The start of the flight of apple sawfly adults can be predicted using a temperature sum of 134 day-degrees above a threshold of 4 degrees C starting from 1 April.
- Soil temperatures at a depth of 5 cm must be used.
- Air temperatures are unreliable, though they can be used to predict the appropriate timing for trap installation for which the recommended temperature sum is 157 degree days above a threshold of 4 degrees C from 15 March.