Petroleum and coal tar derivatives.
(a) Kerosene. Kerosene is used primarily as a solvent for
insecticides, but kerosene itself has considerable insecticidal effect. A refined, odorless
form is normally used as the carrier in household sprays. It has been used as a
mosquito larvacide. Kerosene is generally quite toxic to plants and can be dangerous to
man if not properly handled. Ordinary and deodorized kerosene are available from
military standard stock.
(b) Fuel oils. Fuel oils (diesel oils) have been used extensively as
mosquito larvicides. No. 2 diesel is the material generally used, often mixed with a
spreading agent. The unmixed oil is a standard solvent for outdoor space sprays. It is
available from military standard stocks.
(c) Summer oils. Summer oils are distillation fractions higher than
kerosene which are employed in water emulsion on orchards and shade trees for
control of mites and scale insects. The summer oils are employed against these pests
when the plants are in foliage.
(d) Dormant oils. Dormant oils are more highly sulfonated petroleum
oils than are summer oils and are used against the same pests, but they can only be
used safely when trees are dormant. They affect primarily the egg stage and also work
well on the crawler stage of scale insects. Neither summer nor dormant oils are
standard stock items.
c. Synthetic Organic Insecticides. The synthetic organic insecticides are
relatively new compounds. The first synthetic organic insecticide -- DDT -- was
synthesized in 1874, and its insecticidal properties were first recognized in 1939.
During World War II, research in nerve gases led to the discovery of additional
compounds that are effective insecticides.
(1) Chlorinated hydrocarbons. The chlorinated hydrocarbons are
characterized by having a long residual of toxic material in the environment. They vary
widely in their toxicity -- from aldrin and dieldrin, which are highly toxic, to methoxychlor,
which has relatively low toxicity. The chlorinated hydrocarbons act upon the central
nervous system, causing death through respiratory failure. Changes in recent years
pertaining to pesticide legislation and registration have resulted in the cancellation or
suspension of use for all of the chlorinated hydrocarbons.
(2) Organophosphates. The organophosphates insecticides are generally
more toxic to animals than are the chlorinated hydrocarbons. However, the
organophosphates do not leave highly persistent residues on the treated plants and
animals and are less likely to accumulate in animal tissues. The physiological action of
the organophosphates is the inhibition of the production of cholinesterase, an enzyme
essential to the proper functioning of the central nervous system. Cholinesterase