An introduction to ergot and its management in cereals
Although the disease has relatively little effect on yield, ergots are associated with large amounts of toxic alkaloids (mycotoxins). A good understanding of the pathogen’s life cycle and the risk to cereal crops forms the foundation of management.
Why is it important to manage ergot in cereals?
The disease has very little direct effect on yield but the ergots contain large amounts of toxic alkaloids (mycotoxins). Contaminated grain, fed to stock or used to make flour, can pose a risk to animal and human health. Such grain may be rejected, require cleaning or demand a reduced price.
There are standards for the number of ergot pieces for certified seed (visual inspection):
- Up to three pieces per 500g (regulatory minimum standard)
- One piece per 1000g (higher voluntary standard)
The approved AIC Contract for Grains/Pulses No.2/16 states that: “grain shall not contain more than 0.001% ergot by weight for feed grain and zero tolerance for all other grain.”
The maximum levels for ergot sclerotia are currently defined within the Codex standards at a level of 0.05%. The EC have proposed the lowering of this level to 0.02%. This is likely to apply from July 2021 (affecting the 2021 harvest).
There is currently no EU legislation for maximum levels of ergot alkaloids. However in 2019, the EC proposed the introduction of limits for total ergot alkaloid content of:
- 75 ppb in processed barley, wheat, spelt and oats products
- 250 ppb in processed rye products
- 20 ppb in processed cereal based food for infants and young children
The increased scientific understanding and improvements in agricultural practices and milling techniques (grading, sieving and sorting) have eliminated the severe epidemic outbreaks of ergotism in the UK. There are year-to-year fluctuations in ergot severity that can be explained, to some extent, by variations in weather during flowering.
Which cereal crops are most susceptible?
There are a several strains of the fungus: some infect grasses and cereals, whereas others are restricted to specific hosts.
In order of decreasing susceptibility, the disease affects rye, triticale, wheat, barley and oats (infection of oats is rare). It also affects a wide range of grasses, particularly black-grass.
The disease is favoured by cool, wet conditions during flowering which facilitate spore production and prolong the flowering period, making infection more likely. Late tillering crops and crops with secondary tillers are more susceptible.
Ergot life cycle and symptoms in cereals
Caused by Claviceps purpurea, ergot is not a true seed-borne disease, as it is not carried on or in seed. However, it can be spread by ergots in contaminated seed. It is also one of only two diseases included in the UK Seed Certification Scheme for Cereals (the other being loose smut).
At or near to harvest, ergots fall to the ground where they remain dormant. In the following spring, they germinate and produce mushroom-shaped spore bearing structures (stroma).
The spores are spread by the wind to nearby open flowers of grasses and cereals. The spores germinate in the flower, infecting the ovaries. This infection leads to the production of secondary spores (conidia) encased in a sweet-smelling, sticky secretion – commonly referred to as honeydew – which can lead to the development of saprophytic moulds.
The honeydew attracts insects that carry the spores to other flowers, where further infection can occur. Rain splash and physical contact can also spread the spores. The fungus then grows in place of the grain to form hard, purple-black sclerotium, known as an ergot.
Ergots are formed of a mass of fungal tissue and have a white interior. Ergots can be very large, up to 2 cm in length, and are very obvious in the standing crop and in contaminated grain samples.
Ergots are either harvested with the grain or fall to the ground where they remain as a source of inoculum for the following year. Generally, ergots only remain viable on the soil surface for one year in the absence of host crops, but they may survive longer in stored grain.
Ergot: high-risk factors
- Open pollinated wheat varieties
- Varieties with a long flowering period
- Cool and wet conditions during flowering, which facilitates spore production and prolongs the flowering period
- Grassweeds, particularly black-grass
- Grass margins containing early flowering grass species
- Late and secondary tillering
Ergot sclerotia in wheat grains
Secondary spores (conidia) encased in a sweet-smelling, sticky secretion – commonly referred to as honeydew – are produced on infected grains.
Ergot alkaloids under the spotlight
An article from Crop Production Magazine
How ergot alkaloids can move to apparently ‘clean’ grain has been revealed by our research. Mycotoxins appear to move between flowers and can be detected in grain that appears clear of infection. It was also found that broken ergot sclerotia in harvested grain can be a potentially significant contamination source.
Ergot alkaloids – Avoiding a bad trip on new regulations
Joe Brennan – Policy & Research Officer, nabim
Cereal disease management
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