Fusarium and microdochium in cereals

This complex of diseases, which can be seedborne, soilborne or trashborne, causes a variety of symptoms, including seedling blight, foot/crown rot and ear (head) blight and the production of mycotoxins. Learn about the pathogens and how to manage them.

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Risk assessment for fusarium mycotoxins in wheat

Symptoms of fusarium and microdochium

Many species of fusarium affect cereals (wheat, barley, oats, rye and triticale), as well as grasses.

Fusarium avenaceum, F. culmorum, F. graminearum, F. poae, F. langsethiae, Microdochium nivale and M. majus.

These fungi form a disease complex on seeds, seedlings and adult plants. The seed-borne pathogens Microdochium nivale and M. majus (formerly known collectively as Fusarium nivale) are also included in this group. M. nivale also causes snow mould.

Fusarium seedling blight

M. nivale is the primary pathogen in the group that causes seedling blight. Seedling blight causes pre- and post-emergence damping off. This can result in seedling death and poor establishment. Surviving seedlings may develop a brown lesion around soil level. This can develop into foot and root rot. Symptomless infections can also occur.

Fusarium foot rot/crown rot

Foot rot becomes obvious from late stem extension onwards. It results in dark-brown staining of the lower nodes. Long dark streaks may also appear at the stem base. On older plants, fusarium infection can produce a true foot rot, where the stem base becomes brown and rotten, resulting in lodging and whiteheads. This symptom is less common in the UK but can develop very dry seasons.

Fusarium ear (head) blight

Fusarium species cause a range of symptoms on the ear. Bleached ears often show above the point of infection around the milky ripe stage (GS 75). Later infections may result in infection of the grain without obvious bleaching of the ears. The presence of orange/pink fusarium spores may also be visible on infected spikelