Suppression of Sitotroga cerealella in Shelled Corn by the Parasitoid Pteromalus cerealellae

The parasitoid Pteromalus cerealellae (Ashmead) was introduced at densities of one, five, or 10 pairs into 0.47-liter jars containing 500 g of corn that had been infested with one, five or 10 pairs of the Angoumois grain moth, Sitotroga cerealella (Olivier), adults. The abundance of S. cerealella progeny was significantly reduced by all release rates of parasitoids and at all densities of S. cerealella. As release rates increased from one to 10 pairs of P. cerealellae, the average percentage suppression increased from 85.5 to 99.2 at one pair of S. cerealella, from 77.2 to 98.0 at five pairs of S. cerealella, and from 66.9 to 95.8 at 10 pairs of S. cerealella. However, the degree of suppression was significantly influenced by both the numbers of P. cerealella released and the initial density of S. cerealella. With greater host density, more progeny of P. cerealellae were produced, but releasing more parasitoids did not significantly increase the number of P. cerealellae progeny.