Nicotine Dust for Truck-Crop Insects. 9 
STRENGTH OF NICOTINE TO USE. 
Some of the smaller, frailer aphids, such as the walnut aphids, 
are easily controlled with a dust containing only 2 per cent by 
weight of nicotine sulphate solution, but the ordinary insect against 
which it is used requires at least 4 per cent. This amount, when 
carefully applied, will control most aphids and thrips. For ordi- 
nary commercial purposes a 5 per cent strength is most commonly 
used, and is to be recommended. For certain insects which are more 
resistant to the action of insecticides, from 6 to 8 per cent is re- 
quired, and in some cases a 10 per cent strength is used. If the 
application is carefully and thoroughly made, the lesser strengths 
will do satisfactory work in most cases. 
All formulas in this bulletin refer to the percentage by weight 
of the ordinary commercial solution of nicotine sulphate, which con- 
tains 40 per cent nicotine. As the nicotine only is the active ingre- 
dient, and is the material referred to by some writers, the difference 
in the two is as follows: 
Percentage of the commercial 
solution of nicotine sulphate Per cent of pure 
containing 40 per cent nico- nicotine in the 
tine added to the dust. dust. 
ON op ee ed ee ee ee ee 0.8 
abe hay y WM = he Le en 2 eo Le Se ee ee eee ee 1.6 
Fue Ses ie a es ee eae 2.0 
Dee ek ee ee 2: 
Seep em Coed eaiees ee an Ss St ener am Le Meas Se hee ee 
IU(G Mees ees 2 er eS Se ee ere 4.0 
This is the theoretical amount of nicotine contained in the dust. 
As a matter of fact, some of the nicotine volatilizes during the mix- 
ing, and is lost. Although the manufacturer may put in the full 
amount of the nicotine-sulphate solution shown in the left-hand col- 
umn, his guarantee of the amount of pure nicotine in the finished 
product will be somewhat less than the corresponding amount given 
in the right-hand column. 
As nicotine is the killing agent, the buyer should ascertain which 
of the foregoing methods is used in labeling the dust, and he will 
avoid the mistake of buying a dust containing 4 per cent of the nico- 
tine sulphate solution, thinking it contains 4 per cent pure nicotine. 
LOSS OF STRENGTH. 
Since the nicotine in this dust is very volatile some of the killing 
power is likely to be lost if the dust is held for any length of time in 
open containers. When first used the dust was put up in burlap 
sacks with paper liners, and, as it was used within a short time, there 
was little or no loss of strength. It is the present practice to put up 
practically all the dust in air-tight containers, such as sheet-iron 
drums, but even in these it is not advisable to hold the dust longer 
111633 °—22 2 
