Curtiss et al. C. pomonella Entomopathogens

Washington State is the top US apple producer, but losses from Cydia pomonella (L.), the key pest, can be significant. Conventional and organic insecticide management is challenging, and natural enemies and pathogens are thought to be rare. During the fall of 2023, approximately 14,000 overwintering final instar C. pomonella moth larvae were collected from six apple farms throughout the primary growing regions of the state. Several hundred caterpillars were deceased from unknown causes, but based on their appearance, some appeared to be infected with unknown fungi. The nine most promising dead individuals were surface sterilized and then transferred onto medium that promoted fungal growth. Emerging fungal colonies were isolated, morphologically characterized, DNA was extracted, and they were identified by Sanger sequencing. Three C. pomonella were found infected with entomopathogenic fungi: 1) Beauveria bassiana (Balsamo) (Hypocreales: Cordycipitaceae), 2) Hirsutella/Ophiocordyceps sp. (Hypocreales: Ophiocordycipitaceae), and 3) Metarhizium robertsii Bischoff, Rehner, & Humber (Hypocreales: Clavicipitaceae). Laboratory assays that exposed these fungi to final instar C. pomonella caterpillars confirmed Koch’s postulates and demonstrated that they are indeed infective to C. pomonella. These fungi may have applicability for C. pomonella management in commercial orchards. Genetic sequence data are provided.