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. D ifferences were observed in the pathogenicities of three strains of V. lecanii (DOAM 198499, DAOM 216596 and Vertalec) to the potato aphid M acrosiphum euphorbiae and Sphaerotheca fuliginea, the causal agent of cucumber powdery mildew. The estimated median lethal concentration req uired to achieve 50% mortality (LC50), median lethal time leading to 5 0% mortality (LT50) and aphid net reproductive rate (R-0) indicated th at Vertalec and strain 198499 were more virulent to aphids than strain 216596. The estimated median colonization time for 50% of fungal colo nies (CT50) showed that strain 198499 was the best antagonist of cucum ber powdery mildew. Further comparison suggested that the mean pathoge nicity of V. lecanii strain 198499 to cucumber powdery mildew was almo st equivalent to that of Sporothrix flocculosa, a biological control a gent of greenhouse fungal pathogens. These observations provide convin cing experimental evidence that V. lecanii is biologically active agai nst both arthropods and fungi. The potential of using V. lecanii strai n 198499 in biological control is discussed.