Egg masses of Meloidogyne arenaria race 2 were observed on the second planting of oriental melon by the time of its first harvest under glasshouse conditions in Korea. Time and degree-days above 5°C (DD5) for egg mass formation after April were about 24.5 days and 500 DD5. Higher mean soil temperature shortened the days required for egg mass formation. A threshold temperature for degree-days accumulation of 12.2°C was selected on the basis of lowest coefficient of variation among data sets of time to egg mass formation. We propose the use of DD12.2 for predicting the time to egg mass formation of M. arenaria under these glasshouse conditions.