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    ThesisItemOpen Access
    Phytopathological Causes of Mango Decline in South Gujarat and their Plausible control Measures
    (Plant Pathology Department, N. M. College of Agriculture Gujarat Agricultural University, 1980-07) Chauhan, Himatsinh Lalsinh; Joshi, H. U.
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    ThesisItemOpen Access
    Assessment of Partitioned Growth Stage Yield Losses Due to insect Pests of Cotton
    (Agricultural Entomology Department, N. M. College of Agriculture, Gujarat Agricultural University, 2006-11) Patel, Chamanlal Jethabhai; Purohit, M.S.
    Investigations were carried out during kharif 2002 and Kharif 2003 on "Partitioned growth stage yield losses due to insect pest of cotton" at Main Cotton Research Station, Navsari Agricultural University, Athwa Farm, Surat. Efficacy of insect growth regulators against Helicoverpa larvae and effect of BI cotton on growth parameters of Helicoverpa larvae was also studied under laboratory condition. Study on determination of critical stages for protection against insect pests in cotton revealed ER +PR stages as critical for protection against aphids, jassids and thrips whereas PR+LR stages for whitefly. For spotted bollworm and Helicoverpa infestation to fruiting bodies (squares + green bolls) ER+PR stages ascertained as critical stages. However, significant reduction in open boll damage by bollworm complex was achieved in full protection (FP) only. Incidence of spotted bollworm and Helicoverpa in open bolls and locules was higher in first picking compared to second picking. Reverse was the trend for pink bollwOlIII incidence in open bolls and locules. Full protection treatment recorded significantly higher seed cotton yield (2478 kg/hal. It was followed by ER+PR+LR (2279 kg/hal, ER+PR(2088 kg/hal, V+ER+PR (2054 kg/hal, ER+LR(2045 kg/hal, V+ER+LR (2033 kg/hal, V+PR+LR( 1737 kg/hal and I'R+LR (1682 kg/hal· The yield increase in full protection treatment over control was 91.94 per cent. In rest of treatments the increase in yield over control ranged from 30.29 to 76.63 per cent. When V, ER, PR, and LR stage received no protection the reduction in yield was 199, 741, 445 and 424 kg seed cotton fha, respectively. The corresponding figure in terms of per cent yield reduction over protection provided in these stages were 8.03, 29.90, 17.95 and 17.11, respectively. The maximum avoidable loss in seed cotton yield (47.90 %) was in the treatment of full protection (FP) followed by full protection in reproductive period (ER+PR+LR) (43.35 %). Whereas, treatments not recei·ved protection in ER stage showed minimum avoidable loss (23.25 to 25.68 %) indicating the significance of ER stage protection. Highest cost benefit ratio (I: 3.70) was obtained in ER+LR stage protection. Studies on efficacy of insect growth regulators (lGR) on Helicoverpa larvae revealed that both the lGR, novaluron (Rimon) and flufenoxuron (Cascade) was found effective against Helicoverpa larvae. Early instar larva was found more susceptible than later instar. Post treatment effect of IGR prolonged larval and pupal period, reduction in larval and pupal weight, low adult emergence without much impact on longevity. Effect of BI cotton on Helicoverpa larvae revealed profound effect of BI cotton leaves and squares when fed to the larvae, leading to 90 % mortality in 2nd and 4th instar and 100 per cent mortality in I st and 3,d instar. BI cotton fed survived larva showed prolonged larval period, reduction in larval length, larval weight and pupal weight, but negligible effect on pupal period over larva fed on non-Bt cotton. Debilitating effect was more on BI squares compared to BI leaves.
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    ThesisItemOpen Access
    Studies on Population Dynamics, Bionomics and Control of Diamond Back Moth, Plutella xylostella linnaeus on cabbage in South Gujarat
    (DEPARTMENT OF AGRICULTURAL ENTOMOLOGY N.M.COLLEGE OF AGRICULTURE NAVSARI CAMPUS, NAVSARI, 1993-04) VADODARIA, MAGANLAL PREMJIBHAI; Shah, A.H.
    The present investigations on diamondback moth, Plutslla Kylostella attacking cabbage, cauliflower and mustard crops in South Gujarat region were carriedout at N.M. College of Agriculutre, Gujarat Agri c utural University, Navsari during 1990-91 and 1991-92 comprises the comparative studies in the laboratory on bionomics of diamondback moth under fluctuating temperature (213.7 to 2.5'- ~'<..) and relative humidity (Av. 74.0%) as well as at constant temperature (25 • 1· C) - on cabbage, cauliflower and mustard as different hosts. Studies indicated that pest passes through dIfferent stages i. e. eggs, four distinct larval instars. prepupa, pupa and adult. Effect of temperature and nutrition through host on their measurements and duration of each stage, sex ratio, fecundity as ~ell as longevity are also discussed . Nature of damage. has been also studied a)ongwith preference for oviposition and food preference where;'!"1 it revealed cabbage as most preferred host compared to other crucifer-aus crops. Varietal screening programme indicated • varieties 152-141, Kayer! and Yamuna as least cabbage varieties for oviposition as wei I as in tolerance for infestation. The larval parasitoid Gctesia plutal lae was only found active from December. 1990 to May, 1991 causing 3.26 to 18.85 per cent larval parasitism to 1:.. xylostella. While, survey indicated prevelance of natural enemies existed to an extent of 10.77 per cent in Navsari area, 1.17 per cent • 1n Sural area and 1.21 and 6.2e per cent in Vadodra area showing effect of unjudicious use of pesticides in the area. Population dynamics on ~. xylostella through field monitoring indicated 17.5 to 44.S per cent infestation of heads with peak infestation in the month of January. ~h il e through light trap studies, the pest was found to be start attacking • In second week of September wi th peak between fourth week of December to 1 as t week of February and thereafter declined gradually showing the cool weather to be more fevourable for the maximum infestation by e.. xYlostella. Simi lariy. infestation of prodenia was ~ . found to be started from fourth week of May and peak in October. While higher activity of flea beetle in March and April and peak level of aphid population in the month of DecemberJanuary was found .