Verticillium wilt

Which species are susceptible to Verticillium wilt?

In vegetable gardens, aubergines, tomatoes and sometimes even peppers suffer damage from this fungus. Cases are also found on melon and artichoke.

In ornamental gardens, the disease affects many plants such as asters, delphiniums, phlox, carnations, peonies, oxeye daisies, pelargoniums, dahlias…

But also trees such as apricot tree, olive tree, peach, almond, catalpa, Japanese maple, beech, elm, sumac, Chamaecyparis and bushes such as rose bushes, lilacs and even weeds (amaranth, plantain, goosefoot…)

How to recognise Verticillium wilt?

In vegetable garden (tomatoes, aubergines, potatoes…)

The first symptoms appear on lower leaves with areas, often over half the lamina and on the edges, which soften, become duller, then yellow before browning and undergoing necrosis. Leaves curl while remaining attached to stems. These signs are usually seen when the first fruits on vegetable plants begin to swell. Disease progresses from bottom to top of plant. In chrysanthemum, this leads to generalised dwarfism of the plant.

On trees

Sudden wilting of shoots in summer can be due to verticillium wilt in apricot trees.

Verticillium damage on purple maple

In Catalpa or Japanese maple, one often observes branches wilting one after another, but the plant usually manages to contain the fungus after renewing its sapwood. Cut an affected branch: presence of very dark brown striate streaks just under the bark confirms fungus presence in the sapwood.

→ To learn more about verticillium wilt of Japanese maple, see our advice sheet: “Japanese maples: beware verticillium wilt“

Factors favouring verticillium wilt

Verticillium dahlia persists in soil as microsclerotia for up to 14 years even when conditions are unfavourable. Under fairly cool temperatures between 16 and 25°C and in moist soil, these microsclerotia germinate on contact with roots of tomatoes or aubergines, producing mycelial filaments that penetrate inside roots through tender or slightly wounded areas or at the collar or base of stems. The mycelium reaches the vessels and slows sap circulation. It is in soilless cultures that the disease is most frequent.

When soil temperature exceeds 28°C, the fungus responsible for fusarium wilt is favoured and causes general wilting of the plant. Verticillium wilt therefore affects earlier varieties more and may regress in warm weather, with resumption of plant growth.

Control and treatment of verticillium wilt

In vegetable garden

Aubergines are most susceptible to Verticillium wilt because no tolerant variety exists. However, young plants grafted onto tomato can therefore become immune to the fungus provided graft union is not buried.

In tomatoes, modern varieties are mostly tolerant to Verticillium wilt thanks to addition of gene “Ve”. It is therefore early heirloom tomatoes that cause problems in spring or autumn unless grafted onto resistant rootstocks.

• Cut basal leaves that begin to yellow, thoroughly disinfecting your tool with vinegar for example.
• Pull up entire young plant; do not put it in compost and replace soil to avoid recontamination by spores.
• Practice crop rotation with cycles of at least 3–4 years because fungus can persist several years in soil.
• Create a healthy environment for roots by lightening soil with organic matter or sand.
• Avoid treading and using heavy machinery such as rotavators too often, as they create a plough pan that prevents water from draining deeply.
• Treat sensitive plants preventatively with nettle manure, horsetail decoction or garlic decoction.
• Avoid excess nitrogenous fertiliser.
• Remove weeds, particularly dicotyledons (everything except grasses and bulbs), which often harbour Verticillium in vegetable garden.
• Plant in vitro-grown young plants certified as disease-free.

On fruit and ornamental trees

• If soil is heavy and wet, plant trees on a mound or along a slope to ensure good drainage at root level.
• Do not overwater; a generous watering once a week in summer usually suffices, 1–2 times per week if bush is potted.
• Prune dead shoots but do not cut back to healthy wood, which has probably established strong mechanical and chemical barriers (CODIT compartmentalisation) at boundary with infected tissues.
• Avoid injuring roots or bark of tree.
• Spray Bordeaux mixture or another fungicide onto collar and trunk bark.

• Add a good amount of compost to help tree rebuild its branches.
• You can pour onto soil from a watering can a solution of 10 drops of pure bleach per 10 litres of water (do not overdose, which would kill your young plant) to sanitise the soil.
• If tree dies, avoid planting another susceptible young plant.