8 



Farmers' Bulletin 819. 



that wash down and collect in the bud and in the axils of the leaves. 

 Planters are familiar with this condition and attempt to avoid in- 

 jury by making lighter applications. When such a course is adopted 

 some of the poison injury is eliminated, but extra damage from bud- 

 worm attack follows on account of the insufficient dosage. When 

 Paris-green mixture is used there is always the possibility of dam- 

 age, either from the action of the poison on the leaves or from bud- 

 worm attack following the application of insufficient quantities of 

 the mixture. The normal injury also is increased frequently be- 

 cause some laborers apply more of the mixture than is necessary 

 for budworm control. 



RELATIVE EFFICIENCY AND ECONOMY IN THE USE OF VARIOUS POISONS. 



Owing to this danger of injury to the leaves by Paris green when 

 used in sufficient amounts, and the imperfect protection afforded by 

 smaller quantities, the discovery of a poison that would be safer 

 under all conditions of weather and of application, and one that 

 would at the same time give the greatest budworm control, was 

 much to be desired. 



During the seasons from 1913 to 1922, inclusive, experiments were 

 performed with a large number of mixtures, including the follow- 

 ing poisons, some of which have been used more or less commonly 

 against the budworm : Arsenate of lead, arsenate of calcium, mag- 

 nesium arsenate, antimony sulphid, Paris green, tripotassium arse- 

 nate, orthoarsenite of zinc, antimony arsenate, and antimony oxid. 



These were tested in varying strengths and in combination with 

 corn meal, gypsum, and fuller's earth as carriers. Of all the poisons 

 used, Paris green, arsenate of lead, and golden antimony sulphid 

 gave the most promising results, although these poisons differed 

 greatly in efficiency and cost of application. Corn meal was found 

 to be the most satisfactory carrier. 



Table 1 indicates the average cost per acre per season of antimony 

 sulphid, arsenate of lead, and Paris green, as well as the percentage 

 of leaves free from budworm and poison injury. The cost data are 

 based upon results obtained on 51 plantations, where 476 acres of 

 tobacco were treated throughout the season. It was found that an 

 average of 4.17 bushels of meal were necessary to the treatment of 1 

 acre. In calculating the total cost for the treatment of an acre, 

 com meal was valued at $1 per bushel (48 pounds). The prices per 

 pound of antimony sulphid, arsenate of lead, and Paris green were 

 taken as 35 cents, 25 cents, and 30 cents, respectively. 



Tahle 1. 



-Relative efficiency and economy of antimony sulphid, arsenate of lead, 

 and Paris yreen in controlling the tobacco budworm. 



