Assessment of Helicoverpa armigera (Hubner) Adult Population in Chickpea using Weather Based Indices

Background: Chickpea is the second most important pulse crop grown globally, it is damaged by over 50 insect species in different parts of the world, of which gram pod borer, Helicoverpa armigera (Hubner) poses serious threat to production. Temperature is one of the important abiotic factor influencing the growth and development of an organism, degree day (DD) models are very useful in pest predictions as development of insects and plants is temperature-dependent and can predict the biological phenomenon with greater accuracy. Methods: H. armigera adult population at different chickpea phenological stages viz., from emergence to maturity stage was assessed using the weather based indices viz., growing degree days (GDD) and heliothermal units (HTU) during rabi 2015-16, 2016-17 and 2017-18 at ICAR-Indian Agricultural Research Institute, New Delhi. Results: At different chickpea phenological stages the pest population varied from 0 to 66.3, 0 to 256 and 0 to 124 with respective cumulative population of 148, 555 and 167 male moth catches during three consecutive seasons. Among different phenological stages, highest population was recorded during both pod formation and crop maturity stage during 2015-16 and 2017-18, while in 2016-17 it was maximum during 50 per cent flowering and maturity stage. Among the three seasons, the GDD and cumulative male moth trap catches were found to be highest during 2016-17. The relationship of GDD and HTU with H. armigera was analysed through linear regression and they accounted for 64 and 71 per cent variation respectively in pest population across the seasons. The weather based indices viz., GDD and HTU may thus be useful for predicting H. armigera adult population at different chickpea phenological stages.