Fecundity and Egg Laying in Helicoverpa armigera (Lepidoptera: Noctuidae): Model Development and Field Validation

Models can be useful to help understand population dynamics of insects under diverse environmental conditions and in developing strategies to better manage pest species. Adult longevity and fecundity of Helicoverpa armigera (Hübner) were evaluated against a wide range of constant temperatures (15, 20, 25, 30, 35, and 37.5°C). The modified Sharpe and DeMichele model described adult aging rate and was used to estimate adult physiological age. Maximum fecundity of H. armigera was 973 eggs per female at 25°C decreasing to 72 eggs per female at 37.5°C. The relationship between adult fecundity and temperature was well described by an extreme value function. Age-specific cumulative oviposition rate and age-specific survival rate were well described by a two-parameter Weibull function and sigmoid function, respectively. An oviposition model was developed using three temperature-dependent components: total fecundity, age-specific oviposition rate, and age-specific survival rate. The oviposition model was validated against independent field data and described the pattern of field occurrence of H. armigera egg numbers very well. Our model will be a useful component for population modeling of H. armigera and can be independently used for the timing of sprays in management programs targeting this key pest species.