DISEASES OF SPECIAL CROPS 



apple losses and has been noted in several states, notably 

 Missouri, Nebraska, West Virginia, and North Carolina, 

 in abundance enough to call for printed mention. 



Brown rot produces complete decay of the affected apples, 

 which turn brown, become soft and wrinkled, and soon 

 show pustules of bushy mycelium breaking through rifts 

 and fissures in the skin over the diseased tissue. The 

 diseased fruits may 

 mummify upon the 

 tree or more fre- 

 quently fall to the 

 ground and there 

 shrivel to dry, hard, 

 wrinkled masses, in 

 which the rot fungus 

 winters. 



Powdery mildew, 

 Sphaerothecose 

 (Podosphoera leucotri- 

 c/ia (E.&E.)Salm.). 

 — The general ap- 

 pearance of this mildew is much like that described for the 

 grape ; that is, the surfaces of the leaves are more or less 

 covered with a white or grayish fungous growth, in the 

 later stages of which are found numerous very small black 

 fruiting bodies approximately 0.25 mm. in diameter. This 

 fungus, while of comparatively little significance to old 

 apple trees, causes much injury to nursery stock, often be- 

 coming so serious as to prevent successful budding. Mil- 

 dew has been reported as serious in California and other 

 western states, — in Kentucky, Iowa, Washington, and 



Fig. 37. — Brown rot (sclerotiniose) produced by 

 inoculation. Note the fungus forms the letters 

 A. M. C. Original. 



