2023 Updates and Seasonal Outlook for NS_ 1st Blight Line Post_ April 18

Wednesday, April 19, 2023

2023 Updates and Seasonal Outlook for NS_ 1st Blight Line Post_ April 18


This is the first post for the 2023 season on updates, the outlook for the season, the monilinia blight line, pest alerts etc. We try to publish 2 posts per week (typically on Tuesdays and Fridays) during the monilinia season and after that, we will publish posts as information comes in.


Growing Degree Days (GDD) Summary and 2023 Spring Plant Development Prediction

This year, we are only planning to report GDDs from 13 stations (see Figure 1) because we have research trials and extension needs from those stations. However, there are different ways to obtain GDDs by choosing the station you like. To learn how to obtain GDDs, please read this blog post: http://www.novascotiawildblueberryblog.com/2023/04/2023-wild-blueberry-pest-guide-new.html.

Here is a summary of the most up-to-date GDD from 13 weather stations in wild blueberry fields.

Figure 1. GDD Summary, April 19, 2023


Based on this information, most of the mainland fields in Nova Scotia could start pre-emergence herbicide application when the station hits 150 GDD but before 213 GDD. That said, a lot of areas could start pre-emergence herbicide application anytime soon.


In Figure 3, so far, we are relatively close to average. For comparison, this year’s degree accumulations are on track with the year 2019. It is not a bad idea to look at your records on 2019 management activities.

Figure 2. Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to April 17 for the past 17 seasons in Kentville. Provided by Jeff Franklin (AAFC).

Based on every piece of information I have and confirmed by field observation, we are around 1 week earlier than average and slightly later than the 2022 season (about half a week later than last year)

Winter Weather Review

The Environment Canada weather station in Kentville is used for comparison because historical data is available. A big thank you to Jeff Franklin (AAFC) for providing those data.

Figure 3: Average monthly temperatures from December through March for the past three winters, and for 5- and 10-year averages at Kentville AAFC.



Figure 4: Soil temperatures at 5 cm depth at the Kentville Research Station


Overall, we had both above-average air and soil temperatures most of the time throughout this winter.


Other observations- weeds and winter damage


Low winter kill (damage) on wild blueberry fields across the province.

You might think that you don’t need to control sheep sorrel in your sprout fields because you think it is “clean”. Please look below the top layers or any areas with thick protection layers. You would be surprised how many of them are under protection layers and growers over winter months since we had higher-than-average air and soil temperatures.


Wild Blueberry Floral Bud F2 Stage

Please see the below summary table of the percentage of wild blueberry floral bud at the F2 stage. You can also click on this map to check those numbers. Detailed information is also available under the Wild Blueberry Blog- GDD& Phenology Tracker.

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

5%- April 18


0%- April 18

Westchester Station

0%- April 18



South West Nova Scotia


Queens County

5%- April 19



Hants County




Halifax County




Guysborough County




Colchester County




Pictou and Antigonish County




General Information about Monilinia Blight and Management


It is important to monitor plant development stages in your fields, especially if this disease has occurred in your fields previously. I encourage growers to go out to the fields and see how floral buds are developing.

When looking at fruit buds do not count obviously dead fruit buds. To do that, you can walk your fields in a “W” pattern and collect 20-30 stems randomly. From those collected stems, count the total number of floral buds and the number of buds at the F2 stage or beyond. You can simply dive the number of F2 buds by the total number and times 100. This would you the % of F2. Please don’t count obviously dead floral buds.

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


For monilinia to infect blueberry plants, there should have mummy berry spores, blueberry buds at a susceptible stage (F2 and above) and an infection period of long enough wet period and temperature. Only treat for Monilinia when blueberry buds are at least at 40% and before the next forecasted wet period.

For products to prevent monilinia infection, please refer to Perennia’s updated pest management guide for wild blueberry (2022): https://www.perennia.ca/wp-content/uploads/2018/03/Wild-Blueberry-Pest-Guide-2022_FINAL.pdf.