Modeling Embryo Development of Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) Under Constant Temperature

The alfalfa root weevil, Sitona discoideus (Coleoptera: Curculionidae), is an important pest of alfalfa. The developmental rates of the embryo development were recorded at eight constant temperatures ranging from 8.5 to 30 degrees C. Using 10 models (1 linear and 9 nonlinear), we evaluated the relationship between constant temperature and developmental rate. Embryo development was shortest (8.5 d) and longest (69 d), at 28 and 8.5 degrees C, respectively. The threshold temperature (To) and the thermal constant (K) were estimated using linear regression to be 4.7 degrees C and 207.7 DD, respectively. The two most efficient nonlinear models, the Lactin and the Sharp and DeMichele, gave estimates of T(min) and T(max) of 4.4 and 3.9 and 30.0 and 30.9 degrees C, respectively. This information has potential application in predicting the suitability and optimal time of release of an egg parasitoid of S. discoideus.