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

 

2026 Production Updates and Seasonal Outlook for NS_ 1st Blight Line Post_ May 4

Hello everyone,

As we move into May, we will begin publishing regular blog updates to provide producers with timely information on field development and seasonal management outlooks. Particular attention will be given to blight disease management, including Monilinia Blight (Mummy Berry) and Botrytis Blossom Blight (Grey Mould).

 

Season Progress and Crop Development

This season’s first blight update is being released on May 4, approximately one week later than last year’s first post (April 27, 2025). As many growers experienced, April brought alternating periods of mild temperatures followed by cooler, late-winter-like conditions. These fluctuating weather patterns slowed spring crop development compared with last season.

Despite the slow start, warmer conditions are expected to accelerate wild blueberry growth in the coming weeks, bringing many fields into the critical blight-management period.

 

Mummy Berry Risk and Monitoring

Late-April weather conditions were favourable for the germination of mummy berries and the development of small cup-like structures known as apothecia. These structures produce primary spores that infect susceptible blueberry fruit bud stages (Figure 1).

Producers are encouraged to closely monitor:

• Fruit bud stage progression in crop fields
• Local temperature and moisture conditions
• Field history and disease risk levels

Careful monitoring will help determine optimal timing for effective fungicide applications targeting blight diseases.

Figure 1. Susceptible Fruit Bud Periods

 

Additional Field Management Reminders

This post also includes early-season updates on growing degree day (GDD) accumulation and crop F2-stage development in production fields.

In sprout fields, the window for pre-emergence herbicide application is approaching. Growers may wish to begin planning spray operations and take advantage of suitable field and weather conditions expected over the next several weeks.

 

In This Update

• Wild Blueberry Weather Station GDD and Crop F2 Stage Updates
• General Information on Monilinia Blight and Management Considerations

 

Have a great week, everyone!

Hugh Lyu
May 4, 2026

 

 

Wild Blueberry Weather Station GDDs and Crop F2 Stage Updates

 

During the 2026 growing season, we will provide periodic Growing Degree Day (GDD) updates using selected wild blueberry weather stations located across the province (Figure 2). These updates are intended to support producers in tracking seasonal crop development and improving the timing of key management decisions.

 

Figure 2. Selected Wild Blueberry Weather Stations for GDD Updates in 2026

 

A summary of selected wild blueberry weather stations and their accumulated GDD totals from April 1 to May 3 is presented below (Figure 3).

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

 

When compared with the local wild blueberry GDD model for F2 stage development (Figure 4), it is important to note that we are currently in the early stages of F2 development, during which fungicide applications are generally not required.

Based on the current 14-day weather forecast, several potential infection periods are expected across most Mainland wild blueberry production areas. During this time, many crop fields are expected to reach a stage in which more than 40% of fruit buds have separated their bud scales, indicating increased susceptibility to Monilinia blight.

To support management decisions, we have included additional information below outlining key wild blueberry crop stages and practical guidance on Monilinia Blight biology and management for those interested in reviewing the fundamentals of this disease and its effective control strategies.

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
South West Nova Scotia
Hants County
Halifax County
Guysborough County
Colchester County
Murray Siding/ Truro	25% F2
Pictou and Antigonish County

General Information about Monilinia Blight and Management

 

The following recommendations are intended to support producers in managing Monilinia Blight (Mummy Berry) during the early infection period of the wild blueberry crop.

Key Management Considerations

1. Field History and Risk Awareness
Fields with a known history of Monilinia blight require close monitoring each season. Where infections have persisted for multiple years, producers should carefully track F2-stage development alongside local weather conditions to prepare for timely fungicide applications.

2. Determining F2 Percentage in Your Field
Knowing the F2 percentage is essential for proper spray timing (Figure 5).

To estimate F2 development:

• Walk the field in a random “W” pattern.
• Collect 20–30 stems representing different areas of the field.
• For each stem:
• Count the total number of floral buds.
• Count the number of buds at the F2 stage or beyond.

Calculate F2% for each stem using the following formula:

F2% = (Number of F2 or more advanced buds ÷ Total floral buds) × 100

The overall field F2% is obtained by averaging the F2 percentages from all sampled stems.

3. Infection Risk Threshold
Once crop fields reach approximately 40% F2, wild blueberry tissues—including fruit buds and emerging leaf tissue—become susceptible to infection when environmental conditions favour mummy berry cup development, spore release, and infection events.

4. Fungicide Timing
When fields exceed 40% F2, fungicide protection is recommended:

• Before forecast wet periods, or
• Shortly after an identified infection period.

5. Protection Window
Most registered fungicides provide approximately 7–10 days of protection. A second application may be required if favourable infection conditions persist.

6. Fungicide Selection
Before finalizing a fungicide program, producers should consult their processor’s approved chemical list for the season.

Perennia’s Online Pest Management Guides can assist with product selection and application planning:

• Online Pest Management Guide: https://www.perennia.ca/onlinepestmanagementguide/

7. Resistance Management
To reduce the risk of fungicide resistance development, rotate fungicide groups and modes of action whenever possible.

8. Factsheet Resources

- NS Monilinia Blight Factsheet: https://cdn.dal.ca/content/dam/dalhousie/images/sites/wild-blueberry/pdfs/Monilinia_Blight_Lowbush_Blueberry.pdf.

- NB Monilinia Blight Factsheet: https://www2.gnb.ca/content/dam/gnb/Departments/10/pdf/Agriculture/WildBlueberries-BleuetsSauvages/C310-E.pdf.

 

Figure 5. Wild Blueberry Floral Buds in F1 and F2 stages.