Population dynamics of major defoliators (semiloopers and tobacco caterpillar) in soybean crop

A study was carried out to find out the effect of various weather parameters on the occurrence of major defoliators in soybean crop. Semilooper larval population was recorded late July/early August and their peak activity observed during 33–34, 33–36 and 37–39 standard weeks, in 2012, 2013 and 2014, respectively. Among the weather factors, morning relative humidity showed significant (r=0.954) and positively, highly influence on the larval population per mrl whereas evening humidity (r=-0.644) and sunshine hrs (r=-0.367) negatively and significantly influence the larval population per mrl. The various weather parameters significantly caused 92 per cent variations in larval population per mrl. The moth catches of Spodoptera litura increased from late-August to late-September and this trend was almost similar in different kharifseasons observed. Larval population of S. litura positively correlated with pheromone trap catches during 2014.