abstract

Codling moth, Cydia pomonella (L.), is the key pest of pome fruits in many temperate areas of North America, Eurasia, South Africa, South America and Australia. Many predatory arthropods species are found in organic apple orchards of central Washington; here we use PCR-based gut content analysis of arthropod predators to identify predators that attack codling moth. Predators were sampled from tree canopies, tree trunks and from the understory and were homogenized in a lysis buffer to provide a template for direct PCR. PCR showed 8.9% of 2591 predators had preyed on C. pomonella. Spiders, including 25 genera from 15 families, two carabid beetle species (Pterostichus melanarius (Illiger) and Harpalus pennsylvanicus DeGeer) and the European earwig (Forficula auricularia [L.]) represented 87% of predator specimens analyzed and were 8.2%, 8.3% and 14.7% positive for C. pomonella. PCR products from 38% of predators that appeared positive for C. pomonella COI were sequenced; all showed 99% or more similarity to C. pomonella COI sequences in GenBank. Digestion rates of adult earwigs fed on mature codling moth larvae showed a detection half-life of 3.7 days; half-life from the fecal pellets from the same earwigs was 3.6 days. When fed mature codling moth larvae, the carabid P. melanarius showed a digestion half-life of 3.14 days. Identification of the key predators of C. pomonella can guide the use of selective insecticides and the conservation of these natural enemies, enhancing biological control and supporting stable IPM programs in pome fruit orchards in the western USA.

Comparing three types of dietary samples for prey DNA decay in an insect generalist predator

“…In a recent paper Unruh et al (2016) Yet, the question of the time it takes for prey DNA to travel through the digestive 281 tract of insects and how this varies across different taxa remains. Having a better 282 understanding about the temporal aspects of digestion in insects in general, and 283 particularly in carabid beetles is important.…”

Laboratory and field tests of predation on the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae)

“…Soon after, entomologists started using various PCR based techniques to accurately screen predator species on specific pest taxa using molecular gut content analysis (King et al, 2008). Several species-specific primers for important pest taxa, such as Colorado potato beetle, Leptinotarsa decemlineata Say 1824 (Coleoptera: Chrysomelidae) , rape pollen beetles, Meligethes aeneus (Fabricius, 1775) (Coleoptera: Nitidulidae) (Oberg et al, 2011), codling moth, Cydia pomonella (Linnaeus, 1758) (Lepidoptera: Tortricidae) (Unruh et al, 2016), flea beetles, Phyllotreta spp. (Coleoptera: Chrysomelidae) (Ekbom et al, 2014), cereal aphid, Rhopalosiphum spp.…”

From planning to execution to the future: An overview of a concerted effort to enhance biological control in apple, pear, and walnut orchards in the western U.S.

“…While codling moth is the key pest common to apple, pear, and walnut systems in the western U.S., our investigations focused on predation in apple orchards in Washington State as a representative system. Molecular gut content analysis showed that earwigs, spiders and carabid beetles were responsible for most of the predation events recorded (Unruh et al, 2016). Based on the information generated in this component of the project we can now prioritize conservation efforts for the natural enemies of codling moth, in addition to those of secondary pests, as our IPM programs evolve.…”