Plant Protection Equipments: Aerosols, Insecticide Smokes, Vaporizers
An aerosol or fog is a system of liquid particles of ultramicroscopic size dispersed in a gas; the size of particles is from 0.1 to 50 microns. The aerosol can be produced in a number of ways like 1) spraying a solution of an insecticide in fuel oil on a heated surface 2) spraying through a capillary tube a solution of an insecticide from a container of liquefied gas 3) forcing an insecticide solution between closely apposed an rapidly spinning discs and 4) using a high velocity air stream or gas upon stream of insecticide liquid.
Aerosols are very promising for insect and mite control in enclosed spaces. They do not create residue problems because very small quantities of toxic ingredients are dispersed over large areas.
Burning some combustible material impregnated with insecticides produces insecticide smokes. The smoke generating pellets also contains retardant and oxidizing agents like nitrates, nitrites, chlorates etc. Many insecticides are decomposed by heat and hence not suitable for this type of formulation. The smoke particles are 0.001 to 0.01 micron in size and hence they do not settle on leaf surface satisfactorily.
Organo chlorines can be held in containers and electrically heated to temperatures that allow slow but continuous vaporization. The vapor acts as fumigant. Lindane is the most commonly used pesticide and 10 g of pure dry crystals of lindane produce vapors sufficient to kill insects in 100 of space.