Studies on the role of insect pollination in cucumber yield

Foraging activities of insect visitors were studied during summer 2007 on inbred lines of cucumber hybrid KH-1. The insect visitors in decreasing order of abundance were Formica sp. > Apis mellifera > Bombus haemorrhoidalis >Halictus sp. > other insects > Apis cerana > syrphids. The activity of insects peaked between 09:00 and 10:00 followed by 12:00-13:00 and 15:00-16:00. The foraging behaviour of A. mellifera, B. haemorrhoidalis and Halictus sp. was studied. The foraging speed and foraging rate were maximum in B. haemorrhoidalis followed by A. mellifera and Halictus sp. The bees spent significantly more time per flower during morning hours (15.92 sec/flower) and foraged significantly fewer flowers (5.48 flowers/min) compared to evening hours. There were significantly more nectar foragers (5.71/m²/10 min) than pollen foragers (4.84/m²/10 min). Most pollen foragers were observed during morning hours (6.27/m²/10 min) whereas nectar foragers were most active during noon hours (6.31/m²/10 min). There was no significant difference in the number of bees shifting from one line to another or vice versa. The effect of honey bee pollination, open pollination and hand pollination on quantity and quality of cucumber was also studied. Significant increase in fruit set was observed; highest being in hand pollination (75.68%) followed by honey bee (74.96%) and open (62.09%) pollination. Percentage of misshapen fruits was maximum in open pollination (20.05) followed by hand (14.1%) and honey bee (8.05%) pollination. Honey bee pollination resulted in significantly highest percentage of healthy fruits (92.22%) as compared to hand (85.85%) and open pollination (79.64%). Similarly weight of fruits (1184.5 g), number of seeds per fruit (472.8), fruit size (28.8 cm) and weight of 1000-seeds (29.14 g) was highest in honey bee pollination as compared to other modes of pollination.