Differential variation in development of the B- and Q-biotypes of Bemisia tabaci (Homoptera : Aleyrodidae) on sweet pepper at constant temperatures

Developmental rates of the B- and Q-biotypes of Bemisia tabaci (Gennadius, 1889) were studied at seven constant temperatures (17, 20, 23, 26, 30, 33, and 35 degreesC) oil sweet pepper, Capsicum annuum L. ('Morron'). The egg i ncubation period and the times required to complete development at all imma ture stages decreased with increasing temperature up to 33 degreesC but at 35 degreesC were found to be greater than at 33 degreesC. The relationships between developmental rate of B, tabaci and temperature were influenced by the insect biotype. The lower and upper developmental thresholds as well a s the optimal temperatures and thermal Constant for the preoviposition peri od and all immature stages were estimated by fitting the observed developme ntal rates versus temperature with a nonlinear model and two linear models. For all stages, graphs obtained by plotting the reciprocal of development times against temperature could be described by the modification 2 of the L ogan's model. The simple linear model tT = K+ct suffices for predicting B- and Q-biotype phenologies oil sweet pepper for the temperature range of 17- 33 degreesC. The shortest developmental times as well as the lowest develop mental thresholds and thermal constant were mostly obtained with the Q-biot ype. Overall, the most favorable temperature range appeared to be 31-33 deg reesC, Mean generation times (adult-adult) ranged from 17 d (Q-biotypc) and 18 d (B-biotype) at 33 degreesC to 49 d (B-biotype) and 46 d (Q-biotype) a t 17 degreesC.