Pests & problems

Apple pests and problems

A maggot, some spots, a woolly bit and a tree that only fruits every other year. Here’s what’s what, from the RHS.

Codling moth

The caterpillar of the codling moth, Cydia pomonella, is the classic “maggot” in a maggoty apple. RHS: Codling moth

Inside a codling-damaged apple you’ll find a tunnel to the core and the caterpillar’s droppings (frass). Damaged fruit tends to ripen and drop early. RHS: Codling moth

Codling moths come out in late May and June and lay eggs on or near the young fruit until mid-July. Each caterpillar feeds in the core for about four weeks. RHS: Codling moth

Pheromone traps, put up in May, catch male codling moths. On their own they rarely control the moth, but they show when it’s about. RHS: Codling moth

An apple cut in half, showing a brown tunnel to the core and a small caterpillar inside — A codling moth caterpillar inside an apple (Doug Wilson, USDA Agricultural Research Service).Photo: Doug Wilson, USDA Agricultural Research Service, Public domain, Commons

Apple scab

Apple scab is a fungus, Venturia inaequalis. It makes olive-green blotches on leaves and dark, scabby patches on the fruit. RHS: Apple and pear scab

A light attack of scab only marks the skin, and the apples eat just as well. RHS: Apple and pear scab

Scab survives the winter on fallen leaves, so clearing them up helps. RHS: Apple and pear scab

Scab-resistant apples include ‘Discovery’, ‘Charles Ross’, ‘Ellison’s Orange’, ‘Lane’s Prince Albert’ and ‘Emneth Early’. RHS: Apple and pear scab

A yellow apple with a dark, rough, scabby streak down its skin — Apple scab on the fruit (Fructibus, CC0).Photo: Fructibus, CC0, Commons

Apple canker

Apple canker, caused by the fungus Neonectria ditissima, makes sunken patches of dead bark on branches. It’s worse on wet, heavy soils. RHS: Apple canker Apples prone to canker include ‘Cox’s Orange Pippin’, ‘James Grieve’ and ‘Spartan’. RHS: Apple canker

Woolly aphid

Woolly aphid, Eriosoma lanigerum, covers patches of trunk and branches in fluffy white wax, and its feeding causes soft, lumpy growths in the bark. RHS: Woolly aphid

Earwigs on fruit trees can cut aphid numbers. A flower pot loosely stuffed with hay, hung in the tree, gives them a home. RHS: Woolly aphid

An old scientific drawing of a winged aphid with its wings spread, seen from above — A winged woolly aphid, drawn by Herbert Osborn.Art: Herbert Osborn, Public domain, Commons

Brown rot

Brown rot spreads out from wounds in the fruit, especially ones made by birds, codling moth and scab. It often shows as buff-coloured pustules in rings. RHS: Brown rot

Shrivelled “mummified” fruits left on the tree carry brown rot, so prune them out and bin or burn them. RHS: Pruning apples made easy

Bitter pit

Bitter pit, dark spots on apples late in the season or in store, is linked to a lack of calcium in the fruit, often after dry soil. RHS: Bitter pit in apples

One year on, one year off

Some apples, such as ‘Bramley’s Seedling’ and ‘Blenheim Orange’, tend to crop heavily one year and hardly at all the next. This is called biennial bearing. RHS: Biennial bearing

Not problems at all

In early summer trees shed some young fruit by themselves. This is the “June drop”, and it’s normal. RHS: How to grow apples

Grey-green crusty growths on the branches are lichen, which does the tree no harm. RHS: Pruning apples made easy

Next: apple history →