Laboratory studies on the infection of stink bugs with Metarhizium anisopliae strain FRM515

Abstract

We evaluated the effects of temperature and relative humidity (RH) on the pathogenicity of Metarhizium anisopliae strain FRM 515 to Plautia crossota stali. Low temperature decreased the pathogenicity of the fungal strain: its pathogenicity at 15°C was lower than that at higher temperatures. Mortality rates differed little among stink bugs kept at 80, 60, and 40% RH after treatment with a suspension containing 16×108 conidia/ml; however, when 1×107 conidia/ml was used, the LT50 value at 40% RH was 1.7 times that at 80% RH. Among three species of stink bugs, the susceptibility of Glaucias subpunctatus to M. anisopliae strain FRM515 was similar to that of P. c. stali, whereas Halyomorpha halys was relatively resistant to infection with this strain. [35S]Cysteine-labeled exuviae were degraded by a conidial suspension of M. anisopliae strain FRM515. The radioactivity in the medium increased from 24 to 30 h after treatment to the time when conidia germinated on the surface of the exuviae.