Black Rot Too Far Gone?

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Hope the above images post. I’m 99% sure these are splits and wounds infected with black rot fungus on the trunks of my crabapple trees. Has anyone got an informed opinion on whether these trees can be salvaged with a regime of fungicide spraying, given that the infected tissue extends to the base of the trees? Or do these lesions at the tree base signal that I’m not going to get a hold on the fungal infestation… thanks for your help!


Trying this again:

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Please tell us about your location. How long your tree has been in this condition? Can you take pics of a whole tree?

I tagged @alan for you. Hope he will come by to give you his opinion.


I’m in southeastern Pennsylvania. Trees were planted 3 years ago at roughly 3 inch caliper. They have suffered from excess moisture for the last two years, we have clay soils and the trees were planted on high mounds. Last year I augmented drainage by adding a ditch and a french drain on either side of the trees. Holes dug by the tree bases as tests did not have excessive moisture after these drainages were added. The trees came in relatively full this spring and did not have much leaf drop from excess moisture (small yellow leaves.) At this point I have extensive frogeye spot and the bark is as pictured. The overall pallor of the trees is yellowish. They were fertilized by a tree company three weeks ago. I am quite certain this is frogeye/black rot. The question is if the trees can be recovered from what appears to be extensive fungal infestation. The trees have wild cousins across the street who I think likely spread the fungus to my Donald Wyman crabapples. Thank you!

The usual consensus is that once the fungus in in the tree you can only hope the tree can outgrow the pathogen, which seems unlikely at this point.

You’ve already been ripped off by a tree company, they love to sell “deep root” fertilization- gives there guys something to do when conditions aren’t good for spraying.

The reason it’s a rip-off is because nitrogen is what the prescription is and it is at least as accessible to the tree if you broadcast it and water it in. Nitrogen is very mobile and there is ample research showing there’s no advantage to injecting it into the soil.

So don’t get taken onto a longer more expensive ride. Next they will be selling expensive injections. If you want an accurate, unbiased diagnosis I suggest you make use of your cooperative extension- you can have a pathologist identify the fungus- maybe you have a good horticulturist right there in your county office to help you through the process.

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Is it black rot or black knot?

The growth on the trunk looks to be lichen, quite harmless

Black knot affects plums, cherries, apricots, etc.

Black rot affects apples.

Alan, thank you for the thoughtful response. I’ll try the Penn State extension office and see what they can offer.

I really can’t see what’s going on with the photographs and am basing what I’m saying on your diagnosis of the trees suffering from fungus issues in the trunk tissue more visible to the naked eye.

Incidentally, when old apple trees I manage suffer from the kind of killing fungus that sometimes attacks the bark of trees, I don’t worry about it spreading to other trees because it’s never happened. I also can never predict what trees will die and which will return to vigorous growth.

The only fungus issues I have with younger trees is collar rot that is always lethal and usually related to poor drainage.