JWSS - Journal of Water and Soil Science

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. R_o 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.