32 
BULLETIN 1204, U. S. DEPAKTMENT OF AGRICULTURE. 
LEAD ARSENATE. 
A few tests were made with arsenate of lead. The material used 
had a volume of about 80 cubic inches to the pound, which was fairly 
close to thai of the standard calcium arsenate, but the physical char- 
acteristics of the particles were rather radically different. The lead 
arsenate proved to be only a fair dusting material. It was not as 
satisfactory as either the standard or the light calcium arsenates used, 
so far as could be judged from the dust cloud formed. Two cuts of 
cotton on Shirley were treated solely with lead arsenate for compari- 
son with calcium arsenate in leafworm control, and the mortality 
resulting was hardly as satisfactory as that from similar applications 
of calcium arsenate. This was probably to be expected, as lead 
arsenate is usually less toxic to the worm than calcium arsenate. 
PARTS GEEEN. 
Other tests were made with Paris green. This material differs 
greatly from either of the arsenates tested, being only 33 cubic inches 
to the pound and possessing almost no adhesion between particles. 
This material flowed so readily through openings that the valves 
which had been constructed for using calcium arsenate allowed the 
Paris green to leak through even when completely closed. This was 
corrected as well as possible by packing. It was found at the outset 
that even the slightest opening of the valve gave such a heavy deliv- 
ery of the Paris green that an excessive dosage resulted. In fact, in 
the f iist trips made the material poured out at a rapid rate and was 
whipped directly to the ground without spreading over any appre- 
ciable width. Paris green, if used unadulterated and at a heavy 
dpsage, is injurious to the cotton plants because of the free arsenic 
present, and the day following the flights which had been made with 
straight Paris green it was noted that wherever the plane had passed 
over the cotton there was a row of plants perhaps 10 feet wide 
directly under the plane which had been almost completely burned 
up by the poison. This row was very definitely marked and illus- 
trated the lack of spread of the material. 
Following this experience the Paris green was mixed in varying 
proportions with air-slaked lime, and the following were the charac- 
teristics of the mixtures tested : 
I'arls 
Paris 
green. 
Parts 
lime. 
Cubic 
inches 
per 
pound. 
l 
l 
l 
1 
3 
5 
54 
66 
These three materials were then tested from a plane and behaved 
considerably better than the straight Paris green, as far as delivery 
from the plane and spread in the air are concerned. Still they were 
not satisfactory. The lime flowed too fast through the valves and 
when blown into the air seemed to separate from the Paris green. 
A very peculiar condition resulted. The Paris green was blown 
down over a strip of plants more or less directly under the plane, 
