Can Metarhizium anisopliae Reduce the Feeding of the Neotropical Brown Stink Bug, Euschistus heros (Fabricius, 1798), and Its Damage to Soybean Seeds?

The fungus <i>Metarhizium anisopliae</i> is under development as a bioinsecticide for <i>Euschistus heros</i>. To further elucidate the effect of this fungus on <i>E. heros</i> 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 <i>M. anisopliae</i> to adults and its damage to soybean seeds. <i>M. anisopliae</i> displayed high levels of virulence to adults even at low concentrations of 5 × 10⁶ conidia mL^-1 (98% mortality). <i>E. heros</i> females were more susceptible to <i>M. anisopliae</i> 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.