Improving Conservation Biological Control in Washington Specialty Crops

Paul Bergeron

doi:10.7273/000004415

Historically, management of codling moth (Lepidoptera: Tortricidae) in Washington apple orchards required use of pesticides. Pesticide use can cause outbreaks of secondary pests, such as spider mites. In the 1960s, Stan Hoyt introduced Integrated Mite Management, a conservation biological control program focused on selective pesticide use for conserving the predatory mite Galendromus occidentalis (Nesbitt) to reduce pest mite pressure, while controlling codling moth. However, significant changes have occurred in insecticide use and new technologies have been introduced, such as mating disruption. Management changes have coincided with a shift in predatory mite community composition to include a new predator, Amblydromella caudiglans (Schuster). Previous research suggests A. caudiglans is more pesticide sensitive, warranting updated pesticide selectivity recommendations to conserve this “new”-to-us predator in Integrated Mite Management. I examined pesticide non-target effects on phytoseiid predators used in Washington augmentation and conservation biological control. Results suggest commercially-available predatory mite species for augmentation biocontrol have differential selectivity to pesticides (Manuscript 1). G. occidentalis and A. caudiglans have similar, but not identical, pesticide sensitivity (Manuscript 2). Herbicide and surfactant non-target effects on G. occidentalis and A. caudiglans are limited, but select products cause high acute toxicity to both predators (Manuscript 3). With slight modifications, Washington apple growers can continue using prior selectivity recommendations. Previous research suggests natural enemies move between ground cover and orchard canopies. Additionally, non-pesticide management strategies, such as pollen provisioning or landscape manipulation, improve conservation biocontrol of generalist predators like A. caudiglans. Molecular techniques were used to examine plant resource interactions by a predatory mite community. Results suggest that a variety of plant resources are important across the growing season (Manuscript 4). To examine non-pesticide management strategies, I manipulated orchard herbicide strips to determine affects arthropod community abundance and movement into the orchard canopy (Manuscript 5). Predator abundance and movement moderately increased under herbicide strip manipulation regimes. My work suggests managing the predatory mite community, as opposed to G. occidentalis, can be accomplished with minimal changes to pesticide recommendations. Additionally, increasing focus on non-pesticide management, such as pollen provisioning or landscape manipulation, can theoretically increase conservation biocontrol services for managing secondary pests.

Improving Conservation Biological Control in Washington Specialty Crops

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