DETERMINING TIME OF APPLICATION 291 



not be combined without changing the materials physically, 

 making it difScult to apply them, or changing them chemically, 

 resulting in injury to tree, fruit, or foliage. 



The grower will purchase his materials well in advance of 

 the spraying season at a time when the market is most favor- 

 able. This is usually in early winter. The materials should 

 be stored in such a way as to make them convenient of access 

 and to prevent mistakes in identification of materials and the 

 possible use of the wrong material. Where unskilled help 

 must be employed, especial precautions should be taken to 

 prevent such mistakes. 



3. Determining Time of Application of Materials and 

 Amounts to Use. The grower knows that chewing insects are 

 controlled best with stomach poisons. These may be applied 

 before the insects appear and within comparatively wide and 

 somewhat flexible limits. 



Sucking insects, on the contrary, requiring contact sprays, 

 must be fought with materials applied directly to them. The 

 applications, therefore, may be made only when the insects are 

 present and usually within narrow time limits. 



Fungus diseases require the presence of moisture for an 

 extended period to enable the spores to germinate and the 

 organism to establish itself. Since control measures are ineffec- 

 tive after the fungus is once established on the host, it has 

 become a rule in fruit growing to apply fungicides before 

 rainy weather. 



Consult Spray Program for the Region. Experiment sta- 

 tions have developed spray programs or schedules adapted 

 to certain sections, which through a combination of insecticides 

 and fungicides will control most of the common insects and 

 diseases with a minimum number of applications. Become 

 familiar with the program for your section. Follow it care- 

 fully. Since new or more complete information is appearing 

 each year, the program is subject to change, and the grower 

 must be continually on the watch for better and less expensive 

 methods of accomplishing his purposes. 



