Saskatoon Berry Fungus on Leaves?

by Casie
(Foothills county, Alberta, Canada)

Underneath leaf

South of Calgary (3a-4a).

I noticed yesterday that the leaves on my Saskatoon berries were yellowing. I flipped over the leaves and found ugly bumps. I read that it was fungus and should have dealt with it at the flowering stage. Now it's at the berry stage and I tried a spray of baking soda in water, but there are far too many trees affected.
Do I need to cut them down? Or can I leave them for this year and try to prevent it next year?
Thanks for your help!
Casie

Comments for Saskatoon Berry Fungus on Leaves?

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Aug 10, 2020

Not a Fungus
by: Jacki Cammidge, Certified Horticulturist

I've seen something similar to this on various types and species of trees, and it's a gall mite, which burrows into the leaf to lay its eggs which then hatch out into the juvenile stage, and the 'gall' is the trees attempt to wall off the damage. There is nothing you can do at this stage as the adults ( a tiny fly or wasp) have been and gone already.

Harvest the fruit, then cut off the most damaged parts, or wait for the leaves to fall, then vacuum the leaves with a shop vac, and dispose of them by burning or taking to the landfill. This will eliminate it next year, for the most part.

As it's such a huge infestation, you most likely will have the same issue for the next few years, especially if you have wild trees growing locally, which will always be a source of reinfection.

If it is indeed a fungus, the same treatment applies.

Keep in mind that these types of infections (fungus, or mites) are generally cyclical. You'll see bad cases for a couple of years, then nothing. This is because Mother Nature will find a predator or some other method of restricting the population. Be patient!

PS: if it is fungal in nature, you did the right thing with the baking soda, which changes the pH from acid (which fungus likes) to alkaline. If this is fungus, you would have seen instant results, so as it didn't do anything, that leads me to think it's gall mites.

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