UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 534 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



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Washington, D. C. 



PROFESSIONAL PAPER 



June 28, 1917 



APPLE BLOTCH AND ITS CONTROL. 



By John W. Roberts, 

 Pathologist, Fruit-Disease Investigations. 



CONTENTS. 



Introduction 1 



Description of apple blotch 2 



Cause of the disease 3 



Review of the literature 3 



The fungus . 4 



Cultural relations 8 



Page. 



Weather conditions 8 



Relative susceptibility of apple varieties 9 



Remedial measures 9 



Summary 10 



Literature cited 11 



INTRODUCTION. 



In the more southern apple-growing sections of the United States 

 the disease known as apple blotch is one of the most destructive 

 with which orchardists have to contend. It first came generally to 

 the notice of plant pathologists about 15 years ago and soon after- 

 wards was regarded as important throughout southern apple-growing 

 sections. As early as 1895 the disease was recognized by Mr. M. B. 

 Waite, pathologist of the Bureau of Plant Industry. He photo- 

 graphed the diseased fruits and determined the organism present 

 to be a species of Phyllosticta. His photographs, which are on file 

 in the Office of Fruit-Disease Investigations, show that he was work- 

 ing with typical specimens of the disease. The fact that blotch was 

 previously confused with apple scab by growers, because both of 

 these diseases occur comparatively early in the season, accounts for 

 the rather late recognition of its importance. 



Blotch is not so universally distributed, even throughout the South, 

 as scab. While in some sections it will be found in practically every 



Note. — This bulletin is of interest to plant .pathologists and to the apple growers of 

 the eastern half of the United States, especially those of the more southerly apple-growing 

 sections. 



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