Biting Insects 135 



must be diluted in certain proportions with other substances, 

 to make them harmless to plants and yet poisonous enough 

 to kill the insects which eat the foliage covered by it. This 

 is not difificult, since the insects continue eating and there- 

 fore accumulating the poison, which is distributed in small 

 quantities. It may be added that, if ordinary precautions 

 are taken, there is no danger to man from arsenical poisons. 



Biting Insects. There are two poisons which answer 

 inost purposes in the case of biting insects, — Arsenate of 

 Copper (Paris Green) and Arsenate of Lead. The latter, 

 although acting more slowly, is probably the better for gen- 

 eral use, because it adheres readily to the leaves, and remains 

 therefore longer effective, reducing the need of repeated 

 sprayings. It can be applied in considerable quantity 

 without burning the foliage, the one objection, besides the 

 somewhat higher price, being the difificulty of preparing 

 the mixture for use. This is now overcome by a prepared 

 paste, sold under the name of Disparene and costing fifteen 

 to twenty-five cents per pound, which needs only to be 

 stirred into water.' 



These insecticides are best applied, like the Bordeaux 

 mixture, by spraying, and are preferably applied together 

 with it; for, if the Bordeaux mixture is substituted for ordi- 

 nary water in mixing the insecticide, the possibly injurious ^ 

 effects on the foliage of the Paris Green are avoided. 



The application should be made before the trees show 

 signs of serious injury, and that means as soon as the leaves 

 are out, and they should be kept covered with the poison 



' To be obtained from the Bowker Fertilizer Co., Boston, Mass., who 

 also prepare other insecticides and fungicides. Swift's Arsenate of Lead is 

 also commendable; and the Vreeland Chemical Co. of Little Falls, N. J., 

 prepares a paste, for which superior quality is claimed, at eleven to thirteen 

 cents per pound. 



