Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2015
Publication Date: 11/1/2016
Citation: Mills, N.J., Beers, E.H., Shearer, P.W., Unruh, T.R., Amarasekare, K.G. 2016. Comparative analysis of pesticide effects on natural enemies in western orchards: a synthesis of laboratory bioassay data. Biological Control. 102:17-25. Interpretive Summary: Pesticides are often necessary to manage codling moth and other pests in apple orchards. Unfortunately, some pesticides can disrupt the natural pest suppression provided by predator and parasite enemies of pest insects leading to additional pest outbreaks and additional insecticide applications. Scientists from USDA ARS in Wapato in collaboration with scientists from the Universities of California, Oregon State University and Washington State University measured direct mortality and long-term effects on population growth rates of eight natural enemy species following exposure to eight pesticides. Six of the eight pesticides caused 80% or more mortality of at least one life stage in each of the eight natural enemies. Three pesticides (cyantraniliprole, lambda-cyhalothrin and spinetoram) caused populations to decline in all natural enemy species. The results of the studies are being implemented in a decision aid system to help growers and pest management consultants to use more biorational insecticides and better conserve beneficial natural enemies.
Technical Abstract: Pesticides are commonly used for management of codling moth and diseases in apple, pear and walnut orchards in the western U.S. and these pesticides may disrupt the biological control of secondary pests in these crops. A comparative analysis was made of results obtained from a series of studies of laboratory bioassays of acute mortality and life table response experiments to estimate the lethal and sublethal effects of eight pesticides on seven natural enemy species through use of stage-structured population models. This was made possible through use of similar protocols and measurements in each of the individual studies on single natural enemy species. Even though a number of the pesticides tested were reduced-risk products, all of them with the exception of copper plus mancozeb and chlorantraniliprole, caused more than 80% acute mortality of at least one life stage of one of the natural enemy species at a full field-rate concentration and could thus be considered moderately harmful according to the IOBC classification for laboratory bioassays. The mean intrinsic rate of natural increase of the natural enemy species was negative following exposure to cyantraniliprole, lambda-cyhalothrin and spinetoram, but was not significantly different from the control treatment following exposure to chlorantraniliprole, copper plus mancozeb and novaluron. For comparison among natural enemy species for a single pesticide, there appears to be considerable variation in response that can only be captured effectively from a full life table response experiment and a population-level endpoint, whereas for individual natural enemy species, their population-level response to the range of pesticides tested could frequently be captured by acute adult mortality alone.