Care and intelligence are especially needful with certain insecticides such as poisonous gases, or the operators may suffer.
In 1899, at Maidstone, special prizes were offered for machines for washing hops with liquid insecticides, cream separators (power and hand), machines for the evaporation of fruit and vegetables, and packages for the carriage of (a) soft fruit, (b) hard fruit.
Aphides are provided with a mealy skin, which does not allow water to be attached to it, and thus insecticides for destroying them contain soft soap, which fixes the solution to the skin; paraffin is added to corrode the skin, and the up the breathing pores and so produces asphyxiation.
Insecticides, of which the bisulphide of carbon (CS 2) and the sulpho-carbonate of potassium (KS CS2) remain in use, were injected into the earth to kill the phylloxera on the roots of the vine.
Wash trees infested with insects with one of the many insecticides now obtainable.