Physical assessments of termites (Termitidae) under 2.45 GHz microwave irradiation.

Demands for chemical-free treatments for controlling insect pests are increasing worldwide. One such treatment is microwave heating; however, two critical issues arise when using microwaves as a heat source: intensive labor and excessive energy-consumption. Optimization is thus required to reduce energy consumption while effectively killing insects. Currently, the lethal effect of microwaves on insects is considered to be due to the temperature of the irradiated materials. This study examines how the conditions of irradiation, such as resonance or traveling mode, changed the conversion of electromagnetic energy into heat when 2.45 GHz microwaves penetrated the body of the termite, C. formosanus. Our results indicated that it is possible to heat and kill termites with microwaves under resonance condition. Termites were however found to be very tolerant to microwave irradiation as the permittivity of the insect was low compared with other reported insects and plants. Electron spin resonance revealed that termites contained several paramagnetic substances in their bodies, such as Fe3+, Cu2+, Mn2+, and organic radicals. Interestingly, irradiation with traveling microwaves hardly produced heat, but increased the organic radicals in termite bodies indicating non-thermal effects of microwaves.

Attraction of alates of Cryptotermes brevis (Isoptera: Kalotermitidae) to different light wavelengths in South Florida and the Azores.

The termite Cryptotermes brevis (Walker) (Isoptera: Kalotermitidae) is an urban pest that causes much damage to wood structures. Little has been done concerning the use of control methods for alates. C. brevis is known to have phototropic behavior during the dispersal flights, and this knowledge has been applied for preventative control in the Azores where this species is a serious urban pest. We were interested in determining whether there was a light wavelength preference by the alates of C. brevis to optimize light traps against this species. Six light wavelengths were tested: 395 nm (UV), 460-555 nm (white), 470 nm (blue), 525 nm (green), 590 nm (yellow), and 625 nm (red) in choice chambers, with dark chambers as controls. Two populations were tested, one population in Florida and one population in the Azores (Terceira Island). We found consistent results for both populations, with a preference for the light wavelengths in the white, blue, and green spectrum (460-550 nm). This information can be used to build more effective light traps that can be used by home owners in the Azores to help control this pest.

Corazonin- and PDF-immunoreactivities in the cephalic ganglia of termites.

Antisera against the pigment-dispersing factor (PDF) and corazonin (Crz) reacted with distinct sets of neurons in the cephalic ganglia of termites. The locations of immunoreactive cells were similar but their numbers differed among the eight species examined: PDF-ir occurred in 0-6 cells in each optic lobe and 1-2 pairs of cells in the subosophageal ganglion (SOG), and Crz-ir in 0-2 pairs of cells in the pars intecerebralis, 3-14 cells in each lateral protocerebrum, and 0-6 pairs of cells in the SOG. Staining patterns were identical in the pseudergates, soldiers, and substitutive reproductives of Prorhinotermes simplex. Workers and soldiers were compared in the remaining 7 species. The only caste divergence was detected in Coptotermes formosanus, in which the soldiers differed from the workers by lack of 4 Crz-ir perikarya in the pars intercerebralis and occasionally also by the absence of 2 Crz-ir perikarya in the SOG. Diurnal changes in PDF-ir and Crz-ir were examined in P. simplex kept under long day (18:6h light:darkness) or short day (10:14 h) photoperiods. No circadian fluctuations in the distribution or the intensity of immunostaining were found in the pseudergates and soldiers that were sacrificed in 4h intervals or in the male and female substitutive reproductives examined in 6h intervals.

Feeding preference of Coptotermes formosanus (Isoptera: Rhinotermitidae) for gamma-irradiated wood impregnated with benzoylphenylurea compounds under laboratory conditions.

The feeding preference of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) for 200-kGy gamma-irradiated Cryptomeria japonica D. Don (Japanese cedar) sapwood impregnated with benzoylphenylurea compounds such as hexaflumuron and noviflumuron was examined by three laboratory tests. Although termites were not deterred from feeding on gamma-irradiated wood samples that had been impregnated with hexaflumuron or noviflumuron, termite mortality was significantly higher compared with solvent controls in the no-choice test. All live termites were transferred to paper disks immediately after the no-choice test to investigate changes in mortality with time, and this test also confirmed the effects of hexaflumuron and noviflumuron on worker termites, which showed a significant feeding preference for gamma-irradiated wood. Only the 1480 ppm noviflumuron-impregnated gamma-irradiated wood specimens showed significant differences in mortality in the two-choice test. These results suggest that gamma-irradiated C. japonica wood, which is locally abundant in Japan, may have potential as a bait substrate for benzoylphenylurea compounds.

Molecular and biochemical markers for monitoring dynamic shifts of cellulolytic protozoa in Reticulitermes flavipes.

Lower termites rely on cellulolytic protozoa to aid in the digestion of their wood-based diet. However, despite the major contribution of protozoa to the lower termite digestive system, few techniques have been developed to monitor shifts in protozoan populations. This study investigated whether quantitative real-time PCR (qRT-PCR) and/or cellulase enzyme assays can be used to monitor changes of cellulolytic protozoan populations in the lower termite, Reticulitermes flavipes (Kollar). Previously developed cellulase primer sets were used to test for changes in cellulase gene expression, while three different cellulase enzyme assays were used to assess changes in cellulase enzyme activity. The results from this study indicate that qRT-PCR is a reliable method to monitor shifts in cellulolytic protozoan populations. Specifically, qRT-PCR can serve as a useful monitoring technique during high-throughput screening of novel termite control agents such as cellulase inhibitors, and help to answer questions relating to whether or not such control agents impact cellulolytic protozoan populations.