2023 Updates and Seasonal Outlook for NS_ 3rd Blight Line Post_ April 28

Friday, April 28, 2023

Here is another update before the weekend. I know many growers are planning to put on pre-emergence herbicides in sprout fields this weekend. Best luck!

In this update, growers can see the GDD summary, April rainfall summary for NS (Ryan Snoddon, CBC), and F2 % in several regions.  

Growing Degree Days (GDD) Summary

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

Figure 1. GDD Summary, April 28, 2023


Where are we now regarding plant development in different regions?

Sprout fields pre-emergence herbicide application: Most of the regions/ sprout fields in mainland NS should start pre-emergence treatments. Many growers I talked to this week are planning to put chemicals this weekend. According to wild blueberry plant emergence GDD (213 GDD), growers should get those products to sprout fields before 200 GDD to avoid crop damage.

Mowing height could also affect plant emergence. If you tend to mow low, the old stems from last year are likely to show early emergence. According to the weather forecast, most of the mainland should start seeing plant emergence after mid-late next week. Ideally, for those areas, herbicide application should be completed before next weekend.

Growers in Cape Breton, Antigonish or any late areas/fields that still have GDD below 100 can wait a few days, but if you want to start this weekend, it is fine. Ideally, after mid-next week should set a starting point for growers in those areas to start their sprout herbicide application.

Lastly, a reminder about pre-emergence herbicides. What we currently have available and commonly use pre-emergence spring herbicides are Chikara, Velpar, Ignite, Sinbar, and Spartan. Be mindful if those products are on your management program this year.


Crop fields monilinia blight season: we are walking into the monilinia blight season. Please see the below table for % F2 in different regions according to weather station GDD, personal observation and communication with growers.


If you notice your fields are at and above 40% F2, I expect growers to check their local weather forecast and make an application plan for crop fields before any long wet periods.


I am guessing Antigonish and Cape Breton crop fields are looking at about 1 week to get to 40% F2 GDD (173 GDD), so growers in those areas should start monitoring after next weekend.


I still want to remind everyone that after fields reach 40% F2 and above, a Monilinia blight application should be made before a forecasted wet/rainy period. But, if it is forecasted to be a dry period, then an application can wait until before a new wet period. After the first application, those chemicals should give plants 7-10 days of protection.

April is going to be a very dry month in NS. With only two days left in this month, it is unlikely to catch up on average. (Figure 2).

Figure 2 April Rainfall (CBC)



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

0-5%- April 28



Antigonish County

5%- April 28



Pictou County

10%- April 28



Guysborough County

8-10%- April 28



HRM (Dean, Musquodoboit…)

30%- April 28



Colchester County



33%- April 27


25%- April 27



Cumberland County


Halfway River

51%- April 28


35%- April 27

Westchester Station

10%- April 27

Diligent River

5%- April 28

Port Greville

30%- April 28


20%- April  27



Hants County


Upper Rawdon

30%- April 27



South West Nova Scotia

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