24 THE HOP APHIS IN 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. Kunning 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, 
