Fecundity and life-table parameters of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on tomato crop under alternating temperature regimes: implications for pest monitoring in sub-tropical India

Constant temperatures influencing the biological traits of Helicoverpa armigera (Hubner) is widely documented. However, information was lacking on impact of alternating temperatures on population growth of H. armigera on tomato crop. The impact of 6 different alternating temperatures (ATs) viz. 25:10, 25:13, 25:16, 30:10, 30:13, 30:16°C were studied on its life table parameters on tomato crop inside the climatic chamber. Only 7–13% eggs of H. armigera developed successfully into their respective adults under treated ATs. The immature development period and mean generation time shortened by 36.7 and 35.7%, respectively with enhancement in AT from 25:10–30:16°C. ATs viz. 25:13, 25:16 and 30:10°C favoured the higher oviposition (554.83–625 eggs/female) of female H. armigera. Fitting closely to observed values, the total fecundity (TF) model predicted 21.0°C as the favourable temperature for maximum fecundity (591.3 eggs /female). Under 30:10°C, H. armigera attained maximum intrinsic (0.05635 day−1) and finite rate of increase (1.0579 day−1) on tomato crop. The methodology involving law of effective accumulated temperatures estimated that H. armigera may complete 2 generations in a tomato growing season. These results can assist in planning sustainable pest management modules in preventing potential pest outbreaks and associated economic losses.