Infectivity of metarhizium flavoviride gams and roszypal to the gregarious nymphs of schistocerca gregaria (forskal) and the enhancing effect of phenylacetonitrile on mortality
2004
Gorashi, N.E. | Elhassan, S.M. | Bashir, M.O.,University of Khartoum, Shambat (Sudan). Faculty of Agriculture, Dept. of Crop Protection
Conidia of M. flavoviride Gams and Roszypal (Mfl 5) were formulated in cotton seed oil at different concentrations of square 10 to 10**8 spores/ml, and applied topically to the desert locust gregarious nymphs [Schistocerca gregaria (Forskal)], under the laboratory conditions at 27+0.30 deg C and 74.1+2.11; RH. After infection of the nymphs, food consumption was reduced as well as insect responsiveness to mechanical stimulation, followed by change in colour and finally death clinging to the wire mesh of the cages by their legs. Mortality rate was dose dependent, where 100; mortality was observed at high concentrations of 10**7 and 10**8 spores/ml, five days post-inoculation, while only 36.6; mortality was recorded at lower concentrations of square 10 and 10**3 spores/ml, eleven days post-inoculation. The LD50 was calculated as 1.5x10**5 spores/ml, five days after application of the inoculum. However, mediation of the atmosphere in the cages with phenylacetonitrile, adult aggregation pheromone major component, four days prior to inoculation, predisposed the nymphs severely to the lower doses of square 10 to 10**4 spores/ml previously used. When nymphs were exposed to 0.01; concentration of phenylacetonitrile, a significant increase in insect mortality ranging between 37; and 55; was recorded over the nymphs treated with the fungus only (control)
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