Rosy leaf curling aphid
Rosy leaf curling aphid is a widely distributed but localised minor pest of apple.
Infestations occur on the same trees (often older trees with rough bark) year after year and spread from tree to tree is slow. The life cycle involves overwintering on the tree as eggs.
Some apple varieties, including Cox, Ashmead’s Kernal, Fiesta, Fortune, Gala, James Grieve, Kidd’s Orange Red, Lord Lambourne, Merton Worcester, Sunset, Suntan and Winston are resistant to rosy leaf curling aphid. Others, notably Elstar, Falstaff, Idared, Golden Delicious and Worcester Pearmain, are highly susceptible. Bramley is moderately susceptible.
The aphid hatches in April at early green cluster from overwintered eggs on the bark and infests the rosette leaves which then curl and develop the characteristic red colour.
The severity of infestation by rosy leaf curling aphid should be determined in each orchard when pre-blossom pest assessments are done at green cluster. At least 25 trees should be inspected for presence/absence of the pest, concentrating on localities where the pest was seen the previous year.
It is hard to distinguish between the rosy leaf curling aphid and the rosy apple aphid but the latter does not cause the characteristic bright red coloration of leaves caused by the rosy leaf curling aphid.