In taking up the question of nut diseases it is hardly proper, perhaps, to take too narrow a view of it and I will, therefore, mention some of the other work being done here in Washington that is of interest to the Northern Nut Growers Association.
You all know of the pomological work being done on nuts, and I hardly need mention the work now being carried on by Mr. C. A. Reed, a member of this association. It might be well to remind you that the work was started by Mr. Van Deman some twenty-five years ago, and continued by Mr. Corsa, and a report was issued some fifteen years ago. It was taken up later by Mr. William A. Taylor.
The plant introduction work of Mr. D. G. Fairchild should be mentioned. He is scouring the world for new nuts of all kinds for the northern and southern, eastern and western United States, and introducing them into this country. The diseases of those nuts are studied by Mr. Orton in the Cotton Truck Division of our department.
Outside of the Bureau of Plant Industry also there is some work being done on nut trees. The insects attacking cultivated nuts are studied by Professor A. L. Quaintance, of the Bureau of Entomology, along with the deciduous fruit insects. The insects attacking forest nut trees are studied by Dr. Hopkins of the same Bureau in the laboratory that studies the forest insects. Of course the nut trees, as forest trees, are studied in the Forest Service about which you all know.
One thing more that I would like to say, in way of explanation or apology, is in regard to criticism of the Department for not more thoroughly attacking the filbert blight. Only forty-five thousand dollars are appropriated by Congress for the investigation of the entire fruit disease problem of the United States. That includes the great citrus industry; everything, in fact, from cranberries on Cape Cod and the mouth of the Columbia River to grape fruit in Florida or apples in New York. It includes the subject of all the nut diseases, and that means the problem of the diseases of the pecan, of walnut bacteriosis—that is a big problem—in southern California, and more or less in other parts of California, our great apple industry, the peach yellows, the pear blight, etc. When it comes to parceling that out it only leaves about three thousand dollars for nut diseases, and thirty-five hundred dollars for studying diseases of citrus fruits, so you must not be surprised that we cannot put a group of men on this problem and study it as it should be studied. It is a question of men and means.
Perhaps now some general information might be of interest and set you to thinking.
In the first place in every disease problem, conspicuously so with our fruit and nut diseases, there are two main classes of plants to be considered, our native plants and the foreign plants. The pathologist is always looking to the native origin of a plant in studying its adaptation to the environment in which it is attempted to be grown. A foreign plant may not necessarily be unadapted to another locality. The vinifera grape is thoroughly adapted to California and to much of the Pacific slope beyond the Rocky Mountains, but you know the vinifera grape has a hard struggle in other parts of the United States. This is not only a pathological problem but a physiological one. It cannot stand a soaking rain for two weeks at a time; it cannot stand so much water and humidity but it wants dry, hot sunshine continuously from the time it puts out its leaves in the spring.
Another phase still more interesting is the question of foreign parasites. Many of the worst diseases with which we have to contend are either native diseases attacking introduced plants, or foreign diseases attacking native plants. I will take that up in detail. Nature has fought the battle all out with the native parasites against the native host plants, so we don't have to do it. It's a case of the survival of the fittest. They have won, so when we are dealing with native plants against our native diseases, we have a condition that has been fought out in nature for nobody knows how many thousand years. The result is that unless we disturb the balance too much by cultivating great orchards of a thing that has been grown as scattered individuals, or overforcing it or selecting and breeding towards larger fruit without any regard to foliage and other characters we can go ahead with our breeding and selection and cultivation and trust nature to keep the balance to some extent. We have this natural balance in our favor in dealing with the problem of cultivating native plants. As an example take the pear and apple blight. The pear blight problem is one in which a native parasite on wild crab apples, which occasionally kills a few twigs here and there, attacks the juicy, tender, susceptible, introduced European pear and makes a very serious disease. It is a fight indeed to grow it in so much of the country that pear culture has been very largely suppressed over the eastern half of the United States and part of the Pacific coast. All this trouble has been caused by one little native microbe. Apple culture also, with certain varieties, has been seriously interfered with in some sections.
The apple cedar rust is probably the most striking example of a native parasite attacking a foreign host that we know of, and particularly so as the remarkable evolution in which the parasite has adjusted itself to the new host is taking place right now every year. The apple cedar rust is becoming a more difficult problem clear across the eastern United States to Nebraska. It has occurred as a serious disease since 1905 to 1907. As a botanical curiosity we have known it a long time, but as a serious disease, it is very recent, and nobody knows yet how serious it is going to be.
We have a very striking example of this introduction of a foreign plant and the plant being attacked by a native parasite, in the case of the filbert blight, and I am going to take that up later. The trouble is that we have brought into the United States a European filbert and it has been attacked by a parasite of our wild hazelnuts. The disease is very rare and is seldom seen on the wild hazelnut,—so rare that it was hardly known by scientific botanists, and yet it interferes with filbert culture in the eastern United States and is the one thing more than anything else to make filbert culture unprofitable. We have practically the same proposition in the walnut bacteriosis, not only in the northeastern United States, but in the best walnut districts of California. This bacterial disease which is undoubtedly a disease of our native walnuts—probably the native black walnut—occurs rather rarely, and so feebly developed as to be difficult to find at all on its native host yet it becomes the great serious disease of the Old World cultivated walnut.