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Conditions favorable to treatment. — The treatment should 
never be applied for some time after plowing or cultivating, 
as a firm, compact, moist surface is much more favorable to 
the retention of the vapor. For the same reason about fifteen 
days should be allowed after treatment before cultivation is 
resumed. If the soil is either very -wet or very dry, treatment 
should be withheld. To be in the most favorable condition for 
treatment, the soil should be quite moist and moderately 
permeabte, with a firm, even surface, well compacted by rain 
and having a depth of at least 8 inches. 
Extent of diffusion. — The extent of diffusion of the vapor 
determines the distance apart at which the injections must 
be made in order to reach all parts of the soil evenly and 
effectively. This varies considerably with the amount of the 
dose, the temperature and humidity of the soil, and other con- 
ditions. It has been found more satisfactory to employ smaller 
and more frequent doses rather than a few large ones. A dose 
of 5 or G grams (1-5 to 1-4 ounce) is believed to be thoroughly 
effective through a radius from 12 to 20 inches, though it may 
permeate much farther than that. The general rule is to make 
3 injections per square meter (1 1-5 square yards, nearly) in 
light soils and 4 injections in heavy soils. The arrangement 
of the holes must necessarily vary more or less, according to 
the system of planting. They should be at regular intervals, 
however, so as to cover the ground evenly, and never nearer 
than 1 foot to the base of the vine. It must be remembered 
that to be effective all the ground must be treated, and not 
merely those places where the presence of the enemy is proven 
by its injuries. 
Repeated treatment. — On account of the liability of injuring 
the vines it has been found best to make the treatment in two 
small applications, separated hy an interval of from six to 
ten days. This decreases the density of the vapor, but con- 
tinues its action for a much longer time. It removes the 
danger of injuring the vines, and gives even better results 
upon the insects than would be obtained by one large dose. 
The total amount of carbon bisulphid to be used should be 
divided into as many equal parts as there are injections to be 
made. The holes for the second treatment should, be inter- 
mediate between those for the first. 
Depth of the holes. — The depth of the holes depends some- 
what upon the depth and permeability of the soil, the average 
depth being about 1 foot. A depth of 16 inches is desirable 
upon deep or very permeable soil. 
Season of application. — Treatment may be applied at any 
season of the year; but, as It is followed by a slight check In 
growth, it should not be applied either at the flowering or 
fruiting season, as the check would injure the crop most at 
those seasons. The injury to the vines results from the killing 
of the tender, fibrous, feeding roots. It would therefore be 
better to apply the treatment before these roots have started 
much — that is, early In spring — or after they have become 
hardened — that Js, after fruitage in the fall. The condition of 
the soil usually favors the spring treatment, and the condition 
of the Insect is said to make It more susceptible at that time. 
Spring, therefore, appears to he the most favorable season. 
