Apple tree diseases and pests

Apple Scab

Apple scab is a disease caused by a fungus, which develops mainly in a humid, mild climate, as in Brittany and Normandy. It is one of the diseases commonly observed on apple trees.

Symptoms

Olive-brown spots appear on the leaves, then on the fruits which take on a cracked appearance. On the shoots, black spots and lifting of the bark can be observed.

Prevention

In autumn, prune the shoots whose bark appears to be peeling.
There are preventive treatments based on talc or willow bark infusion to prevent apple scab.

Treatment

In case of infection, copper- or bicarbonate-based treatments can be used. Also remove diseased leaves, shoots and fruits from the bush or those fallen to the ground.

For further reading, consult our advice sheet on Apple scab.

An apple affected by apple scab

Moniliosis

Moniliosis is also a fungal disease that affects the leaves, twigs and flowers and causes apples to rot.

Symptoms

Cankers appear on branches. Fruits appear desiccated and mummified.

Prevention

Spray a copper-based product such as Bordeaux mixture or nettle manure (15 g per litre of dried nettles).

Treatment

Collect and destroy diseased fruits, leaves and branches. Bordeaux mixture sprays can also be used to treat the disease.

For further reading, see our advice sheet on the moniliosis.

Moniliosis on apple

Powdery mildew

Also called the ‘white disease’, powdery mildew is also caused by fungi.

Symptoms

Powdery mildew is characterised by the appearance of a white, powdery coating on leaves, shoots and buds. The foliage may also become deformed and fall off.

Prevention

Powdery mildew develops in a confined, humid and warm atmosphere. To prevent it, promote good air circulation, prune and remove affected parts. As preventive treatment, sprays of horsetail decoction.

Treatment

Remove the parts affected by powdery mildew. To treat, you can use sprays containing sulfur, baking soda, or garlic macerated in oil.

For further reading, consult our advice sheet on powdery mildew.

A leaf affected by powdery mildew

Codling moths

These are butterflies that lay eggs in apples, which become wormy.

Symptoms

Fruits drop early and contain pinkish-white caterpillars. Small holes may be observed in the apples, with sawdust indicating the entry to tunnels dug by the caterpillars.

Prevention

To limit codling moth caterpillar proliferation, install a pheromone trap at the end of May that will catch male codling moths. Another option, install undulate cardboard around the trunk in mid-June, in which the larvae will shelter. You can then destroy this cardboard.

Treatment

Remove affected fruit. Lime-wash the trunk in winter to eliminate codling moth larvae.

Codling moths lay eggs in apples

Aphids

Several types of aphids can attack apple trees: these are green aphids, brown woolly aphids and ash-coloured aphids.

Symptoms

These small green, brown or ash-coloured insects suck the sap from new shoots and leaves, causing them to deform. With green aphids, sooty mould may appear, a blackish coating. With woolly aphids, a white and cottony substance may be observed.

Prevention

Introduce natural predators of aphids such as ladybirds or lacewings into the garden.

Treatment

In winter, apply a treatment based on rapeseed oil to bare shoots. In autumn, lime the apple tree trunk. This will help to eliminate aphids (as well as any other potential pests) that overwinter in the tree.
Placing a glue collar around the trunk at the start of spring helps trap ants that farm aphids and thus limit their development.

For further reading, see our advisory sheet: ‘Aphid identification and treatment’.

Cankers

Cankers that appear on branches and trunks can be caused by bacteria or fungi. It is a common disease in fruit trees that are often pruned, injuries providing an entry point for contamination. It blocks sap flow and leads to the death of various parts of the apple tree.

Symptoms

Cankers appear as peeling or drying of the bark on the trunk and on the shoots. Brownish spots appear, followed by swellings, cracks and necrosis, followed by gum exudation.

Prevention

Prevention involves eliminating the factors that allow cankers to develop: injuries from pruning branches, drought stress, poor root nutrition, soil compaction.

Treatment

Cut diseased shoots with a tool previously disinfected with alcohol and burn them.
Cure cankers that cannot be cut with a metal brush or a disinfected knife and smear the wounds with fungicidal and wound-healing putty.
Spray on the entire tree with Bordeaux mixture.
Carry out copper-based sprays before, during and after leaf fall, as growth resumes.

For more information, see our advice sheet on Tree and Fruit Tree Canker.

Canker

Scale insects

Mealybugs are tiny insects that feed on sap.

Symptoms

There are small waxy or mealy protrusions, brownish or grey, that are immobile.

Prevention

The presence of natural predators, such as ladybirds, lacewings and hoverflies, helps prevent mealybug infestations.

Treatment

To combat mealybugs, spray a solution: mix in 1 litre of water one teaspoon of liquid black soap, one teaspoon of denatured alcohol and one teaspoon of rapeseed oil. Spray onto the affected areas.

For more information, see our care sheet: Mealybug: identification and treatment.

mealybugs

fire blight

Fire blight is a serious disease that can affect certain apple tree species. It spreads rapidly.

Symptoms

Leaves turn black as if they had been burnt by fire. You may also see a sticky white ooze on the bark.

Prevention

Remove the affected parts promptly and with sterilised tools.

Treatment

If the entire bush is diseased, it is best to pull it out and burn it. Notify your local council or the Regional Plant Health Service of the fire blight outbreak.

For further reading, consult our advice sheet: Fire blight: prevent and control this disease.

Other pests can affect apple trees, such as caterpillars, red mites, apple curculio (Anthonomus) and Hoplocampa sawflies.

Additionally, explore our guide: Identify the main pests and diseases of plants, as well as our comprehensive guide on the apple tree planting and care.

Symptoms of fire blight