Ovicidal Effects of Organophosphate Replacement Chemicals on Plum Curculio (Conotrachelus nenuphar Herbst) Eggs
Middleton, Samantha M.
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Plum curculio, Conotrachelus nenuphar (Herbst), is a major pest of tart cherries (Prunus cerasus) in the United States east of the Rocky Mountains. This pest is currently managed through applications of organophosphate insecticides, but the Food Quality and Protection Act of 1996 (FQPA) has restricted use of these compounds. By the year 2010 use of organophosphates on tart cherries will be completely phased-out leaving a significant breach in the available control methods for plum curculio in this crop. For the tart cherry industry to remain viable, replacement pesticides must be developed. Previous research has focused on the control of this pest during its adult life stage, neglecting the possibility of control during the egg, larva, or pupa stages. This study presents research on the effects of various new pesticides as well as the effects of the currently relied on organophosphate pesticide, azinphos-methyl (Guthion®), on the egg stage of plum curculio. The suite of new pesticides tested includes: thiacloprid (Calypso®), thiamethoxam (Actara®), c10thiandin (Clutch®), novaluron (Rimon®), pyriproxifen (Esteem®), and indoxacarb (Avaunt®). Egg toxicity assays were set-up with concentrations of each pesticide ranging from 0 to 100 ppm. The number of hatched eggs was recorded and data were adjusted for mortality (Abbott, 1925). LC50 (lethal concentration at which 50% of individuals die) values were calculated using PROC PROBIT in SAS (SAS Institute, 2002). Pyriproxifen and indoxacarb did not show any variability in their dose-response relationships as compared to the control. Azinphosmethyl and novaluron were the most toxic of the compounds tested with an LC50 value of 0.44 ppm. They were followed in toxicity values by c10thiandin (LC50 = 32.07 ppm), thiacloprid (LC50=57.55 ppm), and thiamethoxam (LC50= 11,537 ppm). Targeting the egg with one of the insecticides (or combination) found to be effective in this study may be able to compensate for the loss of the organophosphates and protect the viability of the tart cherry system both in and outside of Michigan.