Ergot and smut

Two fungi, one page, and one of them is poisonous

Ergot and the smuts both destroy grain by taking the place of it, and both turn parts of an ear black. That is where the resemblance ends.

Ergot replaces a grain with a hard, dark, curved body that sticks out past the husks like a small horn. It is firm all the way through and it is loaded with alkaloids that constrict blood vessels and act on the nervous system. It has killed a great many people.

Smut replaces the grain with spores. The affected part becomes a bag of loose black dust, or on sweetcorn a swollen pale grey gall that blackens and bursts. None of the smuts is poisonous, and one of them is farmed deliberately in Mexico and sold as a delicacy.

They are on one page because a reader who has found something black in an ear needs to know which they have before doing anything else. Squeezing it takes a second and settles it.

Telling them apart

Squeeze it.

An ergot body is hard. It will not crush between finger and thumb, and if you cut one open with a knife it is solid and dense inside, white or pinkish, like a piece of cheese. On the outside it is dark purple to black, often with a fine bloom, curved like a claw, and between about 2 mm and 20 mm long. It stands proud of the husks rather than sitting inside them. On rye it is unmistakable.

A smut is soft. It gives way at once, and what comes out is dry black powder that gets everywhere and blows off on the wind. Under a hand lens the powder is made of spores. On barley and oats a loose smut head emerges from the sheath already ruined, a black skeleton where an ear should be. On wheat, bunt is sneakier: the grains look plump and normal until crushed, when they collapse into a greasy dark powder that smells strongly of rotten fish, which is where the name stinking smut comes from.

Ergot gives itself away earlier in the season too. Infected florets weep a sticky sweet fluid called honeydew in early summer, often with flies and other insects feeding on it. That fluid is full of spores, and the insects carry them to other flowering heads. Sticky ears in June are a warning that hard black bodies will follow in August.

One more thing settles most garden cases. In Britain ergot is found on rye, triticale, wheat, barley, oats and wild grasses. It is not a disease of sweetcorn here. So if the crop is sweetcorn, what you are looking at is smut.

St Anthony’s Fire

Ergotism, the illness caused by eating ergot-contaminated grain, ran through Europe repeatedly for a thousand years, and it took two forms depending on which alkaloids dominated.

The gangrenous form, commoner in western Europe, came from the alkaloids clamping down the small blood vessels. Sufferers described a burning heat in the hands and feet. The blood supply to the extremities failed, the tissue died, and fingers, toes and whole limbs blackened and were eventually lost. The burning gave the disease its popular name.

The convulsive form, commoner in central and northern Europe, brought seizures, violent muscle spasms, a sensation of insects crawling under the skin, hallucinations and psychosis.

The name St Anthony’s Fire comes from the Order of St Anthony, founded in France towards the end of the eleventh century, whose hospitals cared for sufferers. Pilgrimages to their shrines had a reputation for curing the disease, and the likely reason is bleakly practical. Anyone who travelled away from home stopped eating the contaminated rye bread of their own district and began to recover on the road.

Rye is the thread running through the history. It is the most susceptible cereal, it grew where wheat would not, and it was the bread of the poor across northern Europe. Epidemics tracked wet summers, which favour infection, followed by hungry winters, when nobody could afford to discard grain.

The suggestion that ergotism explains the Salem witch trials of 1692 was put forward in 1976 and is still repeated as though settled. It is not. The objections raised at the time have held up, chiefly that contaminated bread would have affected whole households rather than a specific group of accusers. Most historians now put the trials down to social and religious pressures, with ergot as a colourful and unproven footnote.

From poison to pharmacy, and to LSD

The alkaloids that made ergot lethal also made it useful, and midwives knew this long before chemists did. Preparations of ergot were used for centuries to contract the uterus and control bleeding after childbirth. The dose was guesswork and the results were sometimes catastrophic, but the effect was real.

In the twentieth century the individual alkaloids were isolated and turned into controlled medicines. Ergometrine, also called ergonovine, is still used to stop post-partum haemorrhage and sits on the World Health Organization’s list of essential medicines. Ergotamine constricts the dilated blood vessels behind a migraine and treated migraine for decades. Later semi-synthetic relatives such as bromocriptine and cabergoline act on dopamine and are used in Parkinson’s disease and in hormonal disorders.

The shared chemical backbone of the ergot alkaloids is lysergic acid, and that is where the other story starts.

Albert Hofmann was a chemist at Sandoz in Basel, working through derivatives of lysergic acid in search of a circulatory and respiratory stimulant. In November 1938 he made the twenty-fifth compound in the series, lysergic acid diethylamide, which the laboratory shorthand recorded as LSD-25. The pharmacology unit tested it, found it acted strongly on the uterus and made the animals restless, and shelved it as uninteresting.

