Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plant: apple.
- Adult: reproduction is mainly parthenogenetic, unfertilised eggs giving rise to females.
- Fecundity: 30 eggs.
- Eggs: time until hatching, 8 to 18 days, according to temperature.
- Larva: 3.5 to 4 weeks.
- Pupa: 17 to 20 days.
- 1 generation per year, the life-cycle occasionally extends over 2 years.
- The adult appears in April/May in France, north of the river Loire. The female lays eggs on flowers in blossom (stages F2 to F4 (*) ), piercing the calyx beneath the sepals and depositing the egg at the base of the stamens (*) . The egg swells, causing epidermis of the receptacle to burst in such a way that eventually part of it projects from the calyx.
- The young larva digs a gallery along the underside of the epidermis, then burrows towards the centre of the apple (primary attack) (*) . It then attacks other apples (2 to 5), but by burrowing into the fruit directly (secondary attack). Leaving the fruit by a large hole with definite edges, it drops to the ground where it burrows to a depth of 5 to 10 cm and weaves a silky cocoon in which it remains in diapause for 9 to 21 months.
- Pupation in March.
Apple varieties with a large number of flowers in blossom during the laying period are preferred. White flowers are the most attractive. The fine superficial galleries trigger off the formation of characteristically shaped surface wounds (russeting) which deform the fruit (*) . When this occurs extensively on young fruit, they drop off in large numbers. The frass remains in the fruit and smells strongly of stinkbugs. Secondary attacks also cause the fruits to drop prematurely (*) .
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