Future of Rice Yellow Stem Borer Scirpophaga incertulas (Walker) Under Changing Climate

Status of rice yellow stem borer (YSB) during kharif was predicted for future periods (2030, 2050, 2080 and 2100) under A1B emission scenario of changing climate and compared with past (2011) and current (2016) periods for six rice-growing agro-climatic locations in India. Location-specific predictions for YSB severity (high, moderate and low) were developed combining criteria on weather variables and population levels of YSB adults in light trap based on rules of prediction. Validation of weather-based prediction rules on YSB for kharif (22–44 standard meteorological weeks) of 2011–2016 indicated varying degrees of accuracies for locations [> 80% for Ludhiana (Punjab); > 70% for Raipur (Chhattisgarh) and Karjat (Maharashtra)] and seasons [35–61% at Chinsurah (West Bengal); 17–87% at Mandya (Karnataka) and 35–100% at Aduthurai (Tamil Nadu)]. Prediction accuracies for 2016 were > 80% at all locations, but 48% at Chinsurah (West Bengal). Decline in ‘high severity’ during 2016 (the present period) over 2011(the past period) was noted at Raipur (CG) and Mandya (KA). ‘Low severity’ of YSB at present over past periods was documented at Chinsurah (WB) and Raipur (CG) with no changes at Karjat (MH) and Aduthurai (TN). Predicted YSB severity levels for future periods, viz. 2030, 2050, 2080 and 2100 using the temperature and rainfall projections of emission scenario of A1B indicated an increasing moderate severity of YSB at Ludhiana and Chinsurah in 2050 and the absence of high severity among five locations except Chinsurah in 2100. Increase in moderate and high severity levels between 2030 and 2050 followed by its decline in 2080–2100 at Mandya and the lowest severity almost throughout all periods at Aduthurai were the projected YSB status. While extreme weather events, especially high and unseasonal rains and associated fluctuating weather conditions can have negative impact on YSB severity, the future projected status of YSB implies its lesser significance over the present period of 2016 with rare outbreaks in the context of changing climate.