Browsing by Author "Devanesan, S"

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Bees for pollination, crop improvement and agribusiness-some basic facts
(2010) Devanesan, S; Premila, K.S; Shailaja, K.K
Bio- ecology and management of stingless bees
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2000) Raakhee Mohan; Devanesan, S
With the objective of studying the bio-ecology and management of stingless bees, a study was conducted at the College of Agriculture, Vellayani during 1997-99. The bee samples collected from all districts of Kerala were identified to be of the same species viz., Trigona iridipennis Smith. The colony consisted of a queen, workers and few drones during the colony breeding season. The building material used by T. iridipennis was cerumen. The species arranged their brood in clusters. Queen cells were larger than worker brood cells. Food chamber of the species lay outside the brood nest. The food chamber consisted of honey and pollen pots which were larger than brood cells. Feral colonies which were transferred to different types of hives ('~II ablished and this showed that the bees could be hived in artificial domiciles which was a satisfactory step towards domestication. Different management practices were tried. Division of the bee colony could be successfully carried out by transferring half the amount of brood cells, pollen and honey pots along a queen cell to the daughter colony. Wooden hives were found to be more suitable for hiving T. iridipennis since the brood development and honey yield were superior in this type of hive. The studies on the method of extraction of honey indicated the feasibility of collecting honey by keeping the storage pots in trays under sunlight. Observations on the behaviour of T. iridipennis showed that each brood cell was constructed by the summation of activities of several workers. Mass provisioning of the brood cells was noticed. The brood cells were seen used only once. Queen laid egg in the provisioned cell and after the oviposition a worker closed the cell. The bees used their mandibles as a means of defence. The average egg, larval and pupal period of T. iridipennis was found to be 4.7, 18.6 and 21.8 days respectively with a total developmental period of 45.1 days. The species had reduced wing venation. The mandibles were modified. The hind leg of the worker bees had the 'pencillium'. The stingless bee queens were larger than workers Investigations on the foraging behaviour showed two peak periods of activity one at 1200 h and the other at 1500 h. Twenty seven plants were recorded as bee flora. Of the 27 plants recorded, twelve plants (rubber, cashew, coconut, chilly, cannon ball tree, coral creeper, drumstick, guava, rose, birds cherry and tamarind) provided both nectar and pollen. Eight plants (anthurium, bajra, sponge gourd, cinnamon, ixora, mango, touch-me-not and sunflower) noted, were sources of pollen while seven plants (balsam, banana, duranta, euphorbia, hamelia, marigold and phyllanthus) provided nectar only. Two species of spiders (unidentified) and ants (Solenopsis geminata) were found as enemies of T. iridipennis. Stingless bee honey was slightly acidic to taste and had a dark brown colour with the acidity and pH values being 0.294 and 3.98 respectively. The specific gravity was l.394 g/cc. It had a moisture content of 20.7 per cent. Glucose and fructose were 37.1 per cent and 4l.6 per cent respectively. The honey had a higher protein content of 1.49 per cent and ash content of 1.1 per cent.
