My orange tree is about five years old, this is the first time the leaves are turning yellow on the front of the tree and falling off. I have another tree close to it and it look fine.Help
Harris County Texas
That is a sign that something is either wrong in the roots or with the branch(es) that have the yellow leaves. The roots could be suffering from moisture extremes such as dry or soggy wet soil. Look at the base of the branch for signs of a canker wound that has gone most of the way around the branch. If you find such a wound prune that branch out. Soil moisture is an obvious fix but if your tree is in a low area it may be repeatedly affected and can die if poor drainage is for an extended period of time.