TEMPERATURE EFFECTS ON DEVELOPMENT OF 3 CEREAL APHID PARASITOIDS (HYMENOPTERA, APHIDIIDAE)

Temperature is an important climatological variable that influences th e biology and ecology of insects. Poor climatic adaptation can limit t he effectiveness of parasitic insects in biological control. Two exoti c parasites (Syrian Diaeretiella rapae (M'Intosh) and Argentinean Aphi dius colemani Viereck) imported for biological control of the Russian wheat aphid, Diuraphis noxia (Mordvilko), and one native parasite (Dia eretiella rapae) were reared in growth chambers in three fluctuating t emperature regimes with average daily temperatures of 12, 18, and 24 d egrees C. Estimates of temperature thresholds for immature development were 3.3, 3.5, and 2.8 degrees C, for Oklahoman D. rapae, Syrian D. r apae. and A. colemani, respectively. Estimates of thermal requirements for development from egg to adult were 297, 278, and 301 degree-days for the three parasitoids. Dry weights of adults reared in different f luctuating temperature regimes did not differ significantly among sexe s, but adults from regimes with law average temperatures of 12 and 18 degrees C had significantly greater weights than those reared in a reg ime with an average temperature of 24 degrees C. Results suggest that developmental response to temperature will Rot limit the effectiveness of the exotic parasites in biological control.