Browsing by Author "Vasudevan Nair, K P"

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Control of aphis craccivora koch. with fungal pathogens and their impact on the natural enemies of the pest
(Department of Agricultural Entomology, College of Agriculture, 1989) Hareendranath, V; Vasudevan Nair, K P
Studies were made to collect information on the population fluctuation of pea aphid Aphis craccivora Koch. a regular pest of cowpea in relation to time of planting and stage of the crop. The population fluctuation of pea aphid in relation to the prevailing weather factors and the predators were also investigated to collect information on host predator interactions and interrelations. A survey on the occurrence of fungal pathogens associated with pea aphid was conducted in the pulse crops raised at the Instructional Farm, College of Agriculture, Vellayani and adjacent farmers fields. The suspected fungi were isolated and their pathogencity tested in the laboratory. Pathogencity could be proved only in the case of Fusarium pallidoroseum (Cooke) Sacc. Detailed studies were made on its growth, sporulation and pathogenicity using different artificial culture media. It was observed that the cowpea crop planted during November recorded maximum population of pea aphid followed by crop planted during October and December. Lowest population of pea aphid was noticed in the crop planted during March. The active reproductive stage of the crop recorded maximum population of pea aphids. Correlation studies with weather factors and predator population revealed that relative humidity and predator population was positively correlated with the population of pea aphid. Regression analysis of the data obtained indicated that 84 per cent of variation of population could be accounted by the variables under study. Partial regression coefficient of the aphid population and relative humidity was found to be positive and significant. Partial regression coefficient between pea aphid population and predator population was also positive and highly significant. Studies on the pathogenicity of F. pallidoroseum showed that pea aphid infected with the fungus turned pale and assumed a brownish black discolouration. Death occurred in 48 to 72 hours after infection and white mycelial growth appeared on the cadavers 24 to 48 hours after death. Growth, sporulation and virulence of the fungus was found to be superior in Sabouraud medium followed by potato dextrose agar. Sporulation was maximum in 6 day old culture and virulence was highest in 6 day and 7 day old cultures. For mass production of the fungus broken maize grain appeared to be the most suitable media followed by tapioca chips and jack seed as they produced maximum number of spores. Studies on the safety aspects of the pathogen showed that the fungus was not pathogenic to the crop plants tested viz. rice, bhindi, chillies and tomato and also to the predator Menochilus sexmaculata. Bioassay showed that LC50 of the fungus to pea aphid was 3.408 x 10 6 spores per ml. Field experiment to test the efficacy of the fungus in controlling aphid population revealed that the fungus at the rate of 7 to 10 6 spores per ml and 3.5 x 10 6 spores per ml was as effective as the insecticide quinalphos 0.05 per cent. The fungal treatment did not show any harmful effects on predator population in the field.
Effect of potash application on the incidence of brown plant hopper
(Kerala Agricultural University, 1979) Ittyavirah, P J; Vasudevan Nair, K P; Thomas, M J
Effect of residue salt bitters on the yield and foliar yellowing intensity of coconut palm
(Kerala Agricultural University, 1979) Mathai, G; Vasudevan Nair, K P
Effect of soil application of fertilizers and micronutrients on root (wilt) disease and yield of coconut in the back water region of Kerala
(Kerala Agricultural University, 1978) Mathai, G; Vasudevan Nair, K P
Influence of nuclear polyhedrosis on moulting in the larvae of Pericallia Ricini F.
(Kerala Agricultural University, 1980) Vasudevan Nair, K P; Abraham Jacob
Investigations on nuclear polyhedrosis of black hairy caterpillar, Pericallia Ricini fabricius (Arctiidae: Lepidoptera)
(Division of Entomology, College of Agriculture, Vellayani, 1975) Vasudevan Nair, K P; Abraham Jacob
Detailed investigations were carried out on the nuclear polyhedrosis of the black hairy caterpillar,Pericallia ricini (Arotiidae) covering symptomatology, larval susceptibility, effect of the virus on the larval moulting, changes in the number of circulating haemocytes in the infected larvae, nature of causative agent, effect of temperature and sunlight on the infectivity of the virus and the cross infectivity of the virus to other species of lepidoptera. The virus infected larvae exhibited a ll the typical symptoms of nuclear polyhedrosis infection as reported from other lepidopterous larvae. The larvae infected in the early instars appeared paler and thinner. The infected larvae showed loss of appetite and became sluggish. The dead or dying larvae showed the characteristic symptom of hanging head downwards from the top o f the containers with the aid of prolegs. In the advanced stages of infection the cuticle became fragile and it ruptured liberating the liquefied body contents. The susceptibility of the larvae to virus infection decreased with increase in the age of the larvae. The averageincubation period varied from 5*24 days for the second instar to 8 days for the sixth instar larvae. The virus infection inhibited moulting in the later stages of the disease. No significant difference was observed in the THC of healthy larvae and virus infected larvae up to 24 hours after inoculation; there was significant reduction in the THC of diseased larvae after 24 hours of inoculation.
Joint action of nuclear polyhedrosis virus of Spodoptera (Fabricius) with insecticides and its applicability in pest control
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1984) John V Cherian; Vasudevan Nair, K P
Experiments were conducted to study the joint action of nuclearpolyhedrosis virus (NPV) of Spodoptera litura (Fabricius) and five insecticides viz., quinalphos, carbaryl, BHC, monocrotophos and permethrin. The investigation carried out included bioassay of the virus and insecticideson third instar larvae of S.litura, effect of different combinations of the virus and insecticides on larval mortality and the effect of simultaneous and sequential application of virus and insecticides for the control of pest.
On the occurrence of Coccinella Arcuata fabricius (Coleoptera:Cocci nellidae) as a predator of rice thrips in Kerala
(Kerala Agricultural University, 1977) Mammen, K V; Vasudevan Nair, K P
Relative toxicity of the nuclear polyhedrosis virus of Spodoptera mauritia (Biosduval) to different larval instars of the host
(Kerala Agricultural University, 1987) Vasudevan Nair, K P; Abraham Jacob
Bioassay of the NPV of Spodoptera mauritia (Biosduval) showed that LC50 increased with larval age. The LC50 ranged from 3558 PIBS/ml for the second instar to 808700/ml for sixth instar. An inverse relationship between LTSO and concentration of the virus was observed.