Suitability of food resources for Proprioseiopsis mexicanus (Garman), a potentially important natural enemy in eastern U.S. agroecosystems

Authors: FARFAN, MONICA - Colorado State University; COFFEY, JOHN - US Department Of Agriculture (USDA); Schmidt, Rebecca

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2021
Publication Date: 4/26/2021
Citation: Farfan, M.A., Coffey, J., Schmidt-Jeffris, R.A. 2021. Suitability of food resources for Proprioseiopsis mexicanus (Garman), a potentially important natural enemy in eastern U.S. agroecosystems. Experimental and Applied Acarology. 84(2):121-134. https://doi.org/10.1007/s10493-021-00622-6.
DOI: https://doi.org/10.1007/s10493-021-00622-6

Interpretive Summary: Erythritol is an artificial sweetener that is safe for human consumption, which can can be produced as a USDA certified organic product. It has also been demonstrated to be an effective insecticide against a wide variety of pests, including the most serious pest of northwest pears, pear psylla. Mites, such as spider mites and rust mites, can also be difficult to control in pears. Because of this, researchers at the USDA-ARS in Wapato, in collaboration with Washington State University, conducted a study to determine if erythritol was effective against two spotted spider mite and pear rust mite. The researchers also examined whether erythritol was harmful to the western predator mite, an important predator of pest mites in pears. A 30% erythritol solution caused high mortality in both pest mites and caused spider mites to reduce movement. Erythritol solutions were much less harmful to the predatory mite, causing very little mortality. However, egg-laying and prey consumption were reduced, likely because erythritol also reduced predator mite movement. Because erythritol is more harmful to the target pests than the predator, it could likely be used to manage pear psylla and pest mites in pear orchards without substantially impacting predatory mite populations

Technical Abstract: Erythritol, an artificial sweetener, has shown promise as an organic, human-safe insecticide. Recently, erythritol applications were shown to be successful at controlling pear psylla (Cacopsylla pyricola (Förster)) (Hempitera: Psyllidae), the most important pest of pear in the Pacific Northwest, USA. Twospotted spider mite (Tetranychus urticae Koch) (Trombidiformes: Tetranychidae) and pear rust mite (Epitrimerus pyri (Nalepa)) (Trombidiformes: Eriophyidae) can also be highly damaging pear pests. Their common natural enemy, Galendromus occidentalis (Nesbitt) (Mesostigmata: Phytoseiidae), can provide biological control if selective pesticides are used for managing other pests. Through a series of bioassays, we sought to determine if erythritol could also be used for controlling either species of pest mite. We also examined whether erythritol had acute or sublethal impacts on G. occidentalis, through a variety of exposure methods. Effects examined included mortality, fecundity, prey consumption, and locomotion. We determined that a high concentration of erythritol (30%) had efficacy against both pest mite species and caused arresting behavior in twospotted spider mite. Erythritol caused little acute mortality in G. occidentalis, but did reduce fecundity and prey consumption through some exposure methods. Through motion-capture software, we determined that this is primarily due to reduced movement, likely caused by difficulty walking on residues and excessive grooming behavior. Because the predatory mite non-target effects were less acute than those for the two pest mites, we concluded that erythritol could likely be integrated into pear IPM with little or no disruption of mite biological control