An assessment of natural enemy populations relative to pesticide use in Wisconsin cranberry

The Wisconsin cranberry industry began implementing IPM practices in 1989. In part, Integrated Pest Management strives to more judiciously employ pest control materials that are less harmful to the environment. Especially, IPM practices are intended to conserve beneficial natural enemies of pest species. Within the last decade or so, there has been an increase in the number of reduced risk and bio-rational pesticides registered for use in cranberry. Many of these newer products have selectivity that favors survival of natural enemies. This study seeks to assess the impacts that these IPM practices have on natural enemies found in Wisconsin cranberry production. Fourteen farms, along the IPM spectrum and including four growing for the certified organic market, were sampled with sweep nets, yellow un-baited sticky traps and pitfall traps. A total of 16,493 predatory and parasitic insects and spiders were collected. Spray records of each farm were collected and incorporated into a toxicity score based on the EIQ formula established by Cornell University, both for a season toxicity score per farm and for a sample specific toxicity score per sample per farm. Farms were first compared based on toxicity scores and natural enemies. Simple linear regression analysis was performed on total beneficials, exclusively spiders, exclusively syrphidae flies and exclusively parasitoid wasps. Next, timing of pesticide applications relative to natural enemy population levels was examined. No significant relationship between toxicity scores and natural enemy abundance at the α=0.05 level was seen.