278 MANUAL OF FRUIT DISEASES 
Northwest it has been very troublesome in regions of consider- 
able annual rainfall. 
Peach leaf-curl is regarded as the most serious fungous 
disease affecting this fruit in cooler climates. In warmer 
climates, on the other hand, brown-rot assumes this réle. The 
fruit being rarely attacked by the leaf-curl pathogene, the 
losses involved are usually underestimated. The annual toll 
which American peach-growers give to the ravages of this pest 
is said to be three millions of dollars. The character of the 
losses is: (1) loss of leaves in the spring, followed by a forcing 
of a new crop of foliage later that year, which lowers the vitality 
of the tree; (2) partial or total failure of trees to set or hold a 
crop because of defoliation; (3) repeated loss of leaves for 
several seasons in succession, resulting in the death of the 
trees; (4) injury to trees by killing the twigs; (5) stunting of 
nursery stock due to the death of the shoot from the bud; 
curl-affected nursery buds never make good trees. 
Symptoms. 
Most peach-growers are familiar with the symptoms of 
peach leaf-curl, particularly in its later stages (Fig. 75). The 
first evidence of the disease, however, may be frequently over- 
looked. In the spring shortly after the leaves begin to unfold 
there is a puffing and folding of these organs. The leaf-blade 
becomes thickened and puckered along the midrib, causing 
the leaf to curl. The diseased portion becomes yellowish, with 
tints of red. The leaf is thickened, becomes brittle, and finally 
shows a characteristic silvery bloom over the upper surface 
(Fig. 75). Curling may be confined to a part of the blade, or 
the petiole, or may involve the whole leaf (Fig. 75). Affected 
leaves finally die and drop from the tree, in some cases the 
entire tree being defoliated. A new set of leaves is then formed 
from the dormant buds following defoliation. Affected twigs 
show a marked swelling and are stunted in length. Their 
color changes to pale-green and yellow. While the hypertrophy 
