Status of Spodoptera exigua (Hub) on chickpea in future global warming context of India

The present study aims to predict the generation number and duration of beet armyworm, Spodoptera exigua (Hübner) (Noctuidae: Lepidoptera), a major pest of chickpea and using degree days (DD) accumulation in three Time Slice Periods (TSPs) viz., Immediate Future (IF), Distant Future (DF), and Far Distant Future (FDF) at eighteen key chickpea growing locations in India. An ensemble data of maximum (Max T) and minimum (Min T) temperature data from 4 Representative Concentration Pathways (RCPS) 2.6, 4.5, 6.0, and 8.5 based on Coupled Model Intercomparison Project 5 (CMIP5) models was utilized. An increase in Max T ranging from 0.71 °C–4.66 °C and Min T ranging from 0.82 °C–5.26 °C is expected to occur across the three future TSPs in comparison to the reference (BL) period along four RCPs at eighteen locations. A decreasing trend was evident with generation duration while the generation number followed an increasing trend with advancing TSPs in 4RCPs. The increase in generation number was more in RCP 8.5, particularly during FDF period. During this period, among the selected locations, highest generation number with lowest duration was predicted to occur at Prakasam followed by Kurnool whereas Dharwad and Hanumangarh projected to have least generation number with longer duration. The results exhibited significant increase in annual generation number coupled with a decline in the duration in comparison with BL period across the locations, TSPs and RCPS. Major contribution to the total variability in annual generation number was explained by TSP and Geographical location. The results suggest the increased prevalence of the beet armyworm , Spodoptera exigua , on chickpea crop during future time slice periods in India due to the effects of global warming. The results will offer a scope for prediction of location specific insect pest incidence well in advance and serve as major input for pest forewarning system.