Plants use many strategies to protect themselves against insects. Morphological, anatomical, and chemical plant properties play an important role in natural plant resistance to herbivore insects. The effects of triticale genotypes with different wax covers at various growth stages was studied on the fecundity and survival of the grain aphid Sitobion avenae (Fabricius) (Hemiptera: Aphididae). The aphids that fed on the organs of the waxless genotypes survived longer and produced signifi cantly more nymphs. Furthermore, mortality of nymphs on the waxy plants was significantly higher than on waxless plants. The chemical analysis also showed that the waxless plants had lower levels of flavonoids in comparison with waxy plants. Waxless seedlings had lower levels of flavonoids at every studied organ. The obtained results indicate that the level of flavonoids might play an important role in the resistance of winter triticale genotypes to grain aphid. The content of flavonoids was associated with the values of resistance between the waxy and waxless plants. It was concluded that the waxy plants that contained high levels of flavonoids were less preferred by the grain aphid.ces, which indicated no signifi cant change in either periphyton or macrozoobenthos following such episodes.