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2016 - 20192
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Subject: Agricultural Entomology × End date: 2019 × Start date: 2016 × Type: Thesis ×
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    ThesisItemOpen Access
    Bioecology and development of IPM module against fruit flies in cucurbits
    (2019-09) Mudoi, Abhilisa; Saikia, Dilip Kumar
    Fruit flies are the excellent candidates for studies of biodiversity, adaptability in changing climatic conditions and invasion to new areas because of their polyphagous nature, high reproductive potential, wide range of distribution and great economic importance as pests. Therefore, an extensive elaboration of fruit flies was carried out in five different districts under Upper, Central and Lower Brahmaputra Valley Zones of Assam to know the prevalence and diversity pattern of different fruit fly species of cucurbits. Five species of fruit flies viz., Bactrocera cucurbitae Coquillett, B. tau Walker, B. dorsalis Hendel, along with two new species viz., B. scutellaris Bezzi and Dacus longicornis Wiedemann were recorded from different districts of Assam. Out of the five districts, maximum number of 2492 individuals were observed to be trapped in cue lure in Darrang district. The species diversity index (1.285) and richness indices (0.393) of fruit fly was found to be highest in Michajan village of Sibsagar district, whereas the lowest species diversity index, (0.656) was in Dhepor village of Sibsagar district but the lowest richness indices (0.132) was observed in Khataniapara village of Darrang district. In respect of distribution pattern, the fruit flies had clumped distribution in all the five different districts under the present investigation. The morphometric parameters of fruit flies showed that the mean body length was the highest (11.846 ± 0.027mm) in female D. longicornis and lowest (5.631±0.053mm) in male of B. cucurbitae. In general, adult males were short-lived as compared to females, however, the adult longevity of female fruit fly in different cucurbits varied from 63.91 ± 1.16, 60.37±0.41, 49.82±0.50mm in respect of B. dorsalis, B. tau and B. cucurbitae against bitter gourd, bitter gourd and bottle gourd, respectively. Morphometrics of immatures stages revealed that the egg (1.26±0.02 × 0.43±0.02), larval (9.59±0.07 × 1.85±0.01) and pupal (5.82±0.01 × 2.46±0.02) size was highest in B. tau followed by B. cucurbitae with 0.88±0.01 × 0.18±0.01, 8.07±0.07 × 1.12±0.01, 5.21±0.03 × 2.22±0.02mm, respectively. It is imperative to obtain a baseline data on the seasonal occurrence pattern of fruit flies and the influence of abiotic factors on their activities in a particular ecosystem. Therefore, an experiment was carried out under field conditions at the Horticultural orchard, Department of Horticulture, Assam Agricultural University, Jorhat during 2017-18 and 2018-19 to find out a suitable eco-friendly management module against fruit flies of bitter gourd. Insect pests encountered with the crop revealed altogether seven species under three orders with four families viz., B. cucurbitae, B. dorsalis, B. tau, Aphis gossypii Glover, Epilachna vigintioctopunctata F., Aulacophora foevicollis Lucas and Monolepta signata Olivier which were registered as major pests of bitter gourd. Among the natural enemies, a total of sixteen species belonging to three orders and seven families were recorded. Twelve different pollinator species were also recorded during the study period associated with the crop. The seasonal incidence of fruit flies indicated a maximum of 189.90 and 179.60 number of fruit flies were trapped during April, 2017-18 and 2018-19, respectively. Among the different insect pests, the relative abundance of fruit fly, B. dorsalis was the highest with 73.65 in 2017-18 and 69.41 per cent in 2018-19 and the lowest was in case of A. foevicolis and A. gossypii, respectively with 1.69 and 2.65 per cent during the respective years. The correlation study with population build up of fruit fly showed a significant positive correlation with maximum and minimum temperature. As regards to fruit fly management strategies, module IV comprised of good agricultural practices, installation of cue lure @ 10/ ha, destruction of damage fruits, spray of neem based insecticides and spray of spinosad 45 SC @ 0.3 ml/L was found to be the best with 0.90 damaged fruits / m2, followed by module III (2.28 damaged fruits / m2) and module II (3.23 damaged fruits / m2). Similarly, module IV (1.36/ m2) and module III (2.46/ m2) was also found to be superior in suppressing the population of phytophagous beetle, E. vigintioctopunctata. In case of M. signata and A. foevocolis, module III (2.30,2.25) and module IV (1.00,1.18) was almost at par in reducing the population. The maximum yield of 97.43 q/ha with a benefit cost ratio of 2.26 was recorded in module IV, followed by next effective module III (83.93 q/ha) with a benefit cost ratio of 2.08. However, the cue lure barrix fly trap showed maximum efficacy related to trap index of 28.76 and the lowest was recorded in molasses trap with trap index of 21.79.
