Susceptibility and residual effect of indoxacarb formulations on major soybean lepidopteran pests
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Chysodeixis includens and Helicoverpa armigera can negatively impact soybean yield due to defoliation and direct injury on the pods, respectively. Insecticides, such as indoxacarb, are still an important controlling tool to manage these insects. To support Integrated Pest Management (IPM) and Insect Resistance Management (IRM) as well as to reduce product decantation during storage and nozzle clogging in field application, a new indoxacarb formulation (emulsifiable concentrate - EC) was developed to replace the suspension concentrate formulation (SC). The objective of this study was to evaluate the susceptibility and compare the residual effects of two indoxacarb formulations on C. includens and H. armigera on soybean. A dose-response curve and the residual effect from in-field application were obtained using a laboratory strain of both insect pests. Soybean leaflets were collected and dipped into aqueous indoxacarb solutions. The evaluations were performed 96 h after the infestation to calculate the insect mortality percentage and foliar damage. Also, plants were sprayed in the field and leaflets from mid and upper regions of the plants were collected and used to feed third-instar larvae of both species. Results demonstrated that C. includens and H. armigera are similary sensitive to indoxacarb. The residual activity was up to 1 h after application for H. armigera and up to 3 days for C. includens. No difference was observed on this activity between mid and upper regions of the plant. Overall, the enhanced EC formulation is as effective as the SC formulation for the control of both species on soybean.