26 
THE RED SPIDER ON HOPS IK CALIFORNIA. 
Table VII. — Spraying experiments with various combinations against the red spider on 
hops. 
No. 
Date. 
1 
July 15 
2 
3 
4 
5 
6 
...do 
...do 
...do 
July 16 
...do 
7 
...do 
8 
...do 
9 
...do 
10 
July 17 
11 
...do 
12 
...do 
13 
...do 
14 
...do 
Material. 
Application. 
Num- 
ber of 
mites 
present. 
Num- 
ber of 
mites 
killed. 
Per 
cent 
of mites 
killed. 
450 
263 
58.4 
414 
762 
414 
237 
312 
376 
677 
263 
185 
273 
90.8 
98.9 
63.6 
78.1 
87.5 
361 
280 
78.6 
330 
225 
68.3 
164 
111 
67.7 
269 
174 
64.7 
201 
115 
57.2 
273 
191 
70 
163 
157 
96.3 
657 
444 
67.5 
Cost per 
100 
gallons. 
Nicotine sulphate, 40 per cent, 1-750. . 
Nicotine sulphate, 40 per cent, 1-1,000. 
Nicotine sulphate, 40 per cent, 1-2,000. 
Nicotine sulphate, 40 per cent, 1-3,000. 
Nicotine sulphate, 40 per cent, 1-60 
Nicotine sulphate, 40 per cent, 1- 
2,000; lime-sulphur, 1-86. 
Nicotine sulphate, 40 per cent, 1- 
3,000; lime-sulphur, 1-86. 
Nicotine sulphate, 40 per cent, 1-750; 
cresol soap, 1-300. 
Nicotine sulphate, 40 per cent, 1- 
1,000; cresol soap, 1-300. 
Nicotine sulphate, 40 per cent, 1- 
2,000; cresol soap, 1-300. 
Nicotine sulphate, 40 per cent, 1- 
3,000; cresol soap, 1-300. 
Lime-sulphur and nicotine sulphate, 
1-50. 
Lime-sulphur and 40 per cent nicotine 
sulphate, 1-50; flour paste, 4-100. 
Flour paste, 4-100 
Thorough, but 
beaded. 
....do 
....do 
....do 
....do 
....do 
....do 
Thorough, not 
beaded. 
do 
Thorough, but 
beaded. 
Thorough, not 
beaded. 
do 
SI. 66 
1.25 
.62 
.416 
1.08 
.85 
.64 
2.08 
1.67 
1.04 
.83 
. 09 
PURE WATER. 
Spraying with water is one of the most successful and most com- 
monly used methods of controlling the red spider in greenhouses. 
With a strong but fine stream of water the mites are washed from the 
foliage of infested plants and the infestation is reduced to a minimum. 
It was thought possible to wash the mites from the hop leaves by 
spraying water through a coarse nozzle at 200 pounds pressure with 
about as successful results. This experiment was accordingly carried 
out, and although some of the mites were washed off, many were left 
and were later seen to have been uninjured by the force of the spray. 
The hme-sulphur-and-flour paste and the flour paste, 8-100, are so 
cheap that even though between 50 and 70 per cent of the mites could 
be killed by pure water, one of the former materials, which destroys 
about 98 per cent, is preferred. 
VALUE OF A SECOND APPLICATION. 
After a few spraying experiments had been conducted it was seen 
that the sulphur, the lime-sulphur, and the lye-sulphur had no effect 
upon the mites except by actual contact ; therefore the idea of placing 
a material on the vines which would kill the larvae on emergence was 
abandoned. Although nearly 100 per cent of the mites living upon 
the leaves could be destroyed by the spray, the eggs were uninjured 
and the newly hatched larvae reiufested the leaves as badly as before. 
It was therefore decided to spray a second time after all the eggs had 
hatched and yet early enough to prevent any larvae from becoming 
mature. 
