40 BULLETIN 1357, U. S. DEPARTMENT OF AGRICULTURE 
i 
mind the following materials were tested during the season of 1920 9 
by E. L. Chambers: : | 
(1) Carbon disulphide: 5 to 25 cubic centimeters injected between bushes | 
approximately 14 inches apart. 
(2) Carbon disulphide in solution: One-fourth to one-half ounce dissolved | 
in 4 gallons of water applied to 24 square feet. f 
(3) Sodium cyanide in solution: One-eighth to one-half ounce per gallon of | 
water applied to 6 square feet. 1 
(4) Cyanamide: One-half pound to 2 pounds to 40 square feet. 
(5) Acid phosphate: 200 pounds to 1,200 square feet. 
(6) Wood ashes: 200 pounds to 1,200 square feet. 
(7) Tobacco dust: 200 pounds to 1,200 square feet. 
(8) Hydrated lime: 200 pounds to 1,200 square feet. 
These materials were applied over large areas, but no counts were | 
made which would indicate accurately the mortality of the larve § 
and pupe resulting from their use. Although in some instances | 
apparent diminution in number was noted, it could not be definitely 
associated with any particular treatments. ° | 
During 1921 in wholesale rose houses at Doylestown, Pa., a solid | 
bed containing: approximately 800 plants, which had been growing 
there for eight years, afforded an excellent opportunity for further | 
experimental work. These plants were very heavily infested, and in © 
some cases had as many as 23 larve and pup around the roots of a 
single plant. . 
Preliminary tests with various chemicals were made with potted | 
rose plants, in the soil of which a definite number of larve and § 
pupz had been buried at their normal depth of 2 inches. The | 
results are presented in Table 15. ' 
Thirty-nine experiments, based on the results obtained from | 
these preliminary tests, were then conducted in the infested beds on | 
plots containing from 5 to 25 plants each. At approximately five- | 
day intervals examinations of the treated and the check plants were | 
made by digging them up and examining the roots and surrounding | 
soil for the larve and pupe. Thus observations were made on the | 
effectiveness of the materials used as well as on the minimum time | 
required for them to exert their insecticidal action. | 
The results of these experiments indicated that orthodichloro- 
benzene and kerosene nicotine oleate emulsion might prove satisfac- 
tory in practical tests. These materials were therefore applied in 
plots in the ground bed. Orthodichlorobenzene used in three plots 
at the respective rates of 1, 2, and 3 cubic centimeters per plant pro- 
duced mortalities of 36 per cent, 26 per cent, and 52 per cent, respec- 
tively. Injury to the plants, however, was so pronounced, even be- 
fore they were removed for examination, that the use of this chemi- 
cal is precluded. Five plots containing 45 plants were treated with | 
kerosene nicotine oleate emulsion in varying dilutions. This mate- | 
rial proved unsatisfactory and was removed from further considera- 
tion, because it left the soil in a greasy and objectionable condition. | 
Mercuric chloride used at the rate of one-half ounce dissolved in 3 
gallons of water was tried in a pot experiment and on a plot of 15 
plants, where it proved entirely ineffective. The use of wood ashes 
and tobacco dust was tested further in plot experiments and is dis- 
cussed on page 43. 
