

TOBACCO HOENWORM INSPXTICIDE. 9 



HOW TO APPLY ARSENATE OF LEAD TO TOBACCO. 



It is recommended that dry wood-ashes be mixed with arsenate of 

 lead in order to make it dust evenly and to prevent its clogging in the 

 gun. It is also recommended that a dust gun be obtained having a 

 fan diameter of at least 8 inches. However, if a dust gun is secured 

 having a fan diameter of at least 10 inches and a special device to 

 prevent clogging just below the hopper where the insecticide is fed 

 into the delivery pipe, the arsenate of lead may be applied without 

 mixing it with a carrier. 



It is important to use a powerful dust gun and to make a thorough 

 and even application. Do not attempt to apply any dust poison 

 during a strong breeze. Absolute calm is to be preferred and the best 

 applications can be made only under that condition. Make dust 

 applications early in the morning or late in the afternoon wlien the 

 air is still or there is at most only a slight breeze. Thoroughness and 

 evenness of application can not be emphasized too strongly, for an 

 uneven application made in a strong breeze will leave enough live 

 worms to damage the tobacco seriously. 



WHEN TO APPLY ARSENATE OF LEAD. 



The first application should be made when worms become too 

 numerous to be kept off tobacco easily by the hand-picking that is 

 usually done while hoeing, suckering, or topping. Many farmers 

 make only one application, and that at a time when worms are 

 numerous and many of them half grown or larger. It is better to 

 make more than one application, the first one being applied as recom- 

 mended. The time for repeating the application can be deter- 

 mined by the numbers of eggs and young worms appearing upon 

 the tobacco. Worms should be killed during the first week after 

 hatching, for during the second and third weeks they are much 

 harder to kill and they wiU eat many times as much tobacco as is 

 consumed during the first week. 



GRADE OF ARSENATE OF LEAD THAT SHOULD BE USED. 



Arsenate of lead may be divided, broadly, into two forms, triplumbic 

 and diplumbic. Theoretically the triplumbic form may contain 25.58 

 per cent of arsenic oxid, while the diplumbic may contain 33.15 per 

 cent of arsenic oxid. Experiments have shown that the triplumbic 

 form is too slow in its insecticidal action to justify its use against 

 tobacco hornworms. The diplumbic form is the one that should be 

 used. In order to he sure of receiving the diplumbic form, demand that 

 the manufacturer and dealer guarantee that the arsenate of lead you buy 

 contains at least 30 per cent arsenic oxid (As,05) of which not more than 

 1 per cent is free, or water-soluble. This grade was the one used in all 

 the experiments mentioned in this bulletin. It is necessary to have 

 a low percentage of free, or water-soluble, arsenic in order to insure 

 against burning the tobacco. 



