Updating integrated mite management fifty years later: comparing laboratory pesticide susceptibility of a “new” generalist predatory mite to a cornerstone specialist predator

Authors: BERGERON, PAUL - Washington State University; Schmidt, Rebecca

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2023
Publication Date: 5/3/2023
Citation: Bergeron, P.E., Schmidt-Jeffris, R.A. 2023. Updating integrated mite management fifty years later: comparing laboratory pesticide susceptibility of a “new” generalist predatory mite to a cornerstone specialist predator. Pest Management Science. 79(10):3451-3458. https://doi.org/10.1002/ps.7518.
DOI: https://doi.org/10.1002/ps.7518

Interpretive Summary: The management of apple orchards still requires the use of pesticides for the management of pests, including fungal diseases and insects like codling moth and aphids. Some of these products are known to cause outbreaks of pest spider mites because of the off-target effects on beneficial predatory mites. Researchers at the USDA-ARS laboratory in Wapato, WA and Washington State University determined what pesticides have non-target effects on Washington’s two major predatory mites. They found that captan was the safest fungicide for use with predatory mites. The safest group of insecticides for predatory mites were diamides. This information will allow growers to make pesticide use decisions that are less likely to impact their predatory mite community, reducing the need for additional pesticides to control spider mites

Technical Abstract: BACKGROUND: Historically, integrated mite management in Washington apple orchards has focused on the conservation of the predatory mite Galendromus occidentalis (Nesbitt) to reduce secondary pest mite pressure. However, pesticide use has changed to include more selective products, coinciding with a shift in the predatory mite community composition to include a new major predator, Amblydromella caudiglans (Schuster). There is evidence that A. caudiglans is more pesticide sensitive than G. occidentalis. Therefore, updates on pesticide selectivity recommendations are needed to conserve this “new” key predator. Using bioassays, we examined lethal (female mortality) and sublethal effects (fecundity, egg hatch, larval survival) of four fungicides and 11 insecticides on A. caudiglans, to determine if existing conservation recommendations can be applied to this predatory mite. Susceptibility was compared to prior research on G. occidentalis. Results: Mancozeb was the least selective fungicide tested on A. caudiglans; it caused high acute toxicity and sublethal effects. Carbaryl was the least selective insecticide and caused 100% mortality. Captan was the most selective fungicide. Chlorantraniliprole and cyantraniliprole were the most selective insecticides and therefore least likely to disrupt biological control by A. caudiglans. Non-target effects on A. caudiglans and G. occidentalis were similar, but A. caudiglans experienced higher mortality to some broad-spectrum insecticides. Conclusions: All products tested had some non-target effects on A. caudiglans. However, A. caudiglans sensitivity to most tested pesticides was similar to G. occidentalis. In general, existing spray recommendations for conserving G. occidentalis can be adjusted slightly and applied to A. caudiglans conservation