2023 Updates and Seasonal Outlook for NS_ 9th Blight Line Post_ May 19

Friday, May 19, 2023

We have a little bit more to cover in this post as we are facing more production challenges, getting further into the season. Some key words you will hear a lot in the next few weeks: Frosts, Botrytis blossom blight, Pollination, cold damage and disease symptoms (cold damage vs monilinia blight symptoms vs botrytis blight symptoms).




This morning (May 19), we got frosts in some areas and there are three areas with particularly low temperatures (below -2 c). Please take a chance to check your crop fields near those stations/areas I mentioned below.


If you observe any frost damage in your area, please let me know. hlyu@perennia.ca; 900890-0472.


NSW001- Glenholme: -3.1 c

NSW038- Staples Brook: -2.2 c

NSW037 and NSW038- Belmont: -3.6 c


NSW060- Blue Mt.: -2.3 c

NSW061- Moose River: -3.6 c


I don’t think fields in those areas are in bloom yet. Most of the fields should be around 80-90% F2 and in a tight cluster stage.




Chaplin (NSW071): -3.2 c






Growing Degree Days (GDD) Summary and Plant Development Updates

Figure 1. GDD Summary, May 18, 2023

Sprout fields:

Sprout fields in Cape Breton still have a few days for growers to safely apply pre-emergence herbicides. For all of the other fields in NS, the safe window to apply spring herbicides was passed. If you still want to apply pre-emergence herbicides, please contact me and we can look at individual cases.


Crop fields:

Here is a picture of the crop (bud and bloom) development stage in different regions.


1.      Southshore counties and early fields (those stations with GDD above 300) in Cumberland: early flower and beginning of bloom (about 5-10%).

2.      Hants, HRM (Dean and Musquoboit area), Truro and Debert area: in a tight cluster stage with some early flowers

3.      Rest of Cumberland and Colchester: 70-80% F2 and tight cluster stage

4.      Pictou and Gusyborough: 60-70% F2 and tight cluster stage

5.      Antigonish and Cape Breton: passed 40-50% F2


Monilina blight infection risk is still something we should watch very closely since we are still in a critical time. After this long weekend, I would expect that the infection risk will be low to mainland fields but for growers in Cape Breton, you still have another 2 weeks to be out of this year’s monilinia worrying.

Some very early fields will get into 20-30% bloom after this weekend and for most fields, it is looking like we will have another early bloom season. In 2022, the earliest average week for growers to put out bees was the last week of May.


As bloom starts, botrytis blossom blight infection risk increases. I will start to talk about this disease next week.  



Frost Damage? Disease Infection? Monilinia VS Botrytis?


Many growers are wondering how to tell the differences between frost damage and disease infection on leaves and flowers. The UMaine Wild Blueberry Extension team produced a very nice factsheet and this is a good one to print and keep handy.