76 STATE POMOLOGICAL SOCIETY. 



THE BEST INSECTICIDES. 



The insecticides generally used by the fruit grower fall readily 

 into two classes, internal poisons (usually arsenicals) and exter- 

 nal irritants (emulsions, soaps, etc.), the first class being used 

 against leaf-eaters and the second against sap-consumers. Of 

 the arsenicals, Paris green has long been the favorite remedy 

 for the potato beetle and more recently has come into general 

 use against many fruit and shade tree insects. Aside from the 

 killing effect, the qualities to be desired in Paris green are free- 

 dom from soluble arsenic, fineness and uniformity of composi- 

 tion. With standard grades of Paris green, one pound may be 

 used to 150 gallons of water without danger to the foliage. A 

 less c-mount of water makes a stronger solution and increases 

 the danger of "burning" the leaves. Paris green kills promptly 

 but is easily washed from the foliage by rain. In using any 

 arsenical, the danger to the leaves is in direct proportion to the 

 soluble arsenic present in the spray and a small amount is always 

 found in Paris green. 



A recently discovered arsenical compound, arsenate of lead, 

 bids fair to supersede Paris green as an insecticide. It has 

 about the same killing effects as the former but will not injure 

 the most delicate foliage when applied at any practical strength, 

 is white in color, hence it is conspicuous on the foliage and 

 remains for a long time in an effective condition on the leaves. 

 Another feature of superiority over Paris green is that arsenate 

 of lead is easily kept in suspension in the spraying tank, thus 

 insuring a uniform spraying mixture. In our work against the 

 gypsy moth we have found arsenate of lead to give better results 

 than any other arsenical, and use tons of it annually. Against 

 the common leaf-eating insects it is most effective and I have no 

 hesitation in recommending it as superior to Paris green for 

 which it may be substituted in nearly all cases. Recent exper- 

 iments indicate that it may be safely and eft'ectively used in con- 

 nection with Bordeaux mixture. 



As yet arsenate of lead cannot be bought ready made in the 

 market, but the ingredients for making it are cheap and the 

 process is easy. Eleven parts by weight of white sugar of lead 

 are dissolved in hot water and four parts of arsenate of soda 

 dissolved in hot water in another receptacle. \\'hen the com- 



