Wild blueberries are managed on a two-year production cycle, meaning that the plants need to grow for two years for a harvestable crop. During this time, wild blueberry floral buds need to go through three dormancy stages before flowering. Please see previous blogs for more detailed information on the first two dormancy stages, para- and endo- dormancy. Once the blueberry buds have met their para- and endo-dormancy requirements they can enter ecodormancy, which is normally late winter to early spring. Once ecodormancy requirements have been met, then the buds will flower. Wild blueberry producers currently use ecodormancy requirements, based on growing degree days (GDD), to try and predict when the buds will open, and pollinators are needed in the fields. Knowing the requirements that are needed for ecodormancy could help with predicting wild blueberry bloom and allow for more precise placement of managed pollinators for more efficient use of this limited resource.

Wild Blueberry Phenology in the Crop Year - Ecodormancy

Ecodormancy is the second winter dormancy stage of floral buds, where the reaction leading to growth control is driven by external environmental cues, such as warm temperatures⁵. Ecodormant buds will not flower normally, meaning that only some of the buds will open when placed in growth adequate conditions, and the ones that do open will take longer to do so. Ecodormancy will prevent the floral buds from opening until the growing conditions are adequate for flowers, therefore protecting them from fluctuating conditions in the spring. Ecodormancy release relies on an accumulation of warm temperatures and the most common way of measuring the accumulation of warm temperatures is with GDDs⁵.

Ecodormant wild blueberry floral buds in early Spring (© John MacDonald 2024)

GDDs are a measure of accumulated daily heat units during which the plant has potential to be physiologically active and is measured using daily mean temperatures¹. Accumulations of heat units for ecodormancy begin when endodormancy is released. Currently, there are limited experimental results for when endodormancy is released for wild blueberries. Therefore, GDD accumulations for ecodormancy begin at a selected calendar date³, which is currently April 1^st for wild blueberries. Most GDD models include a base and upper temperature threshold, specific to different organisms, at which development may be delayed due to unfavorable growing conditions³. GDD models can be used to predict many crop phenological events, such as pest life cycles for applications of pesticides and floral bloom for placement of pollinators.

GDD models have been created in Nova Scotia to predict phenology of weeds, such as yellow toadflax (Linaria vulgaris), spreading dogbane (Apocynum androsaemifolium), and red sorrel (Rumex acetosella)^2,9,10. GDD models have also been created for predicting flowering in highbush and lowbush blueberries^4,6. More specifically, wild blueberry ramet emergence, tip-dieback, and flowering prediction models have been created in Nova Scotia⁸. The existing model for wild blueberry flowering, however, requires revisions to include early flowering wild blueberry genets and the timing of endodormancy release.

Wild blueberry field during ecodormancy in early Spring (© John MacDonald 2024)

Perennia Food and Agriculture Corporation, Nova Scotia’s technical food development agency, currently has an application called Farm Weather on the Farm Data Tools Website.  This tool will easily calculate GDD accumulations at weather stations, including 55 on wild blueberry fields, throughout Nova Scotia. Please make an account on Farm Data Tools and check out this very useful resource (Farm Data Tools – Farm Data Tools).

The placement of pollinators on wild blueberry fields during bloom can be difficult to plan. Learning more about the phenology stages of wild blueberries, such as endo- and eco-dormancy requirements, may help to create predictive models for the placement of pollinators. These models, based on GDD, could allow more efficient use of managed pollinators, improve wild blueberry production, and support honey bee health.

Written by John MacDonald, ATTTA Seasonal Apiculturist

 

Connecting with ATTTA Specialists

If you’d like to connect with ATTTA specialists or learn more about our program, you can:

visit our website at https://www.perennia.ca/portfolio-items/honey-bees/

Email abyers@perennia.ca

 

References:

1. Baskerville, G.L. and Emin, P. (1969) ‘Rapid Estimation of Heat Accumulation from Maximum and Minimum Temperatures’, Ecology, 50(3), pp. 514–517. Available at: https://doi.org/10.2307/1933912.

2. Blatt, S., De Clerck-Floate, R. and White, S.N. (2022) ‘Development of a growing degree-day model to estimate Linaria vulgaris shoot emergence and prospects for improving biological control efforts’, Invasive Plant Science and Management, 15(1), pp. 9–15. Available at: https://doi.org/10.1017/inp.2022.6.

3. Carlson, J.D. and Hancock, J.F. (1991) ‘A Methodology for Determining Suitable Heat-unit Requirements for Harvest of Highbush Blueberry’, Journal of the American Society for Horticultural Science, 116(5), pp. 774–779. Available at: https://doi.org/10.21273/JASHS.116.5.774.

4. Kirk, A.K. and Isaacs, R. (2012) ‘Predicting Flower Phenology and Viability of Highbush Blueberry’, HortScience, 47(9), pp. 1291–1296. Available at: https://doi.org/10.21273/HORTSCI.47.9.1291.

5. Lang, G.A. et al. (1987) ‘Endo-, Para-, and Ecodormancy: Physiological Terminology and Classification for Dormancy Research’, 22.

6. NeSmith, D.S. and Bridges, D.C. (1992) ‘Modeling Chilling Influence on Cumulative Flowering: A Case Study Using `Tifblue Rabbiteye Blueberry’, Journal of the American Society for Horticultural Science, 117(5), pp. 698–702. Available at: https://doi.org/10.21273/JASHS.117.5.698.

7. Rieger, M. (2006) Introduction to Fruit Crops. Haworth Food & Agricultural Products Press.

8. White, S.N., Boyd, N.S. and Van Acker, R.C. (2012) ‘Growing Degree-day Models for Predicting Lowbush Blueberry (Vaccinium angustifolium Ait.) Ramet Emergence, Tip Dieback, and Flowering in Nova Scotia, Canada’, HortScience, 47(8), pp. 1014–1021. Available at: https://doi.org/10.21273/HORTSCI.47.8.1014.

9. White, S.N., Boyd, N.S. and Van Acker, R.C. (2015) ‘Temperature Thresholds and Growing-Degree-Day Models for Red Sorrel (Rumex acetosella) Ramet Sprouting, Emergence, and Flowering in Wild Blueberry’, Weed Science, 63(1), pp. 254–263. Available at: https://doi.org/10.1614/WS-D-14-00048.1.

10. Wu, L. et al. (2013) ‘Spreading Dogbane (Apocynum androsaemifolium) Development in Wild Blueberry Fields’, Weed Science, 61(3), pp. 422–427. Available at: https://doi.org/10.1614/WS-D-12-00156.1.