Nectar Production and Spectrum of Insect Visitors in Six Varieties of Highbush Blueberry (Vaccinium corymbosum L.) in SE Poland

The attractiveness of plants to pollinators depends strongly on flower rewards, especially nectar and pollen. Nectar mass, sugar concentration, and sugar mass are known to influence the spectrum and abundance of insect visitors. Respective data on nectar secretion in highbush blueberry ( Vaccinium corymbosum ) under the climatic conditions of Poland are scarce. This study was conducted in 2002–2005 to assess flower abundance, nectar production, and insect visitors in six varieties of V. corymbosum in Niemce, SE Poland. Flower abundance ranged from 1.63 ± 0.64 (‘Darrow’) to 4.07 ± 0.95 in thousands of flowers per shrub (‘Northland’). Nectar mass, sugar concentration, and nectar sugar mass increased with flower age, peaking between the sixth and ninth day. Significant differences in nectar characteristics occurred between years and between varieties. ‘Bluecrop’ and ‘Darrow’ produced the largest nectar mass (19.08 ± 7.09 and 16.60 ± 8.31 mg nectar per flower, respectively) and nectar sugar mass per flower (6.39 ± 1.52 and 5.76 ± 1.51 mg sugar per flower, respectively). The estimated sugar yield in the studied V. corymbosum varieties ranged from 9.4 ± 3.3 to 20.7 ± 3.8 g sugar per shrub (‘Croatan’ and ‘Bluecrop,’ respectively). Regarding insect visitors, only honey bees and bumble bees were observed. Honey bees comprised 81%–98% of the total number of observed insect visitors. Highbush blueberry, due to abundant blooming and high per-flower sugar yield, is thus a good source of nectar sugars for honey bees.