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1990 - 19933
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Subject: Entomology × End date: 1996 × Start date: 1990 × Type: Thesis ×
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    ThesisItemOpen Access
    Chemodynamics of Carbofuran in Cucumber
    (Department of Entomology, College of Agriculture,Vellayani, 1993) Anil Abraham, KAU; Naseema Beevi, S
    A field experiment was conducted to study the chemodynamics of carbofuran in cucumber plants when applied as granule in the soil. The insecticide was applied at two doses of 0.5 and 1.5 kg ai/ha at three occasions viz. sowing, vining and flowering stage of the crop. The residues of carbofuran and its metabolites were estimated from the vines, leaves and fruits at different intervals after the insecticidal treatment using gas chromatographic technique. Distribution of the residues in the various portions of fruit and the effect of different periods of storage on the degradation of residues were also studied in detail. A safe waiting period was also arrived so as to avoid residue hazards in consumption of the fruits. The results indicated that absorption and metabolism of carbofuran in the plant begins soon after its application in the soil. Pure carbofuran and the metabolites, 3-OH carbofuran and 3-keto carbofuran were detected in the vines, leaves and fruit samples at 1,3,7,14,21 and 28 days after treatment. When the different portions of the plant were analysed, the highest level of residues was detected at different occasions. Thus in the vines the peak level of residues was seen on the first day after treatment where as in the leaves and fruits it was on the third seventh day respectively. A gradual decline was noticed thereafter and the residues reached almost non – detectable by 28th day after treatment in all parts of the plant. The effect of peeling on residues was studied in a separate experiment and the results indicated that peeling of fruits could reduce the residues considerably. Distibution of carbofuran residues in different fruit portions was studied and the results indicated that maximum accumulation of the residues took place in the top portions of the fruit followed by middle and basal portions. Comparing the carbofuran residues in the flesh and placenta of cucumber fruits when treated at the flowering stage of the crop it was observed that maximum accumulation of residues of carbofuran took place in the flesh portion when compared with the placenta of the fruit (inner core and seeds). Effect of storing the fruits on the degradation of carbofuran residues showed that metabolism and degradation of the chemical continued even after harvest, during the process of storage. For safe consumption of fruits following carbofuran treatment at the flowering stage a waiting period of 25 and 26 days have to be given when applied @ 0.5 and 1.5 kg ai/ha respectively.
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    ThesisItemOpen Access
    Effect of organic amendments on plant parasitic nematodes and soil micro-organisms
    (Department of Entomology, College of Agriculture, Vellayani, 1992) Ajith, K; KAU; Sheela, M S
    Field experiments conducted to evaluate the effect of neem and eupatorium leaves at two levels on plant parasitic and non-parasitic nematodes and soil micro-organisms in the rootzone of bhindi and cowpea in rainy and summer seasons revealed that neem and eupatorium leaf treatments (300g/plant or 15 t/ha) were found effective in controlling Helicotylenchus spp., R. reniformis and M. incognita in the rootzone. Lower dose (150g/plant) of neem was found sufficient to suppress the Helicotylenchus spp. In the rootzone of bhindi. Effect of these treatments persisted up to 75 D A S in rainy season and 45 DAS in summer season. The effect of lower doses also persisted up to 30 DAS. The predatory and saprophytic nematode population build up in the rootzone was enhanced by higher dose of eupatorium. The effect on predatory fauna persisted up to 75 D A S in the rootzone of two crops. But in cowpea the effect on saprophytic fauna persisted only up to 60 D A S. The microbial populations (bacteria, fungi and actinomycetes) were increased in the rootzone of bhindi and cowpea in two seasons by the application of eupatorium leaf at higher dose where as neem leaf (higher dose) reduced the microbial population. Only the fungal population increased by the application of neem leaf at higher dose during rainy season. There was seasonal variation in population build up of fungi and maximum effect was seen in rainy season. The biometric characters (number of leaves, height of plant, root weight and shoot weight) and yield of bhindi and cowpea increased significantly by the higher dose of neem and eupatorium leaf. For increasing the height, lower dose of neem, and, for yield lower dose of neem and eupatorium also were found effective. The population of nematodes in the roots at the termination of experiment was significantly reduced by the higher dose of neem and eupatorium in bhindi while lower dose was found effective protecting cowpea roots.
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    ThesisItemOpen Access
    Control of root-knot nematode (Meloidogyne incognita Kofoid and White, Chitwood) infesting black pepper (Piper nigrum L.) by bacterial pathogens
    (Department of Entomology, College of Horticulture, Vellanikkara, 1990) Sheela, M S; KAU; Venkitesan, T S
    A survey was carried out to study the occurrence and association of bacterial pathogens of the root-knot nematode Meloidogyne incognita infesting the black pepper (Piper nigrum L) covering ten major pepper growing districts namely Kannur, Eranakulam, Idukki, Kollam, Kottayam, Kozhikode, Pathanamthitta, Thiruvanandapuram, Thrissur and Waynad. The survey revealed that six species of bacteria were associated with the nematode namely, Bacillus subtilis.B. .pumilus, B. coagulans, B. macerans. B. circulans and E. licheniformis. B. subtilis, B . pumilus and B. licheniformis were found associated with egg masses, second stage juvenile and adult females while B. coagulans. B. macerans aud circulans were obtained from egg masses and adult females only. These six Bacillus spp. showed ovicidal and larvicidal effect against M. incognita. The pathogenic effect tested with the six Bacillus spp. on M. incognita on tomato as host plant showed that B. circulans (0.9x10^ cells per pot) and B._ macerans (0.8x10 cells per pot) compared with treatment of carbofuran 500 ppm were on par in reducing the larval stage of the nematode population in soil. However among the five species all were equal except B. subtilis (1.8x107 cells per pot) and carbofuran treatment in reducing the root-knot population in roots. Eight common host plants of root-knot nematode were tested for pathogenicity with the five Bacillus spp., B. subtilis (1.5x106 cells/ml), B. punilu3 (1.8x106 cells/ml) B. coagulans (1.2x10 cells per ml), B. macerans (0.8x10 cells per ml) and B. circulans (0.9x106 cells per ml). None of these plants showed any symptom of pathogenesis, withering or disease. Safety testing of these Bacillus spp. carried out by oral administration and subcutaneous injection, on two week old chicks, did not produce any bacterial infection indicating that itwas not injurious.