Diseases and pests of raspberries

Diseases caused by excessive humidity

Les springs and rainy summers tend to encourage the emergence of certain diseases. As the symptoms are quite similar, it can sometimes be difficult to identify them with certainty.

Grey mould or botrytis

Description

The fungus named Botrytis cinerea develops in warm, humid weather during spring and summer.

Symptoms

Brown spots are visible on the canes, especially around the buds. They become larger over time and turn silver-grey. Black dots then appear. Meanwhile, the leaves yellow, and all parts of the plant, including the fruits, become covered with a greyish fuzz.

Prevention

• Water without wetting the foliage
• Avoid nitrogen fertilisers
• Plant raspberry bushes every 80 cm and train the stems to promote good air circulation
• Be careful not to damage the canes, as botrytis develops on wounds
• Spray a garlic decoction made from 100 g of garlic infused in a litre of boiled water.
• Spray every 15 days with a horsetail manure to strengthen the plants

Treatment

A treatment with Bordeaux mixture can be considered in autumn and spring.

Raspberry rust

Description

This is also a fungal disease caused by Phragmidium rubi-idaei, which develops in spring and autumn, favoured by a combination of heat and humidity.

Symptoms

Orange to brown pustules appear on the stems and leaves. By late summer, these spots turn black, indicating that the fungus is releasing its spores to spread the disease. Eventually, the leaves fall.

Raspberry rust is identified by the black spots that follow orange spots

Prevention

• Water without wetting the foliage
• Disinfect pruning tools
• Spray horsetail manure or a garlic decoction
• Collect and burn fallen leaves

Treatment

• Remove affected leaves and stems at the first signs
• Spray Bordeaux mixture

Raspberry anthracnose

Description

This is a fungal disease visible in early summer, between June and July, which develops when the weather is warm and humid.

Symptoms

Leaves become covered with brown circular spots and then yellow. Sometimes, the fungus attacks the stems, which turn brown and break.

Prevention

• Spray nettle manure every 15 days until July
• Make a Bordeaux mixture spray in spring

Treatment

To combat anthracnose, the only solution is to burn all affected parts, including fallen leaves.

Fungal diseases primarily affect the foliage and stems of raspberries

Powdery mildew

Description

This is another fungal disease that develops in humid weather and is favoured by a large temperature range between day and night.

Symptoms

A white powder covers the leaves and stems. The leaves become crinkled and deformed.

Prevention

• Do not plant raspberries too closely
• Spray horsetail manure or a garlic decoction on the aerial parts

Treatment

• Spray Bordeaux mixture
• Burn the parts affected by the disease

Leptosphaeriosis

Description

This is a fungal disease caused by Leptosphaeria coniothyrium, a fungus active in summer and autumn.

Symptoms

The stems and young shoots dry out from the tip. Then the base turns yellow. The stem eventually breaks.

Prevention

Spray Bordeaux mixture or a horsetail decoction.

Natural treatment

• Water the soil with a garlic decoction
• Burn the affected stems.

Burning of darts (Didymella applanata)

Description

This is a disease caused by several fungi that affects raspberry plants in mid-summer and autumn. The fungus enters through cracks in the bark and wounds, overwintering on fallen canes.

Symptoms

Spots ranging from reddish-brown to purple appear on the stems, around the buds. The shoots dry out, and the stems grow poorly or not at all.

The burning of the canes significantly compromises fruiting

Prevention

• Ensure not to damage the stems
• Thin out the plantings in early summer
• Water regularly and limit nitrogen inputs.

Natural treatment

• Cut and burn the affected stems
• Treat with Bordeaux mixture at the start of stem growth.

The raspberry borer

Description

Known as Byturus tomentosus, this grey-brown beetle flies in May and June. In July, the female lays eggs on the flowers, giving rise to cream to yellow larvae that pupate in the fruits or on the bark. The insect overwinters in the soil.

The adult Byturus tomentosus feeds on the aerial parts of the raspberry plant, while the larvae consume the fruits.

Symptoms

The adult feeds on the aerial parts, buds, and green fruits, while the larvae indulge in the ripe fruits of the raspberry plant.

Prevention

• Hoe, rake, and weed the soil to dislodge the insect. Birds or your chickens will take care of eliminating it.
• Plant forget-me-nots between the raspberry plants.

Natural treatments

• Shake the stems to drop the insect and collect them by hand.
• A garlic infusion on flowering raspberries will repel the adults.

The anthonome of the raspberry bush

Description

It is a black beetle that lays eggs in May in flower buds. The white larvae pupate in the soil or in fallen flowers. The insect is only active at temperatures above 18°C. It overwinters in the soil.

Symptoms

The buds are cut, dry, or detach.

Prevention

Simply cover the soil, for example with ferns. A spray of wormwood manure is also effective.

Natural treatment

Collecting and destroying the affected flower buds is sufficient to limit damage.