18 
The old statement that less time is required for small trees or plants 
than for larger ones is found to be an error, and, in fact, it is reason- 
able that an insect is no more easily killed on a small plant than on a 
large one. The limit in application of gas is to apply it at a strength 
and for a length of time, forty to forty-five minutes, as great as the tree 
can stand, and, in fact, the tender terminals of the tree should be 
slightly sealded, which is proof that the gas is of proper strength. 
Treatment of this character is necessary to destroy the more resistant 
scales. For very compact trees with dense foliage from one-fourth to 
one-third more gas should be generated, and this is true also of the 
moister coast regions, or within 10 miles of the coast in the West 
and for winter work on dormant plants in the East. In the case of 
young trees and nursery stock in foliage there is mu_ less danger of 
scalding if the gas be generated slowly, either by employing a greater 
amount of water or using the cyanide in large lumps. 
Trees are fumigated for the black scale in southern California in 
October, or preferably in November, the young black scales in this part 
of the State having usually all emerged by October 1. After the black 
scale has abandoned the leaves and gone back to the twigs and fixed 
itself firmly, the gas is not so effective against it. The red and other 
scales may be treated with gas at any time, but preferably at the sea- 
son already alluded to. The applications are made at night, because 
the action of sunlight powe._ “‘~ increases the scalding effect of the 
gas on the leaves. In California most of the work is done by contract, 
or under the direct supervision of the county horticultural commis- 
sioners, in some cases the tents and material being furnished at a mere 
nominal charge, together with one experienced man to superintend the 
work, while a crew of four men operate the tents, the wages of the 
director and men being paid by the owner of the trees. 
The tents now employed are of two kinds, the “‘ sheet” tent of octag- 
onal shape for large trees, and the ‘“‘ring” tent for trees under 12 feet 
in height. The ring tents, or, as they are also called, the bell tents, 
are bell-shaped and have a hoop of half-inch gas pipe fastened within 
a foot or so of the opening. Two men can easily throw one of these 
tents over a small tree. An equipment of 36 or 40 ring tents can be 
handled by four men. They are rapidly thrown over the trees by the 
crew, and the director follows closely and introduces the chemicals. 
By the time the last tent has been adjusted the first one can be removed 
and taken across to the adjoining row. An experienced crew, with one 
director, can treat 350 to 400 five-year-old trees, averaging in height 10 
feet, in a single night of eleven or twelve hours. The cost under such 
conditions averages about 8 cents a tree. 
With large trees the large sheet tents are drawn over them by means 
of uprights and pulley blocks. Two of these sheets are necessary for 
very large trees, the first being drawn halfway over and the second 
drawn up and made to overlap the first. In the case of trees from 24 
