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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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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.
  • 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.
  • 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.
  • ThesisItemOpen Access
    Effect of different artificial food on the growth and development of honeybee, Apis cerana (Hymenoptera : Apidae)
    (AAU, Jorhat, 2017-07) Borah, HEMI; Deka, M. K.
    Experiment was conducted during 2016 in the Apiary and Apiculture Laboratory, Department of Entomology, AAU, Jorhat to see the “Effect of different artificial food on the growth and development of honeybee, Apis cerana (Hymenoptera: Apidae)”. It was found that the colony strength was found to be maximum (6.50±0.36) and (7.25±0.26) in the treatment 5 (Soybean flour + Sugar solution + Yeast + Vitamins) and lowest was found to be (5.57±0.58) and (6.30±0.82) at treatment 7 that is sugar solution (Control) after 7 and 15 days respectively. The highest egg area (20.22±1.79cm²) and (24.54±1.43cm²) was observed in the treatment 5 and lowest was found to be (16.26±1.97cm2) and (20.32±1.16cm²) at treatment 7 after 7 and 15 days respectively. Likewise, the maximum larval area (17.19±1.68cm²) and (20.35±0.85cm²) was observed in the treatment 5 and minimum was found to be (11.45±0.42cm2) and (13.39±1.51cm²) at treatment 7 after 7 and 15 days respectively. And the highest pupal area (17.62±1.10cm²) and (24.34±0.58cm²) was observed in the treatment 5 and lowest was found to be (11.24±0.57cm²) and (18.22±1.13cm²) at treatment 7 after 7 and 15 days respectively. The maximum pollen area was observed after 7 days (9.32±2.09 cm²) and 15 days (14.49±1.12cm²) in treatment 5 and lowest was found to be (5.48±1.43cm²) after 7 and (8.23±0.99cm²) after 15 days at treatment 7. The highest honey hoarding was observed after 7 days and 15 days of treatment in treatment 5 are (15.10±0.57cm²) and (22.97±1.09cm²) and lowest was found to be (10.96±0.04cm²) and (15.40±0.24cm²) at treatment 7 respectively. The highest length of larvae was observed (0.67±0.02cm) after 5 days of treatment in treatment 5 and lowest was found to be (0.50±0.10cm) at treatment 7. The maximum breadth of larvae was observed (0.35±0.04cm) after 5 days of treatment in treatment 5 and lowest was found to be (0.28±0.10cm) at treatment 7. The highest weight of larvae (0.33±0.02gm) was also observed in treatment 5 after 5 days of treatment and lowest was found to be (0.27±0.02gm) at treatment 7. The maximum length of pupae (1.00±0.06cm) was observed after 12 days of treatment in treatment 5 and minimum was found to be (0.88±0.06cm) at treatment 7. The highest breadth of pupae (0.46±0.06cm) was observed after 12 days of treatment in treatment 5 and lowest was found to be (0.39±0.06cm) at treatment 7. Likewise, the highest weight of pupae (0.36±0.03gm) was observed after 12 days of treatment in treatment 5 and lowest was found to be (0.30±0.02gm) at treatment 7. The enemies occurred in the colonies during the year were wasps, waxmoth, ants, lizard and cockroach. The diseases found in the colonies during observation were Thaisac brood and Nosema. The lowest larval mortality was observed (0.10±1.00%) after 5 days of treatment in treatment 5 and 3 and highest (0.67±0.58%) was found at treatment 7. The minimum pupal mortality (1.26±1.15%) and (0.23±1.00%) was observed in treatment 5 and maximum was found to be (1.67±1.00%) and (0.59±1.15%) at treatment 7 after 7 and 12 days of treatment respectively. However lowest adult mortality was observed (1.33±0.58%) and (0.56±0.58%) after 7 and 15 days of treatment in treatment 5 and highest was found to be (1.67±1.15%) and (0.67±0.58%) at treatment 7 respectively. The various meteorological factors viz. temperature, relative humidity and rainfall influenced the brood area, weight of larvae and pupae. Maximum temperature and maximum relative humidity showed positive correlation with brood area, weight of larvae and pupae. On the other hand, minimum temperature, minimum relative humidity and rainfall showed negative correlation with brood area, weight of larvae and pupae.
