December, ’23 
CAMPBELL: NICOTINE DUST PROGRESS 
497 
Cost of Application 
Figuring in everything, it costs the grower who runs his own machine 
from X to y 7 ^- cents per gallon to apply the spray, while the com¬ 
mercial sprayer charges from 1 to IX cents per gallon, most of them 
charging the latter. 
Thus the cost of application on the average tree in Tulare county is 
4 to 7 cents where the grower owns his own rig, or 8 to 15 cents when 
hired done by a commercial sprayer. In Southern California the average 
cost runs from 6 to 10 cents for the grower, and from 12 to 19 cents for 
the sprayer. 
This was followed by a paper by Mr. R. E. Campbell. 
NOTES ON NICOTINE DUST PROGRESS 
By Roy E. Campbell, U. S. Bureau of Entomology 
Abstract 
This general historical account of the use of nicotine in dusts, is given with 
special reference to recent developments, the properties of carriers, the utilization 
of finely ground tobacco dust, the comparative merits of free nicotine and nicotine 
sulphate, the advisability of a certain amount of moisture, the mechanical devices 
for the application of dusts, data on self-mixing dusters and the possibilities of 
local mixing. An extended bibliography is given. 
When ground tobacco dust, because of variation and slow release of 
its nicotine content, failed to satisfactorily control the walnut aphis, 
Professor Ralph E. Smith began the use of a dust containing a definite 
amount of standardized nicotine sulphate solution added to a dry car¬ 
rier. Following that work, the use of nicotine dust was taken up by the 
Federal Bureau of Entomology, and soon afterward investigations were 
also started in California, New York, New Jersey, Virginia, Connecticut, 
Ohio, Missouri, Maryland, Wisconsin, and other States. It is doubtful 
if in recent years any insecticide has aroused so much interest on the 
part of the economic workers as nicotine dust. 
Kaolin was first used as a carrier because of its availability, ease of 
grinding, and inertness. It was found, however, because of its com¬ 
pound nature, to adsorb and “tie up” too much of the nicotine, and lime, 
being less subject to this objection, was substituted. Refuse sugar-beet 
lime and hydrated lime, together with finely-ground sulphur, also have 
been used most extensively. More recently the carbonates of lime and 
magnesia have proved to have certain advantages, particularly in 
giving off the nicotine very readily. A combination of these occurs 
naturally in dolomite, which is coming into favor as a carrier. 
It soon became evident, after conducting many experiments and ob- 
