These bumps started to show up this year on a Gala limb that was added in 2015. The bumps are not at the graft point. I don’t know if I have a problem or if this is what I see on M111 trunks near the soil line. The bumps are about head high on a limb that is about 1-1.5" in diameter. If needed I can remove the limb below the bumps but I don’t want to if it is not necessary. My Grands like the the sweet Gala apples.
It doesn’t look like any disease I know of. Gala tends to develop root primordia on bark, so maybe this is the beginning of that (looks too bumpy, but photos can exaggerate scale). I wouldn’t remove it but would keep an eye on it to see what happens- any dead cambium is what too worry about. If I was really concerned I’d send a sample to a pathologist, but submitting the photo here may be adequate if someone here knows something about it I don’t.
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Bill,
You might be interested in this article http://www.gardeningknowhow.com/edible/fruits/apples/apple-tree-burr-knots.htm.
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The article suggests burr knots, or what I call root primordia, can weaken branches, but this has never been an issue on hundreds of trees I manage which are prone to developing these- I’ve never seen a single branch break as a result of these formations. Eventually trees prone to develop them usually have them all over every branch anyway, which means there’s not much you can do about them but supplies ample evidence that they aren’t actually a problem anyway.
Burr knots here have never been entry points to disease or insects, although I don’t doubt they can become a problem sometimes, some sites, some regions, but I suspect it is primarily a problem with rootstock burr knots (think 111) , which proximity to the ground makes more tender and vulnerable. Burr knots on branches appear to be more hardened off and not particularly vulnerable to any outstanding liabilities, IMO.
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Thank you
Thanks
Do I need to worry about them on the trunk? My young M111 rootstock has quite a few of them.
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It’s never been an issue I’ve observed in the NE, but the literature suggests that burr knots attract woolly apple aphids. Not that they never exploit them, I’ve just never observed them to destroy the rootsystem of a tree.
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Update on my original post. No health issues were observed from the burrs on my Gala however I eventually removed it for other reasons. Most of my apple trees are on M111 and some have what appears to be borer damage at the burrs and graft union. I dug out what I could find and sprayed the area with neem/water. A couple were girdled partly and I added bridge grafts to them as an insurance policy. All of them survived and are doing well now.
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