Effectiveness of the Entomopathogenic Fungal Species Metarhizium anisopliae Strain NCAIM 362 Treatments against Soil Inhabiting Melolontha melolontha Larvae in Sweet Potato (Ipomoea batatas L.)

Abstract

The effect of fungal entomopathogen <i>M. anisopliae</i> strain NCAIM 362 against <i>M. melolontha</i> larvae in sweet potato was tested under open field conditions when crop management included compost supply and soil cover (agro-foil or agro-textile). Additionally, the effect of <i>M. anisopliae</i> same strain against <i>M. melolontha</i> was compared with the effect of α-cypermethrin under greenhouse conditions. Soil microbial community using Illumina sequencing and soil biological activity were tested as possible parameter influencing <i>M. anisopliae</i> effect. According to the results, compost supply and textile cover may enhance the effectiveness of <i>M. anisopliae</i> under open field conditions, while no effect of fungal treatment was detected under greenhouse conditions. Even if soil parameters (chemical composition, bacterial, and biological activity) were identical, the effect of α-cypermethrin against <i>M. melolontha</i> larvae was significant: lower ratio of larval survival and less damaged tubers were detected after the chemical treatment. Our results suggest that <i>M. anisopliae</i> strain NCAIM 362 is not effective to control <i>M. melolontha</i> larvae, further pieces of research are needed to test other species of the <i>Metarhizium</i> genus to find an effective agent for sustainable pest control in sweet potato.