2 26 THE DISEASES OF FRUITS. 



row leaves, often of a yellowish color, the latter fact giving 

 rise to the common name by which this trouble is known 

 throughout the United States. The tufts of fine-leaved 

 branches are sometimes spoken of as "brooms," or "penny- 

 royal sprouts," and trees that show these are victims to the 

 disease (see Fig. 285). The yellows is a very contagious 

 affliction of the peach and will spread rapidly through an 

 orchard. 



Professor Smith, of the U. S. Department of Agriculture, 

 has made a prolonged study of the yellows, and concludes that 

 it is quite general over a wide range, first becoming prominent 

 in the peach belt of Michigan, where it threatened the leading 

 industry in that section. It is now thought that the yellows is 

 closely related to the phenomenon of variegation, which may 

 be due to an oxydizing enzyme ; that is, a substance not asso- 

 ciated directly with any fungus or micro-organism, but capa- 

 ble of inducing a sort of ferment of some chemical change, the 

 result of which is the destruction of the green of the foliage 

 and rendering the parts unhealthy. It is possible that this 

 ferment may be present to a limited amount in all peach trees 

 and only increases to a destructive extent when certain condi- 

 tions obtain. That it is contagious is abundantly demon- 

 strated by the scientific expert who has transmitted it by bud- 

 ding, and this agrees with the practical working of the disease 

 'n the orchard. 



There is a disease somewhat similar to the above, called 

 Peach Rosette, that threatens destruction in some localities. 



Remedies. — As yet under this head nothing can be recom- 

 mended in the way of sprays. The contagion may come into 

 the orchard in the trees from the nursery, and therefore great 

 care needs to be taken in the purchase of healthy stock. The 

 grower should be able to recognize the disease in its incipient 

 stages and take heroic measures to remove it from the orchard. 

 In many States laws have been enacted for the protection of 

 orchards from this dire pest, and in some localities trees of 

 all ages and by the thousands have been uprooted and burned 

 until at present in such regions the yellows has been checked 

 and peach-growing is restored to its former importance. 



There are many yellow peach trees that are so from lack 

 of congenial soil, situation, and adequate food supply. Manure 



