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2008 - 200912010 - 20121
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Subject: Plant Pathology × Author: Bhandari, Chandra Prabha × Type: Thesis ×
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    ThesisItemOpen Access
    Evaluation of certain biopesticides and fluorescent pseudomonads for their inclusion in ipm programme
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2008) Bhandari, Chandra Prabha; Kumar, J.
    The sharp increase in the use of chemical pesticides in India in recent years has resulted in severe implications in the development of pesticidal resistance in key pest species, pesticidal residues in food chain and degradation in the quality of eco system and human health. It is therefore, important to identify alternatives to chemical pesticide in plant protection without sacrificing the productivity and profitability of agriculture. Among various non chemical options (host plant resistance, cultural, biological and integrated pest management), biopesticides which are target specific, eco friendly and biodegradable are potential alternatives to chemical pesticides and are known to exhibit antifungal activities against certain plant pathogenic fungi. In the present investigation studies were conducted to evaluate Azadirachtin formulations viz., Soluneem and Mycostat, Sodium bicarbonate, vermiwash and two fluorescent pseudomnads [ch-12 and ch- 18] obtained from mid gut of earthworm against nine potential test pathogens under in vitro conditions. The biopesticides were evaluated for their compatibility with bioagents in order to increase their action spectrum. The putative biopesticides were field evaluated against capsicum at six farmers’ fields in the Garampani vegetable belt in Distt. Nainital under natural infection conditions. In this belt, capsicum faces recurrent crop losses due to impact of diseases like root rot, collar rot and dieback. Under in vitro conditions, Mycostat (2000 ppm) resulted into complete inhibition of the radial growth of Sclerotium rolfsii and Sclerotinia sclerotiorum and recorded significantly higher inhibition against Rhizoctonia solani, Fusarium oxysporum and Fusarium solani. While Soluneem (600 ppm) recorded significantly higher inhibition against Helminthosporium oryzae and Fusarium oxysporum. Sodium bicarbonate (500 ppm) recorded complete inhibition of Sclerotinia sclerotiorum but at higher concentration (2000 ppm) Sodium bicarbonate recorded statistically significant inhibition against Rhizoctonia solani followed by Fusarium solani and Sclerotium rolfsii. It was found that Mycostat and Sodium bi carbonate both were fungistatic in their action. Trichoderma harzianum (th-43) showed some degree of compatibility with Mycostat at lower concentrations (1000-4000 ppm) but was incompatible at higher concentrations (6000 ppm). The bioagent showed relatively less sensitivity with Soluneem and Sodium bicarbonate thus could be considered compatible with Soluneem and Sodium bi carbonate. Combination of Sodium bicarbonate and th-43 completely inhibited the mycelial growth of Sclerotinia sclerotiorum, Sclerotium rolfsii, and Rhizoctonia solani however th-43 alone found was found to give lesser inhibition. Combination of Soluneem (600 ppm) and th-43 was highly significant in inhibiting the mycelial growth of Helminthosporium oryza and Fusarium oxysporum while th-43 alone inhibited less growth. Pseudomonas fluorescence (strain ch-18) was found to be highly significant in inhibiting the radial growth of Helminthosporium oryza and Pyricularia grisea and was also significantly effective against Colletotrichum capsici, Fusarium solani , Sclerotinia sclerotiorum, Sclerotium rolfsii, Fusarium oxysporum, Rhizoctonia solani and Colletotrichum graminicola. Pseudomonas fluorescence (strain ch-12) was highly significant in inhibiting the radial growth of Helminthosporium oryzae, Colletotrichum capsici and Pyricularia grisea and was also significantly effective against Rhizoctonia solani, Sclerotinia sclerotiorum, Fusarium solani, Fusarium oxysporum, Sclerotium rolfsii and Colletotrichum graminicola In vitro testing of vermiwash (1kg vermicompost extracted in 1 lit water) against different plant pathogens gave max reduction in dry weight of mycelium against Sclerotium rolfsii but was not much effective against other pathogens. In the field trials, five treatments viz. root dipping in Bavistin (0.05%) + Dithane M-45 (0.25%), root dipping in Soluneem (0.05%), root dipping in Mycostat (0.5%), root dipping in PBAT-3 (Trichoderma harzianum + Pseudomonas fluorescens (0.8%), and root dipping in Sodium bicarbonate (0.8%) were evaluated against capsicum. After 30 days of transplanting, maximum plant stand and minimum per cent disease was recorded in Soluneem (0.05%) followed by Mycostat (0.5%). After 45 days of transplanting maximum no. of plants in branching stage and maximum average plant length was also recorded in Soluneem (0.05%) and Mycostat (0.5%) as compared to other treatments. At 60 days of transplanting minimum % loss due to diseases was recorded in Mycostat (0.5%) followed by Soluneem (0.0.5%) proving the supremacy of the two biopesticides i.e., Soluneem and Mycostat in disease management and giving better plant growth. The study revealed that the two Azadiractin based biopesticides, Soluneem and Mycostat, hold promise in reducing field losses in capsicum but need further evaluation in other vegetables before inclusion in the biointenssive IPM programme.
