MR. S. M. MCMURRAN: I am sorry that in this, my first appearance before this Association I haven't a more optimistic and encouraging subject to talk on than diseases. You men and women who are burdened with establishing this industry have enough on you without contending with diseases, and it was not my intention to talk upon diseases at this meeting, but Mr. Littlepage, Mr. C. A. Reed, and Mr. Jones, and several others, have been urging the matter strongly, which explains my appearance at this time.
Walnut blight is a very common and serious disease on the Pacific Coast.
It may be a native disease, though it has never been reported on native
black walnuts, and it has proved a very serious menace to the seedling
English walnut groves on the Pacific Coast.
This little piece of work I want to tell you about tonight was done through the co-operation of Mr. Jones and Mr. Rush, at Lancaster, Pa., and has just been completed within the last few days. I made a trip through New Jersey, Delaware, and Pennsylvania, about the first of August, and found a number of nuts that had all the appearance of being infected with the walnut blight germ. They had the same appearance as those nuts that you saw this afternoon in Georgetown. I brought them back here and made cultures from them in the laboratory, and after that the problem was absurdly easy. The germ was obtained without difficulty, I obtained a pure culture, and then I went up to Mr. Rush's place, at Lancaster, and made a number of inoculations, of which these few I have here are typical. This nut that you see here was inoculated from a pure culture along with a number of others, and the condition is as you see it, after about a month. Inoculations were also made into twigs, and I will pass these around for your examination.
The one marked, inoculated, has a little canker on it, and on the other you will have difficulty in finding the needle punctures, but you will see them if you look closely.
Now, I hardly know what to say about this disease at this time. As I have stated before, my work has been in the South for the past several years, and no work has been done on this disease in the East prior to this summer. That it must have been here for a long time seems almost a foregone conclusion, because of its wide distribution. Mr. Jones was a little bit conscience-stricken for fear he brought it here with him. Still it is in Delaware and Maryland as well as Pennsylvania, and you can't blame Mr. Jones for that. I think, too, it is less actively pathogenic than on the Pacific Coast, or we would have heard of it before. That it should prove a serious menace to the development of the walnut industry in the East, is too much to assume at this time. It will undoubtedly eliminate a number of the varieties that are considered promising now, but the course that will have to be taken will be to propagate only varieties which are highly resistant or totally immune to the disease. Just what these varieties are going to be in the East we do not know as yet, of course. We should avoid the mistakes that the growers on the Pacific Coast have made of planting seedling trees, and taking the chance of their being resistant to the disease. A great many varieties will be automatically eliminated when the nurserymen bear in mind that this disease is one to be considered, and I want to say, that, in addition to this, the Department will take pleasure in making artificial inoculations and tests on all those concerning which there is any question. We have the germ in culture now and will maintain it, and anyone who discovers a new variety, or has an old one they would like to propagate, can communicate with us, and we will take pleasure in testing its susceptibility.
I think that is about all that can be said on the subject at this time.
This disease has been studied very carefully on the Pacific Coast and a number of publications issued from the California Experiment Station concerning it.
For those who are interested in looking the literature up, I have here the following references: Cal. Station Bulletins, 184, 203, 218, 231, and Circulars 107 and 131.
A MEMBER: Is spraying of any avail?
MR. MCMURRAN: It has helped somewhat, but it has not proved economical on the coast.