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    ThesisItemOpen Access
    Molecular Characterization and Physiological Aspects of Lepidiota mansueta Burmeister (Coleoptera: Scarabaeidae
    (2016) Handique, Gautam; Baruah, A. A. L. H
    The present investigations were carried out in the Department of Entomology and Department of Soil Science, DBT-AAU Centre, Assam Agricultural University (AAU), National Bureau of Agricultural Insect Resources, Bangalore and Tezpur University, during the years 2011-2015 to generate a comprehensive information on the molecular phylogeny as well as some physiological aspects of Lepidiota mansueta, a major white grub species endemic to Majuli river island of Assam. Molecular analysis of genetic diversity revealed that the highest per cent polymorphism and Polymorphism Information Content (PIC) was found for BEM 22 marker which was 80 per cent and 0.799 respectively, while lowest percent polymorphism and PIC was recorded for BEM 11 i.e. 8 per cent and 0.083, respectively. Estimation of genetic similarities among the 18 species of scarab beetles suggested that all species were dissimilar to one another. The similarity value ranged from 0.130 to 0.714. The lowest similarity value was found in between Adoretus renardi and Apogonia blanchardi (0.118) followed by A. blanchardi and Holotrichia sp. (0.130) and the highest similarity value was found between Maladera insanabilis and Onitis philemon (0.769) followed by O. philemon and Adoretus bicolor (0.714). The species L. mansueta had a close similarity to Maladera insanabilis (0.643) while the same was observed to be the lowest with Apogonia blanchardi (0.250). Two major clusters were derived from the dendrogram in which, L. mansueta could be comprehended to be genetically close to M. insanabilis, Catharsius molossus, O. philemon, A. renardi, Anomala pellucida and A. bicolor. However, within this group, L. mansueta stands as an outgroup. Laboratory experiments also revealed distinct sexual dimorphism in the antennal segments between the male and female beetles of L. mansueta. The length and breadth (mean+SD) of pedicel (0.574+0.165; 0.326+0.057), flagellum (1.452+0.272; 0.472+0.113), proximal lamellae (1.699+0.378; 0.767+0.103), middle lamella (1.724+0.174; 0.729+0.092) and distal lamella (1.686+0.137; 0.652+0.097) was significantly higher in males than the females which was recorded to be 0.322+0.014 & 0.214+0.011, 0.797+0.058 & 0.293+0.046, 1.503+0.229 & 0.594+0.069, 1.572+0.190 & 0.577+0.080 and 1.460+0.214 & 0.532+0.027 for pedicel, flagellum, proximal lamellae, middle lamella and distal lamella, respectively. Sensilla located in the antennae of both sexes of L. mansueta beetles also exhibited dimorphism. Scanning Electron Microscopic studies revealed 3 types of sensilla in males and 7 types in females. Wind tunnel bioassays showed clear affinity of adult males and females to prothoracic region (PTR) extracts of males while only males were found to be attracted to the abdominal extracts of females. GC-EAG readings also exhibited clear response of both male and female antennae to the PTR extracts of males while significant response was observed only in male antenna to abdominal extracts of females. GC-MS/FID analysis revealed 4 different compounds in the PTR extracts of males viz., cis-9-Hexadecenal, cis-9-Hexadecenoic acid, Octadec-9-enoic acid and 1-Hexacosene. Likewise, female abdominal extracts also registered 4 compounds viz., cis-9-Hexadecenoic acid, 18-Nonadecenoic acid, Octadec-9-enoic acid and 9,19-Cyclolanost-24-en-3-ol, acetate during the course of study. Microbial investigation of the gut content of third instar grubs of L. mansueta revealed 20 different bacterial cultures. Out of these, 5 bacterial cultures designated as B1, B6, B11, B15 and B19 had the population load with highest colony forming unit/ml. Bacterial flora was considerably varied in size, margins, elevation, gram staining and shape and the variations were based on utilisation of carbohydrates as well as their response to different enzymes. Out of the 5 bacterial cultures, B1, B6 and B15 exhibited cellulose degrading activities in laboratory conditions.