318 MANUAL OF FRUIT DISEASES 
this is due to the increased moisture content of the air about 
such trees. 
Control. 
Wherever possible those conditions which favor the fungus 
should be avoided. Attention should be given to trees planted 
near one another, and to those with a dense foliage. A good 
circulation of air and plenty of sunlight is essential in this 
connection. 
As a fungicide, copper salts have not been generally effective. 
On the other hand, sulfur has proved to be satisfactory. Sulfur 
applied either as fiowers of sulfur (dust) or as lime-sulfur solu- 
tion is a success. Lime-sulfur 1 to 50, with the addition of 
three pounds of iron-sulfate to fifty gallons of the mixture to 
increase the fungicidal properties and adhesiveness, is efficient. 
Sulfur dust is desirable in that less time is required for the 
application. This should be applied early in the morning while 
the foliage is still damp. If the weather subsequent to the 
dusting operation is warm and dry, the fungicide may be ex- 
pected to be more efficient. Rainy periods, on the other hand, 
tend to decrease the efficiency by washing the sulfur away; 
however, this is not serious except in cases of rain periods 
of long duration. The fungicide used for powdery-mildew 
should be applied as soon as the disease appears. The weather 
and consequent abundance of the disease determine the num- 
ber of later applications. In some years two applications are 
sufficient ; in others it is profitable to give the trees five or 
six treatments at intervals of about one or two weeks. In the 
far West the spraying schedule for the Coryneum-blight and 
brown-rot is satisfactory for the scattered form of powdery- 
mildew. When the generalized form, that is on all parts, is 
present (that caused by the cherry powdery-mildew pathogene, 
Podosphera Oxyacanthe), the control problem is more diffi- 
cult. In any case it is best to remove badly ‘diseased 
seedlings. 
