76 
PAPERS ON/ INSECTS AFFECTING VEGETABLES. 
EXPERIMENTS WITH INSECTICIDES. 
During the spring of 1912 the following experiments were conducted 
at Rocky Ford, Colo. 
On April 8 several infested horse-radish plants were sprayed with 
the following mixture: 
Paris green pounds. . 2 
Whale-oil soap do 8 
Water gallons. . 100 
These plants were kept under close observation for several days, 
but no dead larvae were found. 
On April 29 several infested horse-radish plants were sprayed with 
the following mixture: 
Arsenate of lead pounds. . 10 
Whale-oil soap do 10 
Water gallons . . 100 
This experiment was likewise a failure and no larvae were killed. 
In these experiments the poisons were carefully and thoroughly 
applied. The surface and underside of the leaves, and in fact all 
portions of the plants above ground, were coated. This treatment, 
however, failed to kill the ^rvse. This was due to the habit the 
larvae have of resting and feeding under compact webs, where they 
are completely protected from stomach poisons. 
RECOMMENDATIONS FOR CONTROL. 
The experiments indicate that this insect can not be controlled 
with arsenicals. If artificial control measures should become neces- 
sary, much could doubtless be accomplished by burning the dead 
horse-radish leaves and petioles during the winter. After the dead 
leaves are removed the surface of the soil about the roots of the plants 
should be thoroughly stirred with a rake. This cultivation would 
crush or bury the hibernating larvae which were resting in cracks in 
the soil. 
CONCLUSION. 
The investigation of this insect indicates that infestation is limited 
to a few horse-radish plants in one garden at Rocky Ford, Colo. In 
this garden the larvae have evidently been prevented from causing 
much damage by a hymenopterous parasite, and at present no arti- 
ficial control measures are necessary. 
ADDITIONAL COPIES of this publication 
-£*- may be procured from the Superintend- 
ent of Documents, Government Printing 
Office, Washington, D. C, at 5 cents per copy 
