COMPETITIVE INTERACTION BETWEEN STRAINS OF VERTICILLIUM-LECANII ON 2 INSECT HOSTS

Differences were observed in the pathogenicities of two strains of Ver ticillium lecanii (strain numbers 1.72 and 19.79) to the whitefly Tria leurodes vaporariorum and the aphid Macrosiphoniella sanborni. The mea n pathogenicity of a mixture of the two strains was intermediate to th at of the individual strains, attributable to a competitive interactio n during infection. Differences between strains were observed in the p roduction of conidia in vitro and on host insect cadavers. When hosts were infected with the dual-strain suspension, conidia of strain 19.79 only were recovered from T. vaporariorum whereas conidia from both st rains were recovered from M. sanborni.