Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1918-07-09

gists.-(Advt)
ing to the necessity for poisoning con-
siderable areas in this case and to the
inability to leave Imprisoned plants as
checks. is was, of course, impossible to
determine the exact benefit derived from
the treatment. Rough comparisons,
however, based on yields of surrounding
cuts, made it obvious that considerable
gain had been secured and that poisoning
had been a very profitable operation.
Poisonings and Time of Application
In the early experiments the tri-
plumbic form of lead arsenate was used
but was not sufficiently effective, and
the di-hydrogen form of lead arsenate
proved to be a better poison for the
work. Later additional tests demon
strated that a high grade of calcium
arsenate was still more effective and
has the great advantage of being
cheaper than lead arsenate. A number
of tests were made with various mix
lures and dilutions of arsenicals This
work, however is still IN the expert
mental stage and, according to Mr..
Coad it is difficult to prophesy just
what the results will be. 1t is obvious,
however, according to the scientists,
that either a ,di-hydrogen lead arsenate
powder containing not less than 80
per cent of arsenic pentoxid or cal
cium arsenate containing at least AZ per-
cent of arsenic pentoXid will produce an
effective control if handled properly. 1t
also is expected that it will be possible
to dilute these considerably with some
cheap carrier such as lime, though this
has not been definitely determined. The
experiments have shown that a very
fine powder is taken up more readily by
the dew and held in suspension for the
weevils than coarsely powdered chemi-
calls This physical condition is espec-
tally important since the poison is APP
piled in the form of a dust spray.
The time of applying the poison, of
course, varies under different condi-
tions. 1t has proved most effective
when applied just as the cotton OBJ
viously slackens in blooming, but fur
Their work along this line is still to be
done. 1t seems probable that the eff
fective interval between applications is
about one week. 1t is well known that
much more effective poisoning with
dry dust can be done while the dew is
on the plant, as the poison not only
clings to the plant better, but has much
less tendency to drift from the cotton
The most effective time for application
therefore, usually is between 4 p. m. and
8 a. IN. Several machines are on the
market for dust spraying. In the early
with which it was possible to cover
experiments a hand dust gun was used
to acres a day. In order to cover
larger areas, however, special power
machine was developed which will cover
nearly 200 acres per day. The depart
ment now expects to develop an inter-
mediate type which can be sold cheaply
and which will cover 20 to 80 acres per
day.
The amount of poison required for ap-
plication so far has depended more upon
the requirements of the machinery used
than on the amount necessary for thor
oughly busting the cotton. In general
about pounds per acre have been APP
piled, but this is excessive, and with
further improvement in the machinery
and the use of the poison with mix
lures such as lime, smaller amounts
will be effective. In most Of the eX-
periments from 3 to applications were
made, but the effectiveness of these
was considerably reduced by the fact
that they were on such small plats In
the large-scale experiment the effect
of a single application was as great
as was secured from about three APP
plications on a smaller plat. This more
efficient work on the large field was
due, of course, to the fact that there
was practically no migration of weevils
from adjoining areas.
The cost of treatment averaged about
81 per acre for each application. This,
however, may be reduced considerably
when large areas are sprayed and when
improved machinery requiring less poi
son is employed. The cost may be
still further reduced when it is possi-
BILE to mix the poison with other pow
ders. such as lime, which will act as
carriers. Further, it will rarely be nee
essary to poison an entire plantation to
control the weevils, since on emerging
in the spring they always concentrate
near the area in which they passed the
winter. The weevils remain rather close
ly at these points until they have null
tiplied sufficiently to threaten a short
age in the local food supply. For this
reason great part of the cotton is not
seriously infested with weevils until
some time after midseason and then
not often until well along in August.
The control measures adopted must
depend upon conditions in each plan
tation, but by concentrating on the
more heavily infested cuts just before
the wevils become sufficiently abundant
to migrate to the remainder of the cot
ton it will be possible not only directly
to benefit the cotton treated. but to
protect the remainder of the plantation
by preventing the wevl migration. In
this way the cost of the treatment for
a comparatively few acres will be borne
by the benefit derived by the entire
plantation.