Effects of heat shock on survival and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae) adults

Under natural conditions insects are occasionally subjected to thermal stresses. Data concerning the effects of these temperature extremes on tolerance and on life history parameters of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) have been lacking. This study investigated the effects of heat shock temperatures and exposure pattern on survival and on reproductive parameters of H. armigera adults. Adults were exposed to four high temperatures (40, 42.5, 45 and 46.5°C) for time periods ranging from 1.5 to 540min, depending on the temperature treatment and then insects were returned to normal temperature conditions. The survival rate of both sexes declined with the increase in the time of exposure at all high temperatures examined. The lethal time needed to cause mortality in 50% and 90% of the adult population decreased rapidly with the increase in the temperature from 40 to 46.5°C. Mean adult longevity declined significantly with the increase in the exposure time at all heat-shock treatments tested. The values of parameters of fecundity were found to be inversely related to the exposure time of the adults to high temperatures. No eggs were oviposited by adults of H. armigera exposed to 40, 42.5 and 45°C for 360, 120 and 15min, respectively, while adults exposed to 42.5, 45 and 46.5°C for 90, 12.5 and 5min, respectively, did not mate successfully. As the heat shock response is vital for H. armigera adults living in a variable environment, our findings can be used to develop a more profound understanding on the potential for this insect to evolve in response to environmental changes. © 2009 Elsevier Ltd.