Theses

Browse

Search Results

Now showing 1 - 9 of 21

Open 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.
Open 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.
Open 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.
Open 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.
Open 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.
Open 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.
Open 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.
Open Access
DEVELOPMENT OF INTEGRATED PEST MANAGEMENT MODULES AGAINST INSECT PESTS OF BHUT JOLOKIA (Capsicum chinense Jacq.)
(2019-09) Bora, Sasanka Sekhar; Saikia, D. K.
Experiments were carried out under field conditions at the Experimental Farm, Department of Horticulture as well as in the Department of Entomology and Department of Plant Pathology, Assam Agricultural University, Jorhat during 2017-18 and 2018-19 to study the major sucking and chewing pests of Bhut Jolokia causing substantial losses in fruit yield. At present, IPM has been attaining immense importance in the agricultural scenario of India and abroad. Therefore, evaluation of sustainable IPM modules was felt very much necessary in Bhut Jolokia. The result revealed that altogether twenty three numbers of insect pests were associated with the crop and among them aphid (Aphis gossypii Glover/Myzus persicae Sulzar), Whitefly (Bemisia tabaci Gennadius), thrips (Scirtothrips dorsalis Hood), yellow mite [Polyphagotarsonemus latus (Banks)], Cutworm (Agrotis ipsilon Hufuagel) and fruit fly [Bactrocera dorsalis (Hendel)] were considered as the key pests of Bhut Jolokia. Highest incidence of major pests was obtained in the 1st fortnight of April during 2018 as against 2nd fortnight of April during 2019, respectively. A new invasive pest, spiraling whitefly (Aleyrodicus dispersus Russel, Aleyrudidae:Hemiptera) was also reported for the first time in Bhut Jolokia from Assam. Five IPM modules were evaluated against insect pests of Bhut Jolokia, of which module I comprised of recommended dose of fertilizer and farm yard manure+ application of microbial consortium + growth promoter viz., Tricontanol + weeding at 30, 60 and 90 Days after transplanting (DAT) + imidacloprid 17.8 SL 0.4 ml per lt @ 40 days interval was found to be the most effective module in respect of B: C ratio (3.02: 1) followed by module III (Vermicompost 1.25t/ha+ neem cake 500 kg/ha + application of microbial consortium + black polythene mulching + garlic extract @ 10% at 20 and 70 DAT +NSKE 5% at 35 and 100 DAT + installation of sticky trap @ 25 traps /ha) where the B:C ratio was 2.96 with maximum yield of 740.74 gm per plant with next higher yield of 712.13 gm per plant in module I. Hence, module III in comparison to module I seems to be quite promising strategy as it did not require any insecticidal interference keeping natural enemies and ecosystem undisturbed. Out of eight cultivars collected cv. Assam 1 (King) contributed maximum yield of 719.85 gm per plant followed by Assam 4 with 626.67 gm per plant with minimum susceptibility towards pests and diseases. Correlation studies between sucking pests and phenotypic characters indicated that only number of leaves and leaf area index had negative significant impact while other parameters viz., plant height and branches showed no effect. Result of different shade level, 75 per cent shade showed highest plant height and leaf area index of 90.01 cm and 1.81 as against open condition where it was only 53.18 cm and 1.46. The number of leaves and branches of Assam 1 cultivar were to be highest 220.51 cm and 8.75 in open condition, while they were 80.75 cm and 5.13 in 75 per cent shade level. Likewise, for flowering, 116.75 days required in case of 75 per cent shade level, whereas it was only 93.25 days in case of open condition. Similarly, fruit numbers also reduced in case of 75 per cent shade level which was only 27.0 while 92.13 was in case of open condition. Yield per plant was also around 718.13 gm per plant in open condition, whereas it was only 223.63 gm per plant in 75 per cent shade level. The major sucking pests and coccinellid predator population found to be in higher side in open condition also. In 75 per cent shaded area the pooled infestation of aphid, whitefly, thrips and mite was 0.62, 0.35, 0.26 and 0.54 numbers per three leaves whereas, it was 1.69, 1.58, 1.25 and 2.58 numbers per three leaves in open condition. Predatory spider population found highest with 0.34 numbers per plant while coccinellid population was lowest with 0.15 numbers per plant at 75 per cent shade level. But coccinellid population was highest with 0.40 numbers per plant in open condition while 0.18 numbers per plant spider also found at open condition, respectively. RT PCR method confirmed the presence of Cucumber mosaic virus (CMV) on whole seed and seed coat, which indicates that CMV transmitted through seed.
