The black walnut varieties must be rather limited, because of the brooming disease trouble; so we select from those that are quite able to resist it, or that seem immune to the trouble. The Thomas and Grundy varieties lead with us, and two other local nuts, the Adams and the Climax, rate high in our estimation. We have some nice grafts of the Homeland bearing their third crop, which we like very much, and they appear disease free. The Elmer Myers, Michigan, and other varieties are now badly affected with brooming disease.
Several years ago I reported on my observations on the brooming disease. Now, I wish to report a little more upon the subject, especially in regard to how certain varieties have withstood its ravages. I hesitate to make any estimation as to how prevalent the disease is in the wild black walnut today, for it could be quite a controversial subject, with some claiming I was very wrong. Anyway, many of our native walnuts are now affected. Outward appearances are often very deceiving; but, when one cuts the top off a seedling and attempts to graft it, he may be amazed at the broomy growth that soon appears from the stock, should his graft fail to take. Trees that appear healthy, but have made slow or poor growth are often affected. Short, twiggy, upright growth that soon becomes dead or partly so, and arises from the main framework of an apparently healthy tree, is one of the signs that disease is there.
I have claimed there are two, or possibly, three forms of brooming disease, and I am still as convinced as ever. The so-called "witches-broom," as commonly seen in the Japanese walnut, is the form most people seem to think of. The second form is the rapid-growing type, that lops, or arches downward, is gray or green in color of wood, is very brittle and easily broken in the wind, ripping off good sized limbs, and winter-injures badly. An investigation, will, however, show much dead wood comes before severe weather. This form has some broomy, upright growth, like the first, but it is never bunched. The other, or possibly, the third form, is the latent type that doesn't seem to do much harm, merely causing poorly filled nuts. The latent form is difficult to note, and can be detected only by the many short, dead, or partly dead, upright twigs scattered along the main framework of older trees. Cutting off part of the top will cause the typical growth to arise, thus identifying itself.