BIOLOGY AND BOTANICAL BASED MANAGEMENT OF PIERIS BRASSICAE LINN. ON CABBAGE CROP-ECOSYSTEM OF MANIPUR VALLEY

摘要

In 2 sets of experiments were conducted at the College of Agriculture, CAU, Imphal during Rabi, 2006-07, pest fecundity was 165.20 eggs/female & fertility as 88.13%. Mean incubation period was 4.00 days. There were 5 larval instars having total mean larval duration of 16.30 days. The average period of pupation was 40.90 days, while mean adult longevity period was 7.75 days. The total life cycle was completed in 38.35 days on an average. In field evaluation of insecticides against the butterfly, Malathion 50 EC @ 500 ml ha~(-1) proved most effective recording lowest larval population ofl. 11 larvae/plant. Second effective insecticide was Nimbecidine(Azadirachtin 300 ppm) @2000 ml ha~(-1)(2.65 larvae/plant) followed by Melia azedarach (3.50 larvae/plant), Jatropha gossypifolia (3.76 larvae/plant) and Artemesis nilagirica (3.84 larvae/plant) extracts each applied @ 5000 ml ha~(-1) but, did not differ significantly from one, another. The treatment with Vitex trifolia @ 5000 ml ha~(-1) recorded highestmean larval population of 6.74 per plant. The maximum yield of 23.51 t ha~(-1) with increase yield over control of 9.56 t ha~(-1) and 68.53 per cent, closely followed by Nimbecidine, M. azedarach, A. nilagirica, L. camara and J. gossypifolia treated plots , however differed significantly except between Malathion and Nimbecidine treatments. Further, the results indicated that among the aqueous indigenous plant extracts, M. azedarach @ 5000 ml ha~(-1) was found to be significantly most effective against P. brassicae recording lowest mean larval population of 3.50/plant and also accrued maximum yield ((21.981 ha~(-1)) with an increase yield of 6.511 ha~(-1) and 57.56% over control . The extent of avoidable yield loss due to the incidence of P. brassica was estimated to be 40.66% in untreated control which was reduced to 3.19-25.01% in insecticidal treatments. Minimum being recorded in Nimbecidine and maximum in Vitex trifolia extract. Among the botanicals tested M. Azedarach, J. gissypifolia and Ageratumconyzoides, each applied @ 5000 ml ha~(-1) proved to be the safest to the predatory beetle with their corresponding mean adult beetle population of 1.29, 1.28 and 1.27 /plant as against 2.07/ plant in untreated control. The lowest beetle population (0.94/plant) was noticed in the plots treated with Malathion @ 500 ml ha~(-1)which was followed by Nimbecidine @ 2000 ml ha~(-1) with the mean population of 1.10/plant.