EXPERIMENTS WITH INSECTICIDES UPON POTATOES. 1 73 



THE APPLICATION OP PARIS GREEN AND OTHER POWDERED 

 INSECTICIDES. 



When Paris green was first used for the potato beetle it seems 

 to have been applied dry. This was probably partly due to the 

 difficulty of transporting the water and partly (and perhaps more 

 especially) to the imperfect distribution which resulted from 

 sprinkling the plants with watering cans. Since the introduction 

 of improved spraying machinery, the poisons can be more evenly 

 and effectively distributed with water than by dusting. 



None of the poisonous powders are dissolved in the water but 

 are mixed with it and held suspended. The heavier the powder 

 and the coarser the particles the greater will be the tendency for 

 it to settle in it. An efficient agitator is an indespensible part of 

 a spraying outfit. The materials are best applied as a fine spray, 

 as in this way the whole plant can be readily covered and prac- 

 tically none of the solution runs off the foliage. In the case of 

 the copper compounds of arsenic, freshly slacked lime should be 

 added to the water at the rate of 2 pounds to barrel.* This will 

 make the Paris green, etc., adhere better and effectually prevent 

 burning the foliage. Half a pound of good, finely pulverized 

 Paris green can be sprayed on so as to be more effective than a 

 much larger amount applied with a "gun" or other dusting 

 devices. It can also be applied much faster and with less labor. 

 One man with a 4-rowed mechanical sprayer can readily treat 

 20 acres a day, and 30 acres with a 6-rowed sprayer. 



In the experiments here reported upon, the poisons were all 

 applied with a four-rowed mechanical sprayer fitted with a 

 powerful hand pump. As it was desired to take every precau- 

 tion for thorough spraying, two men were on the cart, one to 

 pump, the other to drive and watch that the nozzles did not get 

 stopped: In the first spraying one Vermorel nozzle was over 

 each row and the rows were gone over twice in opposite direc- 

 tions. The other three applications were made with a double 

 Yermorel nozzle. A barrel of spraying materials with two single 

 or one double nozzle for each row will spray an acre. Some 

 power mechanical sprayers, such as the Aspinwall, do not have 



* In case the plants are sprayed with Bordeaux mixture at the same time, the 

 addition of the lime is not necessary. 



