PEACH DISEASES 315 
York State. In 1905 peach-mildew attracted attention in 
Colorado, and in 1907 it was discovered in Nebraska and Utah. 
While peach-mildew is not everywhere destructive, it does 
cause considerable damage at times. Twigs may be checked 
in their growth or even killed; the foliage may be greatly 
reduced in size and efficiency; and the future health of the 
tree may be impaired. Seedlings are often badly affected, 
and nursery stock suffers more than orchard trees. The last, 
however, are not uncommonly affected, which, in case of 
severe infection, may be entirely ruined for market. For- 
tunately, not many trees in a given orchard are extensively 
damaged. 
The susceptibility of varieties is not marked; this is true 
at least for Colorado conditions. In Michigan the popular 
opinion prevails that only those varieties with serrate leaves 
and lacking glands are affected with powdery-mildew. It 
has been found by authorities, however, that this is not always 
true. In Ohio, it has been observed that the Early Crawford 
may be badly affected. At Geneva, New York, the disease 
was found on but eight out of three hundred and fifty varieties : 
Bailey, Conkling, Tillotson, Simmons No. 1, Wright, Morrell, 
Thomas Rivers and Illinois Peach. In western New York, the 
Crawford and especially the Denton are most susceptible. 
Symptoms. 
Injury is done by the mildew-pathogene to the leaves (Fig. 
83), twigs (Fig. 83) and fruits (Fig. 84). Perhaps the fruits 
are least affected of all. Along the lower surface of the foliage, 
particularly at the midrib, are to be found abundant, irregular, 
white blotches—the mildew (Fig. 83). It may also occur 
on the upper surface. As a result of the affection the foliar 
parts crumple and curl, the edges rolling toward and parallel 
to the midrib (Fig. 83). Young leaves, when affected, fall 
prematurely. Older leaves are dwarfed. Signs of the disease 
may first be observed in early summer. 
