Elm Tree Disease Costing State $39 Million Yearly

EAST LANSING - Dutch elm disease costs Michigan residents $30 million each year in the southern half of the Lower Peninsula. That's an estímate of a Michigan State University plant pathologist. The $30 million figure is an estímate of the value of beauty and shade lost to the tree disease and doesn't include another $8.75 million spent annually by local governments, industries, and citizens for control measures. According to John H. Hart MSU department of botany anc [plant pathology, the Dutch elm disease was first found in Michigan in 1950, and since that time it has spread to 56 of Michigan's 83 counties. Within a few years this tree killer is expected to be present throughout the entire state. All efforts to solve the Dutch elm disease problem are going fo be expensive, says Hart. First, the law requires that diseased trees to be removed and burned - a costly operation. Second, removed trees must be replaced if s h a d e is desired and it takes many years before new trees give suitable shade. Hart advises Michigan prop erty owners interested in grow ing elm trees to know: the cause of the disease, how to recognize it and what to do about it. Dutch elm disease is causee by a fungus called "Ceratocystis ulmi," which grows in the water-conducting tissue of the tree. As it grows, the tree forms gums which plug the conducting tissues and cause the tree to wilt and die. Many trees die the same season that infection occurs. Few trees live longer than the second or third season. Adult bark beetles are the culprits responsible for spreading the disease from tree to tree. When the beetles leave diseased elm trees, the fungus spores cling to their bodies. The spores then enter healthy trees through the puncture-like wounds made by the bark beetle during feeding. The two bark beetles which are the major carriers of the disease are the smaller European elm bark beetle and the native elm bark beetle. The European beetle entered the U. S. n 1909, and it is now the most mportant disease carrier. by a graft. Trees 20 feet apart are frequently connected. Plant pathologists using laboratory methods are the only people who can detect the disease with certainty. However, Hart gives a few tips to the layman which in most cases, indícate the presence of the fungus. The most noticeable sign is the wilting of one or more branches of infected trees. Another is the presence of branches with dead, brown leaves hanging among the green foliage of healthy branches. Infection usually occurs one branch at a time when bark beetles are the fungus carriers. A second check is to examine the crotches of and twoyear-old twigs for the oval, dejressed feeding punctures of the bark beetles. Cross sections of branches irovide a third indication of infection. Branch pieces from diseased trees will have a characeristic discoloration. In cross section the discoloration will appear as a ring of brown dots located in the wood just beneath he bark. In spite of these three simple checks, Hart reminds tree owners that professional laboratory methods are the only sure means f detecting the disease. ,