Persimmon wilt is very destructive to the native persimmon (Fig. 4). It is caused by the fungus Cephalosporium diospyri, which was described in 1945 by Bowen S. Crandall[13]. The fungus grows in the wood of the trees, producing discolored streaks. Most trees are rapidly killed, with yellow, wilted leaves making quite a contrast to the normal green trees.
This disease was found in spots from central Tennessee south to the Gulf, east into Florida, and up the coast into North Carolina. The American persimmon seemed to be in danger, as this quickly killing disease appeared to be spreading. The limited work on this disease was discontinued because of the war and the transfer of Mr. Crandall to Peru. However, this summer Mr. Crandall and the senior writer spent two weeks surveying some of the old infections and nearby territory, and were pleased to note that the disease had made very little progress into new territory. On several small areas where the disease was present some six years ago practically all of the larger trees had been killed, but some new small trees were coming up. At Chattanooga National Park, where the wilt was rampant about six years ago, it is continuing to kill trees, but many new ones are coming up. No northward extension of the disease in Tennessee or North Carolina was noted in the limited time spent in inspection.
[Illustration: Figure 4.—Small persimmon trees killed by the wilt.]
What does the disease mean to the grower of grafted persimmons, both native and Oriental? The Japanese or Chinese persimmons do not grow as well on their own roots, although they are quite safe that way as these two species are very resistant to the wilt. In the East, most of the Oriental persimmons are grafted on American root stocks, and trees in one case were killed by the wilt fungus getting in on the susceptible root stock. No attempts to control the wilt have been made, and these recommendations are based on procedure with other diseases and on knowledge of the spore production of this fungus. An owner of a valuable planting of grafted trees in a region where the disease is present should watch his trees for the first indication of trouble. The planting will be safer, if there are no nearby native trees; and if native trees are growing nearby and cannot be removed, they should be given a general inspection. Prompt removal and burning of any infected trees found is advisable. The fact that usually fungus spore production does not take place until after the tree has been dead for a while makes the prospect for control better than with most diseases. Care should be taken not to bring in scions or trees from infected areas.
Most members of the Northern Nut Growers Association have only a few grafted persimmon trees, usually located outside of the infected zone and therefore in little danger. Persimmon scions and trees should not be shipped from infected to healthy regions. The disease has not been reported in nurseries, but it could occur there because it attacks small trees.
[Footnote 13: Crandall, Bowen S. A new species of +Cephalosporium+ causing persimmon wilt. Mycologia 37 (4): 495-498. 1945.]
+Thyronectria Disease of Honeylocust+
Honeylocust is widely distributed both in native stands and in plantations. Some farmers plant this species or leave native trees in their pastures for the pods, which have a high sugar content, up to 38 per cent. J. C. Moore, of the Alabama Agricultural Experiment Station, reported preliminary tests indicating a per-acre yield of livestock feed equal to that of oats.
In many areas the growth of honeylocust is seriously affected by a canker and twig fungus, Thyronectria austro-americana. The disease often kills many twigs and branches and sometimes results in death of the tree. In most areas it causes only slight injury. Bowen S. Crandall and Jesse D. Diller have made a few observations on the prevalence and damage by this disease, which is present from New England south into the Gulf States and west into the Great Plains States.
The fungus causing this disease is morphologically somewhat similar to the chestnut blight fungus, having two spore stages produced in reddish-brown pinhead-size fruiting bodies on the bark. Cankers are produced on the smaller branches, but they usually are not noted until some of the affected ones wilt and die. In the exposed outer wood of a branch cut above or below the canker there are reddish-brown streaks several inches long, indicating that the fungus has grown in the vascular system.