Combining biocontrol agents with different mechanisms of action to control Duponchelia fovealis, an invasive pest in South America

Abstract Duponchelia fovealis (Lepidoptera: Crambidae) is a key-pest of strawberry, causing significant crop losses. In Brazil, the lack of registered chemical pesticides led producers to seek for alternatives. In this context, microbial insecticides can play a key role in integrated pest management (IPM) programs. This work aimed to assess the susceptibility to entomopathogenic fungi (EF) of two natural enemies of D. fovealis commonly present in Brazilian strawberry fields: Podisus nigrispinus (Hemiptera: Pentatomidae) and Harmonia axyridis (Coleoptera: Coccinellidae). Adult susceptibility of these predators to B2 and B3 isolates of Beauveria bassiana ((Balsamo-Crivelli) Vuillemin), and two commercial products (Bovemax® and Methamax®) was investigated under laboratory conditions. The mortality of the predators by direct and indirect contact with EF and the capacity of predators to feed on larvae of D. fovealis previously exposed to EF were determined. The number of larvae consumed by P. nigrispinus was reduced by the direct application of commercial products, whereas no differences among treatments were observed when EF were applied by residual contact. In the case of H. axyridis, a reduction in the number of consumed larvae was observed for the Bovemax® treatment applied by residual contact. A high mortality of P. nigrispinus was caused by the direct application of commercial products, whereas H. axyridis was not affected by any treatment or mode of application. In conclusion, this study suggests that combining biocontrol agents with different mechanisms of action could be used as strategy to reduce the incidence of D. fovealis in strawberry.