Damage Caused
Trees with bunch disease may live for several years in a stag-horned or tufted condition. Affected trees generally set few nuts and the nuts that mature are usually poorly filled and hence low in oil content. It is likely that a part of the unsatisfactory growth and fruiting performance of certain eastern black walnut trees may be due to the disease, even though they do not show the symptoms as they are now known. Severely affected trees are subject to cold injury, and in addition the wood becomes very brittle and is easily broken by storms. Although this disease has been known for several years, it is believed that its seriousness has not been fully appreciated, as it does not cause death as soon as symptoms appear. Several years must elapse before the tree succumbs. In the nut tree plantings made at the Plant Industry Station at Beltsville, Maryland, large numbers of butternut, Japanese walnut, and Persian walnut trees were planted. During the following years, although no records have been kept, several hundred of these trees have become affected and have been removed. Consequently at the present time we do not have any butternut or Japanese walnut trees, and only a few Persian (English) walnut trees left in the plantings. So far, not a single eastern black walnut tree has been removed from the orchards because of the bunch disease. Some trees have shown characteristic symptoms of the disease, but following the removal of the entire diseased limbs the symptoms have not reappeared.