Temperature Effects on the Development of Vietnamese Cotton Bollworm Helicoverpa armigera (Hübner)

Cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) is a major pest of cotton, green onion, groundnut, chickpea, tomato, sorghum, cowpea, etc., distributing widely in Asia, Europe and Africa. This pest often causes great economic damage due to its high reproductive potential and pesticide resistance. It is well established that temperature is one of the most important factors in determining the survival, development, and size of insects, but the effects can be modified depending on the geographic strains. Here, we investigated the effects of constant temperatures on the survival, development and individual size of Vietnamese H. armigera when reared on bean sprouts in the laboratory. The results showed that the survivals from larval hatching to adult emergence from the pupa were lower under lower temperatures. The duration of the developmental stages decreased as temperature increased from 20°C to 30°C. Developmental thresholds for the eggs, larvae, pupae and life cycle were estimated as 11.5, 13.3, 14.4 and 10.2°C, respectively. Thermal constants for the egg, larval and pupal stages were 45.9, 243.9 and 117.6 degree–days above the developmental thresholds, respectively. A thermal constant of 526.3 degree–days above a threshold of 10.2°C was estimated to be required for the life cycle. The size, measured as pupal weight, increased with rearing temperatures. The results of the present study showed that ca. 30ºC is the optimal temperature for H. armigera development and growth. Helicoperva armigera may complete a maximum of 10–11 generations per year in Hanoi, Vietnam. The present results provide important information for predicting the field population phenology of H. armigera in Hanoi, Vietnam.