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Subject: Agricultural Entomology × Author: KAU × End date: 2008 × Start date: 2008 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Population dynamics and management of erythrina gall wasp quardrastichus erythrinae kim.
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 2008) Beena, M P; KAU; Thomas Biju, Mathew
    . Studies were conducted to understand the population dynamics and management of Erythrina Gall Wasp (EGW)Quadrastichus erythrinae. An abstract of the work done and the results are given below. Population dynamics of Q.erythrinae was studied by observing weekly emergence of male and female insects from leaflets and petioles collected from field during the period from January 2006 to June 2007. The results showed that population was high in the months of July 2006, January 2007, April 2007 and June 2007.The present study indicated that the emergence od adult EGW was the highest from petioles. The increase in weight due to EGW infestation and gall production was the highest in the left lateral leaflets. Weekly mean population of EGW emerged during the period of study showed that the total number of male EGW (1096.36) was higher than the female insects emerged (763.13). Weekly mean population of the male and female emerged from the leaflets and petioles was correlated with weather parameters viz. maximum and minimum temperature. Maximum and minimum relative humidity and rainfall prevailed during the time of sampling, previous one week, previous 14 days,week 21 days before and week 28 days before. The results showed significant and positive correlation between population of male EGW and the minimum temperature, while no correlation existed between female population and other parameters studied. Comparison of biometric observation of uninfested and infested plant parts indicated that the weight of the leaflets and petioles increased significantly due to an increase in biomass. Due galling by EGW, the girth of the petioles was shortened to about one third of uninfested petioles. The emergence of EGW was maximum from petioled scored in the damage category ‘9’. Among the four groups of Erythrina stricta Roxb..stricta trees studied, based on the height of the trees, no group turned out to withstand the damage by EGW. Thiomethoxam, imidacloprid, carbaryl and acephate proved superior among the chemical tested insecticides tried against female and male EGW in the laboratory . Neem oil 2 per cent and neem oil-garlic 2 per cent proved superior among the botanical insecticides tried for protecting the newly formed side shoots. Among the systemic /translaminar insecticides applied on the galled plant parts, triazophos 0.05 per cent and imidacloprid .002 per cent were significantly superior in controlling the EGW emergence. In the field experiment conducted to evaluate insecticide-fungicide combination for EGW infestation and protection of the new side shoots, carbaryl 0.1 per cent and combination of imidacloprid 0.002 per cent and carbendazim 0.2 per cent effectively protected the side shoots up to 8 weeks after spraying. Residue analysis of dry pepper berries collected from pepper vines trailed, on the insecticide sprayed crythrina standards showed that residues at the time of harvest from trees sprayed with acephate 0.05 per cent dimethoate 0.05 per cent were below detectable limit. Where as the residues in pepper collected from lamda cyhalothrin 0.05 per cent and triazophos 0.05 percent treated trees was 1.38 ppm and 1.16ppm respectively. An overall analysis and interpretation of the data on population in relation to phenology to E.stricta foliar growth showed that there existed a six monthly cycle of damage by gall wasp resulting in complete defoliation of the trees by about six month followed by the next cycle of regrowth and re infestation .  
