A study was conducted in 1992 at Highmoor Farm, Monmouth, ME to test the effects of fish hydrolysate fertilizer on fruit set, fruit size and fruit quality of apple. Mature, semi-dwarf `Delicious' and `Golden Delicious' trees received 2.76g/1 N, supplied by either fish hydrolysate fertilizer or urea, or received no fertilizer (control). Fertilizers were applied via three foliar sprays applied at seven day intervals, beginning at petal fall. Fish hydralysate fertilizer reduced fruit set of `Delicious' and `Golden Delicious'. Foliar urea increased fruit set and yield of 'Golden Delicious'. Neither fertilizer affected mineral nutrient concentrations of leaves collected in July. Fish hydrolysate increased fruit russeting on both cultivars. Fish hydrolysate is not recommended as a foliar fertilizer for apples.