Population dynamics of major Insect Pests and seed yield of Soybean

The peak larval population of green semilooper (Chrysodexis acuta) was recorded 9.97 larvae/mrl and 100% foliage damage due to foliage feeders at 34^th SW when maximum and minimum temperature was 32°C and 28.2°C, respectively. There was no significant correlation exhibited between the larval population and weather parameters, whereas, first appearance and peak of larval population of tobacco caterpillar was observed 1.24, 9.38 larvae/mrl at 31^st and 37^th SW with 71.6%, 100% foliage damage due to foliage feeders, respectively. The first infested plants 4.4% at 31^st SW and peak infested plants 67.7% at 37^th SW was observed due to stem fly, Melanagromyza sojae when the maximum and minimum temperatures were 32.1, 23.7 and 30.2, 22.2°C, respectively. Thereafter, it was started to decline and again reached second peak infestation 54.4% at 39^th SW and 69.9% at 41^st SW, respectively. The mean % plants infested by stem fly exhibited significantly negative correlation with wind speed. Avoidable seed yield losses due to insect pest complex of soybean from unprotected plot was recorded 14.84 q/ha as compared to protected plots 21.47 q/ha. It clearly showed that when the crop was protected from insect pest complex, the yield losses may be avoided up to 30.8%.