April, ’24] 
DAVIS: SPRAYS FOR SAN JOSE SCALE 
285 
The results presented in this paper are based upon experiments for the 
control of pear psylla in commercial orchards in western New York 
and the particular dosages apply strictly to 2 per cent lime-nicotine 
dust for the control of the same insect in this region. How general 
they will hold for psylla in other regions or for other pests can be de¬ 
termined only by experiments. However, the methods of determining- 
dosage are believed to be of general application for volatile dusts on 
different trees and for various insects. 
Vice-President S. B. Fracker: The next paper is by J. J. Davis. 
COMPARATIVE TESTS WITH DORMANT SPRAYS FOR SAN 
JOSE SCALE CONTROL 
By J. J. Davis, Purdue University , Lafayette, Indiana 
Abstract 
A record of outstanding results obtained for three years (1921-1923) with lime- 
sulphur and oils as dormant sprays for the control of the San Jose scale, Aspidiotus 
perniciosus Comst., Lime-sulphur did not give a sufficient kill to check the scale, 
which corroborated the results obtained by commercial orchardists in southern 
Indiana. Lime-sulphur is still an effective scale control in most sections of northern 
Indiana. Dry lime-uslphur was about as effective as the liquid concentrated pro¬ 
vided it was used at one and one-half to two times the strength recommended by 
the manufacturers. Under conditions existing the past few years in most of southern 
Indiana, the oil sprays are the only ones which have given satisfactory control. 
These include the miscible oils, “petroleum soaps,” and oil emulsions. The summer 
use of oil emulsion cannot be recommended to take the place of a dormant spray al¬ 
though under certain conditions a summer application materially assists in checking 
scale. 1 
The seeming increasing importance of the San Jose scale, Aspidiotus 
perniciosus Comst., and its possible seriousness a few years hence was 
recognized in making our first survey of the important orchard pests 
of Indiana in the winter of 1920-21. These conditions prompted, us 
to begin a series of experiments in the spring of 1921 on the comparative 
value of the sulphur and oil sprays. The lubricating oil emulsion was 
included in the tests during the summer of 1922, following the ap¬ 
parently phenomenal results secured by Ackerman in Arkansas in the 
spring of that year. 
Tn a badly infested orchard at Washington, Indiana, sprayed in August 1923 with 
a two per cent oil emulsion, the scale was sufficiently checked to avoid much of the 
fruit spotting which would otherwise have resulted. A count in this orchard made 
February 1924 revealed 91 per cent dead scale. In part of this orchard an additional 
dormant application of a two per cent emulsion was made in December, 1923 and 
here 100 per cent of the scale were dead so far as our extensive counts revealed. 
