24 PEACH YELLOWS. 



The stocks were healthy (December 13, 1890), and it was only the 

 few buds which had already developed into shoots that I desired to 

 notice here. None of these appeared to be perfectly healthy, and 

 some of them had developed very characteristic symptoms of yellows. 

 Plate xxvi, from photographs, represents two good examples. One is 

 from row 1, the other is from row 3. In both a majority of the winter 

 buds germinated in autumn. Since then there have been new devel- 

 opments. At this date (July 16, 1891), 28 stocks show symptoms of 

 yellows, and the foliage on five or six vigorous shoots, which have 

 grown from inserted buds, begins to take on a peculiar yellow tint 

 very suggestive of this disease. There are cases in each of the rows, 

 but most at present in the S. row. 



This experiment is, in part, a repetition of No. 2. Whether these 

 trees (the stocks) will all perish in the same way remains to be seen. An- 

 other point important to be settled is whether any of the inserted buds 

 will develop into healthy trees. The seedlings will be transplanted 

 at an early date to a locality entirely free from yellows and kept under 

 observation until this can be determined. 



III. EXCISIONS. 



Symptoms of peach yellows, as already noted, frequently appear at 

 first on one branch only, or on one side of a tree, while the rest remains 

 for several or many months, to all appearances, perfectly normal. The 

 symptoms of the disease are progressive from part to part until the whole 

 tree is involved, and this has favored the idea that the disease is local 

 at first and only constitutional or universal after the lapse of considerable 

 time. Generally, in bearing years the earliest plain symptoms are 

 found in the fruit, and this fact has led to a strong popular belief that 

 the disease is communicated from tree to tree by pollen, through the 

 instrumentality of bees or otherwise. There is, however, absolutely no 

 foundation in observation for any such belief. The following experi- 

 ments were undertaken in the hope of determining whether the disease 

 is local or constitutional when the first symptoms appear. Assuming 

 that the cause of the disease is a contagium which has gained an en- 

 trance into the tree through such blossoms as develop into prematurely 

 ripened fruit, then it follows that the disease is first of a local nature, 

 as the appearances indicate ; and it would seem that it might be re- 

 moved, in some cases at least, if the excisions were very prompt and 

 rigorous. Anyway, this was the theory on which I proceeded. 



The experiments are as follows : 



A. Orchard of William Brothers, Dover, Delaware. Trees set 3| years ; both of them 

 cases of 1887; selected out of 27 as being most suitable for this experiment. The 

 limbs which bore affected branches were cut away close to the body of the tree, and 

 the stumps were painted. 



(1) September 16, 1887. Variety, Beers' Smock. This tree seemed to be healthy, 

 except parts of one large limb. This limb showed slight beginnings of diseased 

 sprouts, and bore one peach, wbich was ripe, red-spotted on the skiu and red spotted 

 and streaked in the flesh. The limb was removed. 



