Effect of storage temperature and duration on viability of eggs of Helicoverpa armigera (Lepidoptera: Noctuidae).

The ability to store different insect stadia for prolonged periods provides considerable flexibility and ability to conduct experiments properly. Therefore, studies were undertaken to determine the effect of storage temperature and duration on viability of eggs of Helicoverpa armigera (Hübner). The percentage egg hatch and incubation period were significantly (P=0.01) influenced by egg age, storage temperature, and storage duration. Egg hatch ranged from 0.0 to 96.8% across temperatures and storage durations. None of the eggs hatched when stored at -20 and 0 degrees C. The regression model with the optimum Mallow Cp statistic for any of the identified linear and quadratic terms did not improve the precision of prediction in egg hatch beyond 67.0%. Forecasting of incubation period based on egg age, storage duration, and durationxtemperature was quite effective (R2=84.2%). Day degrees required for egg hatching decreased with an increase in temperature from 10 to 27 degrees C, and egg age from 0 to 3 days. The day degree requirements were highest for 0-day-old eggs at 10 degrees C, and lowest at 27 degrees C. Although the incubation period was higher, the hatchability was lower for 0- and 1-day-old eggs stored at constant 10 degrees C, these eggs can be stored for 10 days at 10 degrees C, with a hatchability of >75.0%. It was safer to store the H. armigera eggs for 10 days at 10 degrees C, which will hatch within 1.6 to 2.0 days after restoration at 27 degrees C with a hatchability of >75.0%. This information will be useful in planning and execution of experiments involving H. armigera on various aspects of research in entomology.