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 role. 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 





