Ergot in harvest 2024 cereals: A pathologist’s paradise (a supply-chain challenge)

Senior Cereal Product Quality Scientist Kristina Grenz recently visited some cereal trials with relatively high levels of ergot. Find out what she discovered and how to manage disease risks.

Ergot (Claviceps purpurea) is a fungal pathogen that infects major UK cereals: wheat, barley, rye, triticale and, occasionally, oats. Although it does not particularly affect yield, it produces alkaloids that are highly toxic when ingested by humans and livestock. The toxins can cause hallucinations, convulsions, gangrenous limbs and even death. History is riddled with cases of ergotism – the Salem Witch Trials, ‘dancing sickness’ and ‘werewolfism’, to name a few.

Thankfully, modern production practices mean ergot is much less of an issue these days. We know far more about the disease and the factors that affect risk. Grain is better segregated and there are effective lab tests and colour sorters to reduce its presence to negligible amounts in food and feed. But it does not mean we can put down our guard. Good grassweed management and extra vigilance with grass strips and flowering margins are essential to keep infection low.

Ergot infections manifest during the summer as dark, elongated masses called sclerotia, which grow instead of individual grains. At harvest, sclerotia are either gathered with the grain or fall to the ground, where they lie dormant over the winter. They bide their time until spring arrives when they germinate and release tiny ascospores that float off into the breeze infecting flowering cereals and grasses, continuing the infection cycle.

From the comfort of my creaky office chair (with my 30 kg lapdog), I looked out of the window many times during the first few weeks of the great British summer of 2024 as it delivered lashings of rain. It had all the markings of a potentially bad ergot year.

When plant breeder Dr Matt Kerton asked if I would like to tour his cereal disease trials in Oxfordshire, featuring some exceptionally high levels of ergot, my colleague (Dr Dhan Bhandari) and I leapt at the chance.

We had barely walked a few metres when Matt pointed out sclerotia on some wheat. Once I got my eye in, I realised that they were everywhere, including in the abundant, neighbouring black-grass, which is a common grassweed host.

There are stark differences in the look of ergot on cereals compared to grassweeds. The cereals featured ‘textbook’ symptoms – a purple-black mass. However, the grassweeds produced many looping, spiralling structures in all sorts of shades, including black, dark grey, purple and browns. The sclerotia were also tiny compared with those found in wheat. It is easy to see how they can easily slip through sieves at harvest.

As expected, infection levels were much higher on more vulnerable secondary and late cereal tillers. Rather than the odd sclerotia on the main tiller, several grains had been usurped by ergot on secondary tillers and, in severe cases, the ears seemed to have more ergot than grain.

Egot sclerotia on wheat

Ergot sclerotia or Jim Henson’s Skeksis? Ergot is possibly the most alien-looking of all cereal pathogens.

Ergot sclerotia on black-grass

Sclerotia of all shapes and sizes

Sclerotia of all shapes and sizes – Ergot morphology changes with host plant. From left to right: black-grass, barley, wheat, and cock’s-foot.

Ergot sclerotia on secondary tillers

The trip hammered home the challenges and importance of managing ergot. Check out our ergot pages for some excellent management tips to help you reduce ergot risk in your crops.

• Pay closer attention to fields with higher grassweed pressure (especially black-grass) and cereal crops associated with more ergot, such as rye and triticale
• Inspect crops (and grass margins) for ergot symptoms prior to harvest
• Harvest higher-risk field headlands and tramlines separately from the bulk of the crop (plants with more susceptible late and secondary tillers are most likely to occur in these areas)
• Check loads carefully before tipping onto a wider heap
• Consider ploughing to bury ergots to at least 5 cm depth
• Consider planting a non-cereal crop
• Avoid open flowering varieties and varieties with a long flowering period
• Avoid sowing contaminated seed – clean farm-saved seed thoroughly to remove ergot
• Check any crops destined for home-use animal feed for ergot
• Some seed treatments may have a small effect by preventing ergot germination (there are no fungicide sprays approved for use on cereals to control ergot infection)
• Sow later-flowering grass species in grass margins

Our grain-contaminants-monitoring project was set up about four decades ago. With the current project phase (led by Fera) nearly complete, we are asking levy payers to complete a short questionnaire (by Monday 30 September 2024) to help the sector council review its investment in this area. No matter how much or how little you know about contaminants, we want to hear from you.