REPORT OF STATE ENTOMOLOGIST, 1898 225 



brought out by numerous experiments, made in the extensive work 

 against the gypsy moth. One advantage is that it can be applied in 

 very large quantities without injuring the foliage. When properly pre- 

 pared, it remains for some time suspended in the water, imparting a 

 milky color, and also adheres to the leaves much longer than either paris 

 green or london purple. Its whiteness is another advantage, because of 

 which, it is readily detected upon green foHage. 



In order to obtain the best results, the poison should be prepared just 

 before using, by dissolving j i ounces of acetate of lead (sugar of lead) 

 in 4 quarts of water in a wooden pail, and 4 ounces of arsenate of soda 

 (50 %) in 2 quarts of water in another wooden pail. As the acetate or 

 sugar of lead dissolves rather slowly in cold water, the process can be 

 hastened by using warm water. The resulting solutions should then be 

 poured into the spraying tank containing enough water to give the 

 desired proportions. In most cases this will mean turning them into 100 

 or 150 gallons of water."^ 



Experiments by those connected with the gypsy moth work and others 

 show that it can be applied in almost any proportion without injuring 

 even the most delicate foliage. In cases where the insect is able to 

 resist the action of considerable poison, as the gypsy moth and canker 

 worm, or where the insecticide must remain on the trees for a consider- 

 able length of time in order to be most effective, as in the case of the elm- 

 leaf beetle, or where the delicate foliage prohibits the use of sufficient 

 paris green or london purple, the arsenate of lead will be found in- 

 valuable. 



One objection to this substance, is the variable composition of 

 the chemicals from which it is prepared. If either is in excess, it 

 should be the lead salt, because that will not injure the leaves. A simple 

 test*^ for soluble arsenic acid, is the addition of a few drops of lead 

 acetate (sugar of lead) solution to a filtered portion of the arsenate of 

 lead solution. A white precipitate indicates the presence of soluble 

 arsenic and more lead acetate (sugar of lead) should be added, or the 

 fohage will be burned by the arsenic. 



Compounds of arsenic can not only be sprayed upon foliage, but they 

 can also be used most successfully in the preparation of poisoned baits, 

 specially for cut worms, the army worm and grasshoppers. Fresh 

 clover or other attractive food is dipped in water and paris green, using 

 considerably more poison than when spraying, and bunches of it are dis- 

 tributed over the infested fields. Some form of a mash as, for example, 

 one composed of i pound of paris green to 50 pounds of bran, well . 



a Proportions recommended by Dr C. H. Fernald. 



6 Smith, F. J, Mass. Board of agriculture on gypsy moth. Report., Jan. 1898, p. 67. 



