Life cycle (Summer fruit tortrix moth)

• There are two generations per annum in the UK.
• Larval development has five instar stages.
• The pest overwinters as a second or third instar larva in a silken hibernaculum in crevices in the bark etc.
• There is often considerable winter mortality which is sometimes an important limiting factor in population development.
• After emergence in spring shortly after bud-burst, individual larvae feed amongst the buds, characteristically tying them and the rosette leaves together with webbing.
• On early apple varieties and on pears, larval feeding produces cavities in the receptacle, which later heal to form corky scars characteristic of early caterpillar feeding.
• Larvae pupate when fully fed, normally around blossom time of Cox.
• First generation adult moths emerge in June.
• Eggs are laid in batches on the foliage. These hatch in 7-10 days depending on temperature (see ‘Forecasting’).
• Cool and wet weather conditions at the time of moth flight and/or during egg-hatch limit population increase.
• Many larvae migrate to the growing points in shoots where they form leaf rolls.
• In July and August more mature larvae feed on fruits before pupation in August.
• A second generation of adults occurs in August and September, depositing eggs on leaves and also directly onto fruits.
• These hatch and the young larvae feed beneath silken webs spun on the under-surfaces of leaves, often at a junction between the main and a side vein.
• In late September and October, larvae have reached the second or third instar stage and migrate to crevices in the bark to overwinter.