Attempts to control cabbage root flies Delia radicum L. and Delia floralis (Fall.) (Dipt., Anthomyiidae) with entomopathogenic fungi: laboratory and greenhouse tests

One laboratory and three greenhouse experiments were conducted to study the pathogenicity and efficacy of Finnish isolates of entomopathogenic hyphemycetous fungi against cabbage root flies. In Petri dishes, exposure to 1.5 × 10¹⁰ spores of Metarhizium anisopliae per dish caused 40–50% mortality of undifferentiated second- and third-stage larvae of Delia floralis , and 1 × 10⁷ spores per dish caused 40–50% mortality of Delia radicum larvae. In one greenhouse test, 1 × 10⁸ and 1 × 10⁹ spores of M. anisopliae and Paecilomyces fumosoroseus reduced the root damage of head cabbage by 20–70% compared with untreated controls, although this was not accompanied by significant reductions in the number of pupae. Only M. anisopliae consistently grew out of larvae and pupae of D. floralis during incubation that followed their recovery from the soil at the end of an experiment testing different formulations of M. anisopliae and Beauveria bassiana , but the frequency of the latent infections of the pest by M. anisopliae was not associated with reduced severity of damage to seedlings of head cabbage.