Browsing by Author "Madhu, Subramanian"
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ThesisItem Open Access Bioecology and management of ginger rhizome maggots(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Sandhya, P T; KAU; Madhu, SubramanianA study entitled “Bioecology and management of ginger rhizome maggots” was carried out at College of Horticulture, Vellanikkara during 2013-2014, with the objective to identify the major species of rhizome maggots on ginger; to study the bioecology of major species of rhizome maggots and to evaluate eco-friendly management measures against the rhizome maggots. Surveys were conducted in farmers’ fields at Vellanikkara and Madakathara panchayats of Thrissur district as well as Pattencheri and Perumatty panchayats of Palakkad district during August, September and October months of 2013, for identification of the major species of ginger rhizome maggots. Three species of rhizome maggots were obtained in all the four locations surveyed which were identified as Mimegralla sp. nr coeruleifrons (Macquart, 1843), Eumerus figurans (Walker, 1859) and Elassogaster sp. nr linearis (Walker, 1849). This is the first report of the incidence of E. figurans in India, Elassogaster sp. nr linearis, is recorded for the first time as a ginger rhizome maggot. Mimegralla sp. nr coeruleifrons was the most abundant species in all the locations surveyed and constituted 96.26 per cent of the total number of maggots collected. E. figurans accounted for 2.96 per cent of the overall population, followed by Elassogaster sp. linearis, forming 0.82 per cent of the maggots collected. Studies on the biology of Mimegralla sp. nr coeruleifrons showed the average incubation period was about 3.75 days, while the mean duration of first, second and third instars was 2.25, 3.15 and 6.70 days respectively. The mean pupal period lasted for 8.80 days. The longevity of adult male and female fly were 43.90 and 51.00 days respectively, with a sex ratio of 1:1. The morphometric observations of the different life stages of Mimegralla sp. nr coeruleifrons showed that eggs, on an average, measured 0.75 mm in length and 0.20 mm in width. The size of the first, second, and the third instar maggots averaged 0.63 × 0.16 mm, 4.2 × 0.90 mm and 8.1 × 1.68 mm in length and width respectively, while the pupae recorded a mean length of 5.36 mm and mean width of 1.65 mm. The adult male and female flies measured 11.2 × 1.30 mm and 13.56 × 2.18 mm respectively. The average fecundity of an adult female fly was 55.4 eggs during an oviposition period of 1 to 3 days. Attempts at documentation of natural enemies revealed that Trichopria malabarensis Rajmohana and Narendran sp. nov. (Hymenoptera:Diapriidae), a gregarious pupal parasitoid, was the most important natural enemy of Mimegralla sp. nr coeruleifrons in the field. An unidentified spider belonging to the family Araneidae was observed to feed on the adult flies in the field. No pathogens were isolated from maggots collected from the surveyed locations. Two entomopathogenic fungi viz. Metarhizium anisopliae (Metschnikoff) Sorokin and Beauveria bassiana (Balsamo) Vuillemin, along with two entomopathogenic nematodes Steinernema carpocapsae Weiser and Heterorhabditis indica Poinar and two insecticides, namely, fipronil and chlorpyriphos were evaluated in the laboratory for their efficacy in managing rhizome maggots. Petri plate bioassay as well as rhizome dip bioassay revealed that chlorpyriphos (20EC) @ 300 g a.i. ha-1 to be the most effective treatment, recording cent per cent mortality within 24 h after treatment. Fipronil 5SC @ 50 g a.i. ha-1 recorded an average mortality values of 90 and 66.66 per cent in Petri plate and rhizome dip assays respectively. Among the entomopathogenic organisms, the nematode H. indica recorded 16.66 per cent mortality while the fungus M. anisopliae recorded 3.33 per cent mortality in the Petri plate bioassay. Both B. bassiana and S. carpocapsae failed to induce mortality in the treated maggots. The entomopathogens failed to record any mortality in the rhizome dip study. The pot culture studies confirmed the above findings with chlorpyriphos and fipronil recording cent per cent and 78 per cent mortality respectively. Analysis of the ginger rhizomes, twenty days after exposure to fipronil, recorded a value of 0.052 mg kg-1, marginally above the detectable limit of 0.05 mg kg-1 of rhizome. Studies on the interaction between the maggots of Mimegralla sp. nr coeruleifrons with Pythium aphanidermatum, which causes rhizome rot