Diaeretiella rapae (M´Intosh) is a cosmopolitan polyphagous and aphid parasitoid, the host of which, the cabbage aphid Brevicoryne brassicae (L.) is one of the economically important pests of the cruciferous plants. In this research, the stable population parameters of this parasitoid as well as its host were estimated and compared at a temperature of 25±1?C, RH 60±5% and a photoperiod of 16:8 (L:D) hours. Intrinsic rate of natural increase of the parasitoid and the aphid were 0.212 and 0.226, respectively. Mean generation time and doubling time occurred at 11.29 and 3.269 days for parasitoid while evaluated 13.07 and 3.06 days for aphid, respectively. Net reproductive rate, finite rate of increase and rw were evaluated 10.5, 1.236 and 4.410 for the parasitoid and 15.92, 1.25 and 4.864 for the aphid, respectively. In conclusion, the aphid stable population parameters were evaluated as more than that of parasitoids.
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