Wild blueberries go through a series of developmental stages before producing a harvestable berry. These stages extend over a two-year period, or production cycle, consisting of a sprout and crop year. During these two years, wild blueberry floral buds undergo three dormancy periods before bud burst and bloom, the flowers then need to be pollinated and germinated, and the seeds need to be fertilized. Read this week’s blog to get an overview of these processes and what is needed to get harvestable wild blueberries.

Wild Blueberries - From Dormant Buds to Ripe Berries

This journey starts with the first dormancy period known as paradormancy. During paradormancy the apical meristem, the growth region at the tip of the stem, has dominance over the lower or lateral meristems, where the floral buds will form [4]. During the fall of the first year, or sprout year, short daylength and cold temperatures drive tip-dieback, or apical abortion. Once apical dominance is broken, then the floral buds can form. The buds then enter a second dormancy period known as endodormancy, which helps the buds survive harsh winter conditions [4]. The buds will acclimate throughout endodormancy as temperatures get colder [1]. This stage can be measured by an accumulation of cold temperatures, known as the chilling requirement. The chilling requirement of wild blueberries is approximately 1000 hours of temperatures less than 0°C [7]. The floral buds will then enter the third dormancy period known as ecodormancy, which prevents the buds from opening too early in the spring [4]. The floral buds deacclimate throughout ecodormancy as the temperatures rise [1]. This stage can be measured by an accumulation of daily mean temperatures, known as growing degree days (GDD). It takes approximately 400 GDDs for the start of bloom, with peak bloom happening around 550 GDDs [6].

Endodormant wild blueberry floral buds (John MacDonald ©, 2024)

Once all three dormancy periods are satisfied, the floral buds will start to burst and these can be measured by the five stages of bud burst, known as T1 to T5 [3].  The T1 stage is known as the bud swell stage when the buds start to expand, and a green tip can be seen. The T2 and T3 stages are known as the early bud burst and bud burst stages, respectfully, when the buds continue to swell and the bud scales are separating. The T4 stage is known as the tight cluster stage when flower pedals become visible and elongated. Finally, the T5 stage is known as early flower which is just before bloom when the flowers are still closed. The next stage is floral bloom when the flowers have fully opened.

The stigma, where the pollen lands on the receiving flower, on individual flowers is only receptive to pollen for up to nine days, where pollination within the first four days will result in the highest fruit set [2]. The bloom period for an entire field is typically three to four weeks [2]. Wild blueberry fields typically contain two species of wild blueberries, Vaccinium angustifolium and Vaccinium myrtilloides, and pollination is incompatible between these species. Wild blueberries are also self-incompatible, so wild blueberry flowers require pollen transfer from a different clone of the same species to get successfully pollinated [2].

Pollination can be one of the most limiting factors in wild blueberry fruit production. Pollination is the transfer from pollen from the anther of one flower to the stigma of another flower on a different clone of the same species. Wild blueberries are entomophilic with respect to pollination, meaning that they need an animal pollinator [2]. The conditions during bloom need to be ideal for the animal pollinators to ensure successful pollination. Wild pollinator populations vary between fields, so managed pollinators are used to get even pollination. Therefore, placement and removal of managed pollinators is crucial in providing efficiencies around pollination.

Bumblebee pollinating wild blueberry flowers (John MacDonald ©, 2024)

Once the pollen is successfully transferred from the anther of one plant to the stigma of another clone of the same species the next stage, known as pollen germination, can start. If conditions are favorable for the flowers, germination typically starts two to three hours after successful pollen transfer [5]. During germination, a pollen tube forms into the ovary at the base of the style, or female flower parts, and extends to an individual ovule. The pollen sperm travels down the pollen tube until they reach the ovule. Pollen germination can take three to four days, if conditions are favorable [5]. The next stage is known as fertilization, when the pollen sperm reaches the eggs and nuclei they are fertilized, and the seeds start forming. Once the seeds are formed, the fruit starts developing around the seed which provides protection and helps with seed dispersal. There are different maturity stages of blueberries from pin head, to green, to red, and then to ripe blue harvestable fruit.

For more information on how to tell if a flower was successfully pollinated, please check back in for the next blog on wild blueberries.

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 attta@perennia.ca

References:

[1] Deslauriers, A., Garcia, L., Charrier, G., Butto, V., Pichette, A., and Pare, M. 2021. Cold acclimation and deacclimation in wild blueberry: Direct and indirect influence of environmental factors and non-structural carbohydrates Agricultural and Forest Meteorology, 301–302: 108349. (ACCLIMATION)

[2] Drummond, F. 2019. Reproductive biology of wild blueberry (Vaccinium angustifolium Ait.). Agriculture, 9(4): 69.

[3] Hildebrand, P.D., and Braun, P.G. 1991. Factors affecting infection of lowbush blueberry by ascospores of Monilinia vaccinii-corymbosi. Canadian Journal of Plant Pathology 13(3): 232–240.

[4] Lang, G.A., Early, J.D., Martin, G.C., and Darnell, R. 1987. Endo-, para-, and ecodormancy: physiological terminology and classification for dormancy research, Horticulture Science, 22(3): 371–377.

[5] Noormets, M., and Olson, A.R. 2005. Observations on the gynoecial pathway for pollen tube growth in sweet lowbush blueberry (Vaccinium angustifolium Ait.), Journal of Applied Botany and Food Quality, 80: 6-13.

[6] 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, Horticulture Science, 47(8): 1014–1021.

