Temperature-Dependent Functional Response of Diaeretiella rapae (Hymenoptera: Braconidae), a Parasitoid of Diuraphis noxia (Hemiptera: Aphididae)
Keywords:Russian wheat aphid, biological control, parasitoid wasp
The effects of host density and temperature on the functional response of Diaeretiella rapae (Mâ€™Intosh) parasitizing Diuraphis noxia (Mordvilko) were evaluated at six constant temperatures (10, 15, 20, 25, 30 and 32.5Â°C) and six host densities (2, 4, 8, 16, 32, and 64 numbers). A type II functional response was obtained at all temperatures tested. The maximum parasitism rate was observed in density of 64 hosts, ranged from 3.00Â±0.67 at 10Â°C to 24.20Â±0.94 at 25Â°C. The searching efficiency (a) was highest at 15Â°C and then decreased linearly as the temperature increased to 32.5Â°C. The searching efficiency ranged from 0.080Â±0.008 h-1 at 15Â°C to 0.032Â±0.017 h at 10Â°C. The estimated value of handling time (Th) decreased linearly with increasing temperature from 10 to 25Â°C. The maximum rate of parasitization was observed at 15, 20 and 25Â°C (32.94, 32.22 and 36.51 nymphs/24 h, respectively). The results suggest that D. rapae has potential as a biocontrol agent of D. noxia and warrants further evaluation in the field conditions.
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