GAMMA RAYS 
X-RAYS 
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ENERGY OF THE QUANTUM (E), 1.24 x 10" ELECTRON-VOLTS 
a) P27 SE S2S6" PLB OS NOUNS 13 14 1S 16M Om omc Omer 
FREQUENCY (/), 3x 10" CYCLES PER SECOND 
1 16215 147 1304129 Wwe 10 9 B87 we) Silke Sai Oe omeeomes 
WAVE LENGTH (A), 10° ANGSTROM UNITS 
Figure 1,--Electromagnetic spectrum showing appropriate ranges of radiation, 
pulse-modulated RF energy have shown evi- 
dence of effects not attributable to thermal 
causes by the investigators (11, 50, 71, 72, 
OF PALSs. 135): 
~ Based on RF heating only, control of in- 
sects by radiation of RF energy into any 
sizable space is impractical (10). Calculation 
of the power required for a special case re- 
vealed that tremendous amounts of energy are 
needed for. a range of only a few feet, with 
power requirements increasing as the square 
of the distance from the radiating antenna. 
Concentration of RF energy into a narrow 
beam reduces the energy requirement, but it 
would still be substantial. 
Several good reviews have been published 
on studies of RF electric fields for pest con- 
trol (5, 56, 102, 105, 112, 136, 137, 140, 145), 
and important Aiiorinc micas involved in applying 
this type of energy have been treated in the 
literature (56, 105, 136, 140, 149). 
Major interest in applying RF energy for 
insect control involved treatment of grain, 
foodstuffs, and wood. The basis for this in- 
terest stems from the nature of absorption 
of energy by materials in a high-frequency 
electric field. The power dissipation depends 
not only on the frequency and intensity of the 

178 
field but also on the electrical charactere 
istics, more specifically, the dielectric prop- 
erties of the materials involved. For certain 
combinations of hosts and insects, their re=- 
spective dielectric properties are favorable 
for differential or selective absorption of 
energy (105, 136, 149), and the insects can be 
killed without damaging the host material. 
Thermal tolerance of the host and infesting 
organism may be sufficiently separated that 
heating by conventional means is a possible 
control measure. RF heating, however, can 
be advantageous if the pest organism can be 
selectively heated, because less energy is 
required to accomplish control. In addition, 
RF dielectric heating is much more uniform and 
faster than conventional heating. 
Studies on stored-grain insect control in 
wheat using a frequency of 39 megacycles per 
second (mc.) showed that all developmental 
stages of several species were controlled by 
exposures lasting only a few seconds (105, 
149). Immature forms were more resistant 
than adults, and differences were noted in 
susceptibility among species. Complete mor- 
tality of the most resistant, however, was 
achieved by RF treatments with resulting 
grain temperatures of 60° to 65°C. in25-gm. 

