Tank Mixtures Differentially Impact Survival of Predatory Mites used to Manage Western Flower Thrips

Abstract

Greenhouses contain a vast array of insect, mite, and disease pests primarily managed by applications of conventional and biorational pesticides including insecticides, miticides, and fungicides. However, biorational pesticides have a narrow range of pest activity. As a result, greenhouse producers tank mix to broaden application activity. Research has demonstrated that tank mixing can result in either synergistic or antagonistic interactions for targeted pests. However, the impact of tank mixing insecticides and fungicides on predatory mites, Neoseiulus cucumeris, used to manage western flower thrips, Franklinella occidentalis, is unknown. The objective of this research was to determine how mixtures of four different pesticides (Conserve, Avid, Cleary's, and Decree), alone and in all possible combinations affect predatory mite survival in a laboratory bioassay. Individual 2-day-old adult mites, isolated in a cell of a bioassay tray, were exposed to one of the 15 pesticide treatments, or a water control. Treatments were replicated 15 times. Trays were held in an environmental chamber and mite mortality was assessed after 24 hours. Mite mortality was differentially impacted by some pesticide treatments when compared with the water control. One pesticide mixture, Conserve + Cleary's, significantly reduced mite survival compared to other pesticide treatments or the water control. Up to 70% of the mites exposed to this treatment died. The combination of Conserve + Cleary's should be avoided as a tank mixture when the biological control agent, Neoseiulus cucumeris, is used to manage western flower thrips.