Effects of the entomopathogenic fungus, Lecanicillium longisporum on survival and population growth parameters of the cabbage aphid, Brevicoryne brassicae (Hemiptera: Aphididae) under laboratory conditions

This study was carried out to determine the effects of the entomopathogenic fungus, Lecanicillium longisporum Zimmermann Strain LRC 190, on survival and population growth parameters of the cabbage aphid, Brevicoryne brassicae (L.) treated by using different conidial concentrations (1×103, 1×104, 1×105, 1×106, and 1×107 conidia/ml). Experiments were conducted at 23±1oC temperature, 60±5 %RH and a photoperiod of 16: 8 h. (L: D) on cabbage seedlings, Brassica oleracea var. capitata under laboratory conditions. Based on the results the longevity of the aphid adults was significantly different based on conidial concentrations of L. longisporum (Petch) Zare and Gams. The shortest longevity of the cabbage aphid adults was 10.70±1.59 days when treated with 1×107 conidia/ml, compared to 22.65±0.94 days in control treatment. The LC50 value was 1.82×106 conidia/ml 7 days after inoculation. Net rate of reproduction (R0), intrinsic rate of increase (rm) and finite rate of increase (λ) were significantly reduced in treated aphids compared to control treatment. There was no significant difference among mean generation times (T) in populations treated with 1×105, 1×106, 1×107 conidia/ml (P>0.05). Fungal infection was detectedin lower rm values and prolonged doubling time (DT) in treated females (3.492 days at the concentration of 1×107 conidia/ml), compared to the control (2.652 days). Considering higher concentrations of L. longisporum can effectively reduce the cabbage aphid longevity, reproduction and population growth under laboratory conditions, it seems that the fungus has ability for biological control of the cabbage aphid.