The effect of temperature on the duration of larval, prepupal, and pupal development of the European leaf roller, Archips rosanus L. (Lepidoptera: Tortricidae) was studied at four constant temperatures (18, 22, 26, and 30°C) where Malus communis L. (apple, Stark Crimson) was used as food. Significant positive linear relationships were observed between development rate and temperature for all life stages. Minimum developmental threshold temperatures were estimated as 5.5–6.7°C for first stages, 5.8–5.7°C for second stages, 5.1–6.3°C for prepupae, and 8.1–6.3°C for pupae, male and female, respectively. Lower threshold of complete development of adult was estimated as 6.05°C (male) and 6.0°C (female). Median development values of degree-days (DD) for first stages, second stages, prepupae, pupae and complete preimaginal development were 57.5–55.2, 55.2–66.2, 33.1–33.9, 137–175.4 and 476.2–526 for male and female, respectively. A degree-day model was developed using from the laboratory data for predicting the first emergence of the pest and spray application time. Estimated degree-day model predicted the emergence within 3–7 days of that observed at the field site in both 2001 and 2002. Accordingly, the degree-day model will be useful to predict the first emergence dates, optimum spray period and to provide a starting point to catches in pheromone traps in the summer for A. rosanus.