34 THE BED SPIDER ON HOPS IN CALIFORNIA. 
Although the red-spider injury is relatively not so great on vines 
invigorated by fertilization, it is present and will be extensive accord- 
ing to the severity of the infestation. 
Clean culture. — In September, 1911, a block in an infested hopyard 
was carefully cleared of all vegetation in an attempt to destroy all 
of the mites present. When examined October 16, however, a few 
mites were observed on some morning-glory which had come up since 
the plat was cleared. The practice of clean culture is very important 
and has a great influence upon an infestation, but it can not be relied 
upon as a complete control. 
GENERAL SUMMARY WITH RECOMMENDATIONS. 
The investigation of the control of the red spider on hops has 
brought out the following points: 
Great financial loss may be caused by the red spider. 
The mites on hops are not affected by any form of dry sulphur, but 
are readily killed by several contact insecticides, the cheapest and 
most convenient of which are flour paste (8-100) or a combination 
of lime-sulphur, 36° Baume (1-100), and flour paste (4-100). To 
get the best results it is essential that the vines should be thoroughly 
sprayed. 
Stripping the vines and burning the leaves is an excellent measure, 
but should not be entirely relied upon as a complete control. When 
the inf estation s severe early in the season and the mites are above 
the point of stripping, spraying operations should be commenced as 
soon as the vines are stripped. 
The infested area must be thoroughly and rapidly covered and must 
be sprayed a second time, 7 or 10 days later. 
Banding with tree tanglefoot will check migrations and is recom- 
mended where the hopyards are infested by food plants of the red 
spider. 
Two later spray applications may be necessary if the mites again 
appear in injurious numbers. 
The red spider on the hopvine may be economically controlled if 
the foregoing measures are carefully carried out. 
CONTROL OF THE RED SPIDER UPON PLANTS OTHER THAN 
HOPS AND COTTON. 
The flour paste, 8-100, as described on pages 24 and 27 of this 
bulletin, is a successful remedy for the control of the red spider 
in its attacks on all plants except sweet pea, carnation, green- 
house roses, and plants having a heavy pubescence on the leaves. 
Experiments have been conducted with this material against the 
mites upon the following plants without the slightest injury to open- 
ing buds, foliage, or fruit; 
