must be palatable to the target insects, or they will avoid it. The insecticides used as
stomach poisons are chiefly the inorganic chemicals and some of the chlorinated
b. Contact Poisons. Contact poisons kill insects by contacting and entering the
body directly through the body wall and into the blood, through the mouthparts and into
the digestive system, or through the respiratory system. These insecticides are used
primarily against insects with sucking mouthparts that would not eat normally applied
stomach poisons. However, they are also effective as stomach poisons if eaten by
insects with chewing mouthparts. Contact poisons may be applied directly to insects'
bodies as sprays or dusts, or they may be applied for residual action on surfaces with
which the target insects will come in contact. Contact insecticides in common use
include organic as well as synthetic organic compounds.
c. Fumigants. Fumigants are volatile chemicals that kill by entering a pest
through the respiratory system. They are used in gaseous form, or as solids or liquids
which rapidly vaporize forming poisonous gases. They are generally limited to use in
tightly sealed containers or enclosures. They are particularly appropriate for killing
insects in stored products where the gas will penetrate cracks, crevices, and tightly
packed material. They are extremely toxic to all animal life; therefore, they are also
effective as rodenticides. Their extreme toxicity makes fumigants particularly hazardous
to use; accordingly, their use is restricted to certified personnel.
Repellents are chemical compounds used as liquids, creams, aerosols, or solids
to prevent biting or other annoyance by insects or other animal life. Repellents are
generally used as a supplement to normal control measures or under conditions where
other control methods are not feasible. Personal protection from the bites of
mosquitoes, biting flies, fleas, ticks, chiggers, leeches, and other pests may be obtained
by the application of repellents to the skin or to the clothing. A personal repellent
a. Not be toxic or irritating to the skin.
b. Give protection for a number of hours under unfavorable conditions.
c. Repel a wide variety of arthropods.
d. Be practically odorless to humans.
e. Not damage clothing.