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    ThesisItemOpen Access
    Bio-efficacy and molecular characterization of the native isolates of Bacillus thuringiensis Berliner
    (Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 2008) Jyothi Sara, Jacob; KAU; Maicykutty, P Mathew
    Bacillus thuringiensis Berliner shortly known as B.t., is a gram-positive, spore forming bacterium that produces proteinaceous crystal containing insecticidal toxins. The host range of B.t. has expanded considerably due to extensive screening programmes. By virtue of its lack of toxicity towards other species of animals and human beings, B.t. has emerged as a safe candidate in the IPM programmes of various agroecosystems. Frequent exposure to one type of B. thuringiensis toxins can develop resistance in insects. Isolation of novel strains is important to overcome the onset of insect resistance. The present study on “Bio-efficacy and molecular characterization of native isolates of Bacillus thuringiensis Berliner” was conducted at the Department of Agricultural Entomology and CPBMB, College of Horticulture, Vellanikkara during the period from 2006 to 2008 with an objective to study the pathogenicity of 20 B. thuringiensis isolates collected from the Western Ghats of Kerala, one of the well known hot spots of biodiversity. The tobacco caterpillar, Spodoptera litura Fb. which was used as the test insect was reared in semi-synthetic diet (Ballal, 2004) and also in natural diet on castor leaves. The preliminary screening was performed for lepidopteran specificity with the ideal dose of 1 x 109 spores per ml showed that three isolates were toxic to S. litura. The per cent mortality caused by the lepidopteran effective isolates, namely, KAU-11, KAU-51, KAU-166 and the reference strain, HD-1 were 76.7 per cent, 80.0 per cent, 86.7 percent, 96.7 per cent respectively. A standardized bioassay was carried out with five different concentrations of all the selected isolates namely, KAU-11, collected from Thusharagiri (Calicut Dt.), KAU-51 from Kolahalamedu (Idukki Dt.), KAU-166 from Nelliyampathi(Palakkad Dt.) and the reference standard HD-1 (B. thuringiensis subsp. kurstaki). The mortality ranged from 63.3 to 100.0 per cent in various isolates and there was no significant difference between isolates. This indicated the equal effectiveness of the native isolates with the standard strain, HD-1. The LC5o value for the isolates was calculated by Finney’s Method of Probit Analysis. The lowest LC50 was obtained in KAU-51, with 6.3095 x 104 spores per ml and highest in KAU-11, with 1.2589 x 106 spores per ml. The lethal time to cause 50 per cent mortality (LT50) ranged from 44.4 h. to 96.0 h. in different isolates. The lowest LT50 was recorded in HD-1, which shows the ability of the standard to cause mortality slightly earlier compared to other isolates. The molecular characterization of the selected isolates was performed with RAPD-PCR technique. RAPD-PCR is a simple and rapid method for determining genetic diversity in various organisms and is a means of creating a biochemical finger print of an organism. Out of the 20 primers screened, 10 primers which produced more than five bands were selected for RAPD analysis. The RAPD data was used to generate a similarity matrix using the NTSyS programme. Clustering was done and dendrogram was drawn using Unweighted Pair Group Method of Arithematic Averages (UPGMA). The results showed that high variability exists between the selected isolates. Further studies are required to identify the subspecies of the efficient B.t. isolates to evaluate the field effectiveness against S. litura and other major lepidopteran pests for its utilization in pest management programmes. More primers need to be screened to study the genetic diversity of the isolates.
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    ThesisItemOpen Access
    Pests of tropical mushroom and their management
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 2008) Princy, John J; KAU; Naseema, Beevi S
    The occurrence of mushroom pests and their extent of damage in five different locations in Thiruvananthapuram district were studied in a survey conducted at monthly intervals for a period of one year from April 2006 to March 2007. An experiment was conducted to evaluate the efficacy of various botanicals and synthetic insecticides for the management of major pests of mushroom in the Mushroom house, Instructional Farm, College of Agriculture, Vellayani. The study revealed that the common pests of mushroom were springtails Seira sp., phorid flies Megaselia sp., sciarid flies, cucujoid beetle Cyllodes sp., staphylinid beetles viz., Staphylinus sp. and Scaphisoma nigrofasciatum Champ, noctuid moth, parasitic mite Poecilochirus necrophori Vitzthum, slugs and snails. Of these, the occurrence of Cyllodes sp., P. necrophori, noctuid moth, slugs and snails in oyster mushroom were reported for the fist time from Kerala. The common pests of mushroom namely Seira sp., Megaselia sp., S. nigrofasciatum, Cyllodes sp. were observed throughout the year in all the five locations. Staphylinus sp. was observed in three locations for a period of one year. P. necrophori and slug population were recorded only in one location from September 2006 to March 2007. Correlation studies between the population and extent of damage with weather parameters revealed that Seira sp., P. necrophori and slugs had positive correlation with relative humidity and rainfall, while it showed negative correlation with maximum temperature. Population of Megaselia sp., S. nigrofasciatum, Cyllodes sp., Staphylinus sp. were positively correlated with maximum temperature and negatively correlated with relative humidity and rainfall Efficacy of various botanicals and synthetic insecticides applied at different intervals after bed preparation on the incidence and extent of damage caused by mushroom pests in mushroom beds showed that lindane 0.05 per cent applied as floor treatment before bedding was the most effective. This was followed by dichlorvos 0.02 per cent and chlorpyriphos 0.02 percent applied at fifteenth day after bed preparation, which were at par. Among the various treatments adapted for the control of pests in mushroom, floor treatment with lindane before bedding has been found superior compared to other treatments. Considering a better control of pests and absence of residues, the floor treatment with lindane can be suggested for getting an effective control of pest, which presumed to result in a consequent higher yield.
