Verticillium & fusarium wilt

Verticillium dahliae, V. albo-atrum and Fusarium oxysporum

also called Verticillium wilt, Fusarium wilt

Soil fungi block the plant’s water vessels: one-sided wilting and brown streaks inside cut stems. There is no cure — remove the plant, rotate, and choose resistant varieties.

Fungus No cure Soil-borneSeed-borneSpread on tools & hands Spreads to neighbors

What you'll see

Slice a stem or a branch lengthways and there are brown or grayish streaks in the ring of water-conducting tissue just under the skin.
Wilting affects one side of the plant, or one branch, while the rest looks well.
Leaves yellow from the bottom upward, often in a wedge shape from the midrib, and hang on rather than dropping.
The plant wilts in the heat of the day, recovers overnight, then stops recovering.
Roots look sound and the soil is moist, which rules out root rot and simple drought.

Why it happens

Two unrelated groups of soil fungi that enter through the fine roots and grow up inside the xylem, the plant’s plumbing. The plant seals off infected vessels to stop the spread, and it is that blockage, as much as the fungus, that causes the wilt. Both persist in soil for years — Verticillium as tiny resting structures, Fusarium as thick-walled spores — and both can travel on seed, on tools and in soil on boots.

Verticillium prefers cool soil and shows in late spring and autumn; Fusarium prefers warm soil and shows in high summer, particularly under glass. Both are worst where the same crop has been grown repeatedly and where plants are stressed by drought or heavy nitrogen.

Treating it

There is no cure. Lift and destroy affected plants with as much root as you can, and do not compost them.
Clean tools, boots, canes and pots thoroughly afterwards so it is not carried to fresh ground.
On a woody plant showing only one affected limb, cut it out well below the staining and feed and mulch generously — some trees wall it off and recover for years.
Do not replant the same family in that ground; move the crop and use a container of fresh compost instead.
Where beds are badly infested and cannot be rotated, grafting tomatoes and aubergines onto resistant rootstocks is the practical answer.

Keeping it away

Grow resistant cultivars — tomato seed marked V and F resists Verticillium and Fusarium respectively.
Rotate susceptible crops on a long cycle and avoid following tomato with potato or aubergine.
Grow in fresh compost, in containers or growbags, where the ground is known to be infested.
Buy clean stock and clean seed, and never move soil between an affected and a clean bed.
Keep plants steadily watered and moderately fed; stressed plants succumb soonest.

Who gets it

Tomatoes, aubergines, strawberries, dahlias, asters, peas and beans among vegetables and flowers, and maples, catalpa, cotinus and olives among woody plants.