TOBACCO HORNWORM INSECTICIDE. 5 



On August 21, 1911, arsenate of lead at the rate of 4f pounds 

 per acre was applied during a breeze. At the expiration of four 

 days only 78 per cent of the worms were dead. On the same 

 date and under the same conditions an application of Paris green 

 at the rate of If pounds per acre killed only 54 per cent of the worms 

 in four days. These experiments emphasize the necessity of making 

 the application of an insecticide when there is very little breeze. 



APPLICATIONS IN RAINY WEATHER. 



On August 28, 1911, arsenate of lead was applied about 7 a. m. to 

 two plats of tobacco at the rate of 5 pounds and 4 pounds per acre, 

 respectively, and Paris gi'een was applied to the check plat at the 

 rate of 2^ pounds per acre. The same day between 11 a, m. and 

 2 p. m. about one-third of an inch of rain fell in dashing showers. 

 On the second day after the application 91 per cent of the worms 

 had been killed by the 5-pound dosage of arsenate of lead, 83 per cent 

 by the 4-pound dosage of arsenate of lead, and only 66 per cent by 

 the 2^-pound dosage of Paris green. On the fourth day after the 

 application the number of worms on the 5-pound dosage arsenate 

 of lead plat was still further reduced. On the other hand, the worms 

 had increased in numbers upon the 4-pound dosage arsenate of lead 

 plat and on the Paris-green plat. These results indicate that arse- 

 nate of lead can be made effective under conditions in which Paris 

 green is practically a failure. 



EXPERIMENTAL ACRE AT CLARKSVILLE, TENN. 



During the summer of 1913 an experimental acre of tobacco at 

 ClarksviUe, Tenn,, was kept free of worms by the use of powdered 

 arsenate of lead from the time worms appeared in destructive num- 

 bers until worms ceased to appear. Four applications were made, a 

 total of 12| pounds being used, an average of a little more than 3 pounds 

 per dosage. The first dosage, only 2^ pounds, was too light, however, 

 and it had to be repeated. Had the first dosage been at the rate of 

 about 4 pounds per acre, undoubtedly two more dosages of about 

 3^ pounds per acre would have been sufficient to do the work accom- 

 plished by the four applications. The total cost of the arsenate of 

 lead and labor (assuming the arsenate of lead to retail at 25 cents 

 per pound) was $3.86, an average cost of 77 cents per week for the 

 five weeks over which the dosages remained effective. 



The first dosage was applied while the worms were small, and the 

 repetition of the dosages at intervals of about 10 days prevented the 

 growth of large worms. No hand worming was done upon this acre 

 and no tobacco was injured either by the worms or by the axsenate 

 of lead. 



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