Browsing by Author "Nasiya Beegum, A N"

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    Characterization, evaluation and formulation of beauveria bassiana (Bals.) strains against rice bug, leptocorisa spp. (Hemiptera:alydidae)
    (Department of Agricultural Entomology, Colllege of Agriculture, Vellanikkara, 2021) Nasiya Beegum, A N; Madhu Subramanian
    The rice bug, Leptocorisaspp. is one of the most important sap sucking insect pests of rice in the tropics. Both nymphs and adults suck sap from developing rice grains during the milky grain stage, leading to discoloured, empty or half-filled grains. Yield loss due to the bug infestation ranges from 10 to 35 per cent. Management of the bug essentially involves spraying with insecticides, for want of safer options. Biological control of rice bug remains hampered by absence of ideal bioagents. The entomopathogenic fungus (EPF), Beauveria bassiana (Bals.) has been reported as infecting rice bug, from several parts of the world, including India. In this context, the present study was undertaken with the objectives of collection, isolation and molecular characterization of local strains of B. bassiana, evaluation against Leptocorisa spp., identification of a cost effective mass production technology for the selected strain of B. bassiana, and formulation of the most effective strain of B. bassiana. Surveys were conducted over two seasons during 2016-17 at major rice growing tracts of Alappuzha, Ernakulam, Thrissur and Palakkad districts of Kerala to collect EPF infecting rice bug. However, EPF infected rice bug cadavers were obtained only from one location i.e., Pattambi in Palghat district.As only one isolate was obtained, a potential fungal pathogen earlier obtained from rice bug at Vellanikkara, Thrissur and maintained at AICRP on BCCP was also included in further studies. The above two isolates were identified through study of colony characters as well as through ITS sequencingand Basic Local Alignment Search Tool (BLAST). The isolate from Vellanikkara was identified as Beauveria bassiana, while the isolate from Pattambi was identified as Choanephora cucurbitarum. The pathogenicity of the two isolates was assessed through laboratory as well as pot culture studies. In the laboratory, B. bassianaisolate recorded more than 90 per cent reduction in population of rice bug nymphs and adults five andseven days after treatment respectively at all concentrations evaluated while C. cucurbitarum recorded only 18 to 53 per cent reduction in bug population. Pot culture studies confirmed the superiority of B. bassianaisolate over C. cucurbitarum with B. bassiana treated pots registering over 99 per cent mortality by 20 th day after treatment as against 27 to 31 per cent mortality in case of the latter.B. bassianaisolate was further evaluated at its most effective concentration, under field conditions in both Thrissur and Palakkad districts.B. bassiana proved to be on par with the insecticide malathion from 10 th day onwards at both locations. The compatibility of B. bassiana isolate with selected insecticides and fungicides was assessed using poisoned food technique. The results showed that the insecticide acephate was the most compatible with 31.29 per cent growth inhibition while the fungicide propiconazole was the least compatible with 85.71 per cent inhibition. Methods for talc based, oil based and aqueous formulations of B. bassianawere standardized.Palm oil was identified as the most suited carrier for oil based formulation through inhibition zone technique as well as through assessment of viability of B. bassiana spores. Glycerol(3%), carboxy methyl cellulose (0.5%) and chitin (5%) formed the best adjuvants for oil based, aqueousand talc based formulations respectively, based on viable cfu count 30 days after storage. All the three formulations were as effective as malathion in reducing rice bug populations in field trials. However, talc formulation was significantly superior to the remaining formulations in terms of yield as well as grain damage. Talc, oil and aqueous formulations had shelf life durations of six, five and four months respectively.
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    Morphological and biochemical bases of resistance to spotted pod borer, Maruca vitrata (FAB.) (Lepidoptera: crambidae) in cowpea
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Nasiya Beegum, A N; Madhu Subramanian
    Cowpea, Vigna unguiculata (L.), is an important legume of the tropics and subtropics. It is used as a grain, vegetable and fodder crop. Cowpea is cultivated as a vegetable crop across an area of 6714 ha in Kerala (DES, 2014). However, the productivity of cowpea, at 625 kg ha-1 is very low, one of the reasons being infestation by insect pests. Among the different insect pests, the legume pod borer, Maruca vitrata (Fab.) is the most important one causing loss of up to 60 per cent in cowpea (Singh and van Emden, 1979). The larvae of the spotted pod borer, as the name implies, bore into buds, flowers and pods and feed on internal tissues. Their concealed nature protects the larvae from natural enemies as well as application of insecticides to a considerable extent, making management of the pest difficult. Exploitation of host plant resistance, which is one of the most effective and eco friendly pest management strategies, has hardly been attempted in case of cowpea. It was in this context that the present study „Morphological and biochemical bases of resistance to spotted pod borer, Maruca vitrata (Fab.) (Lepidoptera: Crambidae) in cowpea’ was undertaken in the Department of Agricultural Entomology, College of Horticulture, Kerala Agricultural University, Thrissur during 2014 - 2015. The objectives of the experiment were to evaluate degree of resistance to pod borer in selected accessions of cowpea, as well as to identify the morphological and biochemical bases of resistance in cowpea to pod borer. Forty eight accessions, obtained from different sources, were evaluated for resistance to the spotted pod borer, M. vitrata. Significant variation was observed between the genotypes to pod borer damage at bud, flower and pod stages. The extent of borer infestation varied from zero to 41.04 per cent. Five accessions, viz., EC 100092, IC 39945, IC 2918, EC 98668 and IC 52110 recorded zero per cent damage at all the three stages. Twenty - six accessions recorded damage varying from 0.1 to 9.29 per cent and were on par with each other. All the above accessions were rated as resistant. Seventeen accessions with borer damage ranging from 11.15 to 41.04 per cent were rated as susceptible. The variety Bhagyalakshmy recorded the highest damage of 32.5, 50.39 and 47.95 per cent for bud, flower and pod respectively. Analysis of morphological basis of resistance to pod borer indicated that pod wall thickness was significantly and negatively correlated with per cent damage. Similarly trichome density was also negatively correlated with pod damage, though the correlation was not significant. Length of flower stalk as well as length of trichomes was positively correlated with borer damage but the correlation was not significant. Significant positive correlation was observed between per cent damage and total protein content, moisture content, total sugars and reducing sugars. However, significant negative correlation was observed in peroxidase and polyphenol oxidase activity with per cent damage. The study confirmed variability among cowpea genotypes in response to pod borer infestation, indicating the potential for utilization of host plant resistance in the management of pod borer in cowpea. It also indicated that the resistance in cowpea to Maruca vitrata could be related to biochemical constituents of the plant, which, however, need to be confirmed.