RF AND MICROWAVE DIELECTRIC-PROPERTIES OF STORED-GRAIN INSECTS AND THEIR IMPLICATIONS FOR POTENTIAL INSECT CONTROL

The permittivities of bulk samples of adult insects of the rice weevil , red flour beetle, sawtoothed grain beetle, and lesser grain borer we re measured at single frequencies of 9.4 and 11.7 GHz in X-band wavegu ide at about 23 degrees C, and permittivities of homogenized samples o f the same species were measured from 0.2 to 20 GHz at temperatures fr om 10 to 70 degrees C with art open-ended coaxial-line probe and netwo rk analyzer Sample densities for the coaxial-line probe measurements w ere determined from the X-band measurements with a linear relationship between the cube root of the dielectric constant and sample bulk dens ity determined from permittivity measurements on bulk samples of the a dult insects in a waveguide sample holder taken with the,short-circuit ed line technique. Since linearity of the cube root of the dielectric constant with bulk density is consistent with the Landau & Lifshitz, L ooyenga dielectric mixture equation, this equation was used to calcula te estimated dielectric constants and loss factors of the insects from measured permittivities and volume fractions determined from measured bulk density and adult insect density determined by air-comparison py cnometer measurements. Estimated dielectric constants and loss factors of the insects are presented graphically for temperatures from 10 to 70 degrees C, and tabulated data are provided for range information an d comparative purposes.