326 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
Tests were made with the material dusted or sown broadcast in 
wheat, scattered along narrow strips, as a line on the surface of the 
ground, in furrows of different types and covered with dry dust. The 
powder, granules and flakes were all used. 
Broadcasting in Wheat 
vSome of our first work dealt with the use of the material sown broad¬ 
cast in the wheat. Varying doses of the granules and powder up to 
60 pounds to the acre were used. Repeated tests with this later dosage 
of granules, even with a five to ten mile breeze gave an almost complete 
kill not only of the chinch bugs but also ground beetles, Colorado potato 
beetles, grasshoppers, wasps, bees, lady beetles, plant lice and other 
insects which became enveloped with the gas. The heavier doses also 
caused some leaf burning. The use of the material for broadcasting 
in wheat fields was abandoned as impractical, the acreage, dosage and 
difficulty of application prohibited its use. 
Calcium Cyanide as a Barrier 
From the beginning the use of the material as a barrier seemed the 
most logical. In the preliminary tests it was used in a narrow strip 
two or three feet wide, in a narrow line on the surface of the ground and 
in a ditch. Dosages were used varying from one half pound to four 
pounds to each 60 feet. The heavier dosages maintained a killing- 
barrier much longer than the lighter ones. It was soon found that for a 
line bander the coarser flakes gave off gas more slowly and therefore 
lasted longer than either the granules or the powder. Later barrier 
work, therefore, dealt mostly with the flakes and our final conclusions, 
on dosage refer to flakes rather than granules or the powder. 
Narrow Strip Barrier with Trap Crop 
The use of the material in a narrow strip was not given a thoro test 
due to the fact that trap crops had not been planted for the purpose. 
Several opportunities for testing the material in strips of sorghum were 
offered and gave satisfactory results with as small an amount as 30 
pounds to the acre. After making a few tests with varying dosages it 
was abandoned for the line barrier. However, with trap crops of cane 
or sudan grass planted about a month before harvest, we believe from 
our observations that it will prove practical. 
Line Barriers 
Our line barriers were made first, on the surface of the ground, 
second in trenches of varying depths and forms and third, tho only in a 
few tests, covered slightly with dry dust. It is [desirable to keep a 
