It is discovered out of practice that walnut trees and locust trees should not be planted near the orchard. The juglone in the root and cortex of walnut trees can cause the stalk cells of many fruit trees to separate. And locust tree is the shelter and source of stink bug.
Its not good to plant candlenut and pine tree near the orchard. Candlenut is the source of violet root rot bacteria. And the spore of the pine tree is dangerous to fruit trees, especially pear tree. Dont plant cypress around the pear tree orchard. The pear rust bacteria will live through the winter and reproduce on the cypress. In the next year, the bacteria will come back and endanger the pear trees. Elm is a natural enemy to most trees. If there is elm near the vineyard, the yard will be destroyed.