Consulting with an arborist is the best first step to take. Do not prune it in winter /spring because the risk of fungal infection is high and don't prune it in autumn because the leaves are needed by the tree to transfer nutrients to it as they die. It can affect a wide variety of plants in your backyard under extremely humid weather conditions. Symptoms:This disease has severely affected the Elm trees all over America. Otherwise, leave wounds open. But hey, do not lose hope. Copyright © Gardenerdy & Buzzle.com, Inc.