4 Farmers’ Bulletin 1282. 
mixed with a dust carrier. This carrier must be fine, light, cheap, 
inert as far as action on foliage is concerned, and of ‘a material 
with which the nicotine will mix freely but not become permanently 
absorbed. 
Kaolin, the first material extensively used, was the best carrier in 
so far as the first four points are concerned, but was found to absorb 
and tie up some of the nicotine, making it unavailable for action on 
the insects. Two forms of lime are now used, namely, refuse lime 
from sugar-beet mills and pure hydrated lime. Finely ground sul- 
phur is also used to a considerable extent for amounts up to about 
70 per cent of the carrier. 
In making the dust, regardless of what carrier is used, a certain 
amount of lime is added. A chemical reaction takes place, in which 
the nicotine is set free from the sulphate. The active ingredient in 
the finished product is therefore nicotine, which is more active than 
nicotine sulphate. Because of this reaction, and also because of the 
fact that the killing 1s done by the nicotine, the dust should be called 
nicotine dust rather than nicotine sulphate dust. 
The use of powdered sulphur in the carrier along with the hme 
makes a more effective dust than when hydrated or sugar-beet lime 
alone is used, because the sulphur releases the nicotine more readily 
than does the lime, and therefore the nicotine-sulphur dust is more 
active than the nicotine-lime dust. By using from 10 to 40 per 
cent of sulphur in the carrier, the amount of the nicotine-sulphate 
solution added can be reduced at least 1 or 2 per cent, and the same 
results obtained as with the higher strengths in lime alone. Sulphur, 
on the other hand, is more difficult to pulverize than lime and is 
heavier. It is also unsuitable for use on melons and other cucurbits, 
which may be severely injured by it. 
To insure killing all the insects, each particle of the dust should 
be impregnated with nicotine. This necessitates thorough mixing 
with the best machinery obtainable. As machinery is expensive, the 
dust is made almost entirely by commercial manufacturers, and sold 
ready to use. It would be entirely feasible, however, for large-scale 
growers and growers’ associations, etc., to install the proper ma- 
chinery and manufacture their own dust, at considerably less cost 
than the present retail price. 
HOW TO PREPARE THE DUST.! 
This dust can be made of the following combinations of materials, 
which act as carriers, to which the desired amount of nicotine sul- 
phate is added: Kaolin and lime; sugar-beet lime and hydrated 
lime; hydrated lime; lime and finely ground sulphur. Various pro- 
1 Adapted from Department Circular 224, U. S. Dept. Agr., ‘‘ Nicotine Dust for Control 
of the Striped Cucumber Beetle,” by W. H. White. 
