Find in Library

Exploring the pathogenicity of a new fungus strain to non-target host pests can provide essential information on a large scale for potential application in pest control. In this study, we tested the pathogenicity of <i>Beauveria bassiana</i> PfBb on the important agricultural pest <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae) by determining the relative activities of protective enzymes and detoxifying enzymes in different larval instars. Our results show that the <i>B. bassiana</i> PfBb strain could infect all six larval instars of <i>S. frugiperda</i>, and its virulence to <i>S. frugiperda</i> larvae gradually increased with an increase in spore concentration. Seven days after inoculation, the LC₅₀ of <i>B. bassiana</i> PfBb was 7.7 × 10⁵, 5.5 × 10⁶, 2.2 × 10⁷, 3.1 × 10⁸, 9.6 × 10⁸, and 2.5 × 10¹¹ spores/mL for first to sixth instars of <i>S. frugiperda</i>, respectively, and the LC₅₀ and LC₉₀ of <i>B. bassiana</i> PfBb for each <i>S. frugiperda</i> instar decreased with infection time, indicating a significant dose effect. Furthermore, the virulence of <i>B. bassiana</i> PfBb to <i>S. frugiperda</i> larvae gradually decreased with an increase in larval instar. The activities of protective enzymes (i.e., catalase, peroxidase, and superoxide dismutase) and detoxifying enzymes (i.e., glutathione <i>S</i>-transferases, carboxylesterase, and cytochrome P450) in <i>S. frugiperda</i> larvae of the first three instars infected with <i>B. bassiana</i> PfBb changed significantly with infection time, but such variations were not obvious in the fifth and sixth instars. Additionally, after being infected with <i>B. bassiana</i> PfBb, the activities of protective enzymes and detoxification enzymes in <i>S. frugiperda</i> larvae usually lasted from 12 to 48 h, which was significantly longer than the control. These results indicate that the pathogenicity of <i>B. bassiana</i> PfBb on the non-target host <i>S. frugiperda</i> was significant but depended on the instar stage. Therefore, the findings of this study suggest that <i>B. bassiana</i> PfBb can be used as a bio-insecticide to control young larvae of <i>S. frugiperda</i> in an integrated pest management program.