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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Publications at this Location » Publication #361772
Research Project: New Technologies and Strategies to Manage the Changing Pest Complex on Temperate Fruit Trees

Location: Temperate Tree Fruit and Vegetable Research

Title: Non-target impacts of herbicides on Tetranychus urticae and its predator, Phytoseiulus persimilis: implications for biological control

Author
item Schmidt, Rebecca
item CUTULLE, MATTHEW - Clemson University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2019
Publication Date: 4/10/2019
Citation: Schmidt-Jeffris, R.A., Cutulle, M. 2019. Non-target impacts of herbicides on Tetranychus urticae and its predator, Phytoseiulus persimilis: implications for biological control. Pest Management Science. 75(12):3226-3234. https://doi.org/10.1002/ps.5443.
DOI: https://doi.org/10.1002/ps.5443

Interpretive Summary: Most research that focuses on non-target impacts of pesticides on beneficial insects and other arthropods have specifically examined the effects of insecticides. There is very little information on how herbicides can harm natural enemies, despite this information being critical to growers who want to implement spray practices that best conserve their beneficial organisms. Researchers at the USDA-ARS in Wapato and Clemson University examined the effects of common herbicides on twospotted spider mite, a pest of many crops wordwide, and one of its most important predators, Phytoseiulus persimilis. The herbicides S-metalochlor, oxyflurofen, and dicamba were determined to be harmful to P. persimilis, while clethodim, halosulfuron-methyl, flumioxazin, and mesotrione were not. This information will allow growers to select herbicides minimally harmful to P. persimilis, reducing pesticide use by promoting biological control, which in turn will result in grower savings and decreased environmental contamination by pesticides.

Technical Abstract: BACKGROUND: A key element of conservation biocontrol is identifying and limiting use of pesticides that have substantial non-target effects on natural enemies to prevent biocontrol disruption. The Phytoseiidae (predatory mites) are one of the most studied natural enemy groups in the field of pesticide non-target effects. While there is substantial research on the non-target effects of insecticides on arthropod natural enemies, research on herbicide impacts is limited. Natural enemies, including phytoseiids, associate with weeds due to the presence of alternative prey, shelter, or floral resources. Therefore, a whole-systems approach to IPM should integrate weed management with biocontrol. We conducted a study to examine the non-target impacts of vegetable herbicides on Phytoseiulus persimilis Athias-Henriot, and the primary pest that it controls, Tetranychus urticae Koch. Two assays were used to assess the effects of direct application and walking on residues. RESULTS: In both assays, S-metolachlor was highly toxic to P. persimilis (80-90% mortality) and had minimal effect on T. urticae. Dicamba, oxyfluorfen, and napropramide also caused moderate levels of P. persimilis mortality (21-74%). Check mortality of P. persimilis was higher in the direct contact (19%) than the residue assay (3%). CONCLUSIONS: Halosulfuron-methyl, flumioxazin, and mesotrione were the most compatible herbicides with biocontrol by P. persimilis, whereas S-metolachlor and napropramide were the least compatible. We also determined that the residue assay may be more useful than direct contact slide-dips for future assessment of herbicide non-target effects. Future efforts should continue to examine the impacts of weed management on natural enemies to better integrate pest management practices.