500 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
especially undesirable in dust made with free nicotine, as the moisture 
has a tendency to absorb the nicotine. An excess of moisture may be 
partially overcome, in some cases, by the use of a drier, such as quick¬ 
lime or plaster of Paris, but here complications may arise because of 
the action of these driers on the nicotine. The use of a solution con¬ 
taining a higher concentration of nicotine would, of course, remove 
both of the above objections in making high-strength dusts, but it in 
turn is objectionable because of the higher cost of the nicotine. 
When the practice of applying nicotine dust as an insecticide was 
first begun, the only machines available were those which had been 
developed for dusting with arsenate of lead and sulphur. These 
machines were utilized for nicotine dusting, and were gradually im¬ 
proved to give a better feed of dust and a larger volume of air, since 
usually it was desirable to apply a greater amount of nicotine dust than 
of materials previously used, and in most cases to run the dust through 
the fan itself, thus breaking up any lumps which might have remained 
in the mixture. In addition, booms were perfected to apply the dust 
to rows or field crops as the machine was driven over them. 
In order to hold the dust as long as possible around low-growing 
plants and at the same time to overcome the effects of wind blowing 
away the dust or fumes, several devices were made. One was a box¬ 
like enclosure, entirely surrounding the machine, into which the dust 
was discharged through individual pipes leading to the rows. Another 
device consisted in merely attaching a piece of canvas, a little wider 
than the strip of rows to be covered, to the back of the duster, and allow 
the canvas to trail behind. The canvas not only holds down the dust 
about the plants, but in dragging it over them, it knocks off many 
insects such as aphids. The increased activity of the aphids, in crawling 
about on the ground or the plants, renders them more susceptible to 
the action of nicotine. Some have used trailers 15 to 20 feet long, but 
the writer has obtained best results on peas infested by the pea aphis 
with one 40 feet long. The only limit to the length of the canvas 
trailer is the ease of handling it in turning at the ends of the rows. 
The canvas must not be long enough or heavy enough to injure the 
plants. It has been found advisable also to hang a weighted piece of 
canvas just ahead of the nozzles. This reaches below the tops of the 
plants and prevents the dust from escaping in front. 
Other devices have been used, such as U-shaped inverted troughs, 
4 feet long, attached to the rear of the dusting machine. A trough 
covers each row to be treated, and the dust is discharged into it. As 
