PEACH DISEASES 283 
Wallace, E., and Whetzel, H. H. Peach leaf curl. Cornell Univ. 
Agr. Exp. Sta. Bul. 276:155-178. 1910. 
Knowles, Etta. The curl of the peach leaves ; a study of the abnormal 
structure induced by Exoascus deformans. Bot. Gaz. 12: 216- 
218. 1887. 
Duggar, B. M. Peach leaf curl. Cornell Univ. Agr. Exp. Sta. Bul. 
164: 371-388. 1899. 
YELLOWS 
Cause not known 
Wherever this disease occurs it is known as yellows, or peach- 
yellows. It is primarily a trouble of the peach and nectarine, 
although it has been observed on almonds, apricots and Jap- 
anese plums. Seedling peaches are said to be more sensitive 
than budded trees. Seedling trees derived from budded fruit 
are equally susceptible. 
The origin of the trouble is unknown. Records of it date 
back to 1760, and in 1806 it was the subject of horticultural 
writings. The first discovery of peach-yellows is thought to 
have been made in Pennsylvania, near Philadelphia. Outbreaks 
of the disease occurred in the East in 1791, 1806, 1807, 1817 to 
1821, 1845 to 1858, 1874 to 1878, and in 1886 to 1888. It 
appeared in Michigan about 1869, or earlier. The disease is 
not known on any other continent than North America, and 
the early records coming from the eastern part of the United 
States would, therefore, seem to show that peach-yellows is 
native to eastern United States. It occurs as far south as 
southern Virginia, west to Arkansas and northeastern Texas, 
north to Canada, and east to New England. 
Peach-yellows is conceded to be one of the most serious 
diseases of the peach in America. It has been extremely 
ruinous in the region outlined in the preceding paragraph. 
Soon after its discovery, hundreds of orchards along the Atlantic 
Coast were destroyed by the disease, causing growers in many 
localities to abandon peach-culture. In one county in Michigan 
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