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

#### **Barna Putnoky-Csicsó 1,2, Szende Tonk 3, Attila Szabó 4, Zsuzsanna Márton 4, Franciska Tóthné Bogdányi 5, Ferenc Tóth 2, Éva Abod 1, János Bálint 1,\* and Adalbert Balog 1,\***


Received: 6 July 2020; Accepted: 20 July 2020; Published: 22 July 2020

**Abstract:** The effect of fungal entomopathogen *M. anisopliae* strain NCAIM 362 against *M. melolontha* larvae in sweet potato was tested under open field conditions when crop managemen<sup>t</sup> included compost supply and soil cover (agro-foil or agro-textile). Additionally, the effect of *M. anisopliae* same strain against *M. melolontha* 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 *M. anisopliae* effect. According to the results, compost supply and textile cover may enhance the effectiveness of *M. anisopliae* 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 *M. melolontha* larvae was significant: lower ratio of larval survival and less damaged tubers were detected after the chemical treatment. Our results sugges<sup>t</sup> that *M. anisopliae* strain NCAIM 362 is not effective to control *M. melolontha* larvae, further pieces of research are needed to test other species of the *Metarhizium* genus to find an effective agen<sup>t</sup> for sustainable pest control in sweet potato.

**Keywords:** field production; sustainable management; pest control; soil properties; microbial community; biological activity; soil DNA analyses; α-cypermethrin
