Impact of Weather Parameters on Seasonal Incidence of Oriental Armyworm, Mythimna separata (Lepidoptera; Noctuidae) Infesting Maize Ecosystem in North Kashmir

Abstract

The investigation on the seasonal incidence of oriental armyworm, Mythimna separata was conducted at the Faculty of Agriculture, Wadura SKUAST-K during kharif 2021. Shalimar composite-6 maize variety was cultivated under the standard practices for Kashmir valley, recommended by SKUAST-K. The pest activity during the crop growth period was monitored by using light traps and visual observations. Findings revealed that adult M. separata on maize emerged in the 18th standard meteorological week (SMW) with its peak in the 24th week and remained active until the 37th week. Similarly, armyworm caterpillars appeared in the 19th to 37th SMW and reached their peak in the 29th week in the maize ecosystem during 2021. Moreover, the percentage of infestation during the Kharif season was found to be minimum of 10 per cent in the 19th SMW, reaching its peak of 63 per cent in the 29th SMW. The infestation gradually decreased and persisted for eight weeks, with 10 per cent infestation in the 37th SMW. The relationship between adult population and weather parameters showed a positive correlation with maximum temperature (r = 0.14) and a negative correlation with minimum temperature (r = -0.22), morning relative humidity (r = -0.52*) and evening relative humidity (r = -0.47*). However, M. separata adult populations showed a significant negative association with rainfall (r = -0.51*). Correlations drawn between important weather parameters and larvae of M. separata showed significant positive correlation with maximum temperature (r = 0.60**) and minimum temperature (r =0.56**), while morning RH (r = -0.36) and evening RH (r = -0.29) showed negative association and rainfall (r =-0.16) also exhibited negative association with the larval infestation of M. separata during Kharif 2021. The study on percentage infestation also demonstrated a significant positive correlation with maximum temperature (r = 0.47*) and minimum temperature (r = 0.53*), while morning relative humidity (r = -0.22) and evening relative humidity (r = -0.29) showed negative associations. Rainfall (r = -0.20) displayed a negative correlation with the per cent infestation of M. separata.