The spread of oak wilt in local areas may be stopped by preventing the underground movement of the disease from tree to tree through natural root grafts. This can be done by (1) poisoning all healthy trees within 50 feet of diseased trees, (2) cutting a ditch 30 inches deep with a small trenching machine between diseased and healthy trees to sever root connections or (3) severing root connections with a tractor drawn plow on which a knife blade is attached. Unfortunately the use of such heavy equipment is not practical in rocky and hilly areas. Chemicals used for killing trees are sodium arsenite and ammate. Ammate is safe to use but does not kill trees as rapidly as the other poison. In some localities 2,4,5-T used as a trunk spray has given satisfactory results in killing small trees. If infected trees are left standing mycelial mats with their numerous spores develop under the loosening bark. It is therefore advisable to cut and burn all parts of diseased trees as soon as possible after symptoms appear. A combination trenching and eradication program was started in the summer of 1950 in the Forest Preserve District of Cook County in Illinois. According to Mr. Noel B. Wysong, Chief Forester, 2 newly wilted trees were found in the Forest Preserve in 1948, 72 trees in 1949, 141 trees in 1950, and 96 trees in 1951. The count for 1952 is not complete but a continued decrease in the number of new infections would indicate good control. There is no information on resistant species of oak. In very rare cases, however, trees have been observed to recover after showing symptoms in the early spring. Future Outlook Among the many things that we need to know yet about the oak wilt disease and its causal fungus one is outstanding. How does the disease jump from one infection center to healthy trees 200 yards, 2 miles or even 100 miles away? Although spread through root grafts may be controlled by severing root connections, the value of such a control measure is limited as long as the agent or agents responsible for long distance spread remain unknown. The discovery of other methods of spread might result in the development of control measures that are cheaper and less drastic than those known at present. A great deal remains to be done and research is increasing in the various states concerned. There is reason to believe that oak wilt can be checked before it reaches devastating proportions comparable to chestnut blight which wiped out our American chestnuts. MR. SLATE: What is the origin of the fungus? Is it a native fungus, or imported? MR. CURL: Yes, it is a native fungus, as far as we know. MR. SLATE: Any evidence that the fungus is mutating to make more virulent strains? MR. CURL: That's something that hasn't been found yet. There are several strains of the fungus, what we call strains, because they will form the sexual stage, and a strain alone will not. There is not too much known about that yet, the strain business.