Impact of floral biology of high-density apple (Malus domestica Borkh.) cultivars on insect pollinators

The variations in floral biology of the eight tested apple cultivars were found to affect the abundance and foraging behaviour of the insect visitors. Apis cerana (3.23 bees/m²/min) was the recorded pre-dominant insect visitor followed by Episyrphus balteatus (2.96 insect visitors/m²/min), Apis mellifera (2.89 bees), Ischiodon scutellaris (2.70 insect visitors) and Eristalis tenax (2.57 insect visitors). The cultivars Gale Gala and Jeromine attracted maximum insect visitors due to more flower spread and higher nectar productivity. The average number of flowers visited by bees per minute was more in Gale Gala, Auvil Early Fuji and Red Cap Valtod due to favourable floral characters and higher nectar sugar concentration. Irrespective of the cultivars, A. mellifera visited comparatively more apple flowers (9.23 flowers/min) and spent less time on a single flower (9.52 s/flower) as compared to A. cerana (8.21 flowers/min, 10.77 s), E. tenax (5.37 flowers/min, 23.51 s) and E. balteatus (5.57 flowers/min, 24.37 s). The top worker A. mellifera (59.52%) outnumbered the side workers (40.48%). The maximum loose pollen grains were observed in E. tenax (7914.27) followed by A. mellifera (5209.80), A. cerana (3165.73) and E. balteatus (670.07). Therefore, it was concluded from the present study that floral biology along with nectar production affected the abundance and foraging behaviour of the insect visitors in the apple cultivars.