Thermal requirements of parasitoid wasp, Diaretiella rapae (Hym.: Braconidae) reared on Schizaphis graminum (Hem.: Aphididae) under laboratory conditions

Wheat, Triticum aestivum L. is of one the most important cultivated crop plants that are grown extensively for food in the world. The green wheat aphid, Schizaphis graminum (Rondani) (Hem.: Aphididae) is an important pest of wheat in Iran causes severe damage to the crop. In this research, thermal requirements of parasitoid wasp, Diaretiella rapae (M'Intosh) (Hym.: Braconidae)on the green wheat aphid, Schizaphis graminum (Rondani) (Hem.: Aphididae) were assessed at five constant temperatures (10, 15, 20, 25 and 27.5ºC), 60±5% RH and a photoperiod of 16L: 8D hours. The results showed that temperature had significant effect on developmental time. The mean of longest and shortest preimaginal period were observed at 10ºC (25.49±0.09 day) and 25ºC (9.24±0.05 day), respectively. Effect of temperature on developmental time of D. rapae was fitted using linear and non-linear models. The lower temperature threshold and thermal constant of D. rapae were 3.21ºC and 229.36 DD, respectively using linear regression model. The non-linear model Berier 1 had relative high goodness- of- fit. T0, Topt and Tmax were fitted well using this model. Therefore, Berier 1 model was determined for the description of temperature-dependent development of D. rapae on S. graminum. In this research, the linear and most common nonlinear thermalmodels and the criteria for selecting appropriate models are evaluated.