Temperature Effects on Development of Three Cereal Aphid Parasitoids (Hymenoptera: Aphidiidae)

Abstract

Temperature is an important climatological variable that influences the biology and ecology of insects. Poor climatic adaptation can limit the effectiveness of parasitic insects in biological control. Two exotic parasites (Syrian Diaeretiella rapae (M'Intosh) and Argentinean Aphidius colemani Viereck) imported for biological control of the Russian wheat aphid, Diuraphis noxia (Mordvilko), and one native parasite (Diaeretiella rapae) were reared in growth chambers in three fluctuating temperature regimes with average daily temperatures of 12, 18, and 24 degrees C. Estimates of temperature thresholds for immature development were 3.3, 3.5, and 2.8 degrees C, for Oklahoman D. rapae, Syrian D. rapae. 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 fluctuating temperature regimes did not differ significantly among sexes, but adults from regimes with law average temperatures of 12 and 18 degrees C had significantly greater weights than those reared in a regime 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.