Najmeh Ebrahimi - Entomology Research Department, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran.
Ali Asghar Talebi - Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.
Yaghoub Fathipour - Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.

Organisms are often exposed to various stresses such as heat. The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a serious pest of cruciferous crops in Iran and the world. The effect of short-term temperature stress on egg stage of P. xylostella and its demographic parameters were studied under laboratory conditions. Diamondback moth eggs were exposed to ۳۰, ۳۵ and ۴۰ °C for durations of ۲, ۴, ۶, ۸ h and then returned to normal temperature condition (۲۵ °C). The results showed that P. xylostella eggs successfully developed to adulthood at short-term (۲, ۴, ۶ and ۸ h) high temperatures stress. The ovipositional period was significantly longer at ۳۰ °C for ۸ h, ۳۵ °C for ۲ h and ۴۰ °C for ۴ h than for other periods of stress. There is a significant difference in the net reproduction rate (R۰) among the short-term high temperature stresses treatments. The highest and lowest R۰ was obtained at ۳۰ °C for ۸ and ۴ h, respectively. The intrinsic rate of increase (rm) was also found to be significantly affected by stress temperatures. The rm-value ranged from ۰.۱۵ ± ۰.۰۰۹ (۳۰ °C for ۴ h) to ۰.۲۲ ± ۰.۰۰۴ (۳۵ °C for ۸ h). Knowledge of the effect of temperature on demographic parameters of P. xylostella could be useful in the integrated pest management for forecasting the population dynamics of this economic pest of brassicas, thereby reducing insecticide inputs, negative environmental impacts and saving hundreds of millions of dollars annually.

Diamondback moth, Demography, crucifers, population fluctuation, Short-Term High Temperature.