Browsing by Author "Sheila, M K"

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    Effect of sub-lethal doses of decamethrin and carbaryl on the orientation, feeding reproductive rate and survival of key pests of brinjal, Solanum melongena L.
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1989) Sheila, M K; Abraham, C C
    The effect of sub-lethal doses of decamethrin and carbaryl at their LD5, LD10, LD25 and LD50 levels on orientational stimuli, feeding, reproductive potential and survival of the three important pests of brinjal, namely, the epilachna beetle H.28 punctata, the aphidsA. gossypii and the leaf hopper A. b. bicuttula have been studied in the laboratory. In all the three test insects, positive orientational stimuli were not detected at all the tested sub-lethal levels of the two insecticides. A decrease feeding rate in H. 28 punctata was detected when the insects were exposed to the sub-lethal dose treatments. In A. crossypii and A. b. biguttula, the reduction in the feeding rate was more pronounced at the LD 50 level of both insecticides.
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    Host resistance in cowpea ( Vigna unguiculata (L .) Walp) to the pod borer Maruca testulalis (Geyer) (PyralidaeiLepidoptera)
    (Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1992) Anitha Kumari, V; Sheila, M K
    An investigation on the host resistance in cowpea ( Vigna unguiculata (L.) Walp) to the pod borer Maruca testulalis (Geyer) was carried out by screening 100 varieties of cowpea during 1990 - 91. These were classified into highly susceptible, moderately susceptible and moderately resistant classes. This study rules out the chance of any of the varieties screened to be resistant to this particular pest. Selected accessions from the three different classes based on the field evaluation, were subjected to artificial infestation by the first instar larvae of M. testulalis on caged plants in the green house. Here too, the susceptibility spectrum was found to be similar to the trend observed in the field trial. The accession V30 was identified to be the most moderately resistant type and V100 as the most susceptible one. In the studies on antibiosis it was found that the larvae reared on moderately resistant type took longer durations of development as compared to the susceptible ones. The larval survival as well- as the adult emergence was lower in the resistant types The highly susceptible accessions produced more females than the resistant lines. The fecundity of F females was adversely affected when the larvae were reared on the moderately resistant accessions. Among the biophysical components, though the pod wall thickness and pubescence of the pods did not show any correlation with the level of borer infestation, the length of flower stalks, disposition of corolla, calyx and seeds and the nature of seed testa, had a positive influence on its distribution. Positive correlations were also detected between the mean percentage of total sugars, crude protein, amino acids and nitrogen in the pods on the one hand and pod damage on the other.
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