ARSENATE OF LEAD FOR TOBACCO HORNWORMS. 3 
in large quantities without causing any noticeable injury, and that 
when applied to a torn or bruised leaf it produces no injury. Paris 
green can not be applied to tobacco in the ‘‘graining” stage (i. e., 
when nearly ripe) in sufficient quantities to do good insecticidal work 
without too grave danger of burning the plant. Arsenate of lead, on 
the other hand, can be safely applied to tobacco in the “graining’’ 
stage in quantities sufficient to produce satisfactory insecticidal 
results. Furthermore, arsenate of lead will cause no irritation to the 
operator as will Paris green; in fact, thus far it has produced no 
noticeable injurious effects upon the operators. 
RESULTS THAT HAVE BEEN OBTAINED FROM THE USE OF ARSENATE 
OF LEAD. 
APPLICATIONS IN FAIR WEATHER. 
On August 24, 1910, Paris green was applied to a plat of tobacco 
at the rate of 1} pounds per acre. On the third day after the appli- 
cation 95 per cent of the worms were dead. However, on the 
fifth day after the application numbers of small worms were seen 
upon the tobacco, which indicated that the dosage was losing 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 application about 99 per cent of the worms had been killed 
by the 5-pound dosage and about 89 per cent by the 34-pound 
dosage. Both dosages of lead arsenate continued to kill worms for 
several days after the Paris green had lost its effect. 
The foregoing applications were made under the most favorable 
conditions; that is, while dew was upon the plants and while there 
was no breeze. The tobacco was about two-thirds grown. 
On August 21, 1911, a dosage of arsenate of lead at the rate of 
4% 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 1? 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 rates of 5 pounds and 4 pounds per acre, 
respectively, and Paris green 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 
