What is this apple disease?

Asked April 24, 2018, 2:33 PM EDT

This is a picture of our Honey Crisp apple trees taken last weekend. One tree had this last year and now a second tree has it. Can you tell us what this is and is there anything that we can do to treat it? We have 4 Honey Crisp trees, 2 Haralson, 2 State Fair, and one MacIntosh. Our trees are about 15 years old. Thank you. Deb Todhunter and Rex Porter 3506 County 9 Blvd Dennison, MN 55018

Goodhue County Minnesota

3 Responses

Thank you for contacting AaE for help.

Determining the problem with your trees is a process. The pictures help but I'll need to ask you a few more questions to hone in on an answer.

First, can you describe any other symptoms that you noticed on the other tree last year? Issues like misshapen or blackened flowers, leaves that wilted then turned brown, evidence of cream or honey colored sticky droplets of liquid anywhere on the tree, fruit that was misshapen, smaller or darker than normal.

Your answers may help point to the cause but then I'll suggest that to be sure, you can send in a sample to the U of MN Plant Disease Clinic. Of course, if I'm unable to figure it out, I'll then point you to the Plant Disease Clinic; so if you want to learn more about their services and costs ahead of time or even skip the middle man (me), check out this link.

Looking forward to getting to the bottom of this.

Sorry for the delay in my response. I am working through my wife and her email.
First, all the apple trees have the problem to some extent. The Honey Crisp maybe more so. I had apple maggot infestation in all trees last year, otherwise it a good crop with nice looking apples. I did get leaves turning yellow and brown around august last season. I also removed a large branch or two that had the symptoms during last season spring pruning. I don't know if the fungus on the bark is casing the problem or is it there because the bark is dead. The fungus is mostly green but with small yellow/orange areas. The problem is in the old growth probably 5 years or older. Younger branches look normal.


I'm slightly leaning toward fireblight but there's not enough information to tell.

Some things to look for this spring as the trees green up:
- look at new shoots as they grow to see if they turn from green to brown to black and take on a burned appearance
- see if new shoots develop a crook at the end

Because Honeycrisp apple trees are only moderately resistant to fireblight, I have my doubts that this is fireblight. Haralson apple trees are resistant whereas Macintosh and State Fair are moderately susceptible. If it is fireblight, it's too far along to save the tree because it's in the trunk.

Here is a link to the U of MN Extension information on Fireblight.

I suggest you send a sample of a branch that shows the symptoms you're seeing to the U of MN Extension Plant Disease Clinic. Their link is in the first answer I sent.