Dielectric properties of apple cultivars and codling moth larvae

Dielectric properties of four apple cultivars and third and fifth instars c odling moth (Cydia pomonella) were measured between 30 MHz and 3000 MHz at 5 degreesC to 55 degreesC, using the open-ended coaxial-line probe techniqu e. Dielectric constant of apples decreased with frequency and decreased sli ghtly with increasing temperature. The dielectric loss factor increased lin early with temperature in the radio frequency range but was nearly constant at the microwave frequencies. Minimum dielectric loss factor of apples was observed at about 915 MHz. Dielectric constant and loss factor were not in fluenced by cultivar; pulp section or degree of ripeness of apples. Firmnes s and titratable acidity in apples decreased, while soluble solids content increased significantly due to ripeness. But these properties were not corr elated with the dielectric properties. Dielectric constant and loss factor of codling moth larvae followed a similar pattern of variation with frequen cy and temperature as for the apples. The dielectric properties of third in stars codling moth were higher than those of the fifth instars in the radio frequency region. Dielectric constant and loss factor of the insect were m uch higher than that of the apples at frequencies lower than 2450 MHz, sugg esting that differential heating may be untenable at 2450 MHz or higher fre quency for codling moth larvae in the apple host.