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Subject: Entomology × End date: 2018 × Start date: 2018 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Evaluation of certain botanicals against cowpea aphid, Aphis craccivora Koch
    (2018) Mohapatra, Swapnalisha; Gogoi, Inee
    Field and laboratory experiments were conducted in the experimental farm, Department of Horticulture, Assam Agricultural University, Jorhat and Department of Entomology, Assam Agricultural University, Jorhat during 2017-18 to evaluate the efficacy of few botanicals in reducing aphid population and to study the natural enemy complex associated with the cowpea aphid. A preliminary laboratory bioassay was carried out to determine the LC50 and relative toxicity of some botanicals (leaf extracts) viz., Pongamia pinnata, Polygonum hydropiper, Ocimum sanctum, Ageratum conyzoides, Lantana camara and Murraya koenigii along with check imidacloprid 17.8 SL and control. From the present work on bioassay, the order of toxicity to Aphis craccivora with respect to LC50 values was as imidacloprid (0.045%) > O. sanctum (0.828%) > P. hydropiper (1.158%) > M. koenigii (2.100%) > A. conyzoides (4.664%) > L. camara (5.779%) > P. pinnata (6.011%) after 24 hours, imidacloprid (0.036%) > O. sanctum (0.480%) > P. hydropiper (0.576%) > M. koenigii (1.209%) > A. conyzoides (3.188%) > L. camara (4.201%) > P. pinnata (4.328%) after 48 hours exposure period and imidacloprid (0.031%) > O. sanctum (0.316%) > P. hydropiper (0.341%) > M. koenigii (0.707%) > A. conyzoides (2.381%) > L. camara (3.200%) > P. pinnata (3.357%) after 72 hours. The order of relative toxicity was imidacloprid > O. sanctum > P. hydropiper > M. koenigii > A. conyzoides > L. camara > P. pinnata for the exposure period of 24, 48 and 72 hours, respectively. On the basis of LC50 values the most effective ones i.e., O. sanctum, P. hydropiper and M. koenigii each @ 5% were taken for further study on bio-efficacy along with neem oil @ 1%, river sand + neem leaf powder @ 10kg/ha (3: 1 ratio), ash @ 10kg/ha, ash + river sand @ 10kg/ha (5: 1 ratio), check imidacloprid 20gm a.i/ha and control. In the bio-efficacy study of the botanicals P. hydropiper leaf extract @ 5% was found to be most effective in reducing the aphid population up to 77.48% followed by neem oil @ 1% (74.11%), O. sanctum leaf extract @ 5% (74.00%), M. koenigii extract @ 5% (70.96%), ash @ 10kg/ha (68.04%), river sand + neem leaf powder @ 10kg/ha (3:1 ratio) (44.48%) and ash + river sand @ 10kg/ha (5:1 ratio) (42.53%) after seven days of spraying. All together five coccinellid predators viz., Coccinella transversalis, Cheilomenes sexmaculata, Harmonia dimidiata, Micraspis discolor and Brumoides suturalis were recorded as natural enemies feeding on aphids. From the correlation studies with weather parameters, aphids showed a significant negative correlation with average relative humidity (r = -0.515) and rainfall (r = -0.514). Among the coccinellid predators, Coccinella transversalis (r = -0.517) and Harmonia dimidiata (r = -0.505) showed significant negative correlation with average relative humidity. All the predators found viz., Coccinella transversalis (r = 0.883), Cheilomenes sexmaculata (r = 0.611), Harmonia dimidiata (r = 0.584), Micraspis discolor (r = 0.770) and Brumoides suturalis (r = 0.605) showed significant positive correlation with their prey i.e aphid, Aphis craccivora.
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    ThesisItemOpen Access
    LIFE CYCLE OF LAC INSECT ON DIFFERENT HOST PLANTS IN ASSAM CONDITION
    (AAU, Jorhat, 2018) Saikia, Priyanka; Das, Purnima
    Field and laboratory experiments were conducted at Lac park and Lac laboratory, Department of Entomology, Assam Agricultural University, Jorhat-13 to study the life cycle of lac insect, Kerria chinensis (Mahd.)and its associated fauna on four different host plants viz., Flemingia semialata (Roxb.), Flemingia macrophylla (Willd.), Flemingia strobilifera (Roxb.) and Cajanas cajan (Linn.). The study was conducted for two consecutive seasons of lac crop i.e., from 14th May to 27th October, 2017 (Season I) and 28th October, 2017 to 20th April, 2018 (Season II). Among the four investigated hosts, F. semialata (Roxb.) was recorded as superior to the other hosts in terms of broodlac production, phukilac production and scrappedlac yield (205.9 g, 98.96 g and 41.51 g) respectively, along with other parameters i.e. highest initial density of settlement (nos./sq.cm), final density of settlements (nos./sq.cm), density at crop maturity (nos./sq.cm), cell size (mm), cell weight (mg), resin weight (mg), fecundity (nos. of crawlers /female cell), broodlac yield (kg) and broodlac ratio (broodalc yield at harvesting/inoculated broodlac), and having lowest per cent of male cells, mortality % and broodlac-scrappedlac ratio. Life cycle in season I was completed in 165.21 days in F. semialata (Roxb.) whereas in season II life cycle took 172.21 days to complete. Likewise, all the parameters showed better results in season II compared to season I. The present investigation has strongly proved that the Kerria species prevailed in the North Eastern part of India is Kerria chinensis (Mahd.) (gene bank accession no. MH562709). Study on natural enemy complex of lac encrustation at lac laboratory, revealed the occurrence of three species of predators viz., Eublema amabilis Moore, Psedohypatopa pulverea Meyr. and Oryzaephilus surinamensis Linn., two species of parasitoids viz., Tachardiaephagus tachardiae (Howard) and Eupelmus tachardiae (Howard) and three species of hyperparasitoids viz., Eurytoma