If you are a new user or
want to learn more about GDD recommendations in wild blueberry management,
please scroll down to the introduction section.
We will select several wild blueberry weather stations each season to report their seasonal Growing Degree Days (GDD) development. We intend to give updates from April 1 to October 31. We will report the following stations in the 2025 production season.
|
GDD
Summary (April 1-22) |
|
|
Wyvern
(NSW003) |
71 |
|
Oxford
(NSW005) |
77.7 |
|
Halfway
River (NSW039) |
68.3 |
|
Salt
Spring (NSW077) |
83.3 |
|
East
Mapleton (NSW078) |
49.1 |
|
Kirkhill
(NSW082) |
60.3 |
|
West
Advocate (NSW091) |
70.5 |
|
Murray
Siding (NSW002) |
78.4 |
|
Debert
(NSW036) |
68.5 |
|
Wentworth
(NSW076) |
72.2 |
|
Westchester
Station (NSW094) |
70.3 |
|
College
Grant (NSW040) |
59.5 |
|
Sunny
Brae (NSW058) |
63.2 |
|
New France
(NSW075) |
61.7 |
|
Skye
Mountain (NSW028) |
48.1 |
|
Keppoch
(NSW029) |
45.2 |
|
West
Caledonia (NSW026) |
83.3 |
|
Dean
(NSW069) |
70.8 |
|
Upper
Rawdon (NSW099) |
70.1 |
Figure 1. Selected Wild
Blueberry Weather Stations and GDD Updates (April 1- April 22)
Introduction (updated on March 24, 2025):
This GDD page was created
to provide wild blueberry growers with information on using GDD and the latest
GDD recommendations in wild blueberry management.
What is GDD, and how can GDD support your
decision-making in wild blueberry field management?
Growing Degree Days (GDD)
is a weather-based indicator that tracks daily temperatures to estimate plant
and insect growth and development. GDD is a supporting tool that improves
growers’ field activity planning, such as pesticide applications, beehive
introductions and harvesting.
In wild blueberry
production, key field activities are conducted based on the crop stages.
Research projects have been undertaken to understand wild blueberry plant
physiology better and provide GDD recommendations on key stages, such as plant
emergence, fruit bud F2, bloom, and fruit stages. The following section will detail
GDD recommendations for Nova Scotia wild blueberry management.
To get started with the
GDD tool and use it to support your wild blueberry management, we recommend
growers select the closest weather station for better accuracy. You can choose
your station from Perennia’s Farm Data Tools GDD
Calculator
or view all weather stations in wild blueberry fields through this link: http://www.novascotiawildblueberryblog.com/p/weather.html.
Growers can obtain
cumulative GDDs through different means, but we encourage growers to use the
GDD Calculator in the Farm Data Tools platform. Each station’s cumulative GDDs
can be compared with recommended thresholds to get an idea of the local wild
blueberry stage, which requires further confirmation by field visits before
making decisions.
GDD is another method of
giving growers better estimates on crop stages so you can plan activities by
comparing the latest local cumulative GDD to recommended numbers. By employing
GDD in your wild blueberry management, growers can improve crop stage estimation
and gain confidence before conducting field activities.
Here is a factsheet to
help you understand GDD in Wild Blueberry Production: https://www.perennia.ca/wp-content/uploads/2018/03/Understanding-Growing-Degree-Days-in-Wild-Blueberry-Production.pdf.
Local Wild Blueberry Growth Stages’ GDD Recommendations
In this section, we
summarize the latest GDD recommendations from researchers and quickly explain
some key points when using them for activity planning.
Sprout Field
The sprout-year wild blueberry
GDD model was initially developed by Dr. Scott White (DAL-AC), who studied
plant emergence and tip dieback stages and their GDDs. With his continuous efforts
and research in recent years, Table 1 shows the latest GDD recommendations for
plant emergence and tip dieback.
Table 1. Wild Lowbush Blueberry Growing Degree Days Model
(White 2012)
*GDD start calculation date: April 1; Base T= 0 °C.
