Gamma Irradiation as a Possible Phytosanitary Treatment against the Greater Wax Moth, Galleria mellonella, Mature Larvae

Larvae of greater wax moth, Galleria mellonella L., can be a devastating pest of honeybee combs in storage. Current control measures may not be adequate or with some drawbacks. Treatment with ionizing radiation could be a possible alternative. Determining the dose, however, requires a detailed study on the radiosensitivity of this stage.

In this study, the sensitivity of the greater wax moth mature larvae to ionizing radiation was examined. Larvae were exposed to gamma radiation dosages (50 to 400 Gy) and effects on rate of development, pupation and pupal eclosion (adult emergence) were investigated. In addition, large scale confirmatory tests were conducted to validate treatment efficacy at statistical confidence levels needed for phytosanitary (quarantine and disinfestations) security. Results showed that radiation sensitivity of G. mellonella mature larvae increased, as expected, with increasing radiation dose. The magnitude of the effect, however, depends on the criterion used for measuring effectiveness. Both pupation and pupal eclosion were significantly affected at 50 Gy dose and no emergence was recorded at 300 Gy. Results of large scale confirmatory trials (>30,000 mature larvae) supported the results of the small scale studies. According to probit analysis of dose mortality data for pupation and pupal eclosion, the LD99 for preventing development of mature larvae to pupae and adults is 576 and 318 Gy, respectively. In addition, the developmental rate of mature larvae to adults was negatively affected. This suggests that a dos