Population dynamics and management of Spodoptera litura Fab in Himachal Pradesh

Abstract

Survey for the incidence of Spodoptera and its species prevalent in four districts (Bilaspur, Hamirpur, Kangra and Mandi) of Himachal Pradesh was conducted during 2015-16. The pest was found associated with a number of vegetable crops (tomato, capsicum, beans, cucumber and cabbage) with 69.23 and 46.85 per cent infestation during 2015 and 2016, respectively. Three species of Spodoptera were rercorded i.e. S .litura, S. littoralis and S. exigua. S. litura was recorded from all the four districts surveyed while S. littoralis has been recorded only from Kangra and Mandi districts and S. exigua from Kangra district only. The fertility table studies of S. litura at 30±1and#8304;C revealed average fecundity of 1760.00±117.50 eggs per female and gross and net reproductive rates of 693.18 and 266.70 female progeny/ female, respectively. The mean generation time (T) of 34.91 days was calculated with maximum mortality in the larval stage (25.94 %). The temperature from 30 to 35and#8304;C was found to be congenial for the growth and development of S. litura. High temperature of 40and#8304;C was proved lethal to all the stages of the insect with very low survival at 15 and 38and#8304;C. The mean lower development thresholds for egg, larvae, pre-pupae and pupae were 8.61, 6.00, 7.90 and 6.18, with thermal requirements of 65.36, 416.6, 53.19 and 222.22 degree days, respectively. There was wide variation in the moth catches in light and pheromone traps, with peak activity of the pest during the month of May. Maximum temperature (Tmax.) was found as the most important factor affecting the moth catches in the traps followed by wind speed. The pheromone trap was found to be 6-15 times superior over the light trap in monitoring the activity of S. litura moths. Under laboratory conditions, emamectin benzoate was found to be most effective against all the larval instars of S. litura followed by fipronil and novaluron. On tomato grown under polyhouse, emamectin benzoate (0.15 x 10-3 %), fipronil (0.04 %), novaluron (0.03 %) and lambda-cyhalothrin (0.36 %) were found to significantly check the larval populations of S. litura. On capsicum grown under polyhouse, the combined application of fipronil (0.007 %) and SlNPV (1x109 POBs/ ml) was found as most effective in controlling S. litura which was at par with the combined application of emamectin benzoate (0.02 x 10-3 %) and SlNPV (1x109 POBs/ ml) as well as novaluron (0.006 %) and SlNPV (1x109 POBs/ ml). The interaction effect of SlNPV (1x109 POBs/ ml) with emamectin benzoate (0.02 x 10-3 %), fipronil (0.007 %) and novaluron (0.006 %) was found as additive while Beauveria bassiana (2 x 108 spores/ ml) formulation with emamectin benzoate (0.02 x 10-3 %) and fipronil (0.007 %) gave antagonistic effects. However, B. bassiana (2 x 108 spores/ ml) was found compatible with novaluron (0.006 %). newline newline newline