Through a joint SASEX/CIRAD, project the effect of Eldana saccharina Walker (Lepidoptera: Pyralidae) damage on stalk yield components was studied in fields at the SASEX farms at Gingindlovu and Empangeni. The formal experiment design consisted of randomised plots to compare natural infestation, artificial infestation and chemical treatments. Damaged stalks from infested plots had lower sucrose, higher fibre and lower stalk mass levels than treated plots. Stalk length and other parameters were also affected, particularly at Gingindlovu, where the level of damaged internodes reached 18%. The relationship between damage level and various other stalk components was also investigated. Stalk weight, stalk length and sucrose parameters were negatively correlated with percentage internodes bored. Increased fibre content, resulting in less juice, was positively correlated with the damage. Results are generally consistent with past studies and with other methods used to assess loss. Information on the effect of stalk mass and height in damaged sugarcane was obtained for the first time in this study. [Author's abstract]