Leaf Diseases Management Reminder and Phomopsis Stem Blight (Canker)- check your fields!

Tuesday, August 8, 2023

 Good afternoon, everyone


As we get further into the season, a lot of other important wild blueberry diseases start to show symptoms, such as Septoria leaf spot and leaf rust, which are two very important leaf diseases to manage in wild blueberry production. These two publications are good references to read. 

Leaf Diseases Management Reminder


NB: Leaf Diseases of Wild Blueberry https://www2.gnb.ca/content/dam/gnb/Departments/10/pdf/Agriculture/WildBlueberries-BleuetsSauvages/0171100029-e.pdf.

AAFC: Diseases of Lowbush Blueberry and Their Identification



Growers should have at least one leaf disease fungicide application in sprout fields before they start harvesting in crop fields. Do we need a second leaf disease application and when is the latest the application can be made? It depends on the weather. If August will be wet and humid (like in 2021), a second leaf disease application might be needed. This year’s weather seems to be heading in that direction so growers should monitor their sprout fields and if early defoliation is observed in patches, then a second leaf disease spray should be planned. Ideally, a second leaf disease spray should be made before Mid-September, otherwise, the control effect will be reduced.


Leaf Diseases Management Reminder Phomopsis Stem Blight (Canker)- check your fields! 

In normal dry years, we rarely see other low-important diseases in wild blueberries, such as Phomopsis stem blight (canker), because they affect only a few stems which are hard to see if you don’t look carefully.

Phomopsis stem blight, in other years, you would just see one or a few stems inside clones, like this photo below and it is not severe enough to have a concern. This year, as we all know, is a wet year. The amount and intensity of rainfall not only wash out roads in fields but also contribute to pest development.  

The infected stem tissue is reddish brown and dead reddish-brown leaves (more photos below). Phomopsis canker’s disease cycle has not been extensively studied in lowbush blueberries, but we understand that the pathogen may spread by water-dispersed spores. The amount of water sitting in fields, especially in low and wet spots, with splashes caused by intensive rainfall periods, is helping the pathogen to move around and infect nearby stems. Eventually, under this year’s rainfall events, this year’s phomopsis canker disease is affecting large areas in wild blueberry fields. I have seen and gotten reports from growers about this disease. The infected areas might look like sprayed with roundup, but if you look closely at the ground, you will find brown dead stems.

I found more large infected areas in sprout fields than in crop fields. Those badly infected areas are in water-sitting spots.  

If you happen to run into your fields and see an empty patch of wild blueberries,\the area might likely have been infected by Phomopsis canker. 

Some of the fungicides that we use in this industry will also offer some benefits for phomopsis canker, such as Bravo, Quilt, Pristine and Merivon, so I don’t think an additional application for this disease is needed. Wet and low spots are normally the trouble areas.

Burn running is likely beneficial for disease control as it reduces infected plant material.