Disease on Fruit Trees

Asked May 15, 2017, 6:25 PM EDT

Help! What's this disease on my Ranier Cherry? How do I treat it?

Linn County Oregon diagnosis of plant problems cherry trees horticulture

1 Response

Hi and thank you for contacting Ask an Expert.
The first picture of the tree limbs is nothing to worry about. That is lichen. It grows on everything in our area. I have it on my fruit trees and it does not harm the tree or affect the quality of the fruit.
The second picture shows small brown dots and that is most likely a fungus that is just getting started. You need to start a spray program for your tree. Start with Rex lime/sulfur (follow the directions), a few weeks later, follow it up with Neem oil spray, again follow the directions. This disease, if it looks like this on all the leaves, is just getting started. A regular spray program will keep it down and next year, probably completely get rid of it.
The Willamette Valley is a haven for fungal diseases. Cherries are more susceptible than other fruit trees however, they are all susceptible to fungal diseases.
Good hygiene for your tree is very important. When the leaves fall, clean them out and do not compost them. The spores from fungus love the wet rainy days and warm weather, they will grow if not completely composted (so throw them away).
Continue the spray program through the summer to completely rid the tree of this disease.
If there are only few leaves with brown spots, remove them (put them in the garbage), but spray the trees. Some of the fungal diseases can grow in the bark and form abscesses - the bark turns outward with a gap and the sap will start to run. This is difficult to stop once it gets inside.
Back to the lichen, if it bothers you and the tree is small, you can pick it off but it really does not harm the tree.
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