Eggplant: diseases and pests

Downy mildew

Description

Downy mildew is a mycosis transmitted by the fungus Phytophthora parasitica that mainly develops during humid years. The fungus overwinters, and the disease spreads through spores carried by rain and wind.

Symptoms

Yellowish-white spots appear on the upper side of the leaves. They grow if a certain level of humidity is maintained. On the underside, a white, sometimes greyish-purple, fluff or down develops. The tips of the leaves eventually die off.

Prevention

• Avoid planting too closely to ensure good aeration of the aubergine plants.
• Avoid overhead watering and prefer watering at the base.
• Properly apply crop rotation.
• A spray of horsetail decoction, diluted to 20%, every 15 days or sodium bicarbonate (3 to 10 grams per litre of water).

Natural Treatments

• Remove diseased plants by burning them, including any fallen debris.
• A spray of Bordeaux mixture will help to slow the disease.

powdery mildew

Description

It is the fungus Leveillula taurica that causes powdery mildew on aubergine, a disease transmitted by rain and wind that carry the spores. It attacks the aerial parts of the plant, starting with the basal leaves. It can develop in dry weather.

Symptoms

Small white spots appear on the leaves, then the fungus invades the upper and lower surfaces of the leaves with a white mycelial felt. The leaves dry out prematurely.

The first signs of powdery mildew attacks are small white spots appearing on the leaves

Prevention

• Avoid planting too closely to ensure good air circulation between plants.
• Choose resistant varieties
• Avoid fertilisers that are too rich in nitrogen
• Avoid overhead watering

Natural Treatments

• Carefully remove affected parts
• Treat with a spray of diluted horsetail decoction at 20%.

Verticillium wilt or verticillium wilt disease

Description

Verticillium wilt is a disease to which vegetable plants in the Solanaceae family are highly susceptible, caused by the fungus Verticillium dahliae. As it affects the plant’s vascular system, the sap can no longer circulate. This is primarily a spring disease that occurs during fruit formation in humid conditions.

Symptoms

The basal leaves soften and wilt, then turn yellow, often on one side of the midrib. They then become beige to brown before completely undergoing necrosis. They remain attached to the stem.

Prevention

• Properly apply crop rotation
• Ensure good soil drainage
• Carry out preventive sprays of horsetail or garlic decoction
• Avoid excess nitrogen-rich fertiliser
• Thoroughly clean the soil of various crop residues, including weeds

Natural Treatments

• Systematically remove contaminated plants and burn them.
• Thoroughly disinfect tools that have come into contact with infested plants.

Alternaria blight or black rot

Description

Once again, the alternaria disease is caused by a fungus, more specifically Alternaria dauci. This fungus thrives in warm, humid conditions from April to October. It survives throughout the winter in plant debris in the soil and can persist for 6 to 7 years.

Symptoms

Round, brown then black spots appear on the leaves. The tissues dry out or rot depending on the weather. The leaves eventually fall off. The fruits are also affected: round, black spots emerge. They become increasingly larger and deepen.

Prevention

• Space the young plants to ensure better air circulation
• Properly implement crop rotation
• Avoid planting aubergines next to tomatoes and potatoes, which are also susceptible to alternaria disease
• Avoid overhead watering and prefer watering at the base
• Apply sprays of horsetail or garlic decoction every 5 days for 10 days.

Natural Treatments

• Carefully remove diseased aubergine plants by burning them
• Collect and destroy any plant debris left on the ground.

Grey mould or Botrytis

Description

Grey mould is a fungal disease caused by the fungus Botrytis cinerea. It thrives in conditions of high humidity and low light, often in greenhouses. It also affects weak plants.

Symptoms

A grey fluff develops on the affected organs, including stems, flowers, petioles of leaves, and fruits. The tissues die, and large brown-red spots appear on the leaves and fruits, which then perish.

Prevention

• Avoid excessive nitrogen fertilisation
• Ensure good soil aeration
• Avoid overhead watering
• Plant garlic between aubergine crops
• Apply horsetail decoction sprays

Natural Treatments

• Remove and burn all affected plants

Fruit anthracnose

Description

Fruit anthracnose is caused by the fungus Colletotrichum melongena and is favoured by humid weather.

Symptoms

Small cylindrical lesions appear on the leaves and black circular spots on the fruits. The leaves wilt and the fruits rot.

Prevention

• Remove plant debris from the soil
• Spray with horsetail decoction

Natural treatments

• Systematically remove contaminated fruits

Cercospora leaf spot

Description

Cercospora leaf spot is a fungal disease caused by the fungusCercospora melongenae favoured by high temperatures combined with the presence of moisture on the leaves.

Symptoms

Round spots appear on the leaves, brown in colour surrounded by a slightly yellowish halo. Gradually, the spots spread and the leaves yellow and progressively undergo necrosis.

Brown spots sometimes surrounded by a yellowish halo are characteristic of cercospora leaf spot.

Prevention

• Avoid overhead watering
• Collect all plant debris at the base of the aubergines after the harvest

Natural Treatments

• Pull up contaminated plants and burn them

Pests of the aubergine

Several pests or insects can attack the aubergine. Firstly, aphids have the ability to move from one species to another. These piercing and sucking insects feed on the sap of the leaves.

Aphids on the underside of aubergine leaves

In themselves, they do not pose a real danger to the plant, but they can encourage the development of sooty mould. Other pests are quite commonly found on aubergines:

Red Spider Mites

Description

Quite difficult to see, red spider mites are arachnids, specifically tetranychids, that appear with a warm, dry spring. They suck the sap from the plants they attack, generally concentrating under the leaves.

Symptoms

The leaves become covered with small yellow spots and then discolour to a silvery colour. Other leaves may be perforated or wilted. Very fine webs appear between the leaves.

Prevention

• Lightly mist the foliage regularly if the weather is very dry. Mulch the soil to maintain some moisture
• Spray a decoction of horsetail or nettle manure
• Limit fertilisers that are too rich in nitrogen
• Encourage natural predators such as lacewings or earwigs

Natural Treatments

• Spray diluted rosemary essential oil in water
• Apply a diluted garlic decoction at 30% on the plant
• Cut off infested leaves and burn them.

Leaf Miner

Description

These miners are fly larvae that burrow galleries in the foliage of aubergines. Egg-laying occurs in spring during mild weather. Once well-fed, the larvae transform into pupae and then into adults. And the cycle begins again…

Symptoms

The leaves are marked with white or brownish streaks. The leaves eventually curl, turn brown, and fall off.

Leaf miner larvae burrowing galleries in the leaves

Prevention

• Implement crop rotation
• Collect plant debris from the ground and weeds
• Remove affected leaves as soon as the first streaks appear

Natural Treatments

• Spray a decoction of tansy

Colorado Potato Beetle

Description

Both the adults and larvae of Leptinotarsa decemlineata eat the leaves and can consume the entire leaf surface of an aubergine in 2 or 3 days. By late September, the beetles hibernate in the soil, at a depth of 10 to 15 cm. They only attack solanaceous plants.

Symptoms

The leaves are eaten, and sometimes only the veins remain.

Prevention

• Implement crop rotation
• Plant beans or garlic near aubergines as they are excellent repellents against Colorado potato beetles

Natural Treatments

• Spray nettle, horseradish, or tansy manure
• Manually collect adult beetles and larvae