pallidiscapus, Cam., Apanteles tachardiae, pp. nov. and Bracon greeni Ashmead. Maximum population of pests were recorded during November, 2017 as compared to May, 2018. Eublema amabilis Moore were recorded more than other pests in lac encrustation F. semialata (Roxb.). The period of investigation in both the seasons (May, 2017 to April, 2018) showed the occurrence of 12 species of phytophagous pests on F. semialata (Roxb.), 11 species on F. macrophylla (Willd.), 3 species on F. strobilifera (Roxb.) and 3 species on C. cajan (Linn.). Four different species of coccinellid beetle viz., Coccinella transversalis Linn., Cheilomenes sexmaculata Fab., Micraspis discolor Fab. and Harmonia dimiata were recorded as natural enemies on crop pests of Flemingia ecosystem. Studies on population density of Archips sp., Somena scintillans Walker, Euproctis sp., Aphis craccivora Koch and Myzus persicae Sulzer were recorded in field condition. Correlation studies revealed that the population density of Archips sp. exhibited significant positive correlation with maximum temperature, minimum temperature, rainfall , wind speed and bright sunshine hours. The population density of S. scintillans Walker showed significant positive correlation with maximum temperature, minimum temperature and rainfall; whereas it showed significant negative correlation with bright sunshine hours. Similarly population density of Euproctis sp. showed significant negative correlation with maximum temperature and minimum temperature. The population density of A. craccivora Koch showed significant negative correlation with minimum temperature, rainfall and wind speed; whereas it showed significant positive correlation with bright sunshine hours. The population density of Myzus persicae Sulzer showed significant negative correlation with wind speed and significant positive correlation with bright sunshine hours. Multiple regression equations were developed for each of Archips sp., Somena scintillans Walker, Euproctis sp., A. craccivora Koch and Myzus persicae Sulzer to predict their seasonal incidences under the agro climatic conditions of Jorhat. The crop calendar revealed that the important pests of host plants viz., Archips sp. were occurred from July to October; Euproctis sp. from April to August; Somena scintillan Walker from August to November; Aphis craccivora Koch from July to February and Myzus persicae Sulzer from September to February in both seasons.
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    ThesisItemOpen Access
    Efficacy of some biopesticides and synthetic insecticides against banana leaf and fruit scarring beetle, Nodostoma subcostatum Jacoby (Coleoptera: Chrysomelidae)
    (2018) Kalita, Biraj; Gogoi, Inee
    Field and laboratory experiments were conducted in the experimental farm, Department of Horticulture, Assam Agricultural University, Jorhat and Department of Entomology, Assam Agricultural University, Jorhat during 2017-18to evaluate in vitro and in vivo efficacy of biopesticides and synthetic insecticides against banana leaf and fruit scarring beetle A preliminary laboratory bioassay was carried out to determine the LC50 and relative toxicity of the treatmentsviz., azadirachtin 0.03 EC, Beauveria bassiana WP, Metarhizium anisopliae WP, imidacloprid 17.8 SL, profenofos 50 EC along with check chlorpyriphos 20 EC and control. From the present work on bioassay, the order of toxicity with respect to LC50 values was profenofos 50 EC>imidacloprid 17.8 SL>azadirachtin 0.03EC>Metarhizium anisopliae WP>Beauveria bassiana WPfor the exposure period of 1,3 and 5 days, respectively.For field bio efficacy, the treatments were tested at three critical stages of growth of the banana plant and among the treatments tested, chlorpyriphos @ 0.05% proved to be the best treatment at all the three stages of growth in perusal of its ability in reducing the beetle population at 3, 7 and 15 days after treatment, followed by profenofos @ 1.5 L/ha and imidacloprid @ 20 g a.i./ha. Among the biopesticides, azadirachtin @ 2.5 L/ha arrayed up itself as the best over the other two. Plants that were bud injected with imiacloprid registered highest pulp to peel ratio, fruit weight, bunch weight, yield and B:C ratio. Seasonal incidence of leaf and fruit scarring beetleon Dwarf Cavendish was recorded at fortnightly intervals from May, 2017 to April, 2018. Highest population and scars were recorded during second fortnight of September, 2017 and lowest during first fortnight of January, 2018. The average population and scars produced by the insect showed positive and significant correlation with various meteorological factors except morning relative humidity. Multiple regression analysis of beetle population and scars produced by Nodostoma subcostatum with different meteorological parameters showed 69.2 % variation in population and 72.6 % variation in scars due to the combined effect of various meteorological parameters. On considering all the above facts and figures and hitherto due to nonexistence of other anticipatory technology, the bud injection method with imidacloprid and azadirachtin proved to be safer and competent preventive technique for reducing the percentage of blemished fruits (<15%) caused due to banana leaf and fruit scarring beetle in comparison to spraying method of application. This technology required very less quantity of pesticides and was able to keep the original superficial fruit peel appearance and significance, which in turn will able to fetch better price on quality fruits in market and provide financial profit to banana growers and traders.