What is causing the leaves on our Prairiefire crab apple to develop black spots?

Asked June 29, 2014, 1:05 PM EDT

We have a Prairiefire crab apple tree located in Urbana, Illinois, that is probably 10 years old. It is described as disease resistant, but just now we notice that green leaves are developing black spots, then turning golden orange. What can it be? What should we do? It has been a rainy spring and June very rainy.


Champaign County Illinois

3 Responses

Although your prairiefire crab apple is labeled as "disease-resistant," it may still suffer from common fruit tree diseases. In the Champaign-Urbana area, fire blight, a bacterial disease, has been very common among ornamental pears, apples, and crab apples. Other diseases that it may have include apple scab, rust, powdery mildew, and chlorosis. If you would like a concrete diagnosis, visit the U of Illinois Plant Clinic located in Turner Hall or the University of Illinois Extension office located in Champaign.

Is there anything I should do? spray? I assume that I should get concrete diagnosis and go from there. Do the possible problems just cause problems this year, or are they potentially fatal to the tree? thank you.

In order to suggest treatment options, we need to diagnose the problem. Fire blight has been a big problem this year because the weather we've had is the perfect climate for the bacterium. Fire blight is fatal to the tree. For more information, please research the diseases mentioned, or bring a sample to either the Plant Clinic or local Extension office.