Selection and characterisation of Beauveria bassiana fungus and their potential to control the brown stink bug

Abstract

ABSTRACT The brown stink bug, Euschistus heros (F.) is one of the most important pests in soybean culture. However, its control has become difficult, due to the ineffectiveness and side effects of commonly used chemical insecticides. Entomopathogenic fungi has potential to be used to control brown stink bugs, with products already registered and marketed in Brazil. However, the natural low susceptibility of the brown stink bug to known isolates has led to the search for new isolates, under laboratory conditions. Thus, the objective of the present study is to select Beauveria bassiana isolates with high virulence against the brown stink bug and characterise their productivity in culture medium. The effect of some fungicides used in soybean crops on some fungi parameters was also evaluated. In addition, the efficiency of the fungi to control stink bugs was evaluated in a greenhouse. Among 24 isolates, Unioeste 76 isolate (B. bassiana lato sensu) was selected due to its higher insecticidal activity (96% insect mortality; 1 × 108 conidia/mL) and productivity in culture medium (5.2 × 109 conidia/g of rice). All fungicides affected the fungal parameters. In the greenhouse, soybean plants were sprayed with fungal suspension (1 × 108 and 1 × 109 conidia/mL) before and after infestation with adult stink bugs. After 14 days, mortality varied from 80 to 90%, respectively for treatment before and after infestation, proving the potential of the fungus. Therefore, field tests should be conducted with the formulated fungus.