26 NEW YORK STATE MUSEUM 



ounces of acetate of lead in four quarts of water in a wooden 

 pail and four ounces of arsenate of soda (50;^ purity) in two 

 quarts of water in another wooden pail. As the acetate of lead 

 dissolves rather slowly in cold water the process can be has- 

 tened by using hot water. Pour the solutions in enough water 

 to make 80 gallons. 



It was at first advised to prepare this poison in the manner 

 indicated above but the difficulty of getting chemicals of the 

 same grade of purity year after year and the ease with which 

 dealers in these substances may prepare this insecticide, has 

 led to the introduction of several brands of arsenate of lead in 

 the prepared paste form. These preparations have been found 

 more convenient than the homemade article and generally 

 speaking their use is advisable. The crystiilline arsenate of 

 lead is not in proper condition to use as an insecticide and 

 therefore it is necessary to get the specially prepared article. 



The value of arsenate of lead over other poisons lies in its 

 adhesiveness to the foliage — it frequently remains on the 

 leaves nearly an entire season in spite of many rains — and in 

 the fact that it can be applied in almost any amount without 

 danger of injuring even the most delicate leaves. Paris, green, 

 london purple and similar arsenical poisons operate more 

 quickly than arsenate of lead but they are also readily washed 

 off by rains, and in the case of an insect like the elm leaf beetle, 

 which feeds for an extended period, it is much better to apply 

 the more adhesive preparation even though the cost be some- 

 what greater. The necessary amount of prepared arsenate of 

 lead is usually stated on the package and it varies somewhat 

 with the method of manufacture. 



The first spraying, as stated above, should be given as soon 

 as the leaves commence to develop and usually it will be neces- 

 sary to 'repeat the treatment at the time the young larvae 

 begin their work, though after the insect has once been brought 

 well under control in a locality, possibly a single thorough 

 spraying each year for the beetles may be suflBcient. Experi- 

 ence has shown that in a localitv where all the elms are thor- 



