2023 Updates and Seasonal Outlook for NS_ June 21_ Botrytis Blossom Blight and Spreading Dogbane Management

Wednesday, June 21, 2023

Botrytis Blossom Blight


We had many wet days starting at the beginning of June (June 1-7) when a majority of mainland fields were in mid to full blooms. Although temperatures were not very high (on average, it was around 10 c during those days), the duration of wetness was long enough for an infection to occur (see the severity rating table below). This year, we had a perfect condition for botrytis blight infection.



During those days, it was wet and windy which hampered growers to apply botrytis fungicides. We are starting to see symptoms of botrytis in crop fields in many regions/fields.


Here are some areas where I observed botrytis symptoms and received reports on botrytis infection, including Parrsboro (Kirkhill and Port Greville, but I am sure other fields in this area should have different levels of infection too), Oxford and Mt. Pleasant fields, Collingwood, Wentworth, Mt. Thom, and growers in Cape Breton also reported there was botrytis infection.

If you didn’t apply botrytis fungicides this year, I strongly suggest you check the fields. A lot of people put on Merivon towards the end of bloom which was helpful for late bloom patches but for early clones and fields, if you didn’t put on something during mid-bloom, you will likely see symptoms. I took some photos and I want to show all of them to you so you can see different angles and levels of infection from Botrytis.

Some key points about Botrytis Blossom Blight symptoms:

-       Only some flower clusters on a stem will be affected

-       Botrytis targets almost open and open flowers

-       As botrytis develops, you can see black hairs, some with gray tips. 


Please click on each photo to see a clear view of botrytis symptoms: 








Spreading Dogbane Management


If you are having trouble with spreading dogbane in your fields, this month towards the beginning of next month would be a good window to control them.


Crop fields: it would be hard and risky to apply chemicals to control dogbane in crop fields, so I recommend growers repeatedly cut above blueberry-canopy vegetation or simply cut them before harvest to make picking easier.


Sprout fields: when spreading dogbane reaches the early bud stage (see the photo below, when you start to see them produce green flower buds, that’s a good time). Currently, the industry standard to control this weed is still Dicamba. This is the active ingredient and the most common brands we are using now are Banvel (if you have leftovers from before) or Enginea (the product local stores carry now).


Rate and application recommendations:

Please spot spray spreading dogbane with Dicamba and be careful to not let chemicals run into blueberry plants.


3 mL of Banvel or Enginea per litre of water+ 2 mL of adjuvant (either activate plus or merge) per litre of water.


So, if you are mixing 5 L of water in your backpack sprayer, you would need 5 L of water+ 15 mL of the product+ and 10 mL of adjuvant.


Spreading dogbane in the early bud stage


Lastly, here is a photo of Cow Wheats in a crop field: