Browsing by Author "Mohandas, N"

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Compatibility of insecticides and fungicides on the mortality of Nilaparvata lugens (Stall.) and on the inhibition of rhizoctonia solani kuhn.
(Kerala Agricultural University, 1993) Babu, K; Reghunath, P; Mohandas, N; Wilson, K I
The compatibility of insecticides and fungicides commonly used for the control of insect pest and disease of rice was studied in the laboratory using Nilaparvata lugens and Rhizocfonia sdanl as lest organisms. By fixing the proportion of constituents in the insecticidal, fungicidal mixture judiciously, it may be possible to reduce the field dose of insecticide as there was synergism in the insecticidal activities of lower dose of quinalphos when combined with different doses of fungicides. The fungicidal effectsof the three fungicides were signifcantly altered when combined with insecticides. Combination with fungicides showed an antagonistic effect at higher levels of captofol, ediphenphosand carbendazim, while at lower concentrations there was enhancement of fungicidal effect.
Control of vegetable pests using chitin synthesis inhibitors
(Department of Entomology, College of Agriculture, Vellayani, 1983) Rajapadmanabhan Vivek, A; Mohandas, N
The dose-effect relationship of two chitin synthesis inhibitors diflubenzuron and triflumuron against three vegetables pests viz., Sylepta derogata, Epilachna vigintioctopunctata and Psera basalis was assessed in terms of the average survival periods when the different larval instars were exposed on treated food materials in the laboratory. The results showed that the earlier instars . In general, the dose-effect relationship had a positive linear trend . The three test insects showed different susceptibility to the chitin sysnthesis inhibitors. S. derogata was least susceptible and it was followed by E. vigintioctopunctata and P. basalis in susceptibility. Besides the mortality observed, various malformations and deformities were also noted in the different life stages of the insects. At the various doses tried the mortality of the larval stages was , in effect, total. The later instars fed with lower cocentrations survived in small percentages and pupated. Some of these pupae were abnormal and some gave rise to abnormal adults fully or partly emerged from the pupal skin.
Effect of phorate applied for the control of bunchy top vector of Banana pentalonia nigroneroosa Coq. on the plant and in the soil environment
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1989) Sitarama Rao, D; Mohandas, N
A series of experiments were carried out for ascertaining the basic problems related to the current recommendations for managing bunchytop disease of banana through the application of phorate. The absorption, translocation and metabolism of phorate applied in the soil was influenced more by the condition and age of the plant than by the dose of the insecticide. Since the application of 2.50 g ai/plant did not result in corresponding increase in the residue content or the bioefficacy in the early phases of crop growth, when compared to the 1.25 dose, the latter can be used without significant loss in efficacy. A definite dose-effect relationship existed between the phorate content of plant and the mortality of P.nigronervosa confined at feeding sites. The median lethal doses of the insecticide content of the plant tissue were higher during declining phase of absorption as compared to those obtained during the active absorption phase. The result indicated the lesser toxicity of some components in the total residue during the later phase of the crop. Application of phorate granules in leaf axils was less effective than the treatment done in the soil and hence the current recommendation to use less quantity of insecticide when applied in the leaf axils has to be altered. A simple technique for the separation, identification and quantification of phorate and its metabolites was developed. Phorate and phorate sulfoxide contents of the total residue showed inverse relationship with each other while the other metabolites did not exhibit a clear relationship among them. Phorate and phorate sulfoxide exhibited more positive direct influences on the morality of the vector than the other metabilites. The absorption and toxicity of the insecticide content in plants did not vary significantly up to 174 DAP, when applied @ 2.50 g ai/plant at different intervals after planting. Absorption was very low when the insecticide was applied at 180 and 210 DAP. For ensuring residues within tolerance limits (0.10ppm) in raw fruits, the insecticide treatment has to be limited to 150 DAP and for ripe fruits the limit can be extended up to 180 DAP. The absorption and persistence of phorate and metabolites was significantly higher in plants grown in summer season than in those grown in rainy season. The absorption of insecticide was high in sandy soils and it was lowest in black cotton soils during the active absorption phase. The insecticide persisted at effective levels for 75 days in sandy, 90 days in lateritic upland and 105 days in black cotton soil. Sulfoxidation of the thioether moiety was the dominent metabolic pathway in sandy soil while desulfuration pathway was predominent in the other three soils. Application of phorate at planting, @ 2.50 g ai/plant, did not adversely affect the soil microflora as observed at the time of harvest of the crop.
Integrated control of sweet potato weevil Cylas formicarius Fabricius
(Department of Entomology, College of Agriculture, Vellayani, 1987) Palani Swami, M S; Mohandas, N
New disease of the Indian honey bee, Apis Cerana Indica F., in Kerala
(Kerala Agricultural University, 1992) Abraham Jacob; Rajan Asari, P A; Mohandas, N
Nuclear polyhedrosis of Opisina arenosella WLK. (= Nephantis serinopa Meyr;) (Cryptophasidae: Lepidoptera) and its utility for the control of the pest
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1985) Babu M Philip; Mohandas, N
The black headed caterpillar, Opising arenosella Hlk. (= Nephantis serinopa Meyrick) is a serious pest of coconut. The slender caterpillars found under the leaves in galleries made of silk and foreign matter feed on the chlorophyll tissues . Philip et al., (1982) reported the occurrence of a nuclear polyhedrosis virus in the larvae of O. arenosella. Basic information for judging the suitability of this pathogen for the control of the pest were lacking. Hence detailed studies were made on the symptamatology, morphology of the pathogen, histopathology, mode of transmission of the virus to the progeny, cross infectivity to other species of lepidoptera, bioassay of the virus , persistence of the virus on coconut foliage , effect of physical factors on the persistence of the virus, safety of the pathogen to non target organisms and the efficacy of the virusin controlling the pest in field.
On the persistent toxicity of various insecticides sprays to first instar caterpillars of Cnaphalocrocis Medinalis guenee, the rice leaf-roller
(Kerala Agricultural University, 1976) Mohandas, N; Nair, M R G K
Residues of fenthion, quinalphos and malathion in paddy grains following surface treatment of gunny bags
(Kerala Agricultural University, 1986) Ambika Devi, D; Mohandas, N; Visalakshy, A
Studies on the chemical control and insect-plant relationships of the rice leafroller, cnaphalocrocis medinalis guenee (Pyraustidae:Lepidoptera)
(Department of Entomology, College of Agriculture, Vellayani, 1975) Mohandas, N; Gopalakrishnan Nair, M R
The series of laboratory and field experiments were conducted to study the relative toxicity of 24 insecticides to noths and larvae of the rice leaf roller, cnaphalocreoois medinalis the relative effiency of these insecticides in controlling the pest in the field and the insect plant relationships between c.medinalis and different rice varieties. Suitable methods for the collection of moths of c.mdinalis from the field for the collection of their eggs and first instar larvae in sufficiently large numbers and for rearing the insect in the laboratory were eveloved.