April, ’24] 
hartzell: dosage estimation 
279 
Mr. William Moore : Did I understand that you sprayed with nico¬ 
tine sulphate and casein? 
Mr. L. A. Stearns: No. 
Mr. H. A. Gossard: We have noted in Ohio at least 2 or 3 cases in 
which casein was used with the spray and more burning resulted than 
where it was omitted. 
Mr. Lawson Caesar : I have seen serious burning from using casein 
with lime sulfur and arsenate of lead. In some cases the burning was so 
severe at the end of the spraying season that I would not care to use 
casein again because of this injury. 
Vice-President S. B. Fracker: The next paper is by Mr. F. Z. 
Hartzell. 
THE ESTIMATION OF DOSAGE FOR VOLATILE DUSTS: AN 
ILLUSTRATION OF THE VALUE OF CORRELATION 
MATHEMATICS TO ENTOMOLOGY 
By F. Z. Hartzell, Vineyard Laboratory , Fredonia , N. Y. 
Abstract 
The term volatile dust is proposed for materials which kill insects by the evolution 
of toxic gases. It is suggested that dosage with such preparations be defined as the 
number of cubic feet of tree volume and tree space occupied by one pound of dust. 
Experiments with volatile dusts for the control of pearpsylla, in western New York, 
have indicated that, for this insect, on the basis of tree volume, one pound of dust 
should not occupy a space of more than 1500 cubic feet, and, on the basis of tree 
space, the maximum volume should be 1900 cubic feet. Correlation and partial 
correlation calculations were used to study the relation of efficiency to dosage, tem¬ 
perature, and percentage of open space. Dosage was found to exert the greatest in¬ 
fluence. The effect of temperature was not as marked as laboratory studies indi¬ 
cate and this was, doubtless, due to the increased convection currents and de¬ 
creased humidity that usually accompany rise in temperature under field conditions. 
The expression “contact dust’’ is ambiguous because it includes 
substances which kill, more or less, by direct contact and those that 
destroy insect life by evolving toxic gases. The term “volatile dust” 
is proposed for the latter class. 
The advent of volatile dusts has introduced problems that do not 
arise in the use of ordinary contact or arsenical dusts, chief of which is the 
envelopment of the plant with a dose of gas lethal to the pest. They 
are problems of open air fumigation. Successful fumigation depends 
upon the density of the gas and the time during which it is allowed to 
act, the former being based upon the amount of materials used per 