in ginger indicated that infection by the fungus could be independent of maggot. While all the plants inoculated with P. aphanidermatum alone, as well as the plants inoculated with P. aphanidermatum along with the maggots of Mimegralla sp. nr coeruleifrons showed rhizome rot symptoms, infestation by maggots alone, failed to produce any such symptoms. The establishment of maggots, at 70 per cent was also greater in rhizomes inoculated with the fungus, as against 42 per cent in rhizomes treated with maggots alone.ThesisItem Open Access Bioefficacy of entomopathogenic fungi against rice bug, Leptocorisa oratorius Fab. (Hemiptera: Alydidae)(Department of Agricultural Entomology,College of Horticulture, Vellanikkara, 2016) Neenu, Chandran; KAU; Madhu, SubramanianA study titled “Bioefficacy of entomopathogenic fungi against rice bug, Leptocorisa oratorius Fab. (Alydidae: Hemiptera)” was carried out at Dept. of Agricultural Entomology to evaluate efficacy of three entomopathogenic fungi namely Beauveria bassiana, Metarhizium anisopliae and Lecanicillium lecanii for the biocontrol of rice bug. The preliminary evaluation comprised of pot culture experiment with the fungi being applied at four different concentrations ranging from 105 to 108 spores ml-1 along with insecticide malathion 500g a.i. ha-1 and an untreated control. Mortality of rice bugs were recorded at 24h interval for 10 days. Ten days after treatment B. bassiana was the most effective among the three fungal pathogens tried, with mortality values ranging from 68.88 per cent at 105 spores per ml to the highest value of 97.77 per cent at 108 spores per ml. This was followed by malathion with 95.55 per cent and B. bassiana at 107 spores per ml with 93.33 per cent mortality respectively, all being on par with each other. M. aniospliae and L. lecanii at the rate of 108 spores per ml registered the highest mean mortality of 71.11 and 62.22 per cent respectively.ThesisItem Open Access Biological control of the tobacco cutworm Spodoptera litura (Fabricius) (Lepidoptera:Noctuidae) using Sycanus collaris (Fabricius) (Hemiptera: Reduviidae)(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2021) Gadikota, Sravanthi; KAU; Madhu, SubramanianSalad cucumber (Cucumis sativus L.) is among the most popular vegetables grown in polyhouses across Kerala, which has been gaining significance in recent years. However, the warm, humid conditions, abundance of food and the relatively low presence of natural enemies encourage build up of arthropod pests in polyhouse cultivation. Among these, the tobacco cutworm Spodoptera litura (Fab.) (Lepidoptera: Noctuidae) is one of the destructive pest. Management of the tobacco cutworm using insecticide based management strategies is not advisable as cucumber fruit is consumed in raw form. Biocontrol could be a more ecologically sound and economically feasible alternative. The reduviid bug, Sycanus collaris (Fab.) (Hemiptera: Reduviidae) is one such potential candidate for biocontrol of S. litura in polyhouses. However, S. collaris remains to be evaluated as a biocontrol agent under Kerala conditions. Hence a study was conducted to investigate the biology, functional response and prey stage preference of the reduviid predator S. collaris as well as to evaluate its potential for the management of S. litura on cucumber under polyhouse cultivation. Biology of S. collaris was studied on larvae of Galleria mellonella. Eggs were hatched after a mean incubation period of 13.21 days. Development of nymphs, normally with five instars, with a mean duration of 12.55, 9.12, 8.88, 10.95 and 15.93 days respectively. After the pre oviposition period of 12.60 days, egg laying continued for 51.86 days. Females died in 13.43 days after laying last batch of eggs. Average fecundity of the bug was 451.56 eggs. Mean longevity of 78.95 days was longer for females than 66.29 days for adult males. Functional response of fifth instar nymphs of S. collaris on third instar larvae of S. litura at different prey densities of 1, 2, 4, 8 and 16 larvae/bug was assessed in laboratory. Nymphs of S. collaris killed up to 5.50 larvae in 24 h at a prey density of 16 larvae per bug. Logistic regression analysis revealed a type II curvilinear functional response with an attack rate of 0.0198 h -1 while the handling time was between 0 to 0.460 h.The prey stage preference of the fifth instar nymphs of S. collaris on S. litura was studied by offering all the five different larval instars larval instars in equal proportions of 2:2:2:2:2 ratio. The predator