206 AGRICULTURE FOR COMMON SCHOOLS 



in blossom, for in so doing many useful insects which aid in 

 pollenizing the blossoms will be killed. As soon as the blos- 

 soms drop, all tree fruits should be sprayed. This will catch 

 the codling-moth on apples. Potatoes should be sprayed as 

 soon as they are a few inches high. Since rains usually wash 

 off the sprays, spraying should be done several times during 

 a season. Then, too, some substances lose their effectiveness 

 after being exposed for a time. 



All experiment stations publish bulletins about insects and 

 spraying. These can always be had free for the asking. 



