Codling moth has one complete and one partial generation per year in southern Britain, though two generations occur in hot summers.
- The first, stronger generation, occurs between mid May and late July.
- The second generation occurs between August and October, and though damaging to the crop, does not contribute to the following year’s population.
- Adults fly at and after dusk on warm evenings at temperatures >15 degrees C.
- Eggs are laid singly on foliage of fruitlets. They hatch 10-14 days depending on temperature. Egg development takes 85.5 +/- 8.9 degree days above a threshold of 10 degrees C.
- Larvae invade fruit (see ‘Damage’) and pass through 5 instars becoming fully grown in about 4 weeks.
- Larvae vacate fruit and spin cocoons under loose bark, in cracks in the trunk or supporting stake etc. or in dead plant material in the ground cover.
- Most larvae over-winter in their cocoon and pupate in Spring, but those that spin by the end of July may pupate and produce a second, usually partial, generation of adults in August and early September.
- Late-developing larvae still inside the fruits after harvest often form their cocoons in cracks in apple bins or other places in fruit stores and pack-houses.