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Subject: Plant Pathology × End date: 1981 × Start date: 1981 ×
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    ThesisItemOpen Access
    Studies on the phyllosticta leaf spot of ginger
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1981) Premanathan, T; KAU; Peethambaran, C K
    Laboratory and field experiments of “The studies on the Phyllosticta leaf spot of ginger” were conducted at the College of Horticulture Campus, Vellanikkara during 1979-1981. The first visible symptom of the disease was observed as chlorotic specks. Fructification was more during the later stages of crop growth. The detailed study on the plant and environmental factors influencing the disease development in the field revealed that the average number of leaves per plant has a significant positive correlation with the disease intensity. Koch’s postulate and morphological studies proved that the pathogen causing the disease is Phyllosticta zingiberi Ramakr. Uninjured leaves and first three leaves, even after injury, failed to exhibit the symptoms on inoculation. Conidia germinated by putting forth single or double germtubes. Sucrose solution (1,000 ppm) supported faster and maximum spore germination and the bipolar germination noted was maximum in this solution. The fungus entered the leaf by direct penetration of epidermal cells without appressoria formation. The pycnidiospores and mycelia of the pathogen were found to survive even after seven months in soil under different depths and moisture conditions. The type Maran was found to be the least susceptible followed by Karakkal and Bajpai, whereas type Vengara was the most susceptible one. Out of the 12 fungicides tried, one per cent Bordeaux mixture and 2,000 ppm Bayer 5072 gave cent per cent inhibition of the fungal growth in both solid and liquid media. Antracol 2,000 ppm and panolil above 500 ppm in solid medium; bavistin 2,000 ppm and cuman above 500 ppm in liquid medium gave cent per cent inhibition of fungal growth. In the field trial cuman, was found to be the most effective fungicide in controlling the disease, followed by Bordeaux mixture and panolil. Maximum rhizome yield was noticed in cuman treated plots followed by Bordeaux mixture.
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    ThesisItemOpen Access
    Seed mycoflora of some vegetables in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Naseema, A; KAU; Balakrishnan, S
    The survey of the seed mycoflora of vegetable seeds revealed the presence of a number of seed-borne fungi. Storage fungi like Aspergillus flavus, Aspergillus niger Penicillium sp. and Rhizopus stolonifer were found to be externally as well as internally seed-borne , in almost all the vegetable seeds taken for the study. A part from these , other fungi like Curvularia lunsta. Fusarium equlecti and Myrothecium roridum from amaranthus , Botryodiplodia theobrease from bhindi, bitter gourd and cowpea, Fusarium oxysporum and Eectria haemtococca from bhindi, Achaetonium macrosporum and Collstrotrichum lagenarium from bitter gourd, Drechalera rostrata from cowpea, Cephaliophora irregularis and Fusarium solani from pumkin were obtained. The seed-borne fungi were found to cause inhibitory effect on the germination of the seeds , from which they were isolated , Maximum inhibition in the germination was found to be caused by storage fungi like Aspergillus flavus, Aspergillus niger. Penicillium sp. and Rhizopus stolonifer . Rotting of the seedlings was caused by Fusarium equiseti on amaranthus, Prechslera rostrata on cowpea . Aspergillus niger and Rhizopus stolonifer on tomato.
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    ThesisItemOpen Access
    Role of weeds in the perpetuation of virus diseases of vegetables and ornamental plants
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Mathew, A V; KAU; Balakrishnan, S
    Virus diseases affecting ten different weed plants and their possible role in the perpetuation of virus diseases of certain cultivated plants were investigated. These ten weeds were affected by 13 virus diseases. All the 13 viruses were transmitted by wedge grafting. Among the 13 viruses studied, 3 viruses, viz., mosaic of Amaranthus viridis yellow mosaic of Micrococca mercurialis and mosaic Stachytarpheta indica were transmitted by sap inoculation and by insect vectors. Eight viruses, viz., yellow vein mosaic of Ageratumconizoides, leaf curl of A. conizoides, yellow vein mosaic of Croton sparsiflorus and Sida cordifolia, yellow mosaic of Micrococca mercurialis, leaf curl of Stachytarpheta indica and Synedrella nodiflora and yellow mosaic mottle of Stachytarpheta indica var. jamaicensis were transmitted by the whitefly, Bemisia tabaci Genn.
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    ThesisItemOpen Access
    Role of the rice root nematode (Hirschmanniella oryzae) in the incidence of sheath blight disease of rice in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Gokulapalan, C; KAU; Chandrasekharan Nair, M
    Rhizoctonia solani causing sheath blight of rice was found to infect a number of common weeds and crops raised in rice fallows in Kerala. The fungus was found to produce leaf and stem blight in groundnut plants. This is the first report of this fungus causing serial blight symptoms in adult groundnut palnts. On Sesbania aculeata (daincha), the fungus produce severe collar rot, this being the first record of this fungus on this crop in India. The occurrence of R.solani under natural conditions on the weeds, Anluda aristata and Monochoria vaginalis are reported for the first time.
