Toxicological and Ultrastructure Studies in Control Greater Wax Moth, Galleria mellonella (L.), Using Gamma Radiation and/or Emamectin

The effect of two substerilizing doses of gamma radiation (80 and 160 Gy) and/or emamectin benzoate at different concentrations and the LC50 value on the greater wax moth Galleria mellonella L. larvae was studied. The amount of food consumed at the different treatments was also evaluated. Obtained results indicated that the maximum mortality percentage recorded was (95.87%) corresponding to 50 ppm of emamectin benzoate. The combined treatment of LC50 and 160Gy increased the larval mortality percentage to reach (95.7%), i.e. this combined treatment had a greater effect against G. mellonella than the application of each one alone. The results indicated that antifeedant activity increased by increasing the combined gamma radiation dose where the maximum antifeedant percentage (84.79%) was corresponding to the treatment of LC50+160Gy. This antifeedant activity may be due to the effect of these treatments on larval mouth parts and its associated sensilla, so an ultrastructure study of mouth parts and its sensitivity was done using a scanning electron microscope (SEM.). The SEM study revealed that different malformations or abnormalities were observed in mouth labium, labrum, mandible and maxillae in the form of shrinkage in these parts, malformation at its edge and even malformation in shape. Also, the mouth parts associated sensilla were malformed and these malformation features were correlated with gamma dose applied. These malformations ranged from twisted, bent, impaired, shrinkage, grooved base or falling of sensilla, leaving their position empty and the area became bare. These different abnormalities or malformations to mouth parts and their sensilla will indirectly lead to larval death as they fail to ingest food.