  • ThesisItemOpen Access
    INTRAGUILD PREDATION AND INTERACTION BETWEEN Coccinella transversalis Fab. AND Coccinella septempunctata L. ON EGGPLANT
    (AAU, Jorhat, 2017-07) Rohman, Mohsin Musaddik; Devee, Anjumoni
    The experiment on Intraguild predation and interaction between Coccinellatransversalisand Coccinellaseptempunctata were carried out during 2015- 2017 at Experimental Farm, Deptt. ofHorticulture and the laboratory, Deptt. ofEntomology, Assam Agricultural University, Jorhat. Two species of aphid viz., Aphis gossypii and Myzuspersicaeandsix species of coccinelliid predators viz., C.transversalis, C.septempunctata,Cheilomonassexmaculata, Harmoniadimidiata, BrumoidessuturalisandMicraspis discolor were collected and identified from eggplant. TheA.gossypii(36.04%) was comparatively more abundant on eggplant than M.persicae(17.04%) at field andA.gossypiiwas found throughout the cropping season. Among the coccinellid predators, C.transversalisand C.septempunctatawere most dominant with their relaiveabundance 1.12% and 0.99%, respectively. Besides aphids, five other insect pestsviz.,Bemisiatabaci, Leucinodesorbonalis, Amrascabiguttulabiguttula, HenosepilachnavigintioctopunctataandMonoleptasignatawere found to infest eggplant during 2015-2017. The coccinellid predators plays important role in control of aphids population. When observed the intraguild predation between dominant predator C.transversalisand C.septempunctata in presence of extra guild prey A.gossypii, it was found thatthemean consumption of A. gossypii by a singleC. transversalis3rd instar and 4th instar grub were 48.10±1.83 and 77.75±2.43, respectively. While, the mean consumption ofA. gossypii bya singleC. septempunctata, 3rd instar and 4th instar grub were 47.80±1.60 and 69.95±1.63, respectively.When both the predator were released together in different combinations like C.transversalis(4th)×C. septempunctata(4th), C. transversalis(4th)×C. septempunctata(3rd),C.transversalis(3rd)×C. septempunctata(4th) andC. transversalis(3rd)×C.septempunctata(3rd) and their consumption were 91.55±0.81, 84.73±0.83, 83.88±0.72 and 72.006±0.81, respectively. The combined effect of these two predators was assessed by Multiplicative Risk Model and it was found that in all combinations, the observed consumption was significantly lower than the expected consumption, except in case of ofC. transversalis(3rd)×C. transversalis(3rd) instar.This indicated that in lower instars for food competition was less in comparison to higher instars. When different instars of C. septempunctatawere combined together in all cases the expected consumption was always significantly higher than the observed consumption. This indicated that there was some harmful or intraspecific effect among the different instars of C.septempunctata, when consumed prey. When both the predators released together in different combinations, the expected consumption of combination of both the predators was significantly higher than the observed consumption and it indicated the antagonistic effect of both the predators in presence of sufficientA. gossypiipopulation.When observedintra and interspecific interaction between both the predators in presence of sufficient A. gossypii, there was no cannibalism in both the species.But in absence ofA. gossypii,C.septempunctata, showed highest intraspecific cannibalism(53.30%) among 3rd and 4thinstar and lowest (13.33%) was observed in between C. transversalis(4th)×C. transversalis(4th). The interspecific interaction in absence of aphids, C. septempunctata(4thinstar)cannibalised maximum(35%) on C. transversalis (3rd) and lowest(10%) was registered by C. transversalis(3rd) on C. septempunctata(3rd) instar. Adults of both the species cannibalised 100% of conspecific and heterospecific grub in absence of aphid.As the experiment was done on petri dish and both the predators showed antagonistic effect, thus it is recommended not to release these two coccinellid predators together in protected cultivations and the experiment should be repeated in potted plants and open field conditions.
