24 
THE RED SPIDEE ON HOPS IN CALIFORNIA. 
the condition and extent of the foliage on the vines. During the early 
part of the work the foliage was light and could be easily sprayed, 
while later on it became dense, and thorough work was quite difficult. 
The results, however, prove the efficiency of the lime-sulphur-and- 
flour-paste spray in killing the red spider on the hop vine. 
FLOUR PASTE. 
The efficiency of flour paste as an arachnicide was indicated in the 
experiment which is recorded under No. 14 of Table VII, but it was 
not until the summer of 1912 that its value was fully realized. During 
spraying experiments with nicotine sulphate and flour paste upon 
the hop aphis it was observed that many of the smaller aphides had 
become pasted to the leaves. From this data it was assumed that a 
solution containing a larger proportion of flour paste should be 
effective against the more delicate aphides and mites, and the follow- 
ing experiments were accordingly conducted upon the red spider on 
hops: 
Table V. — Experiments with flour paste against the red spider on hops. 
Date. 
Formula. 
Number 
of mites 
present. 
Per cent 
of mites 
killed. 
Cost per 
100 gal- 
lons. 
June 18 
Flour paste. S-100 
435 
781 
452 
882 
477 
908 
100.0 
99.8 
99.8 
100.0 
100.0 
99.8 
SO. 176 
J une 27 
do 
.176 
July 12. 
...do .. 
.176 
Aug. 6 
do 
.176 
Do 
do 
.176 
Aug. 9 . 
do 
.176 
Total 
3,759 
i 99.9 
Flour paste, 10-100 
July 16 
805 
908 
99.9 
99.9 
.22 
Aug. 6 
....do: 
.22 
Total 
1,712 
199.9 
1 Average. 
These experiments prove that the flour paste, 8-100 and 10-100, 
is effective against Tetranychus bimaculatus. The spray pastes the 
mites onto the leaves, but has no effect upon the eggs, and in control- 
ling the mites a second application is necessary. 
The neutrality of this spray was proved by the fact that when 
applied upon the foliage and blossoms of the hop, in proportions as 
high as 12 gallons of paste to 100 gallons of spray, no injurious effects 
resulted. When sprayed onto the burrs and delicate hop cones, it 
did not prevent pollination or injure the appearance of the scales. 
When mixed in the spray tank, flour paste has a tendency to settle, 
and in order to do satisfactory work agitation is necessary. It is, 
