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Subject: Plant Pathology × End date: 1992 × Start date: 1992 ×
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    ThesisItemOpen Access
    Associative effect of azospirillum and bradyrhizobium on nodulation and growth of cowpea (viqna unquiculata (l.) walp,
    (Department of Plant Pathology College of Horticulture Vellanikkara, 1992) Sunitha, Menon S.; KAU; Rajendran, Pillai M .V
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    ThesisItemOpen Access
    Combatibility of certain fungicides and insecticides used for the control of major diseases and insect pests infesting the rice crop
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Kalpana, T A; KAU; Sally Mathew, K
    The efficacy of four fungicides and four insecticides alone and in combination was studied at different concentrations recommended, three-fourth and half the recommended concentrations against two major diseases of rice namely, rice blast caused by Pyricularia oryzae Cavara and sheth blight caused by Rhizoctonia solani kahn. And two major insect-pests namely, leaffoldar Cnaphalocrocis medinalis medinalis Guen. And brown planthopper Nilaparvatha lugens stal. At tillering, panicle initiation and flowering stage of the crop. The experiment was conducted in vivo and in vitro conditions during 1989-91, at the college of Horticulture, Vellanikkara, Thrissur. In general combind application of fungicides and insecticides controlled the diseases and insect-pests more effectively than the treatments given separately. At tillering stage, a synergistic effect of fungicide was observed, when it was sprayed along with insecticides. Among different combinations tried, tridemorph (o.1 per cent) + monocrotophos (0.0375%) and carbendazim (0.075 ) + guinalphos (0.025 per cent) were the best combinations against blast and sheath blight respectively. In the case of leaffolder and brown planthopper, quinalphos was found to be the best insecticide, when used alone and also in combination with fungicides. At panicle initiation stage, combined sprays of higher concentrations of carbendazim and monocrotophos was the best combination in controlling both R. solani and N. lugeas. But ediphenphos-phosphamidon combination was found to be the superior against N. lugens. When combind spraying was given at flowering stage, captafol (0.225 per cent) + quinalphos (0.0375 per cent, and carbendazim (0.075 per cent) + monocrotophos (0.0375 per cent) were found to be the best combinations against P. oryzae and R. solani respectively. But, combination of recommended doses of quinalphos with tridemorph and ediphenphos and, phosalone with ediphenphos were the effective treatments in controlling C. medinalis and N. lugens respectively. In in vitro studies, a total inhibition of the test organisms, viz.P. oryzae and R. solani were observed in all the treatments. Whereas, in the case of C. medinalis recommended doses of quinalphos in combination with ediphenphos and carbendazim and phosalone with tridemorph recorded highest mortality; while, highest dose of quinalphos with captafol and phosalone with ediphenphos were the superior combinations against N. lugens. From the above findings it could be concluded that, the fungicides viz. ediphenphos, carbendazim, captafol and tridemorph are compatible with all the four insecticides tried viz. Phosphamidon, quinalphos, phosalone and monocrotophos in controlling the diseases, blast and sheath blight and insect pests leaffolder and brown planthopper.
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    ThesisItemOpen Access
    Characterization and management of bacterial wilt of chillies caused by Pseudomonas solanaceasum E F Smith
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Jyothi, A R; KAU; Koshy Abraham
    Bacterial wilt is one of the most serious disease of chillies in Kerala. The pathogen was isolated from infected chilli plants and its pathogenicity established. Ten isolates of the pathogen viz., five from chillies , two each from tomato and brinjal and one from ginger were used in the study and they werre characterized and identified as blovar III of Pseudomonas solanacearum (Smith) Smith based on the morphological, cultural, biochemical and physiological characters, coupled with its pathogenicity. Twentynine accessions/varieties of chillies were screened for host resistance against bacterial wilt and the study revealed that the variety 'Manjari' (KAU Cluster/CA 33) was resistant to the disease. The accessions CA 205 and CA 207 exhibited moderately resistant reaction. There was no significant correlation between environmental factors and wilt incidence of all the accessions/varieties except CA 408, for which a positive correlation was noticed between soil moisture and wilt incidence.
