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WISCONSIN STATE HORTICULTURAL SOCIETY
cessful and more expensive than spraying, and could not be
relied upon in the case of severe infestations.
REPORT ON THE EFFECTIVENESS OF DUSTING
By PROF. G. W. KEITr.
I have been requested to report to you on those discussions at
the recent scientific meetings in Chicago which related to the
effectiveness of dusting for the control of plant diseases. There
was less work reported on this phase of the subject than on
insect control by dusting, the chief paper being that of Dr. N. J.
Giddings, of. the West Virginia Agricultural Experiment Sta-
tion on "Orchard Dusting versus Spraying."
The recent revival of interest in dusting has led to compar-
ative spraying and dusting experiments at a number of state
experiment stations. An effort has been made to correlate this
work, and Doctor Giddings has acted as leader of the project. Ac-
cordingly, reports on the work in various states have been for-
warded to him and were treated in his paper.
The dusting work that Doctor Giddings reports related to the
apple, and was almost exclusively concerned with apple scab.
He stated that in West Virginia the results thus far obtained
have indicated that sulphur dust is not so effective as either lime-
sulphur or Bordeaux spray for the control of apple scab in those
orchards of that state where the disease is severe.
The evidence from Michigan and Virginia in 1920, he said,
was much more favorable to dust. In Virginia, however, seven
applications were made.
Pennsylvania reported good results from dust in two orchards
in 1920 and just a fair control in a third. In these cases five
applications were made.
In Connecticut in 1920 dust controlled scab well on Greening,
which was but slightly attacked, but showed almost no bene-
ficial effect on Fall Pippin, on which scab was more severe. Four
treatments were made in each case. It was also pointed out that
in Pennsylvania in 1919, when scab was severe, dust failed to
control the disease, whereas it gave more satisfactory results in
1920, when scab was less severe.
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