Foraging Activity of Different Pollinators for Seed Setting and Maximizing Seed Yield of Onion

Abstract

The experiment was conducted at the Regional Spices Research Centre, BARI, Gazipur during rabi season, 2012-13and 2013-14 to identify the suitable pollinator attractant crops for increasing the vigilance of pollinators for higher seed settings and thereby increasing seed yield of onion. In 2012-13, four treatments viz., Onion + Fennel (two rows at every 10 rows of onion including border), Onion + Black cumin (two rows at every 10 rows of onion including border), Onion + Coriander (two rows at every 10 rows of onion including border) and Sole onion were compared to achieve the objectives. In 2013-14, the treatment onion + Dill was included and Onion + Black cumin was discarded. One observer was assigned to each replication and observations were synchronized to run between 10.00 to 11.24 hrs. Therefore, each observer walked down 28 minutes for each treatment. An insect landing on an open umbel was considered to be a ‘visit’. In 2012-13, the highest seed setting was recorded in onion + fennel (69.88%) which was statistically identical to Onion + coriander (67.45 %) and Onion + black cumin (64.15 %) while the highest seed setting was recorded in Onion + Fennel (73.70 %) which was identical to Onion + Dill (70.50%) and Onion + Coriander( 72.37%) during 2013-14. In 2012-13, the highest seed yield (865.5 kg/ha) was obtained from Onion + fennel which was identical to Onion + coriander (838.1 kg/ha) but differed significantly from other treatments while the highest seed yield (1165.34 kg/ha) was recorded from Onion + fennel which was identical to Onion + coriander (1064.59 kg/ha) during 2013-14. In both the years, percent seed setting was lowest in Sole onion (55.93 % in 2012-13 and 57.73% in 2013-14). Accordingly, the lowest seed yield was also recorded from Sole onion (623.3 kg/ha in 2012-13 and 685.44 kg/ha in 2013-14). The best insect pollinator observed was Horse fly for onion crops. The Honey Bee was the second best and Syrphid fly was the third best insect pollinator. The rest of all insects recorded during observation were minor pollinator. Dill and Fennel was the better attractant crop for pollination while coriander acted as intermediate. Keyword: Onion, pollinator, seed yield