c. Since many of our problem species of insects were at one time exotic, it
makes sense to find out where the insects originated and what their natural predators or
parasites are. When this is achieved, the predator or parasite species can be obtained
and established in the new area with the result that the equilibrium position should
ultimately be reached. When this process has been successfully completed, adequate
preventive measures should ensure any significant problems from occurring.
d. Other types of biological control include sterilization of males. A genetic
representation of males of a particular problem species will be collected and sterilized.
The sterilized males will then selectively be placed into problem areas at a
concentration high enough to mate with most females. The result will be production of
sterile eggs, hence, a drastic decrease in the number of offspring. Experiments of this
sort have been successfully carried out with the screwworm fly in Florida and Texas.
This species in the larvae form is parasitic to all forms of livestock. Success to some
extent has also been achieved with the tsetse fly and black fly.
Section III. ALUMINUM PHOSPHIDE, FORMULATED
The US Armed Forces suffered a million loss in semiperishable subsistence
in South Vietnam in fiscal year 1968. The military supply system in South Vietnam
during fiscal year 1968 condemned semiperishable subsistence having a total dollar
value of million. This subsistence consisted primarily of cereal products, including
flour, and was caused by insect infestation. Since that time, the Armed Forces have
approved the use of a newly developed chemical fumigating agent which has proven
effective as a means of controlling insect infestation in stored subsistence. That
fumigant is aluminum phosphide, known commonly as Phostoxin.
4-12. CHARACTERISTICS OF ALUMINUM PHOSPHIDE
a. Phostoxin is the trade name for aluminum phosphide made in tablet or pellet
form and containing 55 percent aluminum phosphide, 41 percent ammonium
carbamate, and 4 percent edible paraffin. The effectiveness of the fumigant is derived
when hydrogen phosphide (also called phosphine or PH3) is evolved by hydrolysis upon
exposure of the tablet or pellet to atmospheric moisture. The initial decomposition of
the tablet or pellet involves the ammonium carbamate component releasing ammonia
(warning gas) and carbon dioxide. Carbon dioxide serves to reduce generation of heat
in the reaction of phosphide with moisture. The tablets or pellets are impregnated with
paraffin to provide a timed delay of this hydrolysis, thus providing a built-in safety factor
for handling and applying the fumigant. The phosphine gas is liberated 15 to 30
minutes after exposure to the atmosphere.