2023 Updates and Seasonal Outlook for NS_ 5th Blight Line Post_ May 5

Friday, May 5, 2023

In this post, I will update you on the GDD summary and plant development, emerged weeds in sprout fields, and F2 stages update


Growing Degree Days (GDD) Summary and Plant Development Updates

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

Figure 1. GDD Summary, May 5, 2023


Wild Blueberry Plant Emergence and Pre-emergence Herbicide Application:


In the central area, plant emergence is starting! It is still in the early emergence stage (less than 5%). Here are some photos I took in Parrsboro and Advocate areas. Since it is early emergence, you need to get down on your knees and look at mowed stems to be able to see them (sitting in the truck won’t work!). Here are my recommendations for different regions and thanks to Dr. Scott White to provide that valuable information.


Our recommendation for this spring is if the nearby weather stations reach 150 GDD, growers can start herbicide application. I would still recommend that based on observation and experience I had in those early regions. This rule (150 GDD to start) is only applied to fields in Guysborough, Pictou, Antigonish, Cape Breton and other high ground or typically late fields for this season for now as other areas passed 200 GDD already.  In other regions, most stations are around 200 GDD which is the point I would be concerned about if anything is applied after this point. Please check your fields!!!


·         Fields in Southshore counties, Hants, Colchester and Cumberland: It is getting too late for fields in those areas. Growers in those areas, please check your fields before putting herbicides into fields. Even if your field starts emergence and the station reaches 200 GDD, you still have a small window but please don’t wait too long (I would say get them done before this weekend!). I said that because I want to make sure herbicides are applied in sprout fields as weeds are up! You might be concerned about putting herbicides in sprout fields after emergence starts, and here are some numbers and information to relax your mind.


§  Velpar: if fields are around 10-15% emergence, it is fine.

§  Ignite and Chikara: don’t apply after 5% emergence as both chemicals can set the plants back.

§  Spartan: if fields are below 10% emergence, it is fine.




·         Other fields outside of the above-mentioned areas: please take advantage of the windows you have before crop fields reach 40% F2.



Crop fields- 40% F2:

A lot of fields in Cumberland and Colchester are above 40% F2. The Advocate area is traditionally a late region, but fields in the region all pass 40%

The below photos are typical symptoms of monilinia blight on leaves and flowers:

Figures 2&3 Monilinia blight infection on flowers (top) and leaves (bottom)



Emerged Weeds in Sprout Fields

We keep talking about some troublesome weeds we have started early but we never get to see them until flowering. Here are a few photos I took this week, and you can look for those young plants in sprout fields now.


Cow Wheat



Narrow-leaved Goldenrods and Mosses



                Lily of the Valley (not a big issue but this is a sign that blueberry emergence will start soon!)



Sheep sorrel after being treated with Kerb
There is a lot of sheep sorrel this spring in both sprout and crop fields. 

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

10% F2- May 5



Antigonish County

10-15% F2- May 5



Pictou County

20% F2- May 5



Guysborough County

20% F2- May 5



HRM (Dean, Musquodoboit…)

>40% F2, watch the weather forecast and prepare for spraying



Colchester County

>40% F2, watch the weather forecast and prepare for spraying



Cumberland County

>40% F2, watch the weather forecast and prepare for spraying


If you are on high ground or typically late fields, please continue monitoring



Hants County

>40% F2, watch the weather forecast and prepare for spraying



South West Nova Scotia

>40% F2, watch the weather forecast and prepare for spraying