I bought this house in May last year. I was excited to see that there were 4 growing fruit trees in the backyard. At that time I knew I would be doing some future tree maintenance.
There were many issues to deal with before I got a chance to really look at my fruit trees. When I finally got settled in and had time to look at my trees, I noticed that there had been wires between the branches. The wires had been used to support the growing branches. The wires had since been cut off between the branches. But the wires around the tree branches were still present and the tree branches had grown around the wires. Look at the picture below and you can see how the tree grew around the wires.
If you tightly tie the tree another object you create at least three issues that result in unhealthy trees: 1) If you are supporting the trunk tightly you don't give the tree the ability to thicken (the tree responds to stress moving back and forth) 2) the tight bonds cuts into the bark giving potential pathogens to enter the tree and 3) if let on the tree long enough the tree will attempt to grow around the wires or rope.
Tying a tree tightly around its trunk can result in its premature death. The living portion of tree lies just beneath the bark. Two layers just under the bark: phloem and xylem transport water, minerals and food up and down the tree. As the tree grows out this living layer meets the wire, rope or string and grows around it cutting the xylem and phloem entirely resulting in premature death. Trees are resilient if the xylem and phloem are not completely cut around the tree will try to heal itself. The best thing to do is remove all dead and decaying bark and wait. Consult an arborist if the tree does not respond.
If you observe a tree with wire or other types of support that are tightly wrapped around the trunk or branches immediately cut them off. If the tree has already started to grow around the wire or strap remove as much of the support as possible, clean up the wound and let the tree heal itself.
If the tree still needs support, support it with arbor tie or a similar soft straps with a ½” to 1” leeway. Don't be cheap and grab the nearest thing handy to strap the tree with, wires and rope are not approved for support. Remember to check the tree in three months to see if the supports need adjusting.
Damage to the tree trunk can also be caused by using a string trimmer near the tree. The string trimmer can cut through the bark and cut the living cambium layer. Never, never use a string trimmer around the tree base.
About ten years ago I removed an old bicycle chain that had been left on a tree I used a bolt cutter to remove as much as the chain that I could. Fortunately the chain had not encircled the entire tree and the tree is still alive! It's located at the front entrance to the Buchanan YMCA in San Francisco.
Enjoy your trees. Take a pruning class to learn how to take proper care of your trees. And you will be rewarded for the fruits of your labor.