Q.What is the disease affecting my apple trees
My apple trees are over 20 years old and have produced well over the years. Last year they became infected with a disease that is killing them. The disease shows up as small bumps and circles on the bark in a series of spirals that circle the tree trunk. This year the trees did not leaf out much or produce any fruit. I believe they are dying and I want to replace them but need to know how to protect new trees from the same fate.
This sounds very much like you are describing Galls.
This is a disease that is generally fatal to the trees.
I've listed some links with more information.
https://www.gardeningknowhow.com/plant-problems/disease/how-to-fix-crown-gall.htm
https://www.gardeningknowhow.com/edible/fruits/apples/apple-collar-rot.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/cankers-on-trees.htm
