| Popis: |
A field experiment was conducted at the College of Agriculture, Iroishemba, Imphal duringRabi, 2020-21 to study the bio-efficacy of certain aqueous indigenous plant extracts against theDiamond back moth(DBM), Plutella xylostella Linnaeus,the Cabbage butterfly(CB), Pieris brassicaeLinnaeus and the Cabbage aphid (CA), Brevicoryne brassicae Linnaeus and their toxic effect on thepopulation of predatory coccinellid beetle, Coccinella septempunctata Linnaeus in cabbage crop var.Pride of India‖. There was moderate incidence of P. xylostella, P. brassicae and B. brassicae in theexperimental crop var. ―Pride of India‖. The insects maintained mean incidence of 14.42 to 22.80 %leaf damage, 9.51 to 16.14% leaf damage and 37.33 to 77.35 aphids/plant, respectively. Thus, thesepests were considered as the regular and major pests of cabbage during the investigation. The resultson the efficacy of bio-rational insecticides against P. xylostella, P. brassicae and B. brassicae revealed that all the insecticidal treatments resulted in significantly suppression of both the pests‘ incidence. Thepooled results based on three applications of insecticide indicated that Margosom (Azadirachtin 300ppm) @ 0.3% spray conc. followed by Melia azedarach, extract applied at the spray conc. of 5.0% werequite effective in reducing the population of the insect pest of cabbage with a record of lower meanleaf damage of 6.92 and 7.61 per cent, respectively and did not differ significantly between them.Against P. brassicae also Margosom (Azadirachtin 300 ppm) @ 0.3% spray conc. registeredsignificantly the lowest mean leaf damage of 7.65 per cent as against 14.73% in untreated check,closely followed by Melia azedarach extract @ 5.0% spray conc.(8.10% LD) and Artemisia nilagiricaextract@ 5.0% spray conc.(8.37 % LD) which had none significant difference one another. Thesignificantly highest mean leaf damage incidence (12.33% LD) was noticed in the plots treated withaqueous extract of Solanum conyzoides when applied @ 5.0% spray conc. Of the aqueous indigenousplant extracts field evaluated against the butterfy, M. azedarach proved the most effective treatment insuppression the pest incidence with minimum mean leaf damage. The results on the effectiveness ofvarious insecticidal treatments against B. brssicae, further showed that Margosom (Azadirachtin 300 ppm) @ 0.3% conc. also maintained its superiority to other treatments in suppression of the aphidpopulation recording the lowest mean population of 9.43 per plant as against 36.46 aphids/plant inuntreated control. It was at par with the mean population recorded in the treatments with Ageratumconyzoides (11.97 aphids/plant), Solanum xanthocarpum (12.01 aphids/plant), Mariandra bengalensis(12.46 aphids/plant) and Artemisia niligirica (12.69 aphids/plant). While, M. azedarach extract exhibitedits inferior performance in controlling aphid with highest mean population of 14.04per plant. The plots treated with Margosom (Azadirachtin 300 ppm) recorded maximum cabbageyield of 22.38 t ha-1 follower by M. azedarach extract treated plots (19.93 t ha-1) with increase yieldover control of 6.50 t ha-1 and 40.93 per cent, and 4.05 t ha-1 and 25.50 per cent, respectively butdeferred significantly from each other as per the yield harvested from the plots of these insecticides isconcerned. The minimum mean yield (18.00 t ha-1 ) was obtained from the plots treated with A.nilagirica with increase yield of 2.12 t ha-1 and 13.35 per cent over control ,but, did not differsignificantly from that of rest insecticidal treatments except yield of Plectralthus ternifolius extract.However, it is amply clear that all the plant extracts were superior in controlling DBM, CB and CA incomparison to untreated control. The extent of avoidable yield loss due to the incidence of P.xylostella, P. brassica and B. rassicae was estimated to be 29.04 per cent in untreated control which wasreduced to 10.95- 19.57 per cent. Minimum being recorded in M. azedarach and maximum in Artemisianilagarica extract. Further, the pooled mean data of three observation periods‘ revealed that amongthe test insecticides M. azedarach @ 5% A. nilagirica, Cinnamomum tamala and Aralia armata eachapplied at the spray concentration of 5.00%, proved to be the safer extracts to the predatory beetleC. septempunctata with their corresponding mean beetle population of 1.56, 1.41, 1.32 and 126 per plantas against 3.27 in untreated control which did not show significant difference from one another. Thelowest beetle population (0.79/plant) recorded in the plots treated with Margosom (Azadirachtin 300ppm) @ 0.30% conc. closely followed by Solanum xanthocarpum and Meriandra bengalensis extracts @5.00% conc. with the mean beetle population of 0.89 and 0.92 per plant, respectively. |
