74 CIRCULAR 270, U.S. DEPARTMENT OF AGRICULTURE 



that they are worth their cost for actual control, although they are 

 very valuable in determining when to spray. Lights are attractive 

 to some insects, but no insect in the Pacific Northwest is attracted 

 in sufficient numbers to warrant the use of lights. 



ORCHARD METHODS AND SANITATION 



The effectiveness of spraying may be increased by planting trees 

 at such a distance apart that the branches will not interlock, by 

 pruning them in such a manner that all parts may be sprayed thor- 

 oughly, and by thinning the clusters of fruit so that only one fruit 

 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 tree hoppers 

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

 young orchards, and clean cultivation may prevent injury by these 

 insects. 



