Sublethal effects of Metarhizium anisopliae on Aphis gossypii at three constant temperatures

In the present study, sublethal effects of Metarhizium anisopliae </em>(LC30</sub>)on Aphis gossypii </em>were evaluated at three constant temperatures of 20, 25 and 30 ºC, relative humidity of 65 ± 5% and a light period of 16h. Data analysis was performed using Age-stage two sex life table procedure. The lowest duration of immature stages for A. gossypii</em> was estimated at 25 ºC (4.37 day). The highest recorded value for female longevity was also recorded at this temperature (16.73 day). Different temperatures had significant effects on total fecundity of treated individuals with sublethal concentration of M. anisopliae</em> and the lowest recorded value for this parameter was obtained at 30 ºC (3.60 nymph). Furthermore, sublethal effects of M. anisopliae</em> on population growth parameters of offspring from treated individuals were also significantly different at temperatures tested. Since the recorded value of birth rate was dramatically lower than death ones at 30 ºC, the estimated value for intrinsic rate of increase (r</em>) showed a negative value (-0.091 day-1</sup>) at this temperature. The estimated values of net reproductive rate (R</em>0</sub>) at 20 and 30 ºC (5.46 and 0.47 offspring/individual, respectively) were significantly lower than recorded value for this parameter at 25 ºC (66.29 offspring/individual). The results obtained revealed that temperatures of 20 and 30 ºC significantly affect pathogenecity of M. anisopliae</em> to A. gossypii</em>. Our findings could increase the efficiency of M. anisopliae</em> in management programs of different pests.