i88 
TREES AS GOOD CITIZENS 
recognized standard preparations will give the best results. 
It is poor economy to use a preparation because it may be 
bought cheap, and it is unwise to experiment with one 
which is unknown. 
The Stomach Poisons. —The standard stomach poisons 
are arsenate of lead and arsenate of lime (calcium 
arsenate). Arsenate of lead is the one most used, because 
it adheres to the foliage longer than any other stomach 
poison, is highly effective, and does no damage to the 
leaves when used in proper dilution. Both arsenate of 
lead and arsenate of lime may be bought in paste or pow¬ 
der form. The powder is to be preferred for the reason that 
it is not injured by freezing or drying. These poisons are 
ready for use when purchased, requiring only the addition 
of water in proportions which will usually be found speci¬ 
fied on the label of the container. 
If there is preference for preparing a poison at home 
the formula for arsenate of lead is as follows: 
Acetate of lead.12 ounces 
Arsenate of soda. 4 ounces 
Water.15 to 20 gallons 
Pour the acetate of lead into a half gallon of water and 
the arsenate of soda into a similar quantity of water in a 
separate vessel. The contents of the two vessels should 
then be poured into a holder, containing from 15 to 20 
gallons of water, and well mixed. 
Because of their poisonous nature , arsenate of lead and 
arsenate of lime must he handled with care . Especial safe¬ 
guards must be used to keep them away from children and 
domestic animals . 
Contact Sprays. —For the killing of sap-sucking in¬ 
sects the contact sprays are required. These materials 
cause death to the insects by coating and clogging the 
breathing pores, by direct action on the nerves, or by caus- 
