Alternative food sources for orchard predatory mites and effects on predation

Authors: Moretti, Erica; BERGERON, PAUL - Washington State University; JONES, CAMDEN - US Department Of Agriculture (USDA); THOMAS-ARCHER, KELLY - US Department Of Agriculture (USDA); Rehfield-Ray, Linda; Schmidt, Rebecca

Submitted to: Western Orchard Pest and Disease Management Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/29/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Predatory mites are important for pest control in orchards. When pest densities are low and predatory mites do not have prey to consume, their populations can decrease. One way to retain predatory mite populations when prey items are scarce is to provide alternative food sources that the predators can consume in the absence of prey. Alternative foods can include nectar, pollen, or other prey, such as insect eggs. Researchers at the USDA-ARS in Wapato, WA, with Washington State University, performed laboratory studies to determine how one predatory mite found in Washington orchards (Amblydromella caudiglans) performs on commercially available food sources, including pear, apple, and cattail pollen, brine shrimp cysts, and moth eggs. The goal of this research was to identify which foods or combinations of foods promote reproduction in the predator and whether the presence of alternative food affects predation rate on target pests, like twospotted spider mite. The predatory mite had the highest reproduction when fed pear and cattail pollen and could not feed on moth eggs. Combinations of foods did not enhance reproduction of this predator compared with the best performing single-sources. The presence of alternative food sources did not decrease predation of the predator on twospotted spider mite nymphs, except for brine shrimp cysts. This food appeared to require increased handling time by the predator, decreasing the amount of time it had available to feed on the pest. These results will help growers identify supplemental food sources that can be used to retain this predatory mite in orchards throughout the growing season, providing control of pests like twospotted spider mite.

Technical Abstract: The addition of alternative or supplemental food sources for natural enemies is a growing component of conservation and augmentative biocontrol. Supplemental foods can be used to retain natural enemies when prey are scarce and to promote survival, fecundity, longevity, and development of natural enemy populations, especially generalist natural enemies that benefit from a wide diet breadth. In laboratory studies, we evaluated the performance of the generalist phytoseiid mite Amblydromella caudiglans (Schuster) on commercially available supplemental food sources, including factitious prey Ephestia eggs and Artemia brine shrimp cysts, and pollens of apple, pear, and cattail. Amblydromella caudiglans is one of the most abundant predatory mites found in commercial apple orchards in Washington and contributes to both twospotted spider mite (Tetranychus urticae Koch) and European red mite (Panonychus ulmi Koch) control. Evaluations included measuring fecundity of A. caudiglans fed exclusively on alternative foods sources alone and in combinations and assessing how the presence of some supplemental foods affects predation on twospotted spider mite nymphs as well as other non-consumptive effects. We identified that A. caudiglans will not consume Ephestia eggs and performs best on cattail and pear pollens. Combinations of food sources do not enhance the performance of this predator compared to the best performing single-sources. The presence of alternative food sources does not decrease predation of A. caudiglans on twospotted spider mite nymphs, unless that food requires increased handing time by the mite (i.e. Artemia brine shrimp cysts). These results lay the groundwork for identifying a way to promote and retain this natural enemy in tree fruit cropping systems.