Design of gamma-radiation facilities for 
treatment of grain and citrus fruit to control 
insects has been considered by several in- 
vestigators (26, 35, 36, 79, 160). A pilot-. 
scale (2-1/2 tons per hour) Co-60 grain- 
irradiating facility is being installed for studies 
on insect control at the U.S. Department of 
Agriculture Stored-Grain Insects Laboratory 
at Savannah, Ga. The operating principle is 
such that it can be "scaled up" for design of 
commercial-sized installations. Since costs of 
radiation treatment will become more com- 
petitive as the technology progresses and be- 
cause of health hazards from chemical in- 
secticides, it is likely that ionizing radiation 
from isotopes and electron accelerators will 
be used to treat large quantities of grain and 
other products in the future. 
Other possible uses proposed for ionizing 
radiation, perhaps further in the future, in- 
clude a portable nuclear reactor for sterilizing 
soil in the field (150). Remote control opera- 
tion could reduce the shielding requirements, 
and it is estimated that such a reactor could 
be built for soil treatment to control nematodes, 
insects, fungi, and weed-seed germination at 
much less than the present per=-acre costs for 
required chemical control (150). Another re- 
port suggests that a 100,000-rad gamma- 
radiation treatment of soil would be sufficient 
to effectively inhibit weed growth as well as 
sterilize insects or nematodes and destroy a 
high percentage of the bacteria and fungi (21). 
Effects on beneficial soil bacteria would have 
to be taken into account, but perhaps com- 
plete sterilization followed by inoculation with 
the desired bacteria might be possible. 
SONIC AND ULTRASONIC ENERGY 
Sound and ultrasound, which are forms of 
radiant energy other than electromagnetic and 
particle radiations, have also received much 
attention for pest-control possibilities. Sonic 
and ultrasonic energy is propagated through 
air or other materials by means of a mechan- 
ical vibratory wave phenomenon associated 
with pressure differences in the medium. As 
with electromagnetic radiation, the frequency 
and wavelength determine the characteristics 
of the radiation. The range of audibility for 
humans falls within the 20- to 20,000-c.p.s. 
183 
frequency range. Vibrations above the human 
auditory response limit are termed ultra- 
sonic. 
Uses of sound and ultrasound for pest con- 
trol can be considered in two general ways: 
(a) By applying intense energy levels, which 
cause death directly by heating, damaging vital 
organs, or inducing fatal audiogenic seizures 
(4, 41, 57, 58, 60); and (b) by using lower in- 
tensities, to which pests respond somehow, 
to affect their behavior in some desired way. 
Killing pests directly with high-intensity sonic 
and ultrasonic energy appears impractical for 
a number of reasons (57, 58, 60). First of all, 
costs of producing the required energy are 
prohibitive. Also, intense energy levels can 
be maintained only in a restricted space, 
and so there is a problem of attracting the 
pests to the energy source. Further, if they 
could be collected, there would probably be 
more economical means of killing them. Using 
sound and ultrasound to influence behavior of 
pests therefore offers more promise for 
practical pest control. 
Insect-Control Possibilities 
An understanding of the ways in which 
insects use sound is important in attempting 
any control based on use of sound. Sound 
production and reception, as well as uses of 
sound by insects, have been studied extensively 
(3, 15, 61, 63, 144). These uses include com- 
munication, such as calling, congregation, and 
courtship songs, and alarm or distress sounds. 
Insects also use sound for protection. Some 
insects mimic other insects and some issue 
defense noises to discourage predators. They 
also use sounds from sources other than their 
own to detect predators and other dangers, 
On the other hand, some predators locate 
their insect prey through the calling sounds 
of the insects (143). 
In their use of sound, many insects employ 
not only frequencies audible to humans but 
much higher frequencies as well. For example, 
songs of some species include frequencies up 
to at least 100 or 150 kilocycles per second 
(kc.) (61, 69a). Responses have been obtained 
from tympanic nerves of moths with stimuli 
of 240 kc. (119). Many studies have been con- 
ducted on the complicated and intricate calls 
