Pathogenicity of the fungus Verticillium lecanii to aphids and powdery mildew

Aspects of the host specificity and pathogenicity of the hyphomycete, Verticillium lecanii, were investigated under laboratory conditions. Differences were observed in the pathogenicities of three strains of V. lecanii (DAOM 198499, DAOM 216596 and Vertalec) to the potato aphid Macrosiphum euphorbiae and Sphaerotheca fuliginea, the causal agent of cucumber powdery mildew. The estimated median lethal concentration required to achieve 50% mortality (LC₅₀), median lethal time leading to 50% mortality (LT₅₀) and aphid net reproductive rate (R₀) indicated that Vertalec and strain 198499 were more virulent to aphids than strain 216596. The estimated median colonization time for 50% of fungal colonies (CT₅₀) showed that strain 198499 was the best antagonist of cucumber powdery mildew. Further comparison suggested that the mean pathogenicity of V. lecanii strain 198499 to cucumber powdery mildew was almost equivalent to that of Sporothrix flocculosa, a biological control agent of greenhouse fungal pathogens. These observations provide convincing experimental evidence that V. lecanii is biologically active against both arthropods and fungi. The potential of using V. lecanii strain 198499 in biological control is discussed.