Sclerotinia is a minor disease that affects jerusalem artichoke in Scotland. Here is what it looks like, the conditions it needs, and the controls that actually work.
What does it look like?
Fluffy white fungal growth appears at the base of the plant or on affected tissue, with black, seed-like sclerotia, roughly 0.5 to 1cm across, forming within that white growth and inside hollow stem cavities where present.
What causes it
Wet weather is what lets the airborne spore stage infect a plant in the first place. Spores spread from around May onwards in wet conditions, a timing that lines up with Scotland's typically damp early summers.
Is this disease active now?
The infectious window opens in May and runs through the wetter months, with wilting and collapse most likely to actually show through summer and into early autumn.
Symptoms
Affected plants can go from healthy to sudden yellowing, wilting and collapse. At the base, the stem develops a soft, wet rot, often starting right at soil level.
Life cycle
The black sclerotia that form in infected tissue drop into the soil and survive there for up to eight years before germinatingA seed sprouting: breaking dormancy and putting out its first root and shoot, given the right warmth and moisture. Full definition →, usually after a winter chilling period, into small cup-shaped structures that release thousands of airborne spores. Less commonly, a sclerotium germinates directly in the soil and infects a plant through direct contact instead.
Why this matters in Scotland
An eight-year soil survival and spore spread from around May in wet conditions describe conditions a damp Scottish early summer meets easily. That figure comes from monitoring the fungus in commercial oilseed rape fields rather than vegetable gardens, though, which limits how directly it applies to a Jerusalem artichoke bed.
Sclerotinia is named as a host across a much wider range of vegetables generally, lettuce, peas, beans, celery, carrots, potatoes, tomatoes and cucumbers among them, which reads as if it should be a routine problem across half the vegetable patch. In practice it doesn't turn up as a real problem on any of those crops for Scottish growers. Jerusalem artichoke is the one exception, and even there RHS names only two problems on an otherwise trouble-free crop: this, and slugs and snails.
Controls: what actually works
All the methods below are backed by real evidence, not just repeated folklore.
Remove and destroy infected plants as soon as they're spotted, rather than composting them
An ordinary garden compost heap doesn't reach the temperature needed to kill the black sclerotia inside infected tissue, so composting an infected plant just spreads viable sclerotia back across the garden in next year's compost.
Avoid overcrowding susceptible plants, and space them to allow air to move freely around the base
The fungus needs wet conditions to spread, and crowded plants both hold humidity longer at their base and give the fungus a shorter distance to reach a neighbouring plant.
Avoid replanting susceptible crops in soil where sclerotinia has appeared before, for as long a gap as practical
Sclerotia surviving in soil for up to eight years is the reason a single infected plant can leave that patch of ground carrying risk long after the plant itself is gone. Farmers rotate away from an infected field for exactly this reason, and the same logic holds at bed scale in a garden.
Myths about Sclerotinia
5 common claims about Sclerotinia, checked: 3 busted1 disputed0 untested1 hold up
“Sclerotinia's resting bodies break down in the soil within a season or two, so ground where it appeared is fine to replant straight away”
The hard black sclerotia the fungus survives as are built for the long haul, not a single winter. Scottish field monitoring on oilseed rape puts survival at up to eight years, and a Kentucky vegetable-disease fact sheet gives a working figure of up to five years for the same structures in a vegetable setting. Either figure rules out treating a bed as clear again after one clean season.
Our read The two figures come from different crop systems (field-scale oilseed rape versus vegetable plots) and land in different places, five years against eight, which says more about how hard this is to pin down precisely than about which number is right. Both agree the sclerotia outlast any single crop cycle by years, which is the part that actually changes what a gardener should do.
What to do: Treat any bed where sclerotinia has shown up as carrying risk for several years, not one season. Plan replanting of susceptible crops around that timescale rather than the calendar.
In Scotland: The eight-year figure comes from Scottish government monitoring of the same fungus in commercial oilseed rape fields, so it reflects Scottish soil and climate conditions directly, even though the crop being monitored differs from a vegetable bed.
3 sources
- FAS Scotland, sclerotinia stem rot in oilseed rapeThe spores can survive within the soil for up to eight years, which is why extending rotationMoving each crop family to different ground each year, on a multi-year cycle, so pests and diseases that build up in soil don't get a repeat host. Full definition → periods is part of managing the disease.
- University of Kentucky Cooperative Extension, Sclerotinia Diseases of Vegetable Crops (PPFS-VG-29)Sclerotia accumulate in soils and may remain viable for up to 5 years, which is why the fact sheet recommends rotating to a resistant cultivarA plant variety that arose or was bred under cultivation and is kept true by deliberate propagation, rather than a naturally occurring wild species. Full definition → or non-host crop for a minimum of 5 years.
- RHS, Sclerotinia diseaseThe black, seed-like sclerotia the fungus survives as can remain viable in soil for several years after the infected plant has died.
“If sclerotinia's white mould is only on part of a vegetable, you can cut that bit off and eat the rest”
Iowa State University's extension guidance on white mould in vegetables states plainly that fruits and pods infected by the fungus are unmarketable, unsalvageable and inedible, without qualifying that by how much of the piece is affected or whether the mouldy part has been cut away.
What to do: Discard vegetables and pods with visible sclerotinia infection rather than trimming and eating the unaffected-looking remainder.
1 source
- Iowa State University Extension and Outreach, White mold, with a focus on vegetablesFruits and pods that are infected by the fungus will be unmarketable, unsalvageable, and inedible, reducing yields and profit.
