HYMENOPTEROUS PARASITES AND HYPERPARASITE S OF SCHIZAPHIS-GRAMINUM (RONDANI) (HOM, APHIDIDAE) ON SORGHUM, IN THE DROME, FRANCE

For 6 years, the abundance and efficacy of parasites of the greenbug, Schizaphis graminum (Rond.), were studied in sorghum fields in the Dro me Department, south-eastern France. The 10 species of primary parasit es recorded included Aphidius ervi Hal., A. matricariae Hal., A. picip es Nees, A. rhopalosiphi de S. P., A. uzbekistanicus Luzh., Ephedrus p lagiator (Nees), Praon gallicum and P. volucre Hal. (Aphidiidae); Apbe linus asychis Walk. and A. varipes Forest. (Aphelinidae). The most com mon parasites belonged to the genera Praon and Apbelinus, but they rar ely had a determinating impact on the limitation of populations of S. graminum. Ten species of hyperparasistes in the families Encyrtidae, C haripidae, Megaspilidae and Pteromalidae greatly reduced the efficacy of the primary parasites. Among the 14 different species of primary pa rasites (over 39 000 mummified cereal aphids) shipped from France to t he United States in the frame of a biological control program against S. graminum, only A. asychis and A. varipes seem to have been establis hed. In contrast, two cooperative biological control programs against cereal aphids in Brazil and Chile were successful, owing to a better s ynchronization in the shipments of exotic parasites by our laboratory and of releases by our collaborators overseas.