Effects of virulence, sporulation, and temperature on Metarhizium anisopliae and Beauveria bassiana laboratory transmission in Coptotermes formosanus

Abstract

Sporulation characteristics and virulence of Metarhizium anisopliae and Beauveria bassiana were examined in relation to laboratory transmission in Coptotermes formosanus. Fungal isolates significantly affected disease prevalence in termite populations. Sporulation of M. anisopliae played a more important role than virulence in producing epizootics within small groups of termites, but this was not the case for B. bassiana. Isolates characterized by quick sporulation (day 2 after death) did not exhibit better transmission in termites than those with high total sporulation (day 11 after death) in either fungal species. An isolate of M. anisopliae ranking highly in all three categories (virulence, quick sporulation, and total sporulation) produced better epizootics than an isolate that was inferior in all three characteristics. High temperatures (35 °C) significantly reduced fungal germination rates, leading to significant reduction of epizootics. M. anisopliae was better than B. bassiana in producing epizootics at 27 °C. Thus, fungal characteristics other than virulence should be considered for the seasonal colonization approach to termite microbial control.