Bui. 712, U. S. Dept, of Agriculture. 



Plate II. 



Apple Powdery Mildew— II 



Fig. 1. — Portion of the terminal growth of a Black Ben Davis tree, showing an early stag'c of 

 foliage infection. FiG. 2. — Branch of a Jonathan tree, showing a terminal spur killed by an 

 infection of the previous year and three spurs blighted during the current season. This branch 

 had been sprayed with lime-sulphur solution and the mildewed leaves were severely burned, 

 while the healthy foliage was unharmed. Fig. 3. — Branch of a Pryor Red tree, showing two 

 years' growth, with lateral buds on the portion infected during the first year pushed out into 

 spur growth. Note the shortened internodes. Fig. 4. — Terminal growth on a Pryor Red 

 tree, showing shortened internodes on the infected portion. The noninfected buds are swelling, 

 while those infected are still dormant. FiG. .5. — Portion of a branch of a I'ryor Red tree, show- 

 ing noninfected cluster buds opening and considerable expansion of healthy foliage, while in- 

 fected leaf buds near the tip of the branch are still nearly dormant. Fig. (j. — An apple, showing 

 injury rasulting from the application of sulphitr-dust sprays in the Yakima Valley in 1917. 

 Fig. 7. — Pryor Rrd apple, showing sulphur injury, the typo of injury which may be expected 

 to follow applications of sulphur sprays after the advent of hot weather in the arid valleys of 

 the Pacific Northwest. 



