Insecticides for corn leafhopper management versus entomopathogenic fungal isolates: In vitro compatibility, physical-chemical interactions, and on-farm assessments

Abstract

This study is the first investigation of the biological compatibility of isolates IBCB 66 and Simbi BB15 of Beauveria bassiana and Esalq-1296 of Cordyceps fumosorosea, registered in Brazil for the management of corn leafhopper Dalbulus maidis, with synthetic insecticides used in the management of sucking insects in the initial growth stage of maize crops. The biological index was used to identify the most compatible synthetic insecticides with each fungal isolate tested and isolate IBCB 66 of B. bassiana was the most sensitive. In addition, most mixtures of synthetic insecticides with mycoinsecticides were physically compatible, except for the mixture of mycoinsecticide based on isolate Simbi BB15 of B. bassiana (OD formulation) with insecticides based on acephate, profenophos + cypermethrin, and dinotefuran + lambda-cyhalothrin, which showed absence of homogeneity. Field trials (on-farm assessments) of two-crop seasons indicate that compatibility of insecticides with mycoinsecticides is a key factor for the effectiveness of mixtures in D. maidis population suppression, reduction of incidence and severity of corn stunt complex (CSC), and yield of corn crops. The mixtures of imidacloprid + beta-cyfluthrin and imidacloprid + bifenthrin with mycoinsecticides based on B. bassiana (isolate Simbi BB15) and C. fumosorosea (isolate Esalq-1296) showed the best results in all parameters assessed. Thus, the association of mycoinsecticides with synthetic insecticides is a promising alternative for the management of the corn leafhopper and CSC pathosystem. However, the compatibility of synthetic insecticides is crucial for the success of the associated use of chemical and fungal agents.