WITH RECOMMENDATIONS. 37 
when the vines are stripped and tied together above the point of 
stripping (PL X, fig. 2) the foliage below this point is matted and 
difficult to spray thoroughly, but that when the vines are tied below 
the first foliage (PL X, fig. 1) the leaves are free and the undersides 
are readily treated. Stripping the vines is a necessary preliminary 
to the successful control of the hop aphis and should be done before 
commencing to spray. 
PICKING OFF INFESTED LEAVES. 
It is the custom of some growers to pick off the infested leaves and 
throw them on the ground. This practice reduces the infestation 
somewhat, but even though all of the removed aphides die, there are 
many scattered ones left upon the vines which will soon cause 
reinfestation. The writer has never observed any good results from 
this practice alone. 
FERTILIZATION AND IRRIGATION. 
Stimulation of the vines helps them to resist the draining effect of 
the aphides and encourages the production of the hops, but does not 
retard the insects in the least, the resulting dense foliage favoring 
their development. Proper irrigation and fertilization invigorate 
the hopvines and are very beneficial, but when an infestation occurs 
they should be supplemented by thorough spraying operations. 
GENERAL SUMMARY, WITH RECOMMENDATIONS. 
The investigation of the life history and control of the hop aphis 
has brought out the following points : 
(1) The hop aphis, if not carefully controlled, always injures and 
may cause a total loss of a large portion of the crop. 
(2) The insect may hibernate upon the plum or the hop. The 
destruction of the hibernating forms will aid in the control of this 
insect. 
(3) The insect is readily killed by several contact insecticides. 
(4) Several applications may be necessary to control an infestation 
successfully. 
(5) If successful control is desired the spraying operations must not 
be delayed and the work must be very thorough; all of the leaves of 
the vines must be wetted on both sides. It is more economical to 
waste a little material than not to apply enough. 
(6) Severe infestations have been successfully checked and clean 
hops obtained where the spraying operations were thorough. 
