Relationships between leafhopper feeding and the resulting effects on forage grasses have not been well defined. Therefore, the morphological and physiological responses of Kentucky-31 tall fescue to various population densities ofForcipata locawere examined in a 2-year field cage experiment. The detrimental effect ofF. locaon tall fescue was reflected primarily in reduced forage quality rather than in yield reduction. Significantly higher neutral detergent fiber concentrations, significantly lower water-soluble carbohydrate concentrations, and significantly lower in vitro digestible dry-matter concentrations were observed. Increased fiber and decreased cell content reduced forage digestibility.