Now, there again, it is not so much a lack of physiological adaptability, because the walnut is thoroughly adapted to our Pacific coast. I suppose most of you know that east of the Rocky Mountains, east of the Great Plains, we have a humid climate and winters more or less cold which corresponds, not with western Europe, not with Germany, England, Spain, France and Italy, but with China and Japan, with Asia, in its climatic conditions. The result is the Chinese and Japanese trees brought to the eastern United States grow well but may grow indifferently in California. On the other hand, the plants of the Mediterranean, France, Germany, Italy and Spain do not, as a rule, thrive when introduced into the eastern United States. There are a few exceptions, like the apple and perhaps the peach. These are not really natives of western Europe, but have been brought from the interior. They are more like the Japanese and Chinese plants which came in by way of Persia and which have been slowly adjusted to the conditions of western Europe. That adjustment has gone so far that the Persian type of peach does better on the Pacific coast than in the East. We are breeding a race of these fruits from China, the Chinese cling group, which does well in the eastern part of the United States, and we have from there a peach that is better for the country east of the Rocky Mountains than the ones that have been modified in Europe.
Now take the other side of this question, the foreign parasite—that is very unfortunate thing—over which we do not always have the control that we do with the foreign host. An equal disturbance of nature takes place when we introduce a foreign parasite, whether it is from a similar climatic region or one not so similar. The chestnut blight is a tremendous example of that sort of thing. This has come into prominence within a decade and it is one of the greatest problems in the pathology of the chestnut. That has turned out to be a Chinese parasite. It was found last summer by the agricultural explorer, Mr. Myers, but the fungus was studied out by Dr. Shear.
The three great American parasites of our native grapes are the black rot, the downy mildew and the Phylloxera, an insect pest, and they caused a great amount of study and work and investigation and great expense when they were introduced into France and South Germany and Italian vineyards, and were fought out only by what might be considered a magnificent effort on the part of the European governments, especially France. On our native wild grapes those diseases are almost trivial, and the wild seedlings in the woods are practically immune, but when we cultivate them and select the tenderer varieties, the black rot is pretty bad, especially on the Concord, and particularly when that is hybridized with grapes of European blood. Nevertheless, we have cultivated them in order to get the large juicy fruits. There are many more examples of this sort.
Now about the cultivated nuts. I wish I could tell you how much I think of the native nuts. I grew up in Northern Illinois and could go out on a day like this and gather two or three bushels of hickory nuts. How I enjoyed the black walnut, especially when it was just shriveled so it would leave the shell—it got rather too rich when it was dried and stale in the winter time—but how delicious it was when just wilted! Also there was the butternut and the wild hazelnut. I used to take a one-horse wagon into the woods on a Saturday and gather enough hazelnuts in the shucks to fill it; then we had hazelnuts all winter. So I am in full sympathy with the Northern Nut Growers Association and I would like to see those nuts grown, if not wild in the woods, at least in cultivation.
There might be a few things of interest to you about the wild hickory nut. According to Farlow's Index of North American fungi of twenty-five years ago, there have been thirty-seven species of fungi collected on that tree. Probably there are twice that number as a matter of fact, but mycologists have collected, described and named thirty-seven species on the Hickoria ovata, the plain shagbark, and the other hickories have similar numbers. The pecan has only three named species in Farlow's Index, but Mr. Rand has got together three times as many I think—I am not sure of the number.
Of the pecan diseases, the pecan scab is probably the most conspicuous fungus trouble. The pecan scab is the most typical fungus parasite of the pecan. It attacks the leaves, fruit, etc. It attacks the vessels or veins of the leaves and frequently enters by means of aphis punctures which break the skin so that there is no doubt but that this particular disease is favored by an aphis. We have investigated this disease quite carefully and carried on a series of spraying experiments for some three years and there is no doubt about our ability to control it. It can be prevented by spraying with Bordeaux mixture. You never can tell how many sprayings will be required. It may take three to ten sprayings to protect the nuts. The leaves are grown mostly within a month—the leaves are pushed out within thirty days and you can spray those leaves and protect them. The weak point in the treatment is that the nut of the pecan grows steadily from the time it starts to way into September. This makes a hard problem in spraying as the nut keeps expanding and forming a new and unprotected surface for an unreasonably long season and they are susceptible to scab attacks all the time, so you have the problem of spraying the nuts all summer. The spray does not stick very well on the nuts. The result is that we advise dodging that parasite by planting the non-susceptible kinds; it is much better and cheaper. It is certainly an encouraging thing that you can plant good varieties, that do not scab badly, and which at the very most require but two or three sprayings to protect them entirely, and in a great majority of cases, no spraying at all. Those already are the great nuts in cultivation, like the Stuart, the Schley and the Frotscher. Most of those good varieties will be occasionally attacked by scab because of a wet season, just as a variety of apple which is very resistant to apple scab is occasionally attacked by that disease.
The pecan has quite a number of leaf-spot fungi and most of those we have tested by spraying. These experiments have been made in the nursery where it is more convenient to spray and where the necessity is, perhaps, a little more pronounced, and there it is, undoubtedly, a proper practice to spray and fight out the pecan leaf diseases. Bordeaux mixture is the thing to be used on all occasions. The pecan resists copper poisoning almost as well as the grape and can be sprayed with safety.
If a pecan tree has crown gall don't plant it. All nursery trees should be rejected in planting if they show signs of this disease. The pecan has fungus root-rot and various wood rot fungi besides the leaf diseases. It also has several other troubles more or less serious. Occasionally in the pecan groves you will find these remarkably white mildewed nuts. That gives way to spraying. Another disease is an internal spot on the kernel which Mr. Rand has been working on and which seems to be due to a fungus. We don't know how to prevent that yet. The pecan has a fungus attacking it that is very similar to the bitter rot of the apple. The pecan anthracnose looks like the bitter rot, has the same pink spore masses and you will be able to recognize it. That may be prevented by spraying, but it is, fortunately, not a serious disease. The northern nut grower will not have so much trouble with that, as it is a southern disease. Here is a physiological trouble that causes blackening of the young nuts on the inside. It appears to me to be due mainly to wet weather, but I don't know its exact nature. It came primarily on a pecan raised in the semi-arid section of Texas and brought into South Carolina, and by the way you can get as much trouble in adapting trees from the western to the eastern United States as in bringing in trees from other countries. In parts of semi-arid Texas the trees are supplied with moisture by sub-irrigation and when we move those pecans to the humid East we get almost as much non-adjustment as when we bring in foreign things. I would suggest that these pecans from western Texas are the very ones to take to Utah and California rather than those from the eastern part of the United States. They are adjusted to dry seasons with moisture at their roots and you will get the best results from them when grown under irrigation.
I will now take up the walnut, Juglans nigra, the common black walnut. There are twenty species of fungi which are known to attack it. Quite a good many of these attack the twigs and cause them to die, and probably half are leaf diseases. One, commonly called white rust, a disease of the leaves, attracts mycologists in collecting, but it has never been of serious economic importance.
Now, as to the butternut, Juglans cinerea. It has about nineteen species of fungi known to attack it, but probably many more will be found when the nut is thoroughly studied.