Production of most pollination-dependent crops, including highbush blueberry (Vaccinium corymbosum), relies mainly on managed hives of the European honey bee (Apis mellifera L.). In highbush blueberry, bumble bees (Bombus spp.), which are the only commercially-available alternative to honey bees, are more efficient pollinators than honey bees, as lower numbers are necessary to achieve full pollination of the crop. The goal of this research was to develop a model of blueberry pollination to test hypotheses about how to best utilize these two pollinators for blueberry pollination. I first analyzed temperature-dependent growth and development of flowers for each of five common blueberry cultivars. Greenhouse and field experiments compared blueberry flower viability at different ages after flower opening, and declining fruit set was found with increasing floral age after one day. Finally, bee activity was observed on blueberry flowers in multiple farms across three growing seasons that included variable weather conditions. Using these data, a deterministic model of blueberry pollination, BLUEPOLL, was developed to predict annual yield from one acre of highbush blueberry (Vaccinium coymbosum L.) under typical spring weather conditions. This model relies upon inputs of highbush blueberry cultivar, weather conditions, and managed pollinator inputs to calculate pollination during the bloom period and subsequent blueberry yield, based on the experimentally-derived parameter estimates. The BLUEPOLL model was used to examine effects of different pollinator stocking levels and combinations on yield and to determine profit-maximizing pollinator input strategies. For the `Bluecrop' cultivar, the profit-maximizing stocking level of honey bees was determined to be 4.5 hives per acre compared to 2.5 bumble bee colonies per acre for fields stocked only with bumble bees. When examining combinations of the two pollinators, under average weather conditions the least-cost input combination when seeking to achieve 80 percent of full crop yield was 0.25 honey bee hives per acre in combination with 1.25 bumble bee colonies per acre. Assuming that rented honey bee hives cost $50 and purchased bumble bee colonies cost $65, the least-cost combination of honey bees and bumble bees would cost a grower $93.75 per acre. This cost rises to $225 or $162.50 when considering the profit-maximizing input level of only stocking honey bees or bumble bees, respectively. Under less suitable weather conditions, the cost per acre increased for all combinations of managed honey bees and bumble bees, indicating that growers should invest more in managed pollination services in years when anticipating poor weather in order to ensure consistent crop yields.
Read
