I was hired by a client whose neighbor had been asking him for years to remove a large oak tree that grew close to the property line between their two lots. One day, my client noticed that most of the foliage of this oak tree had turned brown, on the side of the tree closest to the roadway. My client suspected that the tree had been poisoned—by the neighbor who wanted to remove it.
My client was tempted to, and almost did, confront the neighbor directly, asking him if he had sprayed or otherwise poisoned the tree. Instead however, I was called in to examine the tree and determine the cause of the decline before the neighbor was contacted. Initially looking at the tree from the road, it appeared that herbicide damage could be the cause of the problem. Examining the tree and the environment more closely however, I determined that the causes of the leaf spotting and leaf death were: (1) Anthracnose infection (an airborne, wet weather, foliar fungus disease very common to this species of oak), and (2) gopher damage to the root system of the tree. I determined the Anthracnose infection by examining foliage samples taken from the tree under a dissecting scope in my office. I determined gopher involvement by removing a deep layer of leaf and twig litter around the root collar of the tree, and discovering an active gopher mound in this area. Removal of additional leaf litter beneath the tree uncovered additional recent gopher activity.
The pattern of damage on the tree and on individual leaves did not really fit that of herbicide damage, which helped me to rule out that possibility. Even though all the foliage on some twigs was dead, the twigs themselves were still very much alive. I believe that this oak tree partially defoliated as a reaction to drought stress induced by gopher damage to the root system. The Anthracnose has probably always been there, but was noticed because of the large amount of foliage that had died due to the gopher damage. I expect that the tree will recover and prescribed some supplemental irrigation in the short term to compensate for root loss. Gopher control was recommended too, of course.
My client was relieved that the tree had not been poisoned and that he did not erroneously confront the neighbor about the problem, which would have been an unpleasant, and as it turns out unnecessary, situation.