Drupaceous Fruits 91 



brown-rot and scab, and occurs in the Eastern and Central 

 United States, though unknown outside of the United States. 

 It was first noted about 1903. 



Spots first appear on the leaves as small, gray specks which 

 soon become angiilar and water-soaked, later brown. Single 

 spots measure 1-5 mm. in diameter. The diseased tissue 

 usually drops out, leaving "shot-holes." Badly diseased 

 leaves fall and a large percentage of defoliation is common. 

 On twigs, water-soaked spots surrounding the lenticels 

 appear, developing to a length of four centimeters or more. 

 The diseased areas become sunken and brown in age, and 

 often develop into perennial cankers. On fruit, the specks 

 are at first similar to those on the leaves, but the skin soon 

 breaks and cracks appear. (Fig. 45.) 



Trees that are kept in good growing condition by proper 

 pruning and cultivation are not seriously injured by black- 

 spot. 



Powdery-mildew {Podosphcera oxyacanthce (DC.) De Bary, 

 and S'phcerotheca pannosa (Wallr.) Lev.).- — ^ These wide- 

 spread mildews, in general appearance, are similar to the 

 powdery-mildew of the grape, cherry, lilac, and rose. Some- 

 times the attack is so general, on twig, leaf, and fruit as to 

 practically destroy the crop. When on fruit, the mildew ap- 

 pears first while the peach is small, causing irregular, grayish, 

 moldy blotches. As these enlarge, cracks often develop. 



Sulfur may be used as a dust, or a lime-sulfur spray, 1-50, 

 may be applied. Treatment should be made as soon as the 

 mildew is seen. Two or three treatments may be required. 



Yellows. ^°^' ^^"^ ^^" — Peach yellows has been known in the 

 United States since 1760. From a region near Philadelphia, 

 as a center, it has spread until now it is known throughout a 

 large territory embracing Virginia, Arkansas, Texas, and 

 Canada, and is constantly extending its frontier in every 

 direction. It is not known to occur outside of North America. 

 The disease is of unknown origin, but it has been proved 

 beyond question that it is contagious. The roots of diseased 

 plants, however, do not infect the soil, and trees may safely 