Open Access
Impact of elevated temperature and carbon dioxide on foraging behaviour of Apis cerana F. in oilseed ecosystem
(2019-12) Gogoi, Jaya; Rahman, Ataur
Climate change associated with rise in concentration of atmospheric carbon dioxide and temperature is expected to affect the activity of pollinator and crop production. Oilseeds are an important component of the agricultural produce, next to food grains. The impact of elevated temperature and carbon dioxide on foraging behaviour of Apis cerana F. in oilseed (rapeseed var. TS-38 and sesamum var. ST-1683) ecosystem was studied separately in two experiments using Carbon Dioxide Temperature Gradient Tunnel (CTGT) and Open Top Chamber (OTC) established at Department of Crop Physiology and Department of Entomology, Assam Agricultural University, Jorhat during 2016-2019. In the first experiment four levels of CO2 (2 ambient at 400 ppm each and elevated of 550 ppm and 650 ppm) and 4 levels of temperature (2 ambient, +2°C and +4°C) and in the second experiment 4 levels of CO2 (2 ambient at 400 ppm each and elevated of 550 ppm and 650 ppm) and 4 levels of temperature (2 ambient, +3°C and +3°C) were used to assess the impacts of elevated temperature and CO2 levels on foraging behaviour of Apis cerana F. in rapeseed and sesamum ecosystem. No anesthetic effect was found on Apis cerana when exposed to different concentrations of CO2 viz., 0.04%, 0.05% and 0.065% for 3 minutes, 15 minutes and 30 minutes. The interactive effect of elevated temperature and CO2 on maximum frequency of flower (rapeseed) visit by Apis cerana was recorded in CTGT III (13.92±0.23) at 0800-0900 hours of the day whereas time spent per flower (6.12±0.17 seconds) at 1000-1100 hours of the day, time taken per trip (47.37±0.47 minutes) and pollen load per trip (7.87±0.12 mg) was recorded in field condition (ambient condition) compared to CTGT III (650 ppm CO2, +4°C). The time taken per trip (F=44.1000, P < 0.0001) and pollen load per trip (F=189.5555, P < 0.0001) varied significantly. Similar results were observed in sesamum also with maximum frequency of flower visit by Apis cerana (9.08±0.13) at 0800-0900 hours of the day, time spent per flower (7.20±0.10 seconds) at 0900-1000 hours of the day, time taken per trip (28.91±0.51 minutes) and pollen load per trip (6.11±0.11 mg) was recorded in field condition (ambient condition) compared to OTC III (650 ppm CO2, +3°C). The highest bee mortality rate of 9.46% was recorded in CTGT III followed by 6.57% (CTGT II) and 3% (CTGT I) during the investigation period. The plant height increased with elevated temperature and CO2 whereas the yield attributing parameters like number of siliqua and capsules per plant, number of seeds per siliqua and capsules and 1000 seed weight of rapeseed and sesamum decreased with elevated temperature and CO2 condition. However, with elevated temperature and CO2 level, the stover yield of rapeseed and sesamum were increased whereas harvest index (HI) decreased significantly. The yield was reduced significantly (F= 61.9680, P < 0.0001 and F= 16.2102, P < 0.0001) with elevated temperature and CO2 condition and the highest yield of rapeseed and sesamum was recorded in field condition (10.05±0.23 q/ha and 7.58±0.27 q/ha) compared to CTGT III (6.03±0.23 q/ha and 5.06±0.27 q/ha). Reduction in crop yield at increased temperature and CO2 was mainly attributed to reduction in foraging activity of A. cerana, number of siliqua and capsules per plant, number of seeds per siliqua and capsules, 1000 seed weight and harvest index. The present study revealed that elevated temperature and CO2 level could decrease the foraging activity of pollinator and crop yield.