showed marked preference towards first, second and third instar larvae of S. litura larvae over fifth instar larvae. The predator also showed significantly higher preference to third instar S. litura larvae as compared to fourth instar larvae. Biocontrol potential of S. collaris against tobacco caterpillar, S. litura on salad cucumber in polyhouse conditions was evaluated on KPCH 1 variety of cucumber. The plot in which predator was released recorded significantly lower number of S. litura compared to untreated control. The population of S. litura declined by 63.4 and 89.4 per cent, respectively on the first and third day after release of the predator and no larvae were observed on the five days after bug release. However, the larval population of five per plant showed no reduction after five days, in control plots. The mean yield per plant in which predator was released @ 100 nymphs/50 m 2 recorded significantly higher yield than control plot. The study demonstrated that the reduviid predator S. collaris can be used for inoculative release for the management of S. litura in protected cultivation.ThesisItem Open Access Morphological and biochemical bases of resistance to melon fruit fly, [Bactrocera cucurbitae(Coquillett)(Diptera:Tephritidae) in Bitter gourd(Momordica charantia L.)](Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2014) Manju, Roshni K; KAU; Madhu, SubramanianA study titled “Morphological and biochemical bases of resistance to melon fruit fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) in bitter gourd (Momordica charantia L.)” was undertaken at College of Horticulture, Vellanikkara during 2013-2014 with the objectives of evaluation of the degree of resistance to melon fruit fly in selected accessions of bitter gourd, identification of morphological and biochemical bases of resistance and assessment of the olfactory response of melon fruit flies to fruit extracts of bitter gourd accessions. A field experiment was carried out in Randomised Block Design with ten treatments and three replications at Instructional Farm, Vellanikkara. The treatments consisted of accessions Priya, Preethi, Priyanka, CO-1, VKB-136, VKB-130, VKB-196, IC-0596980, IC-0596981 and IC-0596983. The resistance of bitter gourd accessions to melon fly was evaluated in terms of per cent fruit damage and larval density. The results showed significant variation in fruit infestation among the accessions evaluated. The lowest damage of 9.13 per cent was recorded in VKB-196 followed by CO-1 at 10.17 per cent, both being on par. Four accessions, including Priya (49.08 %), Priyanka (50.99 %), VKB-130 (53.14 %) and Preethi (64.56 %) recorded higher levels of infestation and were on par. Melon fly damage was found to be influenced by the fruit characters of different accessions. Correlation of infestation with fruit characters such as colour, weight, length, width, flesh thickness, spine length, spine form and spine density revealed that spine density and flesh thickness were negatively and significantly correlated with per cent fruit damage (-0.81 and-0.69 respectively) and larval density (-0.74 and -0.69 respectively). VKB-196, which recorded the highest values for flesh thickness and spine density (0.52 cm and 9.83/cm , respectively) recorded the lowest incidence of 9.13 per cent while VKB- 130 with flesh thickness of 0.32cm2 and spine density of 4.81 cm2 recorded higher damage of 53.14 per cent. Analysis of parameters like protein content, moisture content, peroxidase activity and polyphenol oxidase activity showed a negative and significant correlation of peroxidase activity with fruit fly infestation. Studies on olfactory responses of gravid female melon fly to fruit extracts recorded higher response to hexane fruit extract as against aqueous extract. Similarly melon flies showed greater attraction to those accessions which had recorded higher per cent damage, suggesting presence of volatile chemicals which might have mediated response of melon fly towards the accessions. Based on present investigations, VKB-196 and CO-1 may be rated as highly resistant to melon fly, IC-0596983 as resistant, IC-0596981, VKB-136, IC-0596980 and Priya as moderately resistant and VKB-130, Preethi and Priyanka as susceptible. The studies also show that resistance could be mediated by fruit characters like flesh thickness, spine density and peroxidase activity. Sustained efforts could lead to development of melon fly resistant bitter gourd varieties, providing the much needed edge to melon fly management in bitter gourd.