GDD & PHENOLOGY TRACKER

Under this page, you will find two useful tools to help with your management: GDD and Wild Blueberry Phenology Trackers. 

How to Interpret Weather Station GDDs: please compare your current GDD from the interested location (weather station) to the above tables and determine what stage of your files are at. Please note, that variation happens so please make your management decision after you visit your fields. 

Figure 1. Growing Degree Days from Weather Stations located in Nova Scotia Wild Blueberry Fields (running from April 1 to Oct 31)

 *Please use the zoom-in and zoom-out functions to change the size of the map and you will be able to see the exact locations of weather stations. 

*Click on the weather station (location) you are interested in knowing, it will show you the most current accumulation GDD on the date reported. 

*Click on the link under "Current Conditions", and you will be able to see more detailed weather information from the station.

 

Wild Blueberry GDD Tracker

Introduction: Growing Degree Days (GDD) is a measure of heat accumulation based on the daily temperature. GDD helps to indicate and assess crop growth stages such as plant emergence, bud burst, flowering and crop maturity during the growing season. We start to calculate GDD depending on the crop and their GDD models. From the start calculation date, each date will generate a GDD value based on its daily temperature. The accumulation of daily GDD will help to determine where your wild blueberry field stage is at, compared to the model we used in Nova Scotia. 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.

Table 1. Wild Lowbush Blueberry Growing Degree Days Model (White 2012), updated in March 2024

Non-bearing (Sprout) Year		Bearing (Fruit) Year
Stages	Cum. Degree-days	Stages	Cum. Degree-days
Plant emergence- start	213 GDD	Stems with open flowers- start	390 GDD
Plant emergence- 10%	231 GDD	Stems with open flowers- 10%	412 GDD
Plant emergence- 25%	270 GDD	Stems with open flowers- 25%	440 GDD
Plant emergence- 50%	367 GDD	Stems with open flowers- 50%	480 GDD
Plant emergence- 90%	864 GDD	Stems with open flowers- 90%	600 GDD
Tip Dieback- start	690 GDD
Tip Dieback- 10%	834 GDD
Tip Dieback- 25%	940 GDD
Tip Dieback- 50%	1080 GDD
Tip Dieback- 90%	1475 GDD

*GDD start calculation date: April 1; Base T= 0 °C; GDD calculation method: averaging method (GDD = Tmean – Tbase)

*GDD thresholds in this table were updated in March 2024, from Dr. Scott White’s research data

 

Tables. Other Important Wild Lowbush Blueberry Crop Stages and GDDs, updated in March 2024

Percentage of F2	Growing Degree Days
5% F2	110 GDD
10% F2	121 GDD
20% F2	142 GDD
40% F2	166 GDD
60% F2	191 GDD
80% F2	222 GDD

 

Percentage of Blooms	Growing Degree Days
Start	353 GDD
5% Bloom	365 GDD
10% Bloom	380 GDD
25% Bloom	400 GDD
50% Bloom	431 GDD
70% Bloom	470 GDD
90% Bloom	526 GDD

 

Percentage of ripening fruits	Growing Degree Days
First Blue	1142 GDD
10% ripening	1218 GDD
30% ripening	1354 GDD
50% ripening	1445 GDD
70% ripening	1550 GDD
80% ripening	1610 GDD
90% ripening	1693 GDD

*The results in the above tables were based on multiple years of field data from wild blueberry sites in Nova Scotia, developed by Perennia’s Wild Blueberry Specialist (2024). Research in progress. Please use those numbers cautiously. On-going field scouting is encouraged. 

 

How to Obtain GDDs: we continue to improve our communications and provide clear and easy ways for growers to obtain GDDs as desired. Currently, there are three methods we recommend growers use to track GDDs.

Method 1: Perennia’s new Farm Data Tools (farmdatatools.ca). A step-by-step guide on how to use the Farm Data Tools to track GDDs will be available in both factsheet and video formats. Stay tuned and I will let you know when those resources are ready. You can give it a try if you like as it is a fairly simple tool.

Method 2: Check the GDD& Phenology Tracker under Perennia’s Wild Blueberry Blog. Each season, Perennia’s Wild Blueberry will select some weather stations to monitor seasonal wild blueberry plant development in Nova Scotia. The criteria for picking what stations to report is based on research and extension needs. Please see Figure 1.

Method 3: Using a GDD calculator sheet. This sheet can be used for any station if you can access the station’s daily temperatures. To download a copy, please go to: https://www.perennia.ca/wp-content/uploads/2023/03/Wild-Blueberry-GDD-calculator_Perennia.xlsx.

 

Percentage of Wild Blueberry Fruit Bud F2 Stage Tracker

Introduction: Wild blueberry buds are at a susceptible stage when 40% or more of flower buds are at the F2 stage. Current recommendations suggest that fungicide application be considered to protect crops when fields reach 40% F2 or above and weather conditions (temperature and wetness period) are conducive to infection.

The below map gives growers ideas of F2 bud stage development in various production areas in NS. Those data were generated based on my observations and reports from growers in those regions. Please check your field and determine your management plant. If you would like to share information with me about the blueberry plant growth stage in your areas, please contact me at 902-890-0472 or email me, at hlyu@perennia.ca. I appreciate your information.

Figure 2. Percentage of Wild Blueberry Fruit Bud F2 Stage Tracker in NS (running during floral bud development period)