146 
WISCONSIN HORTICULTURE 
June, 1918 
The Possibilities of Dusting 
Prescott J. Mitchell 
For some time past, those in- 
terested in the production of clean 
fruit have felt the need of some- 
thing to supplement the usual 
spray outfit in controlling fungous 
diseases, such as the apple scab, 
which come as epidemics, often at 
times when the spray rig cannot 
get onto the wet orchard, and 
which usually must be controlled 
within a very short time, or not at 
all. 
There have been occasional epi- 
demics of insect pests, also, which 
the slow, heavy spray rig could 
not check, and these have also giv- 
en the commercial fruit grower 
some concern. 
Now a machine which is ideally 
adapted to meet such sudden de- 
mands, and one which is best fitted 
to apply fungicides, and insecti- 
cides rapidly and thoroughly, is 
the duster. 
No doubt most of you have read 
of the duster in the farm papers, 
but in case you have not I will say 
that a duster is a very simply-con- 
structed machine, with a rotary 
fan, driven at high speed by a gas- 
oline engine, producing a strong 
current of air which passes through 
a six inch galvanized-iron tube, 
or in the later models, through 
a huge rubber hose a good deal 
like the familiar air-brake hose, 
and the finely ground material is 
carried by the gust of air onto the 
foliage in a dense cloud, which 
settles down over the trees, the fine 
particles settling in between the 
small hairs on fruit and foliage 
and adhereing. 
The duster applies the materials 
in the form of a finely ground dry 
dust, and, operating without the 
tank of water which the spray rig 
must have, is about a ton lighter 
and hence can go on the land re- 
gardless of moisture conditions. 
Moreover, the dust adheres about as 
well when applied to damp foliage 
as when the trees are perfectly dry, 
so that a duster can operate im- 
mediately after a rain or in foggy 
weather when a spray-rig would be 
forced to wait for the trees to dry. 
The time consumed in filling 
and refilling spray tanks is costly, 
and many a fruit crop has been ru- 
ined because the source of water 
was so far from the orchard that 
the spraying could not be done 
within the time allowed by weather 
conditions. 
Another factor in the time re- 
quired is the rate of application. 
We all know that it is necessary 
to stop at each tree in order to 
get a thorough application in 
spraying; but unless the trees are 
unusualy large, say over thirty 
feet high, the duster may be driv- 
en along at a slow walk, and yet a 
thorough application will be made. 
This is because the dust is so fine- 
ly distributed, for a veritable fog 
envelopes each tree, and the parti- 
cles sift down gradually until the 
entire tree is covered. 
Considering these three factors 
then, the weight of the outfit, the 
time required to replenish it, and 
the rate of application, it is not 
hard to believe the statements of 
those who have actually done the 
woi'k when they say that the dust- 
er is at least eight or ten times as 
fast in operation. There is another 
factor worthy of some considera- 
tion, — the mechanical troubles. 
The duster which I used the 
past season is the same model as 
that used by the Cornell Experi- 
ment Station, and to my personal 
knowledge there has been almost 
no mechanical trouble with any of 
these machines. The duster which 
1 used covered over three-hundred 
acres in two weeks the past season, 
and was driven from one farm to 
another over rough roads, cover- 
ing, probably, about sixty miles 
over roads that would have left a 
spray rig pretty badly shaken up. 
Freedom from nozzles, hose, and 
suction pumps which alternately 
leak and clog with dirt — that’s 
what a duster means ! 
The materials used in dusting 
have undergone some radical 
changes in the course of the ex- 
periments, and are now ground as 
finely as possible. The sulphur is 
ground to pass a 200 mesh sieve, 
and the poisons are also somewhat 
finer than those used in spraying. 
The past season’s work showed that 
the tobacco dust used was not suf- 
ficiently fine, and better control of 
sucking insects is hoped for with 
the material now being prepared. 
Besides the better distribution 
obtained with the finer material, 
less actual sulphur is needed, and 
the cost of materials is thus some- 
what reduced. 
Due, probably, to the breaking 
up chemically of the compound 
serious burning is often experi- 
enced in the use of lime sulphur 
after the leaves have come out ; this 
burning is unknown with the dust, 
and for this reason applications 
may be made at a later period with 
the dust than would be possible 
with the spray. 
The Cornell University Experi- 
ment Station has carried on field 
work in dusting since 1911, and the 
results obtained in these experi- 
ments prove conclusively that dust- 
ing will control chewing insects ; 
that it is probable that tobacco dust 
will control sucking insects, as soon 
as a way can be found to prepare it 
more finely ground ; and that even 
San Jose may be controlled in time 
when the difficulties of preparing 
soluble sodium sulphur dust can be 
