410 ANNUAL REPORT OF THE Off. Doc. 



tually combined with the copper and acetic acid appears to dissolve 

 in water in the spraying tank, and in this way even a reliable article 

 may sometimes cause burning. 



Finally, Paris green when mixed with water is quite heavy and 

 tends to settle to the bottom of the tank, and though all good spray 

 pumps are provided with an automatic agitator, the amount of the 

 poison sent out when the tank is full and when it is nearly empty 

 will differ considerably and the results will be correspondingly un- 

 reliable. 



For these reasons Paris green is less favorably looked upon as an 

 insecticide than was once the case, and other materials are being 

 more used each year in its place. 



Arsenate of Lead. 



This substance is a chemical combination of arsenic and lead, and 

 as the arsenic in it is all combined, no burning from its use results, 

 no matter how strong it is made. It is therefore safe to use on all 

 kinds of trees. 



It is lighter than Paris green, needing little stirring to keep it from 

 settling, and it adheres to the leaves a much longer time, it generally 

 being necessary to spray but twice with it where three times would 

 be needed with Paris green. Thus, though it costs a little more, 

 this cost is more than an off-set by the reduction in number of treat- 

 ments necessary. 



It is made as follows: 



Arsenate of soda (50 per cent, strength), . . 4 ounces. 



Acetate of lead, , 11 ounces. 



Water, , 150 gallons. 



Put the arsenate of soda in two quarts of water in a wooden pail, 

 and the acetate of lead in four quarts of water in another pail, also 

 of wood. When the chemicals are all dissolved, pour the contents 

 of both pails into the spraying tank with the rest of the water, and 

 stir for a few minutes before using. 



Those who prefer to make use of arsenate of lead ready prepared 

 can obtain it from the Bowker Insecticide Company, 43 Chatham 

 street, Boston, Mass., by whom it is sold under the name of Dis- 

 parene, or from several other firms which supply this article. 



Kerosene Emulsion. 



Paris green and arsenate of lead are termed stomach poisons, and 

 are used for insects which bite off and swallow solid food. Kerosene 

 emulsion is a contact poison and is used for those insects which suck 

 the juices from plants and which cannot therefore be destroyed by 

 stomach poisons. 