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    ThesisItemOpen Access
    Fusarium ear rot of maize: Impact on seed health, seed storability & seed production and successive management under field condition
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2012-08) Bhandari, Chandra Prabha; Vishunavat, Karuna
    Fusarium Ear Rot of Maize caused by Fusarium moniliforme, commonly responsible for stalk and ear rot diseases in maize, causes significant qualitative and quantitative losses. Keeping in mind the importance of disease, present investigation was carried out on seed borne nature of pathogen, detection and location of infection in seed and other plant parts, transmission of pathogen from seed to seedling, losses in seed quality and Aflatoxin B1 production in storage, determination of disease severity, disease index, infection rate, area under disease progress curve and losses due to Fusarium Ear Rot incurred on artificial and natural field conditions. Suitable management strategies using different fungicides, bioagents and botanicals have been worked out with a view to formulate an effective management practice against the disease under field conditions. Deep freeze blotter was found to be the best for the maximum recovery of the pathogen from seeds. Histopathology of infected seed revealed location of the pathogen in the pericarp, endosperm and also in embryonal axis of the seed. The symptomatic kernels show the highest recovery of infection as compared to asymptomatic kernels. The pathogen was transmitted from seed to seedling and exhibited the symptoms of Fusarium infection in the form of white fluffy mycelial growth. Fusarium moniliforme, isolated from maize seed, when inoculated on other cereals, caused both pre emergence damping off and stunted seedlings in paddy and sorghum. The Czapex dox iprodione dichloran agar medium showed the highest selectivity to the mycelial growth of the fungus. The best carbon source favorable for the mycelial growth of Fusarium moniliforme is found to be Manitol while the best nitrogen source is Sodium nitrate and sulphur source is Magnesium sulphate. Culture filtrate of Fusarium moniliforme has been found with phytotoxic substances which may inhibit the growth of seedlings. In stored maize seed infected with Fusarium moniliforme revealed higher Aflatoxin B1 concentration than permissible Indian regulatory limit (30 μg kg l). Seed treatment with Polykote + Mancozeb + Dimethoate were found to be effective in which maximum seedling length, seed germination , vigour index and minimum un- germinated seed and seed rot was observed both in polythene and cloth bags at 10 th month of storage period. Polythene bags were found more suitable as compared to cloth bags for seed storage at different storage periods in most of the treatments. Tebuconazole completely inhibited the growth of the fungus at 50 ppm concentration followed by Bavistin at 100 ppm. At 50% concentration, plant extracts of Garlic, Turmeric, Ginger and Thuja reduced more than 65 % growth of Fusarium moniliforme. Trichoderma harzianum isolate Th 3 showed 73.33 % inhibition while Pseudomonas fluorescens isolate Pf6 gave 67.55 % inhibition of Fusarium moniliforme and were found to be the best among different isolates tested. Host cultivar response on artificial inoculation of Fusarium moniliforme was studied during 2010-11 and 2011-12. Among the methods tested for artificial inoculation, tooth prick method was observed to be the best and gave maximum disease severity, disease index, area under disease progress curve and minimum grain yield followed by pin prick and spray method in all the varieties. The rainfall is found directly proportional to both logarithmic and apparent infection rate of the disease. Variety Gaurav showed high degree of resistance to Fusarium Ear Rot under natural field condition. Among all the treatments, irrespective of chemicals, bioagents and botanicals Thiram (ST) @ 0.25% followed by two foliar spray of Folicur @ 0.1% at 15 days interval was found to be the best for both naturally infected cobs and cobs artificially inoculated with said fungus under field conditions for the management of disease. The minimum corn ear worm incidence was observed in treatment with Thiram (ST) followed by foliar spray of Folicur . However, There is no correlation between the methods of inoculation and incidence of corn ear worm but the corn ear worm is found to be directly related with the Fusarium Ear Rot severity.