Insect community analysis in cucurbitaceous vegetables and impact of insecticides on insect pollinators
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2007) Jangaiah, V; Devanesan, S
A study was undertaken to document the various insects associated with cucurbitaceous vegetables in ten locations of Kalliyoor panchayat of Thiruvananthapuram district from March 2006 to February 2007. A field trial was also carried out to assess the impact of insecticides on the insect pollinators, natural enemies and pests. The total number of different species of insects recorded on the cucurbitaceous vegetables was found to be 47. Of these, the important groups of insects observed were Hymenoptera (28 per cent), Coleoptera (21 per cent), Lepidoptera (19 per cent), Hemiptera (17 per cent), Diptera (11 per cent) followed by Orthoptera and Thysanoptera (2 per cent each). Besides the insects, two species of spiders (Araneae) and one species of mite (Acariformes) were observed in three cucurbits. Bees were the predominant insect pollinators identified. Among the four species recorded, Apis cerana indica Fab. was the most abundant in oriental pickling melon and snake gourd. Trigona sp. was abundant in bitter gourd. Apis mellifera L. least visited the cucurbit flowers. Among the three cucurbitaceous vegetables, the highest insect pollinators activity was recorded in oriental pickling melon followed by bitter gourd and snake gourd. The peak period of activity of the pollinators was noted to be during 1000 hr to 1100 hr and 1500 hr to 1600 hr. Maximum foraging activity of different insect pollinators was recorded during the seventh week after sowing in bitter gourd and snake gourd and sixth week after sowing in oriental pickling melon. The population of insect pollinators was more in summer than rainy season. The higher activity of insect pollinators was observed under pesticide free condition in the Instructional farm when compared to farmer’s field where insecticides were frequently applied. The dominant insect pests recorded were Bactrocera cucurbitae Coq. and Aulacophora spp. followed by Aphis spp., Henosepilachna sp., Liriomyza trifoli Burgess, Diaphania indica Saunders, Anadevidia peponis Fb. and thirteen other pests. The highest fruit fly infestation was observed in bitter gourd (38.66 per cent) followed by snake gourd and oriental pickling melon. Pumpkin beetles caused up to 28.99 per cent damage in oriental pickling melon and 22.44 per cent in snake gourd. No infestation was observed in bittergourd. Two species of spiders(Oxyopes javanus Thorell and Lycosa pseudoannulata Boes et st.), three coccinellid beetles (Menochilus sexmaculatus Fab., Synharmonia octomaculata Fab. and Micraspis crocea Mulsant) and two parasitoids (Apanteles sp. and Chrysocharis johnsonii Walker) were the major natural enemies recorded. Foliar application of neem oil 2.0 per cent, imidacloprid 0.002 per cent and malathion 0.2 per cent proved to be safer to pollinators than other chemical insecticides. Imidacloprid 0.002 per cent and malathion 0.2 per cent significantly reduced pest infestation. Neem oil 2.0 per cent and imidacloprid 0.002 per cent were also safer to the natural enemies. The highest yield was recorded in imidacloprid 0.002 per cent treatment followed by malathion 0.2 per cent and carbaryl 0.1 per cent treated plot. Evidently, selective use of insecticides like imidacloprid 0.002 per cent and malathion 0.2 per cent could effectively check pest infestation without harming the pollinators and natural enemies in cucurbitaceous vegetable ecosystem.
Insect fauna on coconut (cocos nucifera L. ) spadix and effect of pesticides on major pollinators
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2006) Shaiju Simon; Devanesan, S
An investigation was carried out to document the different insect species visiting the coconut inflorescence, to find out the variations in the foraging activity of different insect species and to assess the relative safety/toxicity of some commonly used pesticides to honeybees. The study revealed that the coconut inflorescence attracted thirty different species of insects towards it. These insect species visited the inflorescence to feed on either pollen or nectar or both. Bees viz., Apis dorsata, A. mellifera, A. cerana indica, Trigona iridipennis, Braunsapis sp and Eupetersia sp were found to collect both pollen and nectar of which A. mellifera and A. cerana indica dominated. Bees were found to forage on the inflorescence throughout the day and exhibit a peak period of activity during 0900 h in case of A. mellifera and A. cerana indica and during 1200 h in case of T. iridipennis. All these species of bees exhibited two distinct peaks during the day of which the second peak was during 1500 h. They mainly collected pollen from half opened male flowers. Ant species that foraged on the coconut inflorescence in large numbers were Solenopsis geminata, Myrmicaria brunnea, Dolichoderus sp, Camponotus sericeus. They visited the inflorescence for feeding pollen and nectar. The population of ants remained more or less same throughout the day, they visited in higher numbers during 0900 h. They were present on the inflorescence throughout the day and maximum during 0900 h. Other insect species that visited the palm inflorescence were flies (Bactrocera cucurbitae, B. dorsalis, Musca domestica, Hemipyrellia sp., Graptomyza brevirostris and Sarcophaga sp.), wasps (Polistes hebraeus, Chalybion bengalense, Ropalidia variegata, Vespa cincta and Vespa sp.), beetles (Oxycetonia versicolor and Oxycetonia sp.) and moths (Euchromia polymena and Melanitis leda ismene). The maximum population of insects was observed on the 13th day of the male phase and in the female phase it was on the second day. The population fluctuations recorded over a period of one year showed that the occurrence of bees were the highest followed by the population of ants. Bees exhibited a significant positive correlation with maximum temperature and negative correlation with relative humidity and rainfall. The results on the evaluation of pesticides for their safety/toxicity to different species of honeybees indicated that all the chemical pesticides were toxic to honeybees. Carbaryl 0.1 per cent was the most toxic while endosulfan 0.05 per cent was the least toxic chemical. However, both azadirachtin 0.004 per cent and neem oil garlic emulsion 2.0 per cent were the safest treatments to honeybees under laboratory conditions.
