THE USE OF GASES AGAINST SCALE-INSECTS. 
[Reprinted from Bulletin No. 71, Agricultural Experiment Statiou, University of 
California.] 
Some time ago the Agricultural Department was requested by Messrs. 
A. B. and A. S. Chapman, Mr. L. H. Titus, and Mr. J. C. Newton, prom- 
inent orange-growers of Los Angeles County, to conduct experiments 
with the view of determining the efficacy of certain gases as insecticides, 
with special reference to the White Scale, Icerya purcliasi. The follow- 
ing is a summary of results, of which a full report will be published 
hereafter : 
The use of gases for this purpose has been long contemplated, and 
various appliances have been suggested for the ready application of any 
efficacious gas. The ease with which gas penetrates to all parts of the 
tree naturally suggests its use as preferable to washes, which at best 
leave many parts of the foliage and infested branches untouched, even 
when sprayed with the greatest care. In order that the gas may be an 
efficient insecticide it must be so poisonous that even when applied iif 
small quantities it produces fatal results ; for in the application the 
air confined in the tent covering the tree dilutes the gas to a great ex- 
tent. Again, the gas must be capable of being generated quickly in 
sufficient volume. The record below shows that only one of the gases 
employed fulfilled these conditions to a satisfactory extent. Prelimi- 
nary experiments with some others having shown their unfitness for the 
purpose, either on account of expense or because of injury to the foli- 
age, or imperfect action on the insects, their study was not pursued 
further. 
APPLIANCES FOR APPLICATION. 
The tent for covering the tree is made of heavy bed-ticking, thor- 
oughly oiled with linseed oil. This cloth serves the purpose best, as it 
is very closely woven, is pliable and easily folded. 
The support of the tent, devised by Mr. Titus, is a very ingeniously 
contrived scaffolding mounted on wheels, which serve to move it from 
one tree to another. Its dimensions are 26 feet high, with a base 20 by 20 
feet. Its upper part is 20 by 12, and carries upon the top a roller made 
of galvanized iron (6 inches in diameter and 12 feet long), upon which 
38 
