32 
THE RED SPIDER ON HOPS IN CALIFORNIA. 
successfully control the mites. Too much faith should not be placed 
in this operation, however, as spraying may have to be resorted to 
as a final measure. The cost of stripping is about $2 per acre and 
is more than offset by the results obtained. 
Irrigation. — Vines which have not a large supply of moisture dry 
and change color more rapidly than those growing in moister soil, 
so that the work of the red spider is most noticeable on light soil in 
Fig. 8— Hopvine tied high and stripped; lower leaves matted and difficult to spray. (Original.) 
the drier parts of the hopyards. Several growers, believing that 
irrigation of the infested vines would counteract the effect of the 
mites, pumped water onto their yards and gave the soil a thorough 
wetting. The vines responded and put out a few fresh leaves, but 
the mites infested these in the same manner as before and reduced the 
quality of the hops in the same proportion as on unirrigated and 
equally infested parts of the adjoining hopyards. Irrigation will not 
control the mites, but when the soil lacks sufficient moisture it will 