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    ThesisItemOpen Access
    Compatibility of certain fungicides and insecticides used for the control of major diseases and insect pests infesting the rice crop
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Kalpana, T A; KAU; Sally, K Mathew
    The efficacy of four fungicides and four insecticides alone and in combination were studied at different concentrations (Recommended, three-fourth and half the recommended concentrations) against two major diseases of rice namely, rice blast caused by Pyricularia oryzae Cavarn and sheath blight caused by R hizoctonia solani Kuhn, and two major insect-pests namely, leaffolder Cnaphalocrocis medinalis Guen. and brown planthopper Nilaparvatha lugens Stal. at tillering, panicle initiation and flowering stages of the crop. The experiment was conducted in vivo and in vitro conditions during 1989-'91, at the College of Horticulture, Vellanikkara, Thrissur. In general, combined application of fungicides and insecticides controlled the diseases and insect-pests more effectively than the treatments given separately. At tillering stage, a synergistic effect of fungicide was observed, when it was sprayed along with insecticides. Among different combinations tried, triaemorpV. (0.1 per cent) + monocrotophos (0.0375%) and Carbendazim TO. 07‘5 % ) -:- quinalphos (0.025 per cent) were the best combinations against blast and sheath blight respectively. In the case of leaffolder and brown planthopper, quinalphos was found to be the best insecticide, when used alone and also in combination with fungicides. At panicle initiation stage, combined sprays of higher concentrations of carbendazim and monocrotophos was the best combination in controlling both R. solani and N. lugens. But ediphenphos-phosphamidon combination was, found to be the superior against N. lugens. When combined spraying was given at flowering stage, captafol (0.225 per cent) + quinalphos (0.0375 per cent) and carbendazim (0.075 per cent) + monocrotophos (0.0375 per cent) were found to be the best combinations against P. oryzae and R. solani respectively. But, combination of recommended doses of quinalphos with tridemorph and ediphenphos and, phosalone with ediphenphos were the effective treatments in controlling C. medinalis and N. lugens respectively. In in vitro studies, a total inhibition of the test organisms, viz. P. oryzae and R. solani were observed in all the treatments. Whereas, in the case of C. medinalis recommended doses of quinalphos in combination with ediphenphos and carbendazim and phosalone with tridemorph recorded highest mortality; while, highest dose of quinalphos with captafol and phosalone with ediphenphos were the superior combinations against N. lugens. From the above findings it could be concluded that, the fungicides viz. ediphenphos, carbendazim, captafol and tridemorph are compatible with all the four insecticides tried viz.; Phosphamidon, quinalphos, phosalone and monocrotophos in controlling the diseases, blast and sheath blight and insect pests leaffolder and brown planthopper.
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    ThesisItemOpen Access
    Effect of solarization on damping off diseases of vegetables
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Sainamol Kurian, P; KAU; Peethambaran, C K
    The effect of solarization on damping off of chilies caused by Pythium aphanidermatum was studied at the college of Horticulture, Vellanikkara, Trichur during 1991-92. For solarizing, 150 guage transparent polyethylene sheets were used. Both nursery and mainfields were inoculated with the fungus prior to solarization. Atmospheric temperature during the period of solarization ranged from 20°C to 38°C. The soil temperature in solarized plots was always higher (6°C-11.5°C) than the non solarized plots. Maximum soil temperature recorded at 10 cm depth i.n the solarized soil was 51°C while that in the non solarized soil was 42°C. Nursery beds were solarized for 15, 30 and 45 days while the main field was solarized for 35 days . Solarization effectively reduced pre and post emergence damping off in the nursery. In the main field, solarization completely checked the disease. As the period of solari.zation increased, better control of the disease was observed. Neemcake amendment did not improve the disease control even with solarization. The population of fungi, bacteria and actinomycetes were reduced as a result of solarization. The nematode population also was significantly reduced by solarization. Eventhough solarization substantially reduced weed population, its effect was more pronounced on dicots rather than monocots. Root colonization by VA Mycrrhizae was significantly better in solarized plots, compared to control. Growth parameters like, plant height, number of leaves, .shoot and root weight were increased through solarization. Plants grown in solarized plots gave 230% more yield over those in the control plots. However, neemcake amendment didnot favour either plant growth or yield. Availability of plant nutrients like P,K, Ca, and Mg was found to be better in solarized plots. Increase in organic carbon content and EC was also noticed in solarized plots. However, total N content of the soil was not altered by solarization.
