Fusarium Wilt
Act nowFungal disease · does not spread
Fusarium is a soil fungus that enters through the roots and blocks the plant's water-conducting tissue, so the plant wilts even in wet soil. The one-sided yellowing is characteristic, and the stem cut is diagnostic. There is no cure once a plant is infected, and the fungus persists in the soil for years.
What it looks like
Yellowing and wilting that often affects one side of the plant, or one branch, while the rest looks fine. Slice the main stem lengthwise near the base and the tissue just under the skin is stained chocolate brown instead of pale green.
How to confirm it
- Cut the stem lengthwise: brown staining in the ring just under the skin confirms it.
- Yellowing and wilting often affects one side or one branch first.
- Wilting does not recover overnight, unlike heat wilt.
- Worse in warm soil, unlike verticillium which prefers cooler conditions.
What to do
- 1There is no treatment. Remove and bin the plant, roots included.
- 2Do not plant the same family in that spot again — the fungus survives for years.
- 3Grow in containers with fresh mix, or in a different bed, next season.
What it gets confused with
One observation settles each of these.
Verticillium usually shows V-shaped yellow wedges at the leaf edges and prefers cooler soil. Lab testing is needed to be certain, and the management is identical.
Bacterial wilt collapses the plant quickly with no yellowing, and a cut stem oozes sticky white threads in water.
A thirsty plant recovers within hours of a deep soak. A fusarium plant does not.
Preventing it next time
- Buy resistant varieties: the F, FF or FFF codes on a tomato label indicate fusarium resistance.
- Rotate crops on a long cycle and keep soil well drained.
- Clean tools between beds.
Plants affected
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.