Histopathological Effects of Gamma Radiation on the Digestive Tissues of Fifth-Instar Larvae of Ectomyelois ceratoniae (Lepidoptera: Pyralidae): Implications for the Sterile Insect Technique

Ectomyelois ceratoniae (Zeller), the date moth, is a major pest of date palm (Phoenix dactylifera L.), responsible for severe post-harvest losses in arid and Mediterranean regions. The Sterile Insect Technique (SIT) is an environmentally friendly control method whose effectiveness depends on selecting irradiation doses that ensure sterility while preserving insect quality. This study evaluated the histopathological effects of 60Co gamma irradiation on the digestive system of fifth-instar larvae of E. ceratoniae. Larvae were exposed to doses of 0 (control), 250, 300, 350, and 450 Gy, and the mesenteron, proctodeum, and Malpighian tubules were analyzed using Mallory’s trichrome staining. Quantitative measurements included epithelial thickness, intestinal stem cell density, Malpighian tubule diameter, and a histological integrity index. Gamma irradiation induced pronounced dose-dependent alterations. These included thinning and disorganization of the intestinal epithelium, a marked reduction in stem cell density, swelling of Malpighian tubules, and a progressive loss of tissue integrity. Severe degeneration and functional collapse of digestive tissues were observed at doses ≥ 350 Gy. The results indicate that 300–350 Gy represents a critical irradiation range inducing irreversible digestive damage compatible with effective sterilization. These findings provide histopathological reference criteria for optimizing dose selection and quality control in SIT programs targeting E. ceratoniae.