Nutrient Roles in the Wild Blueberry Crop Year Production

 

Hello everyone,

We are hearing increasing concerns about differences in fruit bud size and development across wild blueberry fields this spring. In many crop fields, bud break and separation have begun across the province, giving us clearer insight into how last year’s drought is influencing this season’s crop potential.

Variation in bud size can directly affect development rate, flowering timing, and ultimately yield potential. These differences largely reflect variability in nutrient reserves stored in the plants. Adequate nutrient availability and proper developmental timing are critical for achieving a strong average yield.

Last fall, blueberry wood nutrient analysis conducted by Dr. Harrison Wright (AAFC) indicated that several nutrient levels were lower than those observed in 2024, particularly some key micronutrients. Reduced nutrient reserves following drought stress are likely contributing to the uneven bud development we are now observing.

In this short blog post, we would like to review the fundamentals of nutrient needs during the wild blueberry crop year. Over the coming weeks, we will continue discussing this topic through additional updates and grower resources.

During our next Virtual Wild Blueberry Grower Meeting on May 20, we will welcome guest speaker Jessica D’Entremont (NutriAg), who will provide a brief presentation on nutrient functions and practical approaches to managing nutrient inputs in crop fields, with particular attention to liquid fertilizer products. A second guest speaker will also present on mulching practices in wild blueberry production at the same meeting.

To register for the meeting, please visit:
Wild Blueberries Virtual Grower Meetings 2026 Registration

We hope this short communication helps growers better understand the key roles of nutrients during the crop year, supports decision-making regarding liquid fertilizer use, and contributes to improved berry quality and yield potential.

 

Nutrient Importance in Wild Blueberry Production

Wild blueberries grow naturally in acidic, low-fertility soils; however, adequate nutrient availability remains essential for maintaining plant vigor, optimizing fruit yield, and sustaining long-term field productivity. Nutrients influence every stage of crop development, including vegetative growth, flower bud formation, pollination success, fruit set, berry size, and winter survival.

Plant nutrients are grouped into macronutrients, required in relatively large quantities, and micronutrients, needed in smaller amounts but equally vital for normal plant function. Deficiencies or imbalances in either group can limit plant growth, reduce flowering potential, and negatively affect fruit quality.

Wild blueberry production operates within a two-year cycle. The sprout year focuses on vegetative growth and the establishment of future yield potential, while the crop year relies heavily on stored nutrients and carbohydrates accumulated during the previous season to support flowering and fruit development.

 

Nutrient Function During the Crop Year

Following vegetative growth achieved during the sprout year, plants enter the crop year with pre-formed flower buds and stored nutrient reserves. These reserves largely determine early-season performance, influencing bud break, flowering progression, pollination success, fruit set, and early berry growth.

Recent blueberry wood analysis indicates reductions in several key nutrients — particularly Calcium (Ca), Magnesium (Mg), Zinc (Zn), and Boron (B) — ranging from approximately 13% to 36% below the previous years’ levels. Combined with seasonal stresses, including last year’s drought effects, these reductions highlight the importance of targeted nutrient supplementation during the crop year.

Because crop-year nutrient uptake opportunities are limited, careful selection of nutrients and application timing is critical for supporting reproductive development and maximizing yield potential.

 

Secondary Macronutrient: Calcium (Ca) — Cell Strength & Fruit Firmness

Calcium plays a central role in maintaining plant structure and fruit quality during the crop year. It is essential for cell wall formation, resulting in stronger plant tissues, improved berry firmness, and enhanced post-harvest shelf life.

Adequate calcium availability supports:

• Active root growth
• Shoot tip development
• Reduced fruit breakdown and soft berries

Calcium is relatively immobile within the plant, meaning deficiencies cannot be corrected by redistribution from older tissues. A consistent external supply is therefore required during periods of rapid growth, flowering, and berry formation.

 

Micronutrients Essential for Flowering and Fruit Set

Several micronutrients become especially important during the crop phase of wild blueberry production.

Boron (B) — Flowering & Pollination Success

Boron is one of the most critical micronutrients during the crop year. It supports pollen viability and pollen tube growth, enabling successful fertilization and seed development. Adequate boron directly improves fruit set and berry size, while deficiencies often lead to poor berry formation and reduced yields.

Zinc (Zn) — Growth Regulation

Zinc contributes to plant growth regulation through its role in hormone production. It supports healthy shoot and leaf development and helps synchronize plant growth stages, ensuring uniform flowering and fruit development across fields.

Manganese (Mn) — Metabolic Activity

Manganese functions primarily as an enzyme activator involved in photosynthesis and key metabolic processes. Adequate manganese supports overall plant metabolism and helps maintain energy production required during flowering and fruit growth.

