Thermal Requirements of Sitoibion avenae (Hem.: phididae) and its Prasitoid, Proan volucre (Hym.: Braconidae)

The grain aphid, Sitobion avenae (Hemiptera: Aphididae) is one of the injuriously important pests of wheat and Praon volucre (Hymenoptera: Braconidae) is one of its major parasitoids in Iran. In this research, thermal requirements of the grain aphid and its parasitoid were evaluated at six constant temperatures (10, 15, 20, 25, 27.5 and 30 °C), 60 ± 5 % relative humidity and a photoperiodicity of 16:8 h (light:dark) on wheat crop (Pishtaz cultivar). Developmental time of the grain aphid decreased from 25.46 days at 10 to 8.48 days at 25 °C. The developmental time of the parasitoid decreased significantly as temperature increased whithin the range of 10-25 °C. The relationship between temperature and developmental rates of S. avenae and P. volucre were determined employing linear vs nonlinear models. The lower temperature thresholds (estimated by linear model) were 2.7 and 4.3 °C for aphid vs parasitoid, respectively. Thermal constant from egg to adult emergence for grain aphid and its parasitoid were estimated 176.6 and 284.09 degree-days, respectively. The Analytis-3 developmental model was recommended for description of temperature dependent development of S.avenae while the logan-6 and logan-10 developmental models for P.volucrae, as based on their excellent goodness-of-fit to the data (R2adi, SSE and AIC).