Honey bee pollination increases fruit set and yields in many fruit, but not all. Blueberries are supposed to respond to increased pollinator activity with greater yields. Some fruit growers routinely bring in bee hives to increase pollination, but how many are necessary? Highbush blueberry growers in Washington State usually rent 10 hives of Italian honey bees per acre for pollination services. Hives are placed in fields between 5% and 25% full bloom. High hive density may be more necessary in some areas where rain and cold temperatures during flowering limit pollination. Alternatively, bumblebees are more adapted to pollination of blueberries, but are not available for rent. Researchers in Washington State wanted to see if increasing the density of honey bee hives would significantly increase fruit set and yield in highbush blueberry.

Experiment

Three field sites in Washington State with mature ‘Duke’ plants were stocked with 4 hives per acre while another three sites with ‘Duke’ highbush blueberry were stocked with 8 hives per acre (high hive density). Yield components including fruit set, berry weight, seed number/berry, and fruit firmness were measured at harvest.

Results

Fruit set was not affected by honey bee hive density. Berry weight and seed number per berry did increase with increased honey bee hive density, but firmness was unaffected. Better pollination makes more seeds per berry, and the more seeds, the larger the fruit because seeds stimulate fruit growth. Although there were not more fruit, the increased fruit size caused by better pollination increased total yields making the practice of increased hive density a viable option if production is reduced by insufficient pollination. A positive preliminary cost-benefit analysis showed a gain of $336/acre with the increased yield from high density hives, with the hive rental costs of $80/hive, although a more comprehensive benefit-cost analysis is needed to establish the economic viability.

Source:

Increasing Honey Bee Hive Densities Promotes Pollination and Yield Components of Highbush Blueberry in Western Washington by M. Arrington and L.S. DeVetter. HortScience 53(2):191-194. 2018.

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