ARSENATE OF LEAD AGAINST TOBACCO HORNWORMS. 



operator as will Paris green; in fact, thus far it has produced no 

 noticeable injurious effects upon the operators. 



Since arsenate of lead can be applied to tobacco without injuring 

 the plant, and since it is very much less objectionable from the oper- 

 ator's standpoint, its insecticidal properties should next be discussed. 

 As the dosage and action of Paris green are very widely known, the 

 value of arsenate of lead as an insecticide can the more easily be 

 explained by comparing it with Paris green. The following tables 

 will serve to show the relative values of the two insecticides under 

 different conditions. 



Table I. — Comparison of the insecticidal effects against hornworms of arsenate 

 of lead and Paris green in fair weather. 



1 Taken on 200 plants by ordinary hand-worming. 



2 Many small worms alive. 



Arsenate-of-lead experiments Nos. 1 and 2 were applied under 

 very favorable conditions, i. e., there was dew upon the plants and 

 no breeze. Paris-green application No. 3 was applied under equally 

 favorable conditions. These three experiments killed worms very 

 satisfactorily. The records in Table I were made by counting the 

 worms on 50 plants of tobacco on each succeeding day after the ap- 

 plication. No. 1, 5-pound dosage of arsenate of lead, gave the 

 best results, for on the fourth day after the application only 2 live 

 worms were found in hand-worming 200 hills. The 3^-pound dosage 

 of arsenate of lead was not quite so good, although only 14 live worms 

 were found on 200 plants the fourth day after the application. The 

 Paris-green application No. 3 killed more quickly tlian either of the 

 applications of arsenate of lead, but on the fifth day after the appli- 

 cation numerous small worms were noticed in worming 200 plants. 

 It was thus apparent that the Paris green was losing its effect, owing 

 to heavy dews which tended to puddle it, and to heavy drying winds 

 during the day, which blew some of it from the plants. 



The application in experiment No. 4 was not made under the most 

 favorable conditions. There was a slight breeze during the appli- 



