PATHOGENICITY OF VERTICILLIUM-LECANII CONIDIA AND BLASTOSPORES AGAINST THE APHID, MACROSIPHONIELLA-SANBORNI

Under conditions of laboratory bioassay in which aphids were infected by total immersion in spore suspensions, blastospores of the entomopathogenic fungus, Verticillium lecanii (Zimm.)Viégas, were twice as pathogenic as conidia for the aphid, Macrosiphoniella sanborniGill., on a numerical basis. By comparison, on a live-spore volume basis blastospores, being larger, were only ×0.6 as pathogenic. Blastospores were also, numerically, more pathogenic when healthy aphids were infected from spore-covered leaf discs in the laboratory. LC50s of the 2 assay methods differed by more than × 100. In glasshouses, the 2 spore-types achieved similar levels of control of M. sanborni. © 1979 Le François.