Plants as Affected by Animal Parasttes. 151 
shaken or knocked from the plant directly into the vessel. 
This method is often employed in destroying the potato 
beetle.* Digging out cutworms and white grubst from 
about corn and strawberry plants, and cutting out borers 
from trees and squash vines are often the most effectual 
methods for destroying these insects. 
283. Destroying Insects by Poisons or Caustics is 
the method most generally available. The material used is 
called an insecticide (in-sect’-i-cide), and if satisfactory, 
must be destructive to the insects without injuring the 
plant to which it is applied, or rendering the plant or its 
products unfit for food. The insecticides in most general 
use are certain compounds of arsenic (Paris green, London 
purple, white arsenic), hellebore and pyrethrum powders, 
tobacco, kerosene, and various compounds of soda and 
potash. With the exception of kerosene and tbe alkali 
compounds, all these may be used either as dry powder or 
with water. 
284. The Arsenical Compounds are very effectual as 
insect destroyers, even when largely diluted. When applied 
in water, however, they are liable to injure foliage in pro- 
portion to the amount of soluble arsenic they contain. 
When insoluble in water, they require stirring to keep them 
in suspension. 
285. Paris Green (arsenite of copper), when pure, is a 
nearly insoluble compound, and may be safely used, diluted 
at the rate of one pound to two hundred gallons of water, 
upon the foliage of most plants. For the peach and nec- 
tarine it should be diluted one-half more. Pure Paris green 
dissolves, without sediment, in aqua ammonia. 
* Doryphora d lineat } Lachnosterna. 