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    ThesisItemOpen Access
    Symptomatology etiology and control of sheath rot disease of rice caused by Acrocylindrium oryzae
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1981) Balakrishnan, B; KAU; Chandrasekharan Nair, M
    Sheath rot disease of rice caused by Acrocylindrium oryzae was investigated. The fungus was found to infect rice plants at boot leaf stage. The leaf sheath covering the panicle was found to be comparatively more susceptible to the fungus than the sheath of other leaves. Severe infection caused choising of the whole penicle insids the sheath itself before emergence. The pathogen was isolated from infected tissues of host plants and brought into pure culture. Comparative studies of air isolates of Acrocylindrium oryzae from four rice varieties and two weed hosts did not show much appreciable difference in their morphological characters except light variations in the hyphal thickness and smaller conidial size from those on weed hosts.
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    ThesisItemOpen Access
    Evaluation of newer fungicides against diseases of rice especially rice blast
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1981) Sheela, Paul T; Abi, Cheeran
    The experiments for the evalution of newer fungicides against rice diseases were conducted at the Rice Research Station and Instructional Farm at Mannuthy during the first and second crop season of 1979-80. The objectives of this study were to find out the efficiency of the new foliar fungicide Panolil, against four rice diseases viz., blast, brownspot, sheath blight and stackburn and to evaluate the efficacy of the newer fungicides Panolil, Panoctine and Panoram as seed treatment fungicides. In the bioassay studies in vitro cent per cent inhibition of Pyricularia oryzae was obtained in 1000 ppm of Panolil, 2000 ppm of Panoctine, 500 ppm of Panoram, 250 ppm of Hinosan and Kitazin and 100 ppm of Agallol in potato dextrose agar medium. In all the fungicide incorporated liquid medium no growth was observed. Panolil (500 ppm), Panoctine (500 ppm), Panoram (1000 ppm), Hinosan (1000 ppm), Kitazin (1000 ppm) and Agallol (100 ppm) completely inhibited the growth of Drechslera oryzae in solid medium. In liquid medium also no growth was observed even in lowest concentration of Panoli, Panoctine and Agallol, 250 ppm and above concentration of Panoram and Kitazin. But growth was observed in all the lower concentrations of Hinosan. Cent per cent inhibition of corticium sasakii was not noticed even in 2000 ppm concentration of Panolil and Panoctine. Panoram and Kitazin at 250 ppm concentration and Hinosan at 500 ppm gave 100 per cent inhibition of C. sasakii. In liquid medium no growth of the fungus was obtained in any of the fungicidal treatments except in the lowest concentration of Kitazin. Panolil, Hinosan and Kitazin gave 100 per cent inhibition of Alternaria padwixkii only at 2000 ppm. Panoram at 1000 ppm and Agallol at 100 ppm gave 100 percent inhibition. In liquid medium growth was observed only in the lowest concentration of Panoram and Kitazin and in all the concentrations of Hinosan. The incidence of blast was low in both the seasons and in both the varieties. Two higher concentrations of panolil (1.5 kg/ha and 1 kg /ha) were equally effective as organophosphorus fungicides in reducing leaf infection, while against neck blast, Hinosan and Kitazin were better than Panolil. Brown spot disease was low in both the varieties during first crop and while in second crop season disease was notices only in Jaya. Panolil 1.5 kg/ha was found to be superior to Hinosan and Kitazin in reducing the disease. Sheath blight infection was low and was noticed only during the first crop in the variety Triveni. Panolil was as effective as organophosphorus fungicides in controlling the disease. Stackburn disease appeared on both the varieties in both the seasons. This disease was best controlled by higher concentrations of Panolil. Seed treatment and storage studies were conducted using the seeds collected from the first crop season. Newer fungicides panolil, Panoctine and Panoram and Agallol were used as seed treatment fungicides. The effect of delayed drying and storage, on seed microflora and deterioration of viability were also studied by using the seeds treated with different fungicides. An increased number of fungal flora was observed in untreated seeds compared to the treated ones. Generally the number of seeds associated with fungal flora increased on storage. For both rice varieties Agallol was found to be the best in reducing association of fungal flora on seeds while when the storage period was extended upto 32 weeks the highest concentration of newer chemicals were found to be on par with Agallol. When the seeds were stored for 16 weeks, the influence of delayed drying on germination was pronounced only when the drying was delayed beyond 6 days then the germination fell below 80 per cent. After 24 weeks of storage, the germination fell below 80 per cent even when the drying was delayed for three days. Agallol was found to be the best seed dresser, followed by the higher concentrations of newer fungicides. When the storage was prolonged for 32 weeks, satisfactory germination was obtained only for the seeds dried immediately and pretreated with Agallol and Panoram 1 g/kg and 1.5 g/kg.