24 THE HOP APHIS IX THE PACIFIC REGION. 



aphides become numerous. This is usually from June 1 to 15, though 

 in some cases it may be earlier. It is well to spray first the fields which 

 are most seriously infested. 



It is usually desirable to wait until the vines are stripped before 

 spraying. 



NUMBER OF APPLICATIONS. 



The number of applications which are necessary to control the 

 aphides will vary with the seasonal and local conditions. The object 

 is to prevent injury to the vines and to have the vines practically free 

 of aphides at the time hop picking commences. To obtain good re- 

 sults it is usually necessary to spray the vines from two to four times. 



NECESSITY FOR EARLY SPRAYING. 



Mr. H. N. Ord, who directed some very successful spraying opera- 

 tions in a large hopyard in Oregon, claims that the secret of his 

 success was early spraying. He began before the aphides became 

 very numerous and continued as long as there were any aphides in 

 the field. Yards sprayed under Mr. Ord's direction were practically 

 free from aphides, while the crops of a near-by grower were so severely 

 damaged that 10 acres were left in the field unpicked. 



NECESSITY FOR THOROUGH WORK. 



The insecticides which are used for the hop aphis kill only by actual 

 contact, and if satisfactory results are to be obtained it is absolutely 

 necessary that the spray be thoroughly applied. Running the spray 

 up and down the vine is not sufficient, because all of the leaves must 

 be thoroughly wetted on both surfaces if good results are to be 

 obtained. 



PROCRASTINATION . 



In sections where the aphides are frequently controlled by weather 

 conditions some growers are likely to delay control work, hoping that 

 a hot, dry wind will relieve them of the necessity of spraying. In one 

 hop-growing section of California such a wind has appeared regularly 

 for several years, but during the past two seasons (1911-12), which were 

 favorable for the aphides, it did not arrive. Many growers, depending 

 upon this wind, made no effort to control the aphides until late in the 

 season, when much damage had been done. It was then difficult to 

 make much progress against the insects, and severe injury resulted. 



SPRAYING EXPERIMENTS. 



The nicotine solutions appeared to be the most promising materials 

 and were therefore the most extensively used in the experi- 

 ments. The following tables, arranged according to relative costs, 



