Ergot – What it is and How to Prevent it

26 September 2024

This article is produced as a part of the FAS Crops & Soils Bulletin. Subscribe now to receive the full report in your inbox monthly.

This year brings more concern about ergot in grain crops- something that was also seen last year with some growers having loads rejected for ergot for the first time.

Why is a rejection for ergot so serious?

Ergot contains toxic alkaloids or mycotoxins which can cause serious health problems and even death in extreme cases in both humans and livestock if ingested. Tolerances under the AIC Contract for grains and pulses are 0.001% by weight for feed grain with a zero tolerance for all other grain (e.g. milling or distilling). For those growers unlucky enough to have grain rejected this causes headaches in the form of extra costs from handling and cleaning to a reduction in the value for the crop. Extreme care also needs to be taken when feeding potentially affected grain to livestock with further information here.

There are several ways of trying to clean grain from colour sorters, gravity separators to sieves and aspirators. Care must be taken with disposal of these screenings.

The two forms of ergot

Ergot takes two forms- firstly grain or cereal ergot, which is the type most easily recognised due to its large size, being black and purple in colour, resembling a deformed grain or rat droppings in shape and secondly grass ergot which is much smaller and thinner, looking more like a blackened nail clippings in terms of shape or size. While grain ergot is very easy to identify in a grain pile, grass ergot is very difficult to see, and the first indication of a problem may be that dreaded phone call from your grain merchant.

Ergot's life cycle

Understanding the life cycle gives us a clue as to how to try to control it in future years.

Ergot comes from seed dropped by the previous years crop or indeed from sown seed itself (up to 3 pieces per 500g are permitted as a regulatory minimum standard, 1 piece per 1000g at higher voluntary standard). These germinate and being a fungus grow through the summer to produce mushroom-like spores which are then spread by the wind or even by rain-splash. The danger occurs when cereal crops and grasses are flowering at the same time as when these spores are being released. Cereal and grass ovaries become quickly infected leading to more spores forming on the ovary surface (conidia). This is the sticky, honey-dew phase which attracts insects and spreads the spores further along with a risk of further spread by rain-splash. Cooler and wetter weather at this time not only promotes spore production but also prolongs the cereal flowering period, further increasing the risk of infection. Ergot in the form of a sclerotium then develops in the grain sites in place of the grain or grass seed, ultimately being harvested with the crop or falling to the ground to infect the following years crops.

How can we prevent ergot in future crops?

Plant clean seed with some seed treatments being able to suppress the germination of ergot in seed. Home saved seed can benefit from being run through a cleaner.

This will be most effective where ergot is not a problem in a field. For fields which are infected from the previous years crop or there is a risk of infection from grass margins there are other techniques for management. Breaking this cycle of infection is the key to success.

Think about cropping and varieties- wheat is more susceptible than barley, with barley in turn more susceptible than oats.

Control grass weeds effectively- look at crops and assess how current control methods are working and while effectiveness may change from year to year, is it time to review current treatments and practices.? This also extends to couch grass which can be difficult to control but can help spread ergot.

After falling to the ground, dormant ergot remains viable for only one year. Sowing a different crop type (non-cereal) can help break the cycle. Ploughing as opposed to min-till can also bury the ergot and prevent them germinating. Min-till may exacerbate the problem if grass weeds are an issue.

Consider tipping headlands separately, particularly where there is a grass margin adjacent, and infections are bad.

Grass margins can act as a prolonged source of infection particularly where crops have secondary or later tillers. Grass margin seed mixes should contain later flowering species.

Some varieties of wheat are more open flowering than others, with these presenting a higher risk than more closed flowering varieties. At the same time, varieties with a longer flowering period are also at more risk.

Keep a note of fields where ergot has been a problem or can be seen in growing crops. This can enable targeted husbandry methods e.g. rotation to be used to reduce the infection levels in fields.

Prevention is clearly the best way to mitigate the risk from ergot to your crops with good husbandry and the management tools identified above at its heart.

More information is available in Technical Note 601

George Chalmers, SAC Consulting