Plant emergence GDDs and
sprout field management: The status of plant emergence in sprout fields is critical in
deciding whether to conduct key field activities (Figure 2), such as herbicide
and fertilizer applications. We have the following recommendations to help
growers’ planning, but we strongly recommend that you validate them before
implementing them.
Figure 2. Wild Blueberry Plant Emergence
· Wild blueberry plant emergence
starts at 213 GDD, and growers are encouraged to apply pre-emergence herbicides
between 150-200 GDDs. Most pre-emergence herbicides (Chikara, Ignite, Spartan,
Velpar…) should be used before wild blueberry emergence starts or below a low emergence
percentage (5-10%) for crop safety and better efficacy.
· 50% plant emergence is another critical point
for growers to watch, which can help you decide when to apply post-emergence
herbicides, such as Callisto 480 SC, Venture L, Poast Ultra, etc. After
50% plant emergence, most wild blueberry broadleaf and grass weeds are expected
to emerge and reach control points. For example, it is effective to apply
Callisto to control narrow-leaved goldenrods when pest plants reach about 20 cm
or around 400 GDD in local conditions.
· Fertilizer applications. Growers might consider applying granular fertilizers to sprout fields in the spring. After fields reach 50% plant emergence, wild blueberry plants are expected to require more energy for development. Fertilizer application at this time will benefit plant growth.
Crop Field
In wild blueberry
production, more crop stages and activities occur during the crop year than in
the sprout year. The industry conducted research projects to understand three crucial
wild blueberry crop growth stages and their GDDs to support decision-making,
including fruit bud F2 (Figure 3), bloom (Figure 4) and fruit stages (Figure 5).
Perennia and WBPANS
conducted the studies from 2022 to 2024. We studied wild blueberry sites across
Cumberland, Colchester, and Pictou to establish GDD thresholds for those three growth
stages. We present the crop year's GDD recommendations based on this project
and local practices. Because of regional variations, we encourage growers to
validate the actual field crop stage after referencing the recommended numbers.
Fruit bud F2 stages (Figure
3) and Monilinia Blight Management. According to the industry standard, blueberry
fruit buds above 40% F2 are susceptible to blight infection; therefore,
fungicides should be applied to protect crops during the susceptible period (40-60%
F2).
Figure 3. Wild Blueberry Fruit Bud F2 Stage
Table 2. Wild Blueberry Fruit Bud F2 Stages and GDDs
Bloom stages& GDDs, and field activities during the bloom period. Fungicide applications and beehive introductions during the bloom period are critical to successful disease prevention and pollination.
· Early Bloom Botrytis Blossom
Blight Control. If your fields require fungicide sprays for Botrytis
management, and you want to complete it before bringing bees, 10-25%
(353-379 GDD) would be a suitable window.
· Pollination. Blueberry
growers should coordinate well with their bee suppliers to ensure timely beehive
placement in crop fields. Table 3 gives growers baselines to track bloom
development in their areas, which can be used to determine your bee schedule
based on personal preference and beekeepers’ availabilities.
Figure 4. Wild Blueberry
Blooms
Table 3. Wild Blueberry
Bloom Stages and GDDs.
*GDD start
calculation date: April 1; Base T= 0 °C.
Fruit ripening stages&
GDDs. Fruit
ripening information can help growers manage insects (SWD and Blueberry
Maggots) and determine harvesting schedules. Please refer to Table 4 and the
recommendations below for fruit stage management.
· Insect traps and
monitoring. Growers are encouraged to place insect traps when fields reach the early
ripening stage, which can help determine insecticide application schedules.
· Field harvestable point.
We recommend growers use 1700 GDD (around 90% ripening) as a reference point to
begin harvesting if conditions are favourable.
Figure 5. Wild Blueberries
Table 4. Wild Blueberry Fruit Ripening Stages and GDDs
*GDD start calculation date: April 1; Base T= 0 °C.