August 29, 1950
DR. MacDANIELS: I want to make the remark that this isn't church, you can sit up front if you want to.
The first paper this morning has to do with a nut tree disease that is bothering a good many of us, I think, particularly in Michigan, as you recall from Mr. Becker's paper, the Bunch Disease of Walnuts, by Dr. H. L. Crane and Dr. J. W. McKay. I don't know which one is going to give it. Dr. McKay?
The Bunch Disease of Walnuts
Discussion
(Manuscript too late for publication.)
(Drs. Crane and McKay reported that there had been little further development in knowledge regarding the walnut bunch disease since 1948, when G. F. Gravatt and Donald C. Stout of the U.S.D.A. Division of Forest Pathology reported on it with illustrations at the N.N.G.A. meeting (see our report for 1948 pp. 63-66.) Since then the state of California has prohibited the entry of all walnut nursery trees and scions from the Rocky Mountain states or farther east.—Ed.)
DR. CRANE: I'd like to make one additional remark. You see, we call this trouble "bunch disease" rather than "brooming," to distinguish it from other diseases that are caused by known parasites. We have a disease very similar to this one affecting walnuts and pecan and hickory, and that one has been studied more carefully than has the bunch disease. It is unquestionably caused by virus, and in our pecan orchards we have a situation that exists that is a parallel to what it is in the black walnut. The variety Stuart practically never has shown any symptom of the bunch disease. Yet it performs very much like a lot of our black walnuts do. They just don't bear; they don't have the proper foliage; they don't make the proper kind of growth. So we are not sure whether they are symptomless carriers, that is, in terms of the lack of expression of virus growth and this bunchy condition on them.
Really, we feel that all people that are interested in the walnuts and that are trying to grow them should make careful observations on these trees to study just what the situation is, how it develops, and note the performance of these trees that become diseased; because we feel that it's a much more serious thing than people appreciate at the present time.
In much of Eastern Shore Maryland and of the area around Washington and Beltsville and over in Virginia, a great majority of the trees are affected by it, particularly Japanese walnuts of all types and the butternuts. I feel it is so bad on Japanese walnuts and butternuts that they shouldn't be propagated in the area.