124 REPORT OF THE COMMISSIONER OF AGRICULTURE. 
quantity of earth was thrown upon the lower part of it, to prevent the escape of the 
gas or smoke. The tent was then filled with the smoke or gas experimented with. 
Among the first to make experiments of this kind were Messrs. J. W. Wolfskill 
and Alexander Craw, of Los Angeles; Mr. John Wheeler, of San Francisco; Hon. J. 
DeBarth Shorb, Col. J. R. Dobbins, and Mr. B. M. Lelong, of San Gabriel. The 
substance most commonly experimented with was the liquid bisulphide of carbon 
(CS), but this did not prove entirely satisfactory, owing to the time required for it 
to evaporate and become diffused in the tent, 
Probably no person has spent more time and money in trying to discover some 
effectual method for destroying the scale-insects with gas than has Mr. J. W. Wolf- 
skill, of Los Angeles. Jn a paper read ata meeting of fruit-growers, held in this city 
on the 7th of October, 1887, Ma. Alexander Craw gave an account of the experi- 
ments made by Mr. Wolfskill and himself, from which we extract the following: 
‘* Previous to the year 1884 we had only the Black Scale (Lecaniwm olece), to con- 
tend with in the Wolfskill orange groves. and these scales were easily kept in check 
by an application of whale-oii soap in the form of a spray; one application every two 
years was sufficient. In the fall of the year 1884 we found a few trees on the south 
side of the large grove infested with the Cottony Cushion-scale (Icerya purchasi); 
they became infested from an adjoining grove. We prepared for war, and soon had 
our spraying apparatus at work upon them. As we were.in for extermination, we 
made a very strong solution of the whale-cil soap—so strong it almost defoliated the 
trees—and upon examination it looked as if we had gotten rid of the Icerya. A short 
time afterward, however, we found that the trees were again infested, and we 
sprayed again, using as much as 50 gallons of the solution to each tree; but even 
with all this care, some of the Icerya escaped and scon covered the trees again, 
spreading in a northeasterly direction through the grove. We then cut the trees 
back, letting the branches drop upon a large canvas and afterward burning them; 
we washed the stubs and trunks of the trees with the whale-oil soap solution, but 
even this severe treatment was not efiective, so we concluded that spraying would 
not check this prolific creeping curse. 
“Knowing the fatal effects of a high temperature upon the young of the Black 
Scale, Mr. Wolfskill suggested experimenting with heat; accordingly he had a tent 
constructed, and also a sheet-iron stove that would send the heat into the tent. We 
put the tent over an orange tree, and raised the temperature to 128° Fahrenheit for 
over an hour; this killed the Black Scales, but the Icerya seemed to enjoy the heat. 
The tree was injured,so we gave up ary heat. We next tried steam from a small 
steam-boiler; this cooked the top of the tree, but upon the lower half the Icerya 
were as lively as ever. Our next experiment was with tobacco smoke; this test 
lasted six hours, but had no effect wpon the tree or scales. Sulphur fumes were also 
tried; this bleached the foliage, but did not harm the Icerya; a heavier charge killed 
both the tree and the scales. Among other experiments made under the tent were: 
Concussion from gunpowder; muriatic acid gas; carbonic acid gas; liquid chloro- 
form, and also the gaseous chloroform manufactured under the tent frem chloride 
of lime and methyl! alcohol; arsenic, and other fumes and gases. We had very én- 
couraging results from the liquid bisulphide of carbon; when confined for ten, twenty, 
or thirty minutes, or even for one hour, no satisfactory results were obtained, but 
when it was confined three hours it killed all of the scales, which soon assumed a pale 
buff color. The gas, being a very powerful solvent, also acted upon the eggs, and 
they were destroyed, while the trees were not injured; in fact, a few weeks after- 
ward they started into a vigorous growth. Our efforts were then directed towards 
evaporating the bisulphide quickly; heat, steam-baths, agitation, circulating the air 
in the tent, exposing the bisulphide in shallow pans, and saturating sponges with it 
were tried, but without hurrying matters much, 
“Prof. D. W. Coquillett was so well impressed with our method of treating 
trees that he decided to investigate the subject; accordingly, in the month of Sep- 
tember, 1886, he began experimenting in the Wolfskill orange grove, and soon dis- 
covered that hydrocyanic acid gas would kill the scales and their eggs, but it also 
injured the foliage of the tree. We then united our efforts to remedy this evil, but 
it was something that required very close observation. We found that by with- 
holding the water and allowing the sulphuric acid to come in contact with the dry 
cyanide of potassium in a fine stream we could treat trees without injuring even a 
blossom, while the gas proved fatal to the Black Scale (Lecaniwin ole), Red Scale 
(Aspidiotus aurantit), and the San José Scale (Aspidiotus perniciosus) confined in it 
ten minutes, but the Cottony Cushion-scale Ucerya purchasi) and eggs required a 
confinement of nearly thirty minutes. 
‘We then perfected an apparatus for putting the tent on tall trees quickly. This 
occupied a great deal of time, but we finally succeeded so well that we could change 
the tent from one tree to the other in less than two minutes. Mr. A. B, Chapman 
