Relative abundance of Honey Bees and effect of bee pollination on Onion
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Date
2019
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Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur (Bihar)
Abstract
The present studies on “Relative Abundance of Honey Bees and Effect of bee pollination on onion” were carried out during the year 2018-19 at University Apiary, RPCAU, Pusa. Objectives of this investigation were to study the relative abundance of insect pollinators on onion, foraging behavior of Apis mellifera on onion, quantitative evaluation of nectar sugar concentration of onion and effect of Apis mellifera pollination on onion seed yield. The results indicated that the total sixteen insect species visited onion flowers, viz. 11 hymenopterans, 3 dipterans and 2 lepidopterans. Among these Apis mellifera, Apis dorsata, Apis florea, Xylocopa sp., Eristalis sp., Polistes sp., were found to be most frequent pollinators. The relative abundance (no. of insect/m2/10 minutes) revealed that Apis mellifera (14.02) was most dominant species followed by Apis dorsata (11.16), Apis florea (8.71), Eristalis sp. (4.11), lepidopterans (3.56) Xylocopa fenestrata (3.0), Polistes sp. (2.39) and Halictus sp. (2.11). Irrespective of species, the population was maximum (10.3/m2/10 minute) at 1300 h of the day. The coefficient of correlation between mean population of pollinators species and temperature was found positive and significant while negative correlation was found with relative humidity indicating that temperature plays an important role on activity of insect pollinators.
The result on foraging behavior of Apis mellifera revealed that they started visiting onion flowers in early morning and ceased their activity later in the evening. It remained active throughout the flowering period. The foraging rate of Apis mellifera was minimum in afternoon (11.6 flowers/min) and maximum during evening (24.3 flowers/min) and its foraging speed was maximum in afternoon (12.1 sec) and minimum in evening (6.5 sec) and there was inverse relation between foraging rate and speed. The heaviest pollen load was carried by the Apis mellifera in afternoon which indicated that more pollen were collected by Apis mellifera during afternoon from onion flowers.
The maximum nectar sugar concentration per flower of onion was at 1300 h (14.14%) and the minimum was at 0700 h (8.8%). The coefficient of correlation between mean nectar sugar concentration and temperature was found positive and significant while negative correlation was found with relative humidity indicating that temperature and relative humidity plays an important role in nectar sugar concentration in onion flower.
The seed yield of onion increased significantly by Apis mellifera pollination. The highest number of pod set was recorded in OP (321.9), followed by BP (302.9), XP (283.4) while lowest pod set was recorded in PE (80.1). The number of seed/umbel was recorded 806.4, 755.6, 633.4 and 236.0 in OP, BP, XP, PE, respectively. The number of seed/plant was recorded 2131.3, 1971.1, 1570.1 and 506.4 in OP, BP, XP, PE, respectively. Test weight of onion seeds were 4.2 g, 4.1 g, 4.1 g, and 4.0 g in OP, BP, and XP, PE, respectively. The maximum seed yield/plant was found in OP (8.8 g) plant followed by BP (8.5 g) and XP (6.8 g). The minimum seed weight/plant was obtained in PE (2.2 g). The maximum seed yield in onion was obtained in OP (7.8 q/ha) and minimum yield was obtained in PE (2.0 q/ha), while in BP, XP was 7.3 q/ha and 5.9 q/ha, respectively. Maximum germination percentage in onion was recorded in BP (87%) followed by XP (85%), OP (84.6%). The minimum germination percentage was recorded in Pollinator Exclusion treatment (83.1 %). The yield increase over Pollinator Exclusion was highest in open pollination (290%) followed by 265%, 195% in BP, XP, respectively. The result depicts that insect pollinators provide an important pollination service to the onion seed production. Among different insect pollinators, Apis mellifera was found most efficient pollinator of onion. Utilization of Apis mellifera bee colonies for seed production in onion will be highly remunerative as due to pollination, higher quantity of quality seed is produced.
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