38 
than oil is found in a product obtained from the leaves of the common 
prickly pear cactus (Opuntia engelmanni), which grows in abundance 
in the Southwest. The liquor is obtained by soaking chopped-up 
leaves in water for twenty-four hours. It is given body and color by 
the addition of glue and yellow ocher or venetian red, and is applied 
to both sides of the canvas and rubbed well into the fiber of the cloth 
with a brush. 
Some practical experience is necessary to fumigate successfully, 
and it will therefore rarely be wise for anyone to undertake it on a 
large scale without having made preliminary experiments. 
BISULPHID OF CARBON VAPOR. 
In line with the use of hydrocyanic-acid gas is the employment of 
the vapor of bisulphid of carbon to destroy insects on low-growing 
plants, such as the aphides on melon and squash vines. The treat- 
ment, as successfully practiced by Professors Garman and Smith, 
consists in covering the young vines with small tight boxes 12 to 18 
inches in diameter, of either wood or paper, and introducing under 
each box a saucer containing one or two teaspoonfuls (1 or 2 drams) 
of the very volatile liquid bisulphid of carbon. The vines of older 
plants may be wrapped about the hill and gathered in under larger 
boxes or tubs, and a greater, but proportional, amount of the liquid 
used. The covering should be left over the plants from three-quarters 
of an hour to an hour, and with 50 to 100 boxes a field may be treated 
with comparative rapidity. 
Bisulphid of carbon has proved also to be the most effective means 
of disinfecting grape cuttings suspected of being infested with 
phylloxera.* The cuttings are inclosed in a tight barrel or fumi- 
gating box, and the bisulphid of carbon, poured out in a shallow dish, 
is put on top of the cuttings. An ordinary saucerful of the chemical 
is enough for a box 3 feet cube. The treatment lasts from forty-five 
to ninety minutes. This is a pretty strong fumigation, but the dor- 
mant condition of the cuttings makes this possible. 
REMEDIES FOR SUBTERRANEAN INSECTS. 
Almost entire dependence is placed on the caustic washes, or those 
that act externally, for insects living beneath the soil on the roots of 
plants, including both sucking and biting insects, prominent among 
which are the white grubs, maggots in roots of cabbage, radishes, 
onions, ete., cutworms, wireworms, apple and peach root-aphides, the 
grape phylloxera, and many others. 
The insecticide must be one that will go into solution and be carried 
down by water. Of this sort are the kerosene emulsions and resin 
“Bul. 192, Cal. Agr. Exp. Sta., 1907. 
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