Can Metarhizium anisopliae reduce the feeding of the neotropical brown stink bug, Euschistus heros (Fabricius, 1798), and its damage to soybean seeds?

Abstract

The fungus Metarhizium anisopliae is under development as a bioinsecticide for Euschistus heros. To further elucidate the effect of this fungus on E. heros behavior, we monitored the feeding activities of adults treated with the fungus at 1 × 108 conidia mL−1 on soybean in the pod-filling stage (R5) through electropenetrography (EPG) AC-DC. We also determined the virulence of M. anisopliae to adults and its damage to soybean seeds. M. anisopliae displayed high levels of virulence to adults even at low concentrations of 5 × 106 conidia mL−1 (98% mortality). E. heros females were more susceptible to M. anisopliae than males, exhibiting a lower LT50 for mycosed adults (7.1 and 9.7 days, respectively). The EPG experiment showed that fungus-treated adults spent significantly less time on probing activities (reduced by 86% at day four and ceased at day five) than untreated insects, and the number of waveform events per insect significantly decreased. This information is valuable for managing stink bugs at the field level, as it shows that even though the insect is alive, its feeding is compromised, consequently minimizing the damage inflicted to the crop. This study paves the way for further research employing entomopathogenic fungi in pest control.