78 CIRCULAR 2 7 0, U. S. DEPARTMENT OF AGRICULTURE 



remains. Water sprouts and suckers should be removed, for aphids 

 and other insects often occur on them in large numbers. 



Boxes, boards, sacks, and rubbish should not be permitted to 

 accumulate in or near an orchard, as they afford excellent protection 

 to larvae of the codling moth and other hibernating insects. 



Alfalfa and other leguminous cover crops are necessary in most of 

 the bearing orchards of the Pacific Northwest. Their use sometimes 

 interferes with the control of certain insects, such as the treehoppers 

 and the tarnished plant bug. Cover crops are not so necessary in 

 young orchards, and clean cultivation may prevent injury by these 

 insects. 



