284 THE MONTHLY BULLETIN. 



When a tree once shows the yellows it is practically worthless to the grower, as 

 the fruit on the affected parts is almost always insipid or bitter, more subject to rot, 

 and a detriment to the market if sold ; moreover, no cure has ever been found, 

 another crop can not be expected from the tree, and worst of all is the chance of 

 spreading the disease to the rest of the orchard. 



It has been conclusively proven that the yellows can be communicated from one 

 tree to another by buds from diseased trees and by root grafts. It seems that if the 

 smallest piece of living matter from a diseased tree is established on a healthy one, 

 the disease will follow. While the seeds from premature peaches rarely germinate, 

 they do sometimes, and then will produce diseased trees. It is the general opinion 

 that the disease is also spread from tree to tree in the orchard in some other way 

 not yet discovered. This idea is based chiefly on the fact that in orchards where the 

 diseased trees are constantly kept cut out as fast as they appear, there is a much 

 smaller total percentage of trees lost than where they are allowed to stand. Also 

 the disease seems to gradually extend from centers where it first starts. 



It will be seen that the nursery is the chief menace. If buds are taken from trees 

 with the yellows, even if they have not yet shown any of the symptoms, the disease 

 will in all probability appear in the trees that grow from such buds. There should 

 be little danger in stock from nurseries outside the yellows territory if it is certain 

 that the budding wood is from nearby trees. Nurseries within the yellows line can 

 only be sure of their buds by getting them from trees outside the yellows districts. 

 Another source of danger from the nursery is in the use of pits for seedlings from 

 districts infected with yellows. The pits so much used from the "natural" trees in 

 the mountain regions of the South, or from the Ozark region and Kansas are t>y no 

 means free from this danger. The yellows is common on the seedling trees in the 

 southern mountains and at least the rosette is a similar danger in the West. 



CAUSE OF THE DISEASE. 

 The cause of the yellows is yet unknown. A great many theories have been 

 advanced, but most of them have been disproven and the others have not yet been 

 tested. The disease is much like the mosaic disease of many plants, and some others 

 that seem to be due to a disturbance in the enzyme activities of the plant: but that 

 does not explain the cause. The most common opinion now is that it is due to the 

 presence of an organism not yet found or too small to be seen by the microscope. 



A great many cures for yellows have been advocated, but even those in which their 

 advocates had unbounded faith, founded on their experience, have failed when tried 

 by others. The prompt removal and destruction of the diseased trees, recommended 

 since 1828, is the best and most practiced method of control in the orchard ; but it 

 must be kept up annually and thoroughly. Since the Michigan yellows law was 

 passed in 1S75, a number of states have passed yellows control laws, generally with 

 the intent to enforce the destruction of diseased trees in the orchards. Many of 

 these laws are not well enough drawn to accomplish their purpose, and some fail 

 through lack of enforcement. In most peach-growing regions education and sad 

 experience have brought about the general use of these methods in keeping down 

 the disease. The nursery inspection and quarantine laws should be effective in 

 preventing the spread of the disease into new territory. There is no evidence yet, 

 however, that yellows will develop on stock from an infected nursery if planted in 

 the South far beyond the yellows line. 



There is a possibility of finding varieties resistant to the yellows, but none have 

 been yet found that are immune. Some varieties develop the disease before others 

 in mixed orchards, and some trees have been known to stand for many years after 

 those around them have perished from the yellows. 



A number of other diseases may be confused with the yellows. Of these the pre- 

 maturing from the work of borers has been mentioned. Another is the little peach 

 which can not be told from yellows in the early stages on nonfruiting stock. The 

 little leaf or California yellows is another. It is distinguished by the dropping of 

 the leaves, the failure of the fruit to develop, and recovery with a better water- 

 supply. Severe pruning, girdling, and other injuries will produce shoots like those 

 from yellows, and lack of fertility, borers and many other causes will make yellow 

 foliage. The foliage of trees with the yellows disease is usually yellow, but not 

 always, and there are many more peach trees with yellow foliage that do not have 

 the yellows than that do have it. 