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    ThesisItemOpen Access
    Behavioural ecology of cowpea aphid,aphis craccivora koch (aphididae:hemiptera)mediated by tri-trophic interactions
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2008) Jaba Jagdish; KAU; Haseena Bhaskar
    The study entitled “Behavioural ecology of cowpea aphid, Aphis craccivora Koch (Aphididae: Hemiptera) mediated by tri-trophic interactions” was carried out in the farmer’s fields and Department of Agricultural Entomology, College of Horticulture, Vellanikkara. The objectives of the study include evaluation of temporal and spatial dynamics of population of A. craccivora and associated natural enemy fauna, monitoring the patterns of dispersal, polymorphic transition and phenological relationship of A. craccivora in cowpea and assessing the role of plant, pest and natural enemy mediated semiochemicals in the population build up of A. craccivora and natural enemy fauna in cowpea. Field survey was carried out in the cowpea fields and glyricidia, a major alternate host of A. craccivora during May, 2007 – March, 2008 to study the population dynamics of A. craccivora (Koch) and its predators. The population of A. craccivora in cowpea was significantly high in November sown crop with the population reaching its peak in the first fortnight of December. In the field, the highest population was recorded from the East direction followed by North. Among the different plant parts, a significantly higher population of the aphid was recorded on leaves followed by pods. The aphid population showed a significant positive correlation with sunshine hours and wind speed whereas; the correlation with relative humidity though significant was negative. The predatory complex of A. craccivora on cowpea comprised of the coccinellids Cheilomenes sexmaculata (Fabricius), Coccinella transversalis (Fabricius), Scymnus latemaculatus (Motschulsky), Scymnus pyrocheilus (Mulsant), Psedaspidimerus trinotatus (Thunberg), Micraspis discolor (Fabricius), 9Harmonia octomaculata Fabricius) and Brumoides suturalis (Fabricius) and the syrphids Dideopsis aegrota (Fabricius) and Ischiodon scutellaris (Fabricius). C. sexmaculata was the most abundant predator on A. craccivora in cowpea. The populations of C. sexmaculata, C. transversalis, and the total population of the syrphids had shown a significant positive correlation with the prey population suggesting their density dependant relationship with the prey. In glyricidia, a higher population of A. craccivora was recorded during the second fortnight of December. The most abundant predator of A. craccivora in glyricidia was S. pyrocheilus. Correlations between the population of the aphid on glyricidia and weather parameters were not significant. However, temperature showed a significant correlation with the populations of the predators, C. sexmaculata, M. discolor and S. latemaculatus. C. sexmaculata and M. discolor also showed a significant negative correlation with relative humidity. Pot culture experiment was conducted to study the population buildup of A. craccivora and development of alate morphs. Higher population build up of the alates was recorded on leaves followed by pods that coincided with 48th day after sowing. Studies on the dispersal pattern of the alate morphs using yellow sticky trap showed maximum dispersal of the alates during day compared to night. More dispersal was found to occur during the crop season, June – July than February-March. Maximum alates were caught in the sticky traps installed in the north direction of the field. Trap installed at 1m distance from the potted plants caught more dispersing alates. The role of semichemicals originating from the host plant, the aphid and predators were studied using a four arm olfactometer. While A.craccivora responded more towards the water extracts of cowpea, the predatory coccinellids, C. sexamculata responded more to the hexane extract. Cowpea was found to be the most preferred host plant to A. craccivora in the olfactometer. Though the aphid showed more attraction towards the leaf of cowpea, it preferred the shoot tip to other plant parts in glyricidia. While A. craccivora prefered low density of conspecific population, C. sexmaculata showed more attraction towards high aphid population density in the olfactometer. The coccinellid predators C. sexamculata and C. transversalis responded more to the olfaction cues of aphid infested leaves of the host plants than the uninfested leaves. The predators showed a negative response towards the eggs of these predators in aphid colonies. In response to host plant odour, antennal and leg movements were observed in the aphid, the leg movement becoming faster as they reached closer. On locating the host plant, the antennal movement stopped in the aphid. The coccinellids also responded to prey odour by walking towards the prey. On reaching the prey, the predators tapped the aphid before they started feeding on it.