Pathogenicity and Virulence of Entomogenous Fungus, Verticillium lecanii (Zimm.) Viegas on the Pea Aphid, Acyrthosiphon pisum (Harris)

Pathogenicity and virulence of entomogenous fungus, Verticillium lecanii, was studied on the pea aphid, Acyrthosiphon pisum. Vertalec, a commercial product of V. lecanii, was evaluated under controlled conditions. Second instar nymphs were inoculated with conidial suspensions at concentrations ranging from 104 to 108 conidia/ml, and sterile distilled water (containing wetting agent) as control, then caged on cutted alfalfa stems. Each concentration was replicated three times with 30 aphids treated per replicate. Temperature, relative humidity and photoperiod were maintained at 23±1 °C, %97±3, and 16:8 (L:D), respectively. Aphids were monitored daily over 12 days for mortality and nymph production. All newborn nymphs and dead aphids were removed daily. Vertalec significantly increased aphid mortality (mean mortality because of mycosis increased form %45.55±6.93 at 104 conidia/ml to %95.55±4.45 at 108 conidia/ml). The LC50 value for pathogen was 5.l4×l04 conidia/ml. LT50 values for 105, 106, 107 and 108 conidia/ml were 10, 8, 6.5 and 5 days, respectively. At 104 conidia/ml LT50 value was not determined at experimental period. Ro values significantly decreased with increasing conidial concentration (mean R0 altered from 28.l5±5.38 in control to 5.15±1.81 at 108 conidia/ml). Results indicated that vertalec can be an effective agent against pea aphids. Further studies are recommended for its evaluation under natural conditions.