I was hoping someone may be able to help me identify this problem with my Magnolia tree. I am in Toronto. The tree is about 30yrs old, 25′ tall and in a west facing backyard. Last year I noticed a few of these brownish looking bumps on one of the main branches that has a crack in the bark about 4 ft long. I didn’t do anything thing about it, hoping it was something transient. This year there appears to be more of the brownish bumps. Is it scale or a fungus and what should I do about it?
Thank you in advance for your help
Looking at your excellent photo, I hate to tell you that your Magnolia has a scale infestation. Below, you will find a link to a good website outlining several courses of action you can take to control this pest, being aware that this information is from Iowa so the insecticidal information may not apply in Ontario.
I would suggest starting with the hand picking method and pruning out large infested branches/twigs, then a spring application of dormant oil spray, followed up with an insecticidal soap spray during the crawler stage of development in mid-late summer/early fall. If there is sooty mold on the branches, I would suggest gently washing this off using warm water and a soft toothbrush or nail brush.
Hope this helps.