Pathogenicity of an Entomopathogenic Fungus, Beauveria bassiana, to Eysarcoris lewisi (Distant) (Hemiptera: Pentatomidae)

Abstract

Eysarcoris lewisi is a plant bug that causes pecky rice. The virulence of 11 isolates of an entomopathogenic fungus, Beauveria bassiana, was compared by bioassays on adults, and four isolates showing high virulence were selected. The virulence of these four isolates was further compared by bioassays on adults and 4th instar nymphs, and isolate Nb-60, which showed high virulence against both stages, was selected. The virulence of this isolate to 2nd, 3rd and 5th instar nymphs was also examined by bioassays. LC₅₀ values of this isolate against adults, and 2nd, 3rd, 4th and 5th instar nymphs were estimated to be 5.4×10⁶, 7.1×10⁵, 2.0×10⁷, 1.3×10⁷, and 4.7×10⁶ conidia/ml, respectively. There were significant differences in the virulence of this isolate among nymphal instars, and it was suggested that these differences were related to days from inoculation to first ecdysis. Judging from these results and the ecological characteristics of E. lewisi around paddies, B. bassiana would be a good candidate for use as a microbial control agent against this bug.