Spray Materials are conveniently divided into two classes, insecticides and fungicides.
Commerce in vinegar, dried fruits, insecticides and fungicides is also regulated in some states.
Organic esters of phosphoric acids are used as insecticides.
Insecticides seldom avail, for the insects are very resistant to poisons.
You can readily see that there is no way of getting at the beetle with insecticides after they have gotten under the bark.
Most aphides are readily controlled by means of insecticides, such as nicotine-sulphate, or kerosene-emulsion.
Some insecticides, such as resin wash, act both as a caustic application and a suffocating covering.
The application of these insecticides requires more care, and is therefore more troublesome.
There was a time when black walnut hulls were purchased by producers of insecticides.