﻿40 BULLETIN 1357, V. S. DEPARTMENT OP AGRICULTURE 



mind the following materials were tested during the season of 1920 

 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. 



(3) Sodium cyanide in solution: One-eighth to one-half ounce per gallon of 

 water applied to 6 square feet. 



(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 iK)unds 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 larvae 

 and pupse 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 larvae and pupae 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 larvae and 

 pupae had been buried at their normal depth of 2 inches. The 

 results are presented in Table 15. 



Thirty-nine experiments, barsed 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 larvae and pupae. 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. 



