Potential use of Beauveria bassiana in combination with Scleroderma guani for improved control of Apriona germari

Abstract

Beauveria bassiana, an important entomogenous fungus, and Scleroderma guani, a hymenopteran parasitoid, are the two main biological control agents for managing the spread of Apriona germari. The aim of the present study was to assess the potential value of combining the two agents for the purpose of controlling A. germari. First, the relative virulence of B. bassiana against both A. germari and S. guani was determined. The results showed that among the seven strains of B. bassiana, isolate BI05, which was isolated from another cerambycid, was far more virulent against A. germari (mortality, 71.75%) than it was against S. guani (mortality, 34.82%). The parasitic efficiency of S. guani against the larvae of A. germari was significantly affected by the size of the host and the host to parasitoid ratio. In this study, third-instar A. germari larvae and a 1:3 host:parasitoid ratio of inoculation were used to evaluate the parasitization rate achieved by S. guani that were previously exposed to B. bassiana BI05. The mortality of A. germari treated with the previously inoculated S. guani was 73.30%. This was significantly greater than that of S. guani alone or B. bassiana alone (57.20% and 46.21%, respectively). The results indicated that the efficiency of both S. guani and B. bassiana are improved when used in combination, and this is promising for future control of A. germari.