5 
the appearance of the first winged generation and its consequent migra- 
tion to hop, or (b) in the fall after hop-picking and after the lice have 
once more returned to the plum and are making their preparations for 
the laying of winter eggs. The latter time will, perhaps, be preferable, 
for the reason that in the fall the plum trees will be less susceptible to 
the action of the washes and a stronger solution can be applied without 
damage to the trees. (2) All wild plum trees in the woods through a 
Fic. 5.—The Hop Plant-louse, male—enlarged. 
hop-growing country should be destroyed. (3) The hop vines should 
be either burned or thoroughly drenched with kerosene emulsion as 
soon after the crop is harvested as possible with a view of killing the 
males, and thus preventing the impregnation of the females. If these 
measures are carefully followed, comparative exemption from lice may 
confidently beexpected. 
Atthe present time it is too late for preventive work, and the only 
thing which can be done to lessen the damage to the crop is to destroy 
the lice upon the vines by spraying with an insecticide mixture. Such 
spraying can, with care, be made quite effective, and the individual hop 
grower will have the satisfaction of knowing that whatever work he 
does upon his own yard will not be thwarted by the carelessness of 
neighbors, as during the summer the lice can not migrate except by crawl- 
ing from one yard t» another. 
Substances to be used.—Of all the different substances experimented 
with in 1888 none gave more satisfaction than properly prepared kero- 
sene emulsions and fish-oil soaps. 
Formula for kerosene emulsion. 
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