Impact of density dependent factors on seasonal incidence of Spodoptera litura (Fab.) on soybean in Dharwad

Abstract

Field experiments were conducted at MARS, UAS, Dharwad during kharif 2017-18 and 2018-19 on seasonal incidence of Spodoptera litura in two different soybean varieties, JS 335 and DSb 21. The crop remained vulnerable to S. litura from 31st MSW to 37th MSW which followed an increasing trend from 0.40 to 4.80 larvae per meter row length (mrl) in variety JS 335 during 2017-18. The highest leaf damage of 35.77% were recorded during 37th MSW in JS 335 whereas, it was 28.85% in DSb 21 during the respective MSW. During 2018-19, S. litura infestation commenced on 30th MSW in both the varieties which attained peak population during 37th MSW. Correlation studies indicated that a highly significant and positive relationship (r=0.77) between maximum temperature and incidence of S. litura during 2017-18 whereas, morning relative humidity showed a significant and negative correlation (r= -0.64) with S. litura incidence during 2018-19.