and x-rays) is capable of killing arthropods, its employment is impractical for control
purposes. However, sublethal doses of ionizing radiation may produce sterility in
arthropods (see paragraph 1-6d). Electromagnetic radiation (gamma rays and x-rays) is
most useful because it is more penetrating than alpha or beta particles. Neutron
radiation possesses a number of undesirable qualities that render this technique
d. Ionizing Radiation and the Screwworm Fly. The most spectacular
example of arthropod control through the use of ionizing radiation may be seen in the
case of the screwworm fly. Sterilized male flies are released to mate with wild female
flies, which mate only once in a lifetime. Either there are no eggs produced or the eggs
that are produced are not fertile. The fly population declines as a result. Repetition of
the procedure for several generations leads to the eradication of the pest from the area.
This could also be considered biological control. The procedure is worthy of mention
because it demonstrates the dramatic potential of ionizing radiation in arthropod control.
Eradication is a term that, prior to the ionizing radiation control method, had not been
used. In the past, the term control meant maintaining populations of arthropod pests at
levels that are acceptable from a health, damage, or nuisance standpoint. The very fact
that we now use eradication implies that ionizing radiation is indeed a very powerful tool
in the control of arthropods; nonetheless, the measure does have its drawbacks.
(1) To execute the program, large numbers of male flies must be reared in
laboratory facilities and sterilized with X-rays or gamma rays.
This can become costly in time, space, manpower, and money.
(3) The area to be treated needs to be relatively small and isolated to
prevent reinfestation from adjacent areas.
e. Screwworm Fly Eradication Programs. The most notable example of
screwworm fly eradication programs took place on the island of Curacao off the coast of
Venezuela and on the peninsular portion of Florida. The ionizing radiation technique
was quite successful. In Florida, for example, the program was carried out during the
winter months when the fly population was low and was isolated in the warmer,
southern portion of the state.
1-7. CULTURAL CONTROL
Cultural control measures involve careful nonchemical changing of the
environment to make it less favorable for a particular pest, thereby managing its
population (includes habitat manipulation and sanitation). Some cultural control
a. Crop rotation.
b. Tilling of the soil.