Thermal Tolerance of Beet Armyworm Moths, Spodoptera exigua: Effects of Age, Temperature Acclimation, and Gamma Radiation

Abstract

Upper temperature limits were established for beet armyworm moths, Spodoptera exigua (Hubner) (Noctuidae), under controlled humidity–air flow conditions. Preliminary tests determined that a one-hour exposure to 45°C resulted in an approximately 50% reduction in the number of moths capable of flight following a 24-h recovery period. Subsequent tests using 45°C as the stress temperature indicated a rapid decline in thermal resistance of moths with increasing age. Moths maintained at each of 3 temperature regimes (22, 27, or 32°C) for 72 h post-emergence were inconsistent in their flight capabilities following exposure to the stress temperature. Developmentally acclimated moths whose pre-adult stages were reared at these 3 temperatures showed decreased heat resistance at the lower temperature, but inconsistent responses at the higher temperature. Flight capability of irradiated moths in the absence of heat stress was unaffected; however, flight capability following exposure to 45°C significantly decreased as dosage (20, 40, 80 krads) increased