“Sclerotinia is really an oilseed rape and farm-crop problem, home vegetable gardens with a normal mixed planting are unlikely to see it”
A Kentucky university extension fact sheet aimed specifically at vegetable growers lists more than 150 plant species as hosts, and its own vegetable table names beans, beets, all the cole crops, lettuce, okra, onion and garlic, parsnip, peas, peppers, potatoes, radish, spinach, squash and tomatoes among them. RHS separately describes it as affecting a very wide range of plants, listing lettuce, beans, celery, cucumbers, tomatoes and peas by name alongside ornamentals such as Delphinium and Dahlia.
Our read A mixed vegetable garden growing several of those crops together is not the low-risk setting the claim implies; if anything the wide host range means a mixed bed offers the fungus more potential hosts in one place, not fewer.
What to do: Don't assume a home vegetable plot is safe from sclerotinia just because it isn't a commercial oilseed rape field. Watch any of the wide range of susceptible crops, particularly legumes, brassicasThe cabbage family: cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi, swede, turnip and more, sharing the same pests, diseases and rotation rules. Full definition →, lettuce and root vegetables, for the disease's characteristic white cottony growth during wet weather.
2 sources
- University of Kentucky Cooperative Extension, Sclerotinia Diseases of Vegetable Crops (PPFS-VG-29)Sclerotinia diseases have a host range of more than 150 plant species, including fruits, ornamentals, agronomic crops, weed species and a long list of common vegetables, herbs and cover crops set out in its own table.
- RHS, Sclerotinia diseaseThe fungus affects a very wide range of plants including vegetables such as lettuce, beans, celery, cucumbers, tomatoes and peas, as well as ornamentals.
“Rotating vegetables around the plot doesn't really protect against sclerotinia, since it attacks almost every vegetable anyway”
Rotation is a genuine, recommended part of managing this disease, but the fungus's host range makes it a weaker tool for sclerotinia than for most other soil-borne problems. A Kentucky extension fact sheet lists beans, beets, brassicas, lettuce, onion and garlic, parsnip, peas, peppers, potatoes, radish, spinach, squash, tomatoes and watermelon as all being hosts, which covers most of a typical vegetable garden. The same fact sheet's actual non-host rotation options are cereals and grasses (corn, wheat, barley, oats, sudan grass), not other vegetables.
Our read This is why the claim reads as neither fully busted nor fully true. Swapping which vegetable goes in a bed each year, tomatoes one year, beans the next, isn't real rotation against sclerotinia if both crops are hosts; the fungus doesn't care which host it gets. Genuine rotation for this disease means breaking the bed out into a non-host cover crop or cereal for several years, which is a bigger ask than the usual four-bed vegetable rotation most gardeners already run.
What to do: Don't rely on a standard vegetable rotation alone to clear sclerotinia risk from a bed. If a bed has had an outbreak, consider putting it down to a genuinely non-host cover crop such as oats or ryegrass for a season or more rather than just moving to a different vegetable.
2 sources
- University of Kentucky Cooperative Extension, Sclerotinia Diseases of Vegetable Crops (PPFS-VG-29)Recommends rotating to a resistant cultivar or non-host crop for a minimum of 5 years, and lists non-host cover crops as cereals and grasses such as corn, sorghum, wheat, barley, oats and Sudan grass, while its own susceptible-crop table covers most common vegetables.
- FAS Scotland, sclerotinia stem rot in oilseed rapeExtending rotation periods is recommended as part of managing the disease, alongside ploughing to bury spores below germination depth.
“Giving plants more space and better airflow around the base genuinely cuts the risk of sclerotinia taking hold”
Three separate extension and horticultural sources independently name spacing and airflow as a real control point for this disease. Crowded plants let the fungus reach a neighbouring plant across a shorter distance at soil level. Give rows enough spacing and prune to keep air moving through the canopy; proper plant spacing for better airflow is a standard cultural practice.
What to do: Space susceptible crops to the wider end of their recommended spacing and avoid letting foliage crowd together at the base, particularly through wet spells in early summer.
3 sources
- RHS, Sclerotinia diseaseWhen plants are crowded, the fungus only has to grow a short distance through soil contact to reach a neighbouring plant, increasing infection risk.
- Iowa State University Extension and Outreach, White mold, with a focus on vegetablesMaintaining good airflow throughout the plant canopy, achieved through sufficient row spacing and pruning, helps prevent an environment conducive to the disease.
- University of Kentucky Cooperative Extension, Sclerotinia Diseases of Vegetable Crops (PPFS-VG-29)Lists properly spacing plants to allow for improved air flow among its standard planting and cultural practices for managing Sclerotinia diseases.
Frequently asked questions
What should I do first if I find sclerotinia in my garden?
Start with remove and destroy infected plants as soon as they're spotted, rather than composting them. After that, avoid overcrowding susceptible plants, and space them to allow air to move freely around the base. Work through the rest in order of how well-evidenced they are if the first two aren’t enough on their own.
Is there a spray that works?
No. There are no amateur chemical treatments available for sclerotinia. The controls that work are cultural: the measures listed above.
When are sclerotinia most active in Scotland?
Check the seasonal activity section above. Scottish timings can run a few weeks behind the UK-generic figures.
Sources
3 sources, recorded with what each was used for
- RHS1: identification, symptoms, the wet-weather infection trigger, life cycle including both infection pathways, sclerotia soil survival, removing and destroying infected plants, crowding and airflow, absence of a chemical control
- RHS1: confirming sclerotinia directly on Jerusalem artichoke's own growing page, and the crop's overall robustness framing
- FAS Scotland14: the eight-year soil-survival figure, May spore-spread timing, and rotation advice, all from field-crop monitoring in Scotland