Garden
Plant Problems
Fusarium Wilt: The One in Your Tomato Bed Cannot Touch Your Beans
One side of the plant yellows and wilts while the other looks fine, and a cut stem shows a brown ring inside instead of ivory. The important part: each fusarium wilt attacks one kind of plant. The one that killed your tomatoes cannot infect beans, lettuce or corn. Plant a resistant variety, and use that bed for something else.
What you are looking at
Two signs, and the second one is the confirmation.
The wilting is lopsided. UC IPM describes plants that "turn yellow starting with one side or branch and gradually spreading through the plants, eventually killing them." A whole plant flagging evenly in the afternoon is usually thirst. One branch yellow and limp while the branch beside it looks well is a vascular disease, and that asymmetry is the tell.
Cut the stem across, low down. Just under the skin is a ring of water-carrying tissue that should be pale, near ivory. In an infected plant it is browned — UC IPM's "browning of the water-conducting tissue." That is the fungus blocking the plumbing, which is why the leaves above it behave like a plant that cannot drink.
You need a clean cut and decent light. The ring is thin, and on a young stem it is a thread rather than a band.
The part that changes what you do next
Most people meet this disease and conclude the soil is finished. It is a reasonable thing to think and it is wrong, and the correction is one sentence from UC IPM's own tomato page:
"Disease is caused by a fungus that infects tomatoes only."
NC State states the general rule: "Fusarium species are often host-specific, attacking only a single host species or group," and gives the scale of it — "Examples in North Carolina include wilts of blackberry, tomato, eggplant, pepper, watermelon, soybean and ornamentals."
So there is no such thing as "fusarium in my soil" in the way people mean it. There is a tomato fusarium, and a watermelon fusarium, and a pea fusarium, and they are not interchangeable. The one that took your tomatoes out last August is still in that bed and it cannot do anything to beans, lettuce, corn, brassicas or carrots.
That is the difference between losing a crop and losing a bed. It also means "fusarium wilt" is not really one disease — it is a family of host-locked diseases that look alike and share a name, which is worth knowing before you read a page that treats them as one thing.
And you cannot tell it from verticillium by looking
This page will not pretend otherwise. UC IPM: "Verticillium and Fusarium discoloration are extremely difficult to distinguish, although Fusarium discoloration tends to be darker."
Both cause "leaf yellowing and discoloration of the water-conducting tissues." Both are soil fungi. Both block the plumbing. The darker browning is a lean, not a diagnosis, and any page that hands you a confident visual test for telling them apart is claiming more than the source does.
The good news is that it mostly does not matter for what you do next, because verticillium is host-specific in the same broad way and the response is the same either way: resistant varieties, and grow something unrelated in that ground. If you genuinely need the name — you are deciding on a long rotation, or a perennial — a lab test on a sample is the only honest way to get it.
What to do about it
Four steps. The third is the one that saves you a season.
- Cut a stem and look for the brown ring. Low on the main stem, a clean cut across. Pale ivory ring means look for another explanation. A browned ring means a vascular wilt, which is either fusarium or verticillium.
- Do not try to name which one. UC IPM calls the two extremely difficult to distinguish, with fusarium tending darker. That is as far as the evidence goes, and it is far enough — the response is the same for both.
- Work out what you can still plant there, which is most things. The fungus is locked to its host. A bed that lost tomatoes to fusarium will grow beans, corn, lettuce, brassicas, onions, carrots and squash without any trouble from it. Move the tomatoes; do not abandon the bed.
- Buy resistance next spring. UC IPM's first recommendation for tomatoes is planting resistant varieties, which are indicated by the letters F or FF after the variety name — FF meaning resistance to two races. This is the single most effective thing available to a home gardener, and it costs nothing extra at the point of buying seed.
There is no cure for an infected plant. Nothing you spray reaches a fungus inside the water-conducting tissue, and the plant that is wilting now will not recover. Pull it, and get the residue out of the bed rather than composting it.
For a bed you must reuse for the same crop, UC IPM also mentions removing residue and soil solarization before planting. Both are real, both are work, and both are second-best to simply growing that crop somewhere else for a few years.
Why it does not go away on its own
UC IPM notes the fungus makes "resistant structures that can survive in the soil in the absence of a living host." It does not need your tomatoes in order to wait for your tomatoes.
That is the argument for treating this as a permanent feature of that bed rather than a bad year. It is also, read the other way, the argument for the host-lock being useful news: the thing waiting in that soil is waiting for one crop, and you have a whole garden of others.
What this page cannot tell you
How many years it survives. UC IPM says the resistant structures persist in the absence of a host and does not put a number on it on the page we are citing, so we are not going to either. Rotation advice that names a specific number of years is common and we have not found it sourced for home gardens.
And which crops in your garden have their own fusarium. We hold this problem against 19 crops in our database, but that record is attached to a page written about tomatoes — which is exactly the trap this page is about. Treat the tomato detail here as sourced and the rest as the general principle, sourced separately to NC State.
Questions about fusarium wilt
If I had fusarium wilt in a bed, can I plant tomatoes there again?
Not the same variety, and not soon. The fungus makes resistant structures that survive in the soil without a host, so it will still be there waiting. Your options are to grow tomatoes elsewhere, or to grow a variety marked F or FF, which UC IPM gives as the primary control. Everything that is not a tomato can go in that bed straight away — the fungus that causes tomato fusarium wilt infects tomatoes only.
Is fusarium wilt in the soil dangerous to the rest of my garden?
No, and this is the most useful thing on this page. NC State: 'Fusarium species are often host-specific, attacking only a single host species or group.' The strain that killed your tomatoes cannot infect beans, corn, lettuce, brassicas, onions or carrots. There are other fusarium wilts — of watermelon, pea, eggplant and others — but they are different fungi with their own hosts, and having one does not give you the others.
How do I tell fusarium wilt from verticillium wilt?
By eye, you mostly cannot, and be suspicious of any page that says otherwise. UC IPM calls the two 'extremely difficult to distinguish,' noting only that fusarium discoloration 'tends to be darker.' Both yellow the leaves and brown the water-conducting tissue. The practical answer is that it rarely matters: both are soil fungi with no cure for an infected plant, and the response — resistant varieties, and grow something unrelated there — is the same. A lab test is the only reliable way to name it.
Can I spray anything to save a plant with fusarium wilt?
No. The fungus is inside the water-conducting tissue of the stem, and there is nothing a home gardener can spray that reaches it. A plant showing the brown ring will not recover. Pull it out, take the residue away rather than composting it, and put your effort into the two things that do work: a resistant variety next time, and using that ground for a different kind of crop.
Sources
Every planting date, depth, and temperature on this page traces to these university extension guides. Where they differ, the ranges above hold the whole spread.
- University of California Statewide IPM Program (UC IPM) — Fusarium Wilt on Tomatoes — Home and Landscape
- NC State Extension — Fusarium Wilt of Blackberry
The short version: a brown ring inside the stem means a vascular wilt, there is no cure for that plant, and the bed is still good for everything that is not the crop you lost.
The one thing to buy next spring is a variety with F or FF after its name.