GENERAL SUMMARY, WITH RECOMMENDATIONS. 37 



when the vines are stripped and tied together above the point of 

 stripping (PI. 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 

 he 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. 



