My crabapple tree is having a hard time. It's fighting Japanese beetles, spider mites and now this "thing" on some leaves. It starts by creating a red spot on the leaf and eventually there's some "thingies" that pops out.

Does anyone know what it is and how to get rid of it? I live in Québec, Canada.

Leaf with sickness Other side with sickness

Sorry, my gardening vocabulary is fairly limited! :)


3 Answers 3


Cedar-Apple Rust

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This National Gardening Association report has good information about the problem. This is from part of that report.

The first symptoms on apples are pale yellow spots on the upper surfaces of the leaves and on developing fruits in mid to late spring.

The spots gradually get bigger and turn orange or red, and you may see black dots in the upper surface of the spots. In mid to late summer, if you turn the infected leaves over, you'll see tiny tubes growing out of the spots.

The ends of these tubes split open and curl back, releasing spores into the air.

  • I am losing the battle on mine against Frogeye Spot. I spray every three weeks for several years but I purchased the home too late and I fear the battle is lost. Compared to my fight, is rust easier to win the war against?
    – Evil Elf
    Commented Aug 21, 2017 at 12:20

In addition to the information here Found on a Red Cedar. What is it?, if you have any Red Cedar (Juniper) trees on your property, check them over - if you see evidence of this infection on them (and you will) clip out the affected parts now, as it says in the answer. There is no other treatment available.

Unfortunately, if there are other Red Cedars in the vicinity which are not on your property, meaning you are not able to cut them in any way, you cannot interrupt the life cycle of this particular gymnosporangium infection; I'm afraid that means your crab apple will continue to have the problem ongoing. If this is the case and you decide to remove the tree because it's unsightly, the presence of this infection in the neighbourhood precludes planting any other tree in the Rosacaea family, which includes apples, crabapples, hawthorn and others, for they will suffer the same fate.

  • I do have cedar trees; for an hedge. Although, they are eastern white cedar, not red. According to this, white cedars are not an alternate host. Obviously, I can't control what my neighbors have. Commented Aug 21, 2017 at 21:48
  • @MaximeMorin I find the American use of common names somewhat confusing! Eastern Red Cedar is actually a Juniperus, whereas Eastern white cedar is Thuja occidentalis or American arborvitae - genus Juniper and genus Thuja are different members of the same plant Family, but its Juniper that's the partner in this rust infection, not Thuja. Unfortunate, because it means you can't exert any control over this infection, it's obviously beginning its life cycle on Junipers elsewhere.
    – Bamboo
    Commented Aug 21, 2017 at 22:06

Yes its rust, best thing to do is remove the tree entirely including the stump as it will reshoot from the base and those bits will be infected too- the fungus is systemic and has infected every part of the tree, burn all affected parts, don't compost or bury any bit too, plus its often another plant is also infected too, so do a hunt around your garden and remove that plant too, often the other plants are unrelated to the main one. clean up all dead leaves in the entire garden- as the wind will spread this about- fungicides are all but useless on this problem as once spotted its often too late. sorry for the bad news.

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