April, '10] NORTON : PEACH DISEASES 229 



buds, producing small, narrow and usually yellowisli foliage, and later 

 clusters of weak shoots, followed in three to six years by death. It 

 was first known near Philadelphia over one hundred years ago and 

 is now found from Canada south to central Delaware and Maryland, 

 from thence extending southward east of the mountains to Georgia. 

 "Westward it is serious in Ohio, Michigan, etc., and occurs west of the 

 Mississippi as far south as Arkansas. It has not spread southward 

 very much in JMaryland and Delaware, in twenty years. In the 

 region where it is found, it is constantly present, but has had several 

 much more serious outbreaks; sometimes destroying ninety per cent 

 of the orchards in one year. 



Yellows can be transmitted to a healthy tree by union with a living 

 portion of a diseased tree, but in no other known manner, except to 

 some extent by means of diseased pits, of which, however, only a small 

 percentage usualh' germinate. (Warren [X. J. 1906] got twenty-seven 

 per cent germination from 620 natural pits and only two per cent 

 from 321 of four varieties of canning house pits; see also Phillips' 

 work in Virginia.) It has been noticed that in orchards where dis- 

 eased trees are kept cut out, fewer new cases appear, indicating some 

 other kind of infection. 



The disease is present in the tree some months before it is apparent 

 and may show first only in a part of the tree. It cannot be cut out 

 in such cases, and though diseased wood is lacking in lime and has 

 an excess of potash, it cannot be corrected by fertilizers. It also 

 attacks apricots, almonds and Japan plums and similar diseases occur 

 in several herbaceous plants and some other trees. It is not due to 

 root aphis, lack of iron, or any kind of impoverished soil ; if anything, 

 the trees making more vigorous growth being more subject to yellows. 

 Overbearing, also, is against the disease rather than favoring it. 



Many fungicides, including Bordeaux mixture sprayings and many 

 secret remedies have been tested without success. No case of recovery 

 is well authenticated. Many theories as to cause have been tested 

 and inoculations with many fungi and bacteria have been tried without 

 success. 



The distribution indicates a relation to a certain climatic zone and 

 many observations point to an increase of yellows after injurious 

 weather conditions, such as drouth, following severe winter or late 

 spring freezes. Individual trees show great resistance and some 

 varieties seem more resistant in some cases than others. None are 

 immune, not even naturals. Trees have lived in infected districts 

 for fifteen to thirty years and then died of the disease. (Morse cites 



