The development of the lesser appleworm, Grapholita prunivora (Walsh), was studied using immature apples as the food source. Degree-hour developmental rates for all life stages were calculated. Developmental rates in degree-hours at 25°C for the eggs, four instars, pupae, and adults were 1,503 (4 d), first larval ecdysis 1,109 (3 d posthatch), second larval ecdysis 1,941 (5 d posthatch), third larval ecdysis 3,186 (8 d posthatch), pupation 5,196 (13 d posthatch), and adult 8,925 (22 d posthatch), respectively. It was determined that 8.5°C was the lower thermal threshold for development of lesser appleworm eggs. Comparisons of growth, survival, and reproduction were made between two different laboratory populations, the wild type and a golden color sport (strain).