UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 534 4 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. PROFESSIONAL PAPER June 28, 1917 
APPLE BLOTCH AND ITS CONTROL. 
By JoHN W. ROBERTS, 
Pathologist, Fruit-Disease Investigations. 
CONTENTS. 
‘ Page. Page 
InELOdUeHONEe eat eee eee toes eee ie lEWieather CONGILIONSPas22 ne -seseseeinccieso acl 8 
Description of apple blotch ....-.------------ 2 | Relative susceptibility of apple varieties... .. 9 
Cause of the disease.......------------------- 3.| Remedial measures. ..........22------------- 9 
Review of the literature........-----.------- eS Lata Vine eae eiesicis ceeoietes nee aisisi arse > 10 
IDNe Mtl sUSee hose teen es sae tos-2 = - c= <= 4.\\ Diterature)/ cited 4... cs ccceccccecsescnsse~>- il 
Cultural relations.....---.-----.-<-=--------- 8 
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 
(ote oet ne eels | SS So. ob Ae aoe 
Nore.—This bulletin is of interest to plant pathologists and to the apple growers of 
Se aS half of the United States, especially those of the more southerly apple-growing 
sections. 
81030°—17 1 
