4 FAEMEBS BULLETIN 867. 



ADVANTAGES IN THE USE OF ARSENATE OF LEAD. 



Hand-worming, as has been stated, is impossible upon a large 

 scale because of the scarcity of labor, its relatively high cost, and its 

 general inefficiency. Under average conditions of infestation hand 

 worming will cost at least SIO an acre, and even with this amount of 

 labor, damage by worms can not be prevented entirely, for the most 

 vigilant wormer will overlook many worms. On the other hand a 

 thorough appHcation of arsenate of lead wiH be effective for a period 

 of at least 10 days following the application, and under favorable 

 conditions wiU keep the tobacco clean for that period. The records 

 at hand do not show that Paris green can be expected to exert satis- 

 factory control for a period longer than from five to seven days. 

 Arsenate of lead adheres to tobacco longer than does Paris green, 

 and rarely does it cause any burning of the plant. The authentic cases 

 of injury by arsenate of lead have been so few, and the attendant 

 damage so slight as compared with that caused by Paris green, that the 

 probabihty of damage is not considered by farmers who have used 

 arsenate of lead long enough to become thorouglily famihar wnth its 

 action. 



In addition to its longer period of effectiveness and the greater 

 safety to the plant, arsenate of lead is not now much more costly per 

 application than is Paris green, and when the longer period of effec- 

 tiveness is considered it is the more economical. This poison is also 

 very much less irritating to the skin than is Paris green and, so far, 

 there has been no complaint of its having produced sores upon work- 

 men who applied it. 



SOME EARLY TESTS OF ARSENATE OF LEAD IN COMPARISON WITH 

 PARIS GREEN. 



APPLICATIONS IN FAIR WEATHER. 



On August 24, 1910, Paris green was applied to a plat of tobacco 

 at the rate of H pounds per acre. On the third day after the appli- 

 cation 95 per cent of the worms were dead. On the fifth day 

 after the application, however, numbers of small worms were seen 

 working upon the tobacco, which indicated that the dosage was los- 

 ing its effect. On August 25, 1910, powdered arsenate of lead was 

 applied, in the same field, to one plat at the rate of 5 pounds per 

 acre and to another plat at the rate of 3^ pounds per acre. On the 

 fourth day after the appfication about 99 per cent of the worms had 

 been killed by the 5-pound dosage and about 89 per cent by the 

 3i-pound dosage. Both dosages of lead arsenate continued to kill 

 the worms for several days after the Paris green had lost its effect. 



The foregoing appUcations were made under the most favorable 

 conditions — that is, when the dew was on the plants and when there 

 was no breeze. The tobacco was about two-thirds grown. 