  • ThesisItemOpen Access
    Development of bio-intensive IPM module against insect pests of rice
    (AAU, Jorhat, 2017-07) Borah, Binita; Das, Purnima
    Field experiment were carried out carried out in ICR (Instructional cum Research) Farm during Sali and Ahu season 2016-2017. Incidence of major pest stem borer, leaf folder, caseworm, whorl maggot and gundhi bug and their natural enemies viz., coccinellid, spiders, and dragonfly/damselfly were recorded throughout the crop growth period. However, the stem borer, leaf folder, caseworm, whorl maggot and gundhi bug were more prominent during Sali season, 2016 and stem borer, leaf folder, caseworm, whorl maggot and gundhi bug were prominent during Ahu season, 2017. Among all the pests, the stem borer was most dominant (6.16% DH) and leaf folder was least dominant (3.93%) at early stage of crop during Sali season, 2016 whereas, during Ahu season, 2017 the whorl maggot was most dominant (9.76%).The correlation study revealed that the infestation of different pests and their natural enemies was influenced by the weather parameters in both the years. Correlation studies during Sali, 2016 revealed that infestation of stem borer had significant negative relation with Tmax (r= -742) and significant positive relation with RH (mor) (r =0.795). The infestation of leaf folder had significant negative relation with Tmin (r =-0.804), RD (r =-0.499), RH (mor) (r =-0.760); and the infestation of caseworm had significant negative relation with Tmin (r =-0.848), RD (r=-0.535); whereas it showed significant positive correlation with RH (mor) (r =+0.709). Gundhi bug had significant negative relation with Tmax (r =-0.775), with Tmin (r=-0.930). Correlation studies during the Ahu season, 2017 showed that the infestation of whorl maggots had significant positive relation with Tmax (r =+0.741) and Tmin (r =+0.972) and the infestation of stem borer had significant positive relation with Tmax (r =0.726) and Tmin(r =0.942) and no significant relation was found between gundhi bug and meteorological parameters during Ahu, 2017. Out of the eight treatment tested, the treatment combinaton of Beauveria bassiana WP @ 10gm/lit along with sub-lethal dose of chlorpyriphos 20EC @ 1ml/lit was found to be most effective in reducing the infestation of stem borer, leaf folder,case worm and whorl maggot during during Sali and Ahu 2016-2017.
  • ThesisItemOpen Access
    POPULATION DYNAMICS OF APHIDS AND THEIR ROLE IN INCIDENCE ON VIRAL DISEASES OF POTATO, Solanum tuberosum L.
    (AAU, Jorhat, 2017-07) Debbarma, Dipendu; Bhattacharyya, Badal
    Field and laboratory investigations were carried out to know the population dynamics of potato aphids and their role in disseminating viral diseases at Assam Agricultural University, Jorhat during 2016-17. Experimental results delineates the presence of only one species of aphid (Myzus persicae Sulzer) and found active from 2nd week of December, 2016 to 1st fortnight of February, 2017. The lowest (0.19 / leaf) and highest (2.56 / leaf) population of M. persicae was recorded on 15th December, 2016 and on 26th January, 2017, respectively. Correlation studies between weekly mean population of aphids / leaf and different meteorological parameters registered significant negative correlation with the morning (r=-0.843) and evening (r=-0.673) relative humidity. However, other meteorological parameters viz., maximum and minimum temperature, total rainfall and BSSH were found to be non significant. Altogether eight different species of coccinellids viz., Mecraspis discolor (Fab.), Cheilomenes sexmaculata (Fab.), Coccinella transversalis (Fab.), Coccinella septempunctata L., Brumoides suturalis (Fab.), Propylea sp., Harmonia dimidiata (Fab.) and Coelophora saucia (Mulsant) and one species of spider (Neoscona sp.) were recorded during the course of the study. The maximum population of coccinellids (0.32/plant) coincided with the peak aphid population (2.56/leaf). Correlation studies of M. persicae with their aforementioned natural enemies revealed a highly significant positive relationship. Significant negative correlation with morning relative humidity was registered for both cocinellids (r=-0.734) and spider (r=-0.809) population. However, other meteorological parameters viz., maximum and minimum temperature, total rainfall and BSSH were found to be non significant. The first incidence of viral disease was observed after 42 days of sowing of potato and the maximum disease incidence (28.39%) was recorded on 2nd week of February, 2017. Altogether ten alternate hosts of M. persicae viz., Melastoma melabathricum L., Mikania micrantha Kunth, Chromolaena odorata L., Ageratum houstonianum Mill., Solanum nigrum L., Hibiscus rosa-sinensis L., Lycopersicon esculentum Mill., Capsicum annum L., Solanum melongena L. and Spilanthes calva DC. were recorded from the vicinity of the experimental plots. Out of these, potato leaf roll virus was detected only in Melastoma melabathricum L. besides potato leaves and M. persicae.