Management of stingless bee Trigona iridipennis Smith (Meliponinae: Apidae) in the homesteads of Kerala
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2002) Nisha, M M; Devanesan, S
With the objective of studying the management of stingless bees, Trigona iridipennis Smith in the homesteads of Kerala, studies were conducted at the College of Agriculture, Vellayani during 2000-2001. Different management practices were tried. Division of the• bee colony could be successfully carried out by transferring equal amount of brood cells, pollen and honey pots along with queen to the different hives VIZ., wooden, bamboo and earthen pot with different capacities. Bamboo hive with capacity 1500cc was found to be more suitable for hiving T. iridipennis since the brood development, pollen storage, population buildup and honey storage were superior in this type of hive. Observations on handling of bees indicated that wooden hives were easy to handle compared to bamboo and earthen pot. Brood development and pollen storage were shown maximum during the month of February, while maximum honey storage was noticed during the month of April. Bee strength increased as the colony got established well. Presence of queen cells and drones were noticed from November to March during which population build up existed. The bee strength was also found to be maximum in bamboo hive which had maximum brood, pollen and honey storage. Investigation on the reuse of emptied honey pots by the bees indicated that the bees reused it for reconstruction of worn off honey pot parts beneath and nearby. Investigations on the foraging activity of T. iridipennis showed two peak periods of activity one at 1200h and the other at 1500h and with maximum activity during July. It was observed in the present study that 76 plants were visited by the stingless bees for nectar or pollen or both. Of this twenty plants provided both nectar and pollen. Thirty five plants provided nectar only and 20 plants provided pollen only. The Trigona honeys collected from different tracts around Kerala varied widely in colour from light yellow to dark amber colour with all intermediate shades. The percentage of moisture varied from 18.96 to 20.48 in different districts of the state and pH ranged from 3.76-4.4. In all the honey samples the acidity ranged from 0.17-0.29 while the ash content varied from 0.17-0.19 per cent. The specific gravity also ranged from 1.3507-1.3775. The observations of reducing sugar indicated that it ranged from 77.12-69.85 per cent. The refractive index value also indicated variation from 1.4855 to 1.4891. The values on glucose and fructose per cent varied from 35.92-33.53 and 38.16-39.74 respectively. The glucose fructose ratio observed indicated variation from l.17 -1. 05. The sucrose per cent also seen varied from 1.23-l.81 and the values on specific heat varied slightly from 60.50-60.9. A dipteran fly Hermetia illucens L., a mite, Amblyscius sp. and Megachile disjuncta was newly identified as pest of T. iridipennis. Solenopsis geminata was also observed to attack weak colonies. No disease incidence was noticed.
Pathogenesity of thai sacbrood virus to the ecotypes of Apis cerana indica Fab. in Kerala
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1998) Devanesan, S; Abraham Jacob