Temperature-dependent development rates of Bracon vulgaris, a parasitoid of boll weevil

The duration of development of Bracon vulgaris Ashmead, parasitoid of the boll weevil Anthonomus grandis Boheman, was determined at nine constant temperatures between 18 degrees C and 38 degrees C. Nonlinear regression analysis was used to test the fit of temperature-dependent development rates to the Sharpe and DeMichele and Lactin et al. models. At the highest tested temperature (38 degrees C) all the parasitoid eggs died before hatching and no evidence of development was observed. The high values of R-2 for the models of Sharpe and DeMichele (0.8432 to 0.9834), and Lactin et al. (0.9071 to 0.9795) indicated that these models are suitable to estimate the development rate of B. vulgaris as a function of temperature. B. vulgaris showed tolerance to high temperature which is represented by the high value of H-H (change in enthalpy associated with high-temperature inactivation of the enzyme) for the prepupa stage of this insect obtained with the Sharpe and DeMichele model. According to that model, B. vulgaris exhibits thermal stress at 35.7 degrees C, which indicates that maximum thermal stress estimated by this model was close to the real one.