Five years later Hofmann went back to it, on what he described as an unusual hunch. On 16 April 1943, resynthesising the compound, he absorbed a trace through his skin and spent the afternoon in a state he could not account for. Three days later, on 19 April, he deliberately took 250 micrograms of it, expecting that to be a cautious dose. It was several times a full one. His journey home from the laboratory by bicycle, accompanied by his assistant, is the best-known bicycle ride in the history of chemistry.

The connection gets repeated in a way that invites a dangerous conclusion, so be clear about what it does not mean. The sclerotium growing in an ear of rye contains no LSD. LSD is a laboratory product, made from lysergic acid through a chemical step that does not happen in a field. The ergot body holds the mixture of alkaloids above, and eating it produces vasoconstriction, gangrene and convulsions. The medieval sufferers who hallucinated were losing their fingers at the same time.

Why ergot faded, and why it came back

Ergotism became rare in Europe through a combination of changes, none of them a treatment. Grain cleaning improved, and gravity separators and brine flotation could take the bodies out of a batch. Ploughing buried them, rotations broke the cycle, and bread wheat displaced rye across much of the continent. Ergot did not go away; the grain supply stopped carrying it to the table.

It has become a live agricultural issue again in Britain over the last two decades. Reduced cultivation and direct drilling leave the bodies near the surface where they can germinate, grass weeds in cereal crops give the fungus a place to build up, and rye and triticale have gained ground. Great Britain works to a contractual zero tolerance for ergot in grain outside animal feed, and the European Union set legal maximum levels for the alkaloids in 2022, which apply in Northern Ireland and not in Great Britain.

For a gardener the practical version is short. Growing a few square metres of rye or ornamental barley, expect to see it in a wet summer, and do not eat the crop.

The smuts, and the one people eat

Loose smut of barley, wheat and oats is carried inside the seed. The fungus infects the flower one summer, sits dormant in the embryo of the grain, and grows up inside the plant the next year to emerge as a ruined ear. It is controlled almost entirely by using certified treated seed, which is why it is now rare in commercial crops and turns up mostly where somebody has saved their own.

Bunt, or stinking smut, works differently. Its spores coat the outside of the seed and infect the seedling as it germinates. The grains that result look sound and are full of dark spores that smell of rotting fish, and a very small number of bunted grains will taint a whole batch of flour. Clean treated seed handles it.

Corn smut on sweetcorn is the outlier. Instead of a dusty head it makes swollen galls, sometimes as big as a fist, silver-grey and firm at first and later black and papery as the spores mature. It gets in through wounds and through the silks, and it is worse in hot dry summers followed by rain, and worse on plants that have been damaged by hoeing or by hail.

British growers treat it as a disease and throw it away. In Mexico it has been eaten since before the Spanish arrived, under the name huitlacoche, and it is prized rather than tolerated, with a dense earthy flavour somewhere between a mushroom and a truffle. It is grown deliberately in parts of the United States and sold to restaurants. We have written about that side of it separately in Huitlacoche, the disease that became a delicacy.

If that tempts you, two conditions apply. Take the galls while they are firm and pale, since a black papery one is past eating. And be certain the crop is sweetcorn, which in Britain does not carry ergot, rather than a cereal that does.

What to do about it

Buy certified treated seed every year and never save seed from an affected crop.

Rotate so that cereals do not follow cereals, and give the ground two years off where ergot has appeared.

Choose oats or barley over rye and triticale if ergot is a problem on your ground.

Mow verges, headlands and rough grass before the seed heads open.

Bury the ergot bodies deeper than 5 cm and then leave that ground undug for a year.

Cut out and bag smutted heads before they burst, and pick corn smut galls off while they are pale.

Cut and bin a small stand showing ergot rather than trying to clean it.

Never eat, mill or feed grain containing ergot, and do not pick the bodies out and keep the rest.

What it gets mistaken for

Sclerotinia also leaves hard black bodies, inside hollow rotted stems of beans, lettuce and dahlias, under dense white mould.

Sooty mould is a black film growing on honeydew that wipes off a leaf and leaves it green underneath.

Rust makes raised pustules that shed orange or brown powder from leaves and stems rather than destroying the ear.

Insect galls are made by the plant, stay firm and dry, and never turn to powder.

Blackened, shrivelled ears after a hard frost at flowering are frost damage, and they are empty rather than full of anything.

Black tips and dark speckling on otherwise sound wheat grains are usually sooty moulds growing on ripe ears in a wet harvest, which spoil the appearance and carry none of this risk.