- 23 - 



Inadequate poIUnation of blueberries may be expressed in two ways. 

 Flowers receiving no pollination will abscise without fruit set. Flowers 

 partially pollinated may set but produce small fruits. The blueberry nor- 

 mally contains up to 85 seeds, and seed number and fruit size have been 

 shown to be highly correlated. Thus, any reduction in seed set will likely 

 result in production of smaller fruit. 



Studies of the effect of cross- vs self-pollination of the highbush 

 blueberry have not all been in agreement, but most careful studies show that 

 pollination with pollen of a different cultivar results in slightly 

 increased fruit size and sometimes earlier ripening fruit. Most studies of 

 the rabbiteye blueberry agree that cross-pollination is important and that 

 two or more cultivars should always be planted together. 



Blueberry cultivars appear to differ in attractiveness to bees. Two 

 cultivars identified as "unattractive" are 'Coville' and 'Earliblue', and 

 these require more honeybee colonies per acre for adequate pollination. 

 Attractiveness of cultivars to bees seems to be conditioned by nectar volume 

 and nectar sugar content. 



Blueberries are generally not a preferred Pood source For honeybees. 

 Blueberries are a very poor source of pollen. Consequently, bees may 

 overfly blueberries to forage on other plant species nearby. A major 

 problem in Arkansas fields is the presence of dandelions during the blue- 

 berry bloom period. Bees may be seen foraging on dandelions rather than 

 blueberries. Since bees tend to continue foraging on a plant species that 

 they start on, we recommend that bee colonies not be placed in blueberry 

 fields until the blueberries have some open blossoms. Do not withhold bees 

 past 25 percent open bloom, however, or reduced set will result. Pistil 

 receptivity lasts only 5 to 8 days. 



I consider the bumblebees to be more effective pollinators for blue- 

 berries than the honeybees. They are less intimidated by adverse weather and 

 bumblebees can be seen foraging in blueberry plantings on cold, windy days 

 (common in Arkansas during blueberry bloom) when honeybees remain in their 

 hives. Unfortunately, however, bumblebee pollination is not reliable due to 

 population fluctuations. Modern agricultural practices have greatly reduced 

 bumblebee (and other native bee) populations in many areas, and the only 

 recourse to ensure adequate pollination is to place honeybee colonies in the 

 fields. 



Generally, a set of 80 percent of the blossoms is needed to yield an 

 excellent crop of blueberries. To achieve this goal, recommendations for 

 introducing honeybees into blueberry plantings have been made by most blue- 

 berry producing states. The numbers of colonies recommended per acre vary 

 among states and are associated with the extent of native bees. Michigan, 

 for example, with 12,000 acres of blueberries, recommends up to 5 colonies 

 per acre. In Arkansas, with our less concentrated acreage and still 

 available native bees, we recommend 1 to 2 colonies per acre. A rule of 

 thumb developed in Michigan is that i f 4 to 8 bees are observed per bush 

 when temperatures during bloom are in the 70s and 80s (degrees F), pollina- 

 tion will be adequate. 



