Ethephon (ETF) has been used in agriculture as an ethylene releaser type of plant growth regulator. The aim of this work was to determine the ecotoxicological effects of ETF on the survival and the antioxidant metabolism of the insects using a model organism Gafieria mellonella L. 1758. A toxicity test was performed to determine the lethal doses of ETF on larvae. According to probit assay, the LD50 and LD99 values for force fed larvae were 344 and 419 mu g/5 mu l, respectively, 30 d after treatment. Analyses performed with 10 doses <= LD50 at 24 and 48 h upon feeding larvae revealed that the malondialdehyde level increased at 300 and 330 mu g/5 mu l doses, whereas glutathione-S-transferase activity increased only with a 360 mu g/5 mu l dose of ETF at 24 h. However, an increase in glutathione-S-transferase activity was evident at all ETF doses at 48 h. An increase in glutathione peroxidases activity was determined at 250, 300 and 330 mu g/5 mu l at 24 and 48 h. All ETF doses caused an important increase in catalase activity at 24 h but remained unchanged at 48 h. Superoxide dismutase activity also elevated at doses >250 mu g/5 mu l at 24 h when compared to the control. Same changes in superoxide dismutase activity were also olorved at all doses of ETF except for 360 mu g/5 mu l at 48 h. These results showed that ETF induced oxidative stress resulted in toxic effects that affected on the survival of model organism G. mellonella.