  • ThesisItemOpen Access
    DIVERSITY OF SPIDERS (ARANEAE) IN TEA
    (AAU, Jorhat, 2018-01) Hazarika, Somar; Bora, D.K.
    A survey was conducted to study the diversity of spiders in different tea gardens viz., conventional, organic and small grower tea gardens of Jorhat district from May, 2016 to April, 2017. The results revealed a total number of 2954 specimens of spiders collected under 16 genera, 8 families and 20 species viz., Cyrtophoracicatrosa, Nephila kuhlii, Argiope pulchella, Cyclosa mulmeinensis, Neoscona sp, Cyclosa spirifera, Cyclosa bifida, Araneus mitifica, Oxyopes sitae, Oxyopes shweta, Oxyopes sp, Rhene danieli, Phintella vittata, Telamonia dimidiata, Tetragnatha sp, Leucauge decorata, Heteropoda ventoria, Xysticus sp and Perdosa peaudoannulata. Among all the species, Castianeira furva has been recorded for the first time from this region. Species richness (R = 3.07) and evenness (E = 0.96) was recorded the highest in Deha T.E. (organic garden) and was found lowest for Saikia T.E (small grower garden) i.e., 2.51 and0.89 respectively. However, species diversity was recorded highest in conventional garden, Dhloi T.E. (H’ = 2.88). The correlation studies revealed that the spider population exhibited significant positive correlation with total rainfall (r = 0.776) and non-significant for maximum temperature, minimum temperature and evening relative humidity while, a significant negative correlation was observed with morning relative humidity (r = -0.797) and bright sunshine hour (r = -0.676). Some morphological and biochemical characters of seven selected tea clones (TV 1, TV 2, TV 7, TV 9, TV 12, TV 18, TV 23) in the Experimental Garden of Plantation crops, Assam Agricultural University, Jorhat were examined to determine their effects on common insect pests and spider population. The results showed that all the clones were susceptible to the pests, TV 23 being more susceptible compared to others (H. theivora 6.22 no/bush, O. coffeae 18.35 no/leaf, Hyposidra sp 3.43 no/bush). However, no significant difference for spider populations was found to exist amongst the clones. With respect to morphological characters, the examined clones showed significant difference for total number of branches, leaf area and trichome densities. The differences in leaf moisture contentwere also significant. Moreover, it was found that the phenol content of examined clones gradually decreased due to pest infestation and the reduction was highest in TV 23 (22.43%). The linear correlation among morphological and biochemical attributes of selected tea clones with pests showed that total no of branches and leaf area had a non significant negative correlation with H. theivora (r = - 0.664, - 0.333), O. coffeae (r = -0.277, -0.175) and Hyposidra sp (r = -0.156, -0.179) while trichome density had significant negative correlation with H. theivora (r = -0.643) O. coffeae (r = -0.475) and Hyposidra sp (r = - 0.493). However, the moisture content showed a non-significant positive correlation for H. theivora (r=0.064) but established a negative association with O. coffeae (r = -0.446) and Hyposidra sp (r = -0.370). Regarding insect pests, both the reduction in phenol content and spider population exhibited a significant positive association. A field experiment was conducted in the Experimental Garden of Plantation crops, Assam Agricultural University, Jorhat, during 2016 and 2017 to investigate the effect of pesticides on common insect pests and spider population in tea plantation. On the basis of the pooled data of two year observations recorded at 1st, 5th and 10th days after application and revealed that all the treatments showed significant differences over control. Among the treatments thiomethoxam 25% WG @ 0.01% was found to be most effective against H. theivora followed by deltamethrin 2.8 EC @ 0.02% and azadirachtin @ 0.003%, whereas spiromesifen 240 SC @ 0.2% was found to be least effective against H. theivora population. The pooled data on the efficacy of different pesticides on O. coffeae revealed that spiromesifen 240 SC @ 0.2% was most effective followed by ethion 50EC @ 0.25%, deltamethrin 2.8 EC @ 0.02% and azadirachtin @ 0.003% whereas thiomethoxam 25% WG@ 0.01% @ was found to be least effective against O. coffeae population. Among all the treatments ethion 50EC @ 0.25% was found to be most toxic on spider population followed by deltamethrin 2.8 EC @ 0.02% and B. bassiana @ 2% was found safer to spider population which was followed by azadirachtin 5 EC 0.003%.
