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 flowers 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, 

 Podosphcera Oxyacanthce) , the control problem is more diffi- 

 cult. In any case it is best to remove badly diseased 

 seedlings. 



