Laboratory Assessment of Plant Losses by <i>Sphenarium purpurascens</i> and Control with Entomopathogenic Fungi in Oil Emulsions

This study addresses the agricultural impact of the grasshopper <i>Sphenarium purpurascens</i> and evaluates the efficacy of entomopathogenic fungi (EPF), <i>Beauveria bassiana</i>, and <i>Metarhizium robertsii</i>, formulated in vegetable oil emulsions as sustainable pest control agents. The losses caused by <i>S. purpurascens</i> at different developmental stages (N4, N5, and adult) were assessed in five economically significant crops (<i>Medicago sativa</i>, <i>Zea mays</i>, <i>Helianthus</i> sp., <i>Cynodon dactylon</i>, and <i>Cucurbita pepo</i>), revealing a marked preference for <i>Helianthus</i> sp. and <i>C. pepo</i>, with consumption rates reaching 0.92 g/48 h during N4 and N5 stages, while adults showed preference for <i>M. sativa</i> (1.18 g/48 h) and <i>Z. mays</i> (1.15 g/48 h). The viability of EPF in oil emulsions (20% and 40% concentrations) was evaluated, demonstrating that formulations with <i>Azadirachta indica</i> and <i>Moringa oleifera</i> maintained over 99% fungal viability compared to the control absolute with distilled water (DW). The effectiveness of EPF against <i>S. purpurascens</i> adults was tested, with EPF on <i>M. robertsii</i> combined with <i>Persea americana</i> achieving 100% mortality within 72 h. Finally, the pathogenicity and dispersion of EPF in oil emulsions were evaluated, demonstrating that, at 240 h, the <i>B. bassiana</i> + <i>A. indica</i> strain (with three inoculated insects) achieved 100% mortality. It was observed that the number of inoculated adults directly influenced the mortality of <i>S. purpurascens</i>. These findings highlight the potential of EPF as a sustainable pest management strategy, emphasizing the need for further field trials to optimize its application and mitigate agricultural losses caused by <i>S. purpurascens</i>.