Monitoring pollinator activity in an apple and pear orchard, linked with the analysis of the nectar composition

Fruit production is of major importance in Flanders, with a production of 318 000 tons of apples and 374 000 of pears (2014), with Conference and Jonagold as main cultivars. In apple, it is believed that cross pollination can increase yield and improve yield stability and fruit quality and therefore, pollen donors are planted within the orchard, and pollinators such as honeybees (Apis mellifera L.) are commonly introduced. In contrast to apple, pear growers pay little attention on pollination. One problem is the limited attractiveness of pear nectar for pollinators, probably because of the relatively low sugar concentration and/or unattractive sugar composition. In this contribution we monitored the pollinator activity in an apple and pear orchard after introducing managed bumblebee hives, on the base of standardized transect walks. Furthermore, we compared the sugar content in the nectar between apple and pear flowers. Overall, flower visitation by bumblebees was very low, especially on pear where no bumblebees were observed. A first analysis confirms our hypothesis of higher sugar concentrations in the nectar of apple flowers (Jonagold) compared to pear flowers (Conference). Furthermore, the percentage sucrose was noticeably lower in pear nectar (3%) compared to apple nectar (63%). This likely explains the low attractiveness of pear flowers compared to apple.status: accepte