  • ThesisItemOpen Access
    PEST COMPLEX OF BHUT JOLOKIA AND THEIR MANAGEMENT
    (AAU, Jorhat, 2017-07) Thangjam, Rojeet; Borah, R.K.
    Field and laboratory experiment on pest complex and their natural enemies, identification and detection of insect vectors, integrated management of important pest of Bhut Jolokia and cost benefit ratio of different treatment modules were carried out during rabi (2014-15 and 2015-16) at Horticultural Orchard, Department of Entomology and Department of Plant Pathology, Assam Agricultural University, Jorhat (Assam). Altogether 110 species of arthropods were found to be associated with Bhut Jolokia at Jorhat, out of which 19 species were identified as pest, 64 as natural enemies and 27 species as casual visitors. Among the different insect pests recorded, 6 species were identified as “major” and they were Aphis gossypii (Glover), Myzus persicae (Sulzer), Bemisia tabaci (Gennadius), Bactrocera latifrons (Hendel), Scirtothrips dorsalis (Hood) and Polyphagotarsonemus latus (Banks). Among the natural enemies recorded, 44 species of predators, 13 species of parasitoids and one species of entomopathogenic fungus belongings to different orders have been reporting for the first time adding the number of natural enemies in Bhut Jolokia ecosystem. Moreover, among the dipteran predators, Syrphid fly (Lathyrophthalmus arvorum) has been reporting for the first time from Assam. All the genotypes of Bhut Jolokia collected from Assam, Manipur and Nagaland showed susceptible to viral diseases. However, the lowest incidence was observed in KCM2 (33.33%) and KCN1 (33.33%). Among the insect pests, 3 species viz., B. tabaci, A. gossypii and M. persicae have also been identified as a vector of Chilli Leaf Curl Virus (ChLCV), Cucumber Mosaic Virus (CMV) and Potato Virus Y (PVY), respectively during the investigation and they were confirmed through DAS-ELISA and PCR technique. Among the different treatment modules, module M2 that includes seedling root dip treatment with imidacloprid 17.8 SL @ 40g a.i./ha for 30 minute just before transplanting + growing of border crop (okra) + spraying of imidacloprid 17.8 SL @ 40g a.i./ha at 20 days after transplanting at 15 days interval (4 sprays) was found to the best performer in suppressing the population of aphid and whitefly followed by module M4 that includes seedling root dip treatment with imidacloprid 17.8 SL @ 40g a.i./ha for 30 minute just before transplanting + growing of border crop (maize) + spraying of lambda cyhalothrin 5 EC @ 25g a.i./ha starting from 20 days after transplanting (4 sprays) which were significantly superior over untreated control module M6. All the treatment modules had also significantly reduced the viral disease incidence as compared to untreated control. But the module M2 was the most effective in reducing the viral disease incidence followed by module M4 in both the seasons. However, these two modules greatly affect the population of coccinellids and spiders. The insecticidal treatment modules had significant effect in reducing the insect pest population and also the incidence of viral diseases thereby increasing the yield of Bhut Jolokia during the investigation. The highest yield was obtained in module M2 (3564.44kg/ha) followed by M4, M1, M3 and M5 (2687.94, 2303.98, 2100.15 and 1511.41kg/ha, respectively). The results on cost benefit ratio revealed that the highest was recorded in module M2 (1: 4.85) followed by M4 (1: 3.37) and M1 (1: 2.13).