| Summary: | There is an urgent need to develop biological control methods against the eriophyoid mite, <i>Phyllocoptes gracilis</i>, which causes significant losses in organic raspberry production in Europe. The use of entomopathogenic fungi (EF) is a sustainable alternative to conventional chemical pesticides, reducing the risks of pesticide resistance and other negative environmental impacts of agriculture. The objective of this study was to assess the pathogenicity of three strains of EF, two of <i>Beauveria bassiana</i> and one of <i>Metarhizium anisopliae</i>, on <i>P. gracilis</i> under laboratory conditions. Fungal spore suspensions (1 × 10<sup>7</sup> spores per mL) were sprayed on detached leaves infested with <i>P. gracilis</i>. Treated mites were kept under controlled conditions (25 ± 3 °C, 72 ± 10% relative humidity and photoperiod of 16:8 (light/dark)) and mite mortality was assessed three, five and seven days after inoculation. At all three measurement points (days after inoculation), the mortality of <i>P. gracilis</i> was highest for <i>B. bassiana</i> strain BB 1.1 and <i>M. anisopliae</i> strain MA 10.1. Our data demonstrate that EFs are promising candidates for the development of biological control agents against <i>P. gracilis</i> in raspberry crops.
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