Fusarium wilt: how to recognise and treat it

Disease

Symptoms

Wilting and yellowing that often starts on one side of the plant, a branch or even a leaf; lower leaves yellow first.
At first the plant seems to recover overnight, but the wilt soon becomes permanent; growth is stunted and few fruits form.
A cut stem shows brown or reddish-brown water-conducting tissue — lines lengthways, dots or a ring in cross-section.
White, pink or orange fungal growth may appear on dead stems in wet weather; the whole plant usually dies.

There is no cure — remove and dispose of affected plants, including roots, as soon as possible.
Do not grow the same kind of plant in that soil for at least 4–5 years, or replace the soil or grow in raised beds with clean soil.
Dispose of pots that held infected plants, or clean them with a disinfectant along with benches and capillary matting.

There is no fungicide for gardeners that cures or controls Fusarium wilt; rely on resistant varieties and rotation.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Grow resistant varieties (tomato labels marked F or FF) or tomatoes grafted onto resistant rootstocks.
Buy seed, cuttings and young plants from a reliable, disease-free source.
Rotate crops for 3–5 years; the fungus survives in soil for many years, but each strain attacks only its own plant group.
On acid soil lime to pH 6.5–7.0, use nitrate rather than ammonium nitrogen and avoid overfeeding; solarise the soil before planting.

Figures checked against these sources.