UNITED STATES DEPARTMENT OF AGRICULTURE 
¥ BULLETIN No. 684 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. PROFESSIONAL PAPER August 19, 1918 
THE SOURCES OF APPLE BITTER-ROT 
! INFECTIONS. 
By JoHn W. Roserts, Pathologist, Fruit-Disease Investigations. 
CONTENTS. 
Page. Page 
i nOMUC hI OMe sts Eee a cece LEE ee 1 | Sources of infection—Continued. 
SOUIMGES On ime Ns GoosoosososaucunuSeasooe 4 Otherhostiplantss.-ss.cscccsecce-cisscces 19 
MITA CGE TS Seeman eee eee eee 4 Infected fruits of the current year......-. DO 
BiGber-rotCcamkerssee nes pases ae eee tone 7 | Relation to control measures.........-.----- 21 
Cankers other than those of bitter-rot... 7aleGeneralisummanyee sassemesaae cea ee eee eee 22 
IMEC ANCSSe ciate cc miecinint oils asec in Sue See ASislwiterature cited s .e ccscaccsiecec see cecieece cee 24 
INTRODUCTION. 
In the more southern apple-growing sections of the United States 
the disease having the common name bitter-rot or ripe-rot and 
caused by the fungus Glomerella cingulata is one of the most de- 
structive with which growers have to contend. In some seasons it 
is undoubtedly the most destructive. The financial loss from apple 
bitter-rot is increased by the fact that whereas such diseases as scab, 
blotch, and blight destroy the crop in early spring or prevent its 
setting at all, bitter-rot does not ordinarily begin until July and 
usually does not complete its ravages until September or even later. 
The grower, then, may during the early part of the season spend 
his time and money spraying for the control of other diseases, such 
as scab and blotch, and of insect pests, only to see his fruit finally 
succumb to bitter-rot in midseason, often despite his best efforts to 
prevent it. As compared with the control of scab and blotch, which 
are also important apple diseases in the South, the control of bitter- 
rot is difficult of accomplishment. In the case of scab and blotch, 
definite times can be set for the application of sprays for control 
51135°—18—Bull. 6841 
