I have not taken the time to search the records, but probably only about 25% of the samples that are received at the Plant Clinic actually involve a disease problem. Many involve insects, but the greatest number of diagnoses involve environmental, site, or “people” stress. If you are sending a sample for diagnosis, it is extremely important to provide plenty of facts, descriptions, sample material, and even photos. Remember, “garbage in means garbage out.”
Recently, some of the more common disease problems we have dealt with on ornamental plants include Verticillium wilt, oak wilt, Dutch elm disease, Sphaeropsis blight, cankers of many types, Rhizosphaera needle cast on spruce, Septoria leaf spots, anthracnose, oak leaf blisters, crown gall, Pythium root rot, white pine decline, and iron chlorosis.