Meta-analysis and review of pesticide non-target effects on phytoseiids, key biological control agents

Authors: Schmidt, Rebecca; BEERS, ELIZABETH - Washington State University; SATER, CHRIS - Washington State University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2021
Publication Date: 6/25/2021
Citation: Schmidt-Jeffris, R.A., Beers, E.H., Sater, C. 2021. Meta-analysis and review of pesticide non-target effects on phytoseiids, key biological control agents. Pest Management Science. 77(11):4848-4862. https://doi.org/10.1002/ps.6531.
DOI: https://doi.org/10.1002/ps.6531

Interpretive Summary: Predatory mites (phytoseiids) are among the most important natural enemies of pests in agriculture and are the most studied natural enemies in the field of pesticide non-target effects. Understanding how pesticides affect natural enemies is key to integrating the use of chemical pesticides with the conservation of beneficial insects that reduce pest populations. Although there are many studies examining the effects of pesticides on phytoseiids, these studies have not been systematically reviewed in over 30 years, which excludes hundreds of new pesticides. Meta-analyses are a useful tool for quantifying trends across many scientific papers and a meta-analysis of how pesticides affect phytoseiids could indicate trends that growers can use to make improved and more informed pesticide application choices. Researchers at the USDA-ARS in collaboration with Washington State University conducted a meta-analysis summarizing research from 154 different papers on pesticide effects on phytoseiids. This analysis allowed specific insecticides, fungicides, and miticides to be sorted into least and most harmful categories. It also indicated that phytoseiid species differ in pesticide sensitivity, indicating that growers should be informed of the species that are important in their crop and location and adjust their spray programs accordingly. The project also highlighted key areas where more research is needed to optimize phytoseiid conservation, including examining effects of herbicides, newer pesticides, and several specific phytoseiid species that have not been previously studied

Technical Abstract: Knowledge of pesticide non-target effects on natural enemies is a key element of successful conservation biological control. Due to their importance in many agricultural systems worldwide, the phytoseiid mites are the most well-studied natural enemies in the area of pesticide selectivity. The wealth of literature associated with this topic allows for a thorough meta-analysis of pesticide non-target effects and may also indicate general trends relevant to many cropping systems. We conducted a meta-analysis using 2,386 observations from 154 published papers examining the impact of pesticides on lethal (adult and juvenile mortality) and sublethal (fecundity and egg hatch) effects. Insecticides and herbicides were equally harmful to phytoseiids, but research on herbicide non-target effects is relatively scarce. Specific insecticides, fungicides, and miticides were sorted into least and most harmful categories. Phytoseiid species also differed in sensitivity, with Galendromus occidentalis, Neoseiulus californicus, and Typhlodromus pyri among the least sensitive species. Variability in sensitivity may be in part due to pesticide resistance; the greatest differences between species were within older mode of action groups, where resistance development has been documented. It has been speculated that specialist phytoseiids, which closely associate with Tetranychus spp. spider mites, have more opportunities for resistance development due to their necessary proximity to a pest that rapidly develops resistance. Effect sizes were higher for generalist phytoseiid species, supporting this hypothesis. This meta-analysis highlights pesticide types (herbicides) and mode of action groups where more research is clearly needed. Our analysis also allows for more robust generalizations regarding which pesticides are harmful or selective to phytoseiids