Q.What are these red patches on my apple tree?
As can be seen in the photo, my apple tree has these red patches on the trunk. I had someone suggest canker but it doesn’t seem to match. It looks really bad so hoping to find out what it is before it spreads further. We have had a lot of rain recently and I think this has appeared within the last two weeks.
Any help would be greatly appreciated thank you
These areas are called burls or burr knots.
It is the tree creating a place from which it can grow roots if needed. It is uncommon in selected apple varieties, but there are some varieties that are prone to it. Many rootstocks get it because they are selected partly for their rooting ability. One of the goals of breeding apple rootstock is to select varieties that root easily, but do not tend to form arial burr knots. They can be a problem. They tend to get larger, not smaller and can disrupt flow of nutrients up the tree, causing stunting or weakness.
They can be caused by bacteria, fungi, insects, mechanical damage, freezing, genetics, graft incompatibility, etc, etc, etc. If the tree grows fine with them, then there doesn't seem to be any reason to try to treat them.
You may also want to contact the garden center you purchased the tree from. They may offer a replacement tree for you.