Population dynamics of stem fly and defoliator pests of soybean and their natural enemies in relation to weather parameters

Abstract

The field experiment was carried out at Polasa Farm, Regional agricultural research station Jagtial during the Kharif, 2014-15 and 2015-16. Study about pre dominant lepidopteran insect –pests in soybean crop noticed that the tobacco cut worm, (Spodptera exigua Hubner), green semi looper(Crysodexis acuta Walker), and tobacco caterpillar (Spodoptera litura Fab) along with stemfly, (Melanagromyza obtusa Zehnter) as non lepidopteran pest were noticed at various growth stages of cropgrowth. The peak activity of stem fly (37.84%) was observed during 37th standard week per meter row) for the year 2014 and for the year 2015 to a maximum infestation of 35.70 per cent during 30th std.week. The peak activity of caterpillar pests i.e., S. litura (7.6 larvae per meter row) for the year 2014 was observed during 34th std.week and for the year 2015 (12.4 per meter row during 36th std.week and C. acuta (0.7 larvae per meter row) during 36th std. week for the year 2014 and for the year 2015 (2.20 larvae/mrl on 37th std week. S. exigua (1.6 larvae per meter row) for both the years 2014 and 2015 was observed during 32th std.week Among the natural enemies, one predators namely, spiders (Oxyopes sp. was observed to prey on the insect pests.The biocontrol agent’s one species, lynx spider, Oxyopes sp. population recorded on the crop during Kharif , 2014 ranged from 0.15 to 0.40 /mrl and 0.15 to 0.60/ mrl during Kharif, 2015.