Resistance of oriental fruit moth (Lepidoptera: Tortricidae) to insecticides in apple orchards in southern Brazil

Abstract

Oriental fruit moth (Grapholita molesta) is the most important pest of apple orchards in Brazil. For many years, insecticides have been the only tool used for its control. The aim of this work was to characterize the management of apple orchards by the system for Assessment of Environment Impact of Agricultural Technology Innovations (AMBITEC-AGRO) and to relate it with the resistance status of G. molesta populations. Insecticide resistance was estimated by toxicology and enzymatic activities of glutathione S-transferase (GST), esterases (α-β EST), and acetylcholinesterase (AChE). The phytosanitary strategies adopted by the four apple production orchards in southern Brazil were analyzed in: Vacaria (RS population), Fraiburgo (SC1 population), São Joaquim (SC2 population), and Porto Amazonas (PR population). Oriental fruit moth field populations were reared in laboratory for bioassays with chlorpyriphos, carbaryl, deltamethrin, and tebufenozide insecticides and were compared with a reference susceptible population. Larval mortality rates were recorded for seven days. GST, α-β EST, and AChE assays were performed with third- and fourth-instar larvae. Results indicated that oriental fruit moth populations collected in Vacaria, Fraiburgo, and São Joaquim showed tolerance to carbaryl and chlorpyriphos, whereas the population collected in Porto Amazonas was more susceptible. SC2 and PR populations were more tolerant to deltamethrin, while RS and SC1 populations were more susceptible. No population was tolerant to tebufenozide. RS population showed the highest activity for AChE, GST, and α-EST. The findings of this study suggest that the AMBITEC-AGRO system was a suitable method to evaluate the phytosanitary activity of apple orchards and to relate it to the resistance status of G. molesta populations.