[7] Yarborough, D.E. 2012. Establishment and management of the cultivated lowbush blueberry (Vaccinium angustifolium), International Journal of Fruit Science, 12(1–3): 14–22.

Honey bees rely on more than just good nutrition to stay healthy, but also depend on a stable and diverse gut microbiome. This internal community of microbes supports digestion, strengthens immunity and helps honey bees resist disease. But parasites like Nosema spp. can invade the gut and disrupt their microbiome, threatening colony health.

Bee Alert: Attack of the Microsporidia

Nosema spp. are a microsporidian parasite that attacks the midgut of adult honey bees¹. The genus is being reviewed as Vairimorpha.  It is a spore-forming organism that is phylogenetically related to fungi ². Three types of microsporidia are known to infect honey bees Nosema apis, Nosema ceranae, and Nosema neumanni ³. Of these, N. apis and N. ceranae are the most common and widespread. The size of N. apis is about 6x3 μm, and N. ceranae are around 4.7 x 2.7 μm ³.  Transmission occurs when bees ingest spores through contaminated food or during grooming ³. Once inside the digestive tract, the spores attack the gut lining, damaging the tissue and can potentially spread to the hemolymph, which may cause septicemia ³.

Nosema ceranae specifically targets the midgut epithelium, which is the tissue responsible for nutrient absorption ⁴. As infection occurs, the bee’s ability to digest and absorb nutrients declines. This damage may lead to dysentery and weakened immunity. Dysentery is more common in N. apis ³ with the dominant species being N. ceranae. While most beekeepers might assume that increased sucrose consumption is a sign of healthy, active bees, infected bees often consume more sucrose and are less likely to share food with their colony, which can disrupt social dynamics due to behavioural changes and impact the whole colony ⁴.

Figure 1: Nosema Spores (circled) Viewed Under a Microscope (400X) (ATTTA©2020)

Beyond damaging the gut lining, Nosema spp. also disrupts the balance of beneficial microbes that live in the bee’s digestive system. Core bacteria like Snodgrassella alvi play a crucial role in maintaining gut health. Snodgrassella consumes oxygen in the ileum, creating an anaerobic environment for beneficial microbes ⁶. It also forms biofilms that protect the gut lining and has been shown to reduce spore loads of N. ceranae in infected bees ¹. These microbes are essential in stabilizing the gut environment and supporting immune function.

However, the effectiveness of microbial defense against pathogens can be influenced by diet. A recent study has shown that nutritional stress can accelerate the reproduction of N. ceranae, especially in early stages of infection ⁵. Bees fed low-quality pollen, such as Eucalyptus grandis, which lacks essential proteins, lipids, and the amino acid isoleucine, tend to carry higher spore loads than those fed diverse, polyfloral pollen ⁵. This highlights the importance of a nutritionally rich diet in maintaining gut health and resisting infection.

Figure 2: Healthy Bees (ATTTA©, 2024)

Poor nutrition does not just affect the spore loads of Nosema but also alters the composition of the gut microbiome. From studies, it has also been found that poor diets can have a reduction in bacteria like Lactobacillus and Bifidobacterium, which are both core gut bacteria in honey bees ⁵. Bifidobacteria, for example, are involved in producing hormones and signal molecules that may influence immunity and development in the gut ⁶. When these microbes decline, bees may become more vulnerable to infections like Nosemosis, as their immune defenses are compromised ⁷. This disruption in the microbiome can have broader implications for colony health, like reduced longevity and overwintering success.

The honey bee gut is not just a site of digestion but also an important ecosystem that is vital for defending against pathogens and supporting proper health. When parasites like Nosema spp. damage the midgut, they disrupt nutrient absorption and the balance of beneficial microbes, making bees more vulnerable to disease. Beekeepers should regularly monitor for Nosema to help protect colony health. The Atlantic Tech Transfer Team of Apiculture offers Nosema testing to help detect this disease. Supporting gut health through good nutrition and monitoring to identify when treatment is necessary helps maintain strong and healthy hives!

Written by Kaitlyn Newton, 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 attta@perennia.ca

References:

1    Motta, E.V. and Moran, N.A., 2024. The honeybee microbiota and its impact on health and disease. Nature Reviews Microbiology, 22(3), pp.122-137.

2.     Zhang, Y., Su, M., Wang, L., Huang, S., Su, S. and Huang, W.F., 2021. Vairimorpha (Nosema) ceranae infection alters honey bee microbiota composition and sustains the survival of adult honey bees. Biology, 10(9), p.905.

3.     Galajda, R., Valenčáková, A., Sučik, M. and Kandráčová, P., 2021. Nosema disease of European honey bees. Journal of Fungi, 7(9), p.714.

4.     Lau, E., Maccaro, J., McFrederick, Q.S. and Nieh, J.C., 2024. Exploring the interactions between Nosema ceranae infection and the honey bee gut microbiome. Scientific Reports, 14(1), p.20037

5.     Castelli, L., Branchiccela, B., Garrido, M., Invernizzi, C., Porrini, M., Romero, H., Santos, E., Zunino, P. and Antúnez, K., 2020. Impact of nutritional stress on honeybee gut microbiota, immunity, and Nosema ceranae infection. Microbial ecology, 80, pp.908-919.

6.     Bonilla-Rosso, G. and Engel, P., 2018. Functional roles and metabolic niches in the honey bee gut microbiota. Current opinion in microbiology, 43, pp.69-76.

7.     Meehan, D.E. and O’Toole, P.W., 2025. A Review of Diet and Foraged Pollen Interactions with the Honeybee Gut Microbiome. Microbial Ecology, 88(1), pp.1-14.