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    ThesisItemOpen Access
    Etiology and management of powdery mildew disease of pumpkin (Cucurbita moschata Poir)
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Veena, S S; Rema Devi, L
    The present investigation was undertaken to correctly identify the causal organism of pumpkin powdery mildew disease in Kerala and to find out the environmental factors responsible for the occurrence of infection. Attempts were also made to screen different pumpkin lines to identify resistant ones to powdery mildew. The efficacy of different antifungal compounds against the disease were also tried. The study was conducted during 1990 -92 at College of Horticulture, Vellanikkara. Detailed symptomatology of the disease was worked out. The time taken for getting infection varied in resistant moderately resistant and susceptible plants. The fungus causing powdery mildew disease of pumpkin in Kerala was identified as Sphaerotheca fuliginea (Schlecht) Poll. Teleomorphic stage of the pathogen was not observed. From the cross inoculation studies it was clear that S. fuliginea from pumpkin cannot infect non-cucurbitaceous crops and weeds. Even in cucurbits it could infect only bittergourd and ivy gourd. The optimum temperature for germination of S. fuliginea was at 25°C followed by 20°C. The spores germinated at very high relative humidity while it was inhibited in water. Preliminary screening of 57 lines of pumpkin was conducted during 1990 season and 28 lines were selected from this for further studies. All the lines were found infected in both the seasons. But the degree of susceptibility and the age at which they became susceptible were varied. Only the line showed consistency in resistant reaction. Climatic factors like temperature, relative humidity, rainfall and sunshine hours were recorded for an year and was correlated with the disease severity. Incidence of the disease was indirectly correlated with rainfall. However, the influence of climatic factors were more pronounced during the initial stages of the crop. Laboratory and field experiments were conducted to find out the efficacy of five antifungal compounds and water on S. fuliginea. All the chemicals and water inhibited spore germination at varying concentrations. Effect of those chemicals and water were also tried under field conditions on line P. 46. At the end ofone week after spraying Carbendazim recorded maximum disease reduction. Disease at the time of harvest was least in Sulfex treated plants. Even water spray could reduce the disease considerably. Maximum yield was recorded from plants sprayed with Calixin. The best cost effective method to check powdery mildew infection of pumpkin was by spraying water.
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    ThesisItemOpen Access
    Seed-borne fungi of common vegetables and their role in causing Seedling diseases
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1992) Mathew George; KAU; Balakrishnan, S
    A number of fungi were found associated with vegetable seeds, both externally and internally, during the present study. This include nine species of Fusarium, eight species of Aspergillus, four species each of Chaetomium and Penicillium. Other fungi like Corynascus sepedonium, Curvularia clavata, Gilbertella persicaria, Gonatobotryum apiculatum, Humicola fuscoatra, Paecilomyces inflatus, Rhizopus oryzae, Scytalidium sp., Syncephalastrum racemosum, Talaromyces flavus and Zopfiella Karachiensis were also found to be seed-borne in vegetables. In amaranthus, Fusarium sp. 3 caused significant inhibition of germination and significant incidence of damping off. In chilli, Aspergillus flavus was found to be a serious seed- borne fungus while in tomato Penicillium purpurogenum caused considerable inhibition of germination of seeds as well as incidence of damping off of its seedlings. Fusarium pallidoroseum, Chaetomium brasiliense, Gilbertella persicaria and pericillium sp. Were found to be serious pathogens in snake gourd. Culture filtrates of most of the fungi tested during the persent study caused significant inhibition of germination of seeds, inhibition of elongation of plumule and radical, and wilting of seedlings of the corresponding vegetables. While most of the culture filtrates were found to be thermostable, culture filtrates of some of the fungi lost their toxicity by boiling. When the inhibitory effect of different seed treatment fungicides against different seed-borne fungi was studied, Luzem 45 (mancozeb) was found to be the best one and it could completely inhibit the growth of nine species of fungi at the minimum concentration tested. Hexacap (captan) was ranked second while Blue copper 50 (copper oxychloride) was found to be the least effective fungicide in inhibiting the growth of different seed-borne fungi. When the different seed treatment fungicides were tested for their efficacy in increasing the germination of seeds and decreasing damping off of seedlings, Hexacap treatment had shown maximum effect in all the vegetable tested. The other fungicides in the order of their efficacy were Bavistin and Luzem 45. When the mean value of effect of different fungicidal seed treatment methods were compared, slurry treatment was found to be the best in case of amaranthus, and chilli while dry treatment gave maximum effect in tomato, ash gourd and snake gourd.