What is the hard brown growth on my young Autumn Brilliance Apple Serviceberry tree? - Ask Extension
Can you help identify the odd brown growths on my young Autumn Brilliance Apple Serviceberry (Amelanchier x grandiflora) tree that I first observed on...
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What is the hard brown growth on my young Autumn Brilliance Apple Serviceberry tree? #660772
Asked July 06, 2020, 9:35 PM EDT
Can you help identify the odd brown growths on my young Autumn Brilliance Apple Serviceberry (Amelanchier x grandiflora) tree that I first observed on Saturday. The tree was planted in March and has been doing well. It looks like crown gall, but I am not certain. I only found two of them, one on each of two small branches. I immediately clipped off the branch twigs with the growth, took a picture (see attached images), and saved the sample in a baggie. As of this evening, I have not seen any other growths.
Montgomery County Maryland
Expert Response
We are not certain if this is a nodule due to rust fungus (a common ailment of Serviceberry), bacteria (not common on Serviceberry), or an insect gall. Rust fungi produce pinkish to orange spores when in their infectious stage, which typically occurs by now but may yet occur here. You can monitor any left on the tree (possibly even one of these, if you keep them in a plastic bag with a slightly damp paper towel) to see if spores appear in the next week or two. Symptoms tend to eventually look like the image of the infected Hawthorn on this page: https://extension.umd.edu/hgic/topics/rust-diseases-trees
Crown gall is bacterial in nature and incurable. That said, Serviceberry is on the resistant plants list and the growth here doesn't quite resemble typical crown galls, which tend to have a very textured or warty surface.
https://extension.umd.edu/hgic/topics/bacterial-crown-gall
https://extension.umn.edu/plant-diseases/crown-gall
An insect or mite causing a gall is not unusual for trees, but we are not aware of any that feed on Serviceberry. You can cut open one or more of them with pruners and see if there are any chambers or visible insects inside. (Sterilize your pruners afterward, just in case it's a pathogen, to avoid spreading it next time you prune this tree.)
In any of the above cases, pruning out the growths is all you can do. (Insect galls don't require removal.) Depending on their cause, impacts to the tree's overall health are unknown, but probably not serious. On a young tree with multiple growths, however, you will understandably be looking at substantial growth removal if they keep appearing. For this reason alone, if it does not stop spreading on its own or with trimming, you may need to replace the tree. For now, monitor the tree for any further symptoms.
Miri
Crown gall is bacterial in nature and incurable. That said, Serviceberry is on the resistant plants list and the growth here doesn't quite resemble typical crown galls, which tend to have a very textured or warty surface.
https://extension.umd.edu/hgic/topics/bacterial-crown-gall
https://extension.umn.edu/plant-diseases/crown-gall
An insect or mite causing a gall is not unusual for trees, but we are not aware of any that feed on Serviceberry. You can cut open one or more of them with pruners and see if there are any chambers or visible insects inside. (Sterilize your pruners afterward, just in case it's a pathogen, to avoid spreading it next time you prune this tree.)
In any of the above cases, pruning out the growths is all you can do. (Insect galls don't require removal.) Depending on their cause, impacts to the tree's overall health are unknown, but probably not serious. On a young tree with multiple growths, however, you will understandably be looking at substantial growth removal if they keep appearing. For this reason alone, if it does not stop spreading on its own or with trimming, you may need to replace the tree. For now, monitor the tree for any further symptoms.
Miri