 

Management and Liquid Fertilizer Product Selection in 2026 Crop Fields

The crop year provides only limited opportunities to supplement nutrients. Integrating liquid fertilizers into scheduled fungicide applications allows producers to efficiently support crop nutrition without additional field passes.

Producers should focus on two key application windows.

1. Bud Break / Bud Separation

(Monilinia Blight Spray Timing)

Nutrients to consider

• Boron (B)
• Zinc (Zn)

Locally available products

• BoronMax — 0.3 L/acre
• ZincMax — 0.5 L/acre
• Zinc DL — 1.0 L/acre

 

2. Flowering Period

(Botrytis Bloom Blight Spray Timing)

The objective is to support successful flowering, fertilization, and early berry development.

Nutrients to consider

• Calcium (Ca)
• Boron (B)
• Magnesium (Mg)
• Zinc (Zn)

Locally available products

• SillCalMax — 1.0 L/acre
• BoronMax — 0.3 L/acre
• ZincMax — 0.5 L/acre
• TruPhos Magnesium — 1.0 L/acre
• Cal-Bor-Moly — 3.0 L/acre
• Zinc DL — 1.0 L/acre

 

2026 Production Updates and Seasonal Outlook for NS_ 3rd Blight Line Post_ May 11

Hello everyone,

This upcoming week’s weather forecast continues to bring double-digit daytime temperatures along with frequent rainfall. These conditions are ideal for crop fields as fruit buds continue advancing into higher percentages of F2, with some fields progressing toward F3 and F4 stages (Figure 1).

We are still too early to observe open flowers (F5) across most mainland production areas. As a result, many crop fields remain vulnerable to Monilinia Blight infection, especially during upcoming wet periods.

This will be a critical week for blight fungicide applications across much of the province.

Below is this week’s regional spray outlook.

 

 

 

 

 

Cape Breton

·         Crop fields remain slightly early for blight management at the beginning of the week.

·         Blight fungicide applications should be planned toward late week or before the weekend, depending on local bud development and weather conditions.

·         Pre-emergence herbicide applications remain safe in sprout fields.

 

Antigonish, Guysborough, and Pictou Counties

·         Crop fields have reached approximately 20–30% F2, indicating early development stages.

·         There has been minimal to no blight risk from recent conditions, but fields should begin receiving blight protection by mid-week, particularly in Pictou County, where development is advancing more quickly.

·         Pre-emergence herbicide applications remain safe in sprout fields.

 

All Other Mainland Production Regions

• Early and average fields have reached ~40% F2 or higher prior to the weekend.
• If blight fungicide has not yet been applied, plan to spray this week as soon as weather conditions allow.
• Higher-elevation or later-developing fields — especially in Cumberland and Colchester Counties — are also expected to enter blight season this week.
• This is the key spray week — please plan applications at the first suitable opportunity.

 

Sprout Fields

• Sprout fields are beginning to show early plant emergence.
• When using Chikra or Ignite, scout fields carefully. These “hot” herbicides may damage emerging shoots if new growth is present.
• Velpar, Sinbar, and Spartan applications can continue this week, but timing is becoming late if operations extend into next week.

 

We will provide another update before the end of the week as conditions continue to evolve.

Have a great week — and let’s hope Mother Nature stays calm during this busy spraying period.

 

Hugh Lyu
May 11, 2026

 

 

Wild Blueberry Weather Station GDDs and Crop F2 Stage Updates

 

 

We will continue providing updates on F2 stage percentages across different production regions as information becomes available throughout the season.

 

Table 1. Percentage of Wild Blueberry Floral Bud F2 stage

 light green (0-20% F2), dark green (20-30% F2), yellow (30-40% F2) and red (40-100% F2)

Wild blueberry production regions, NS	The average percentage of floral buds at F2
Cape Breton	15% F2
Cumberland County
Halfway River	>40% F2
Oxford	>40% F2
Westchester Station	>40% F2
Colchester County
Murray Siding/ Truro	>40% F2
Belmont	>40% F2
Debert	>40% F2
Londonderry/ Baseline Rd.	>40% F2
Greenfield	>40% F2
Camden	>40% F2
South West Nova Scotia
Weymouth	>75%F2
Caledonia	>70%F2
Annapolis	>55%F2
Hants County
Upper Rawdon	>40% F2
Halifax County
Dean	>40% F2
Guysborough County	25-30% F2
Pictou County	30% F2
Antigonish County	25-30% F2

 

2026 Production Updates and Seasonal Outlook for NS_ 2nd Blight Line Post_ May 8

Hello everyone,

It has been a wild week with rain and wind across Nova Scotia. We are now entering the active wild blueberry growth stage, with quick bud break occurring in many crop fields after the last two days’ high temperatures. At the same time, growers are facing challenging spraying conditions while trying to understand variable crop development this spring.

Carryover effects from the 2025 drought continue to influence crop fields. Many fields show variable numbers and sizes of fruit buds, resulting in uneven bud development. The spring conditions have also resulted in slower crop development this season, approximately 1 week behind 2025 in many areas. The last two days’ high temperatures contributed to a significant jump in crop stages, as measured by F2 percent, marking the beginning of this year’s blight management.

Below are several highlights to support your planning over the next few days.

 

1. Sprout Fields — Pre-Emergence Herbicide Applications

 

It remains a good window for pre-emergence herbicide applications in sprout fields.

Herbicides such as Chikara, Ignite, Spartan, Involve, Velpar, and Sinbar can still be safely applied across all production regions through this week and into mid-next week, before next weekend.

If applications have not yet been completed, prioritize sprout-field herbicide treatments over the next several days. From a weed-growing perspective, the main weeds, such as sheep sorrel and hair fescue, have been actively growing since early spring.

 

2. Crop Fields — Monilinia Blight (Mummy Berry) Management

 

Fungicide products such as Proline or Soratel should be timed carefully based on the crop fields’ bud development and weather risk.

 

a. Bud Susceptibility

 

Blueberry fruit buds become susceptible to Monilinia blight once buds begin to scale and move beyond the F2 stage (Figures 1 and 2).

 

b. When to Plan the First Blight Spray

·         When crop fields reach approximately 40% F2, infection risk increases significantly.

·         Fungicide applications should be planned at this stage in coordination with forecast weather conditions.

 

Using the Wild Blueberry Growing Degree Day (GDD) model:

·         160 GDD serves as an important alert point.

·         Once local weather stations exceed 160 GDD, growers should monitor fields closely (Figure 3).

·         After this threshold, a fungicide application may be required within only a few days, depending on rainfall and infection risk.

 

c. Regional Development and Current Blight Risk (Table 1)

 

Still Early for Blight Management

·         Pictou

·         Guysborough

·         Antigonish

·         Cape Breton

Most fields in these regions remain below critical infection risk.

 

Cumberland and Colchester Counties

 

• Early-developing or lowland fields have reached approximately 160 GDD and more than 40% F2 development. For these early fields, where F2 percentages are high or crop stages are more advanced, fungicide applications should be planned before the Sunday–Tuesday rain period, or applied shortly after next week’s wet conditions if spraying opportunities are limited.

 

• Late-developing or higher elevation fields are progressing more slowly; however, following the Sunday–Tuesday rainfall events, these fields are also expected to enter the infection risk stage. Growers should therefore plan fungicide applications next week as conditions become conducive for disease development.

 

Field Variability Due to 2025 Drought

 

We are observing and hearing variability within fields:

·         Differences in stem length

·         Variable fruit bud numbers

·         Uneven bud size, vigor, and bud break rates

These conditions reflect differences in stored plant reserves following last year’s drought.

 

As a result:

·         Stronger buds are advancing quickly.

·         Smaller or weaker buds are breaking later.

·         Crop development may appear uneven across individual fields.

 

Field scouting is essential this year. Do not rely solely on regional timing — check your own fields carefully.

 

Upcoming Weather Considerations

 

A weather system forecast from Sunday through Tuesday/Wednesday is expected to bring significant rainfall.

 

 

Final Thoughts

This season continues to highlight how strongly previous-year stress and current weather conditions influence wild blueberry development. Careful scouting, flexible spray timing, and attention to field variability will be especially important in 2026.

 

 

 

 

Figure 1. Susceptible Fruit Bud Periods

 

 

Figure 2. Wild Blueberry Fruit Bud F1 and F2 Stages

 

 

 

Wild Blueberry Weather Station GDDs and Crop F2 Stage Updates

 

Figure 3. Accumulated Growing Degree Days (April 1–May 7, 2026)

Figure 4. Wild Blueberry F2% and GDDs

 

We will continue providing updates on F2 stage percentages across different production regions as information becomes available throughout the season.

 

Table 1. Percentage of Wild Blueberry Floral Bud F2 stage

 light green (0-20% F2), dark green (20-30% F2), yellow (30-40% F2) and red (40-100% F2)

Wild blueberry production regions, NS	The average percentage of floral buds at F2
Cape Breton
Cumberland County
Halfway River	>40% F2
South West Nova Scotia
Weymouth	>75%F2
Caledonia	>70%F2
Annapolis	>55%F2
Hants County
Halifax County
Guysborough County
Colchester County
Murray Siding/ Truro	>40% F2
Belmont	>40% F2
Debert	>40% F2
Londonderry/ Baseline Rd.	>40% F2
Greenfield	35% F2
Camden	>40% F2
Pictou and Antigonish County