Effects of irrigation on the performance of cotton bollworm,<i>Helicoverpa armigera</i>(Hübner) during different pupal stages

Abstract

Abstract Pupation of cotton bollworm, Helicoverpa armigera (Hübner), occurs in the soil. This may be a weak link in the life-cycle, exploitable through cultivation, in the control of this important pest. We evaluated the effects of irrigation on the performance of H. armigera. It did not affect the numbers of larvae entering the soil. However, irrigation treatments made on the 2nd, 3rd and 10th day after larvae entered the soil significantly reduced moth emergence (27, 19 and 28.7% emerged from the respective treatments, compared to 93.7% emerging from the control). Irrigation did not affect the time taken from the larva entering the soil to female adult emergence, but it significantly delayed the time in males. Realized fecundity of the emerging H. armigera adults was significantly decreased by irrigation treatment, especially on the 10th day, with a mean of only 367 eggs laid per female. Irrigation after larvae entered the soil substantially decreased survival of H. armigera, and the increase in the size of the generation following irrigation was only 2.8 times for the irrigation treatments on the 3rd and 10th day after larva entered the soil, respectively, compared with that of the control treatment. We suggest utilizing irrigation practices to suppress overwintering pupal numbers, in order to control the spring generation of H. armigera. Keywords: Helicoverpa armigera irrigationsoil moisturepupationperformance Acknowledgements We thank Professor Marvin K. Harris of Department of Entomology, Texas A&M University of USA, the Editor Professor Mark A. Jervis, Associate Professor K. Murugan of Department of Zoology, Bharathiar University of India, and the anonymous reviewers provided helpful comments on the manuscript. This research was supported by the National Key Basic Research Project '973' (2006CB102007), the International Foundation for Science (C/4164-1), the National Natural Science Foundation of China (30700527), the Innovation Foundation of Science and Technology for the Youth of Nanjing Agricultural University (KJ07003) and the State Key Laboratory of Integrated Management of Pest Insects, and Rodents (Grant No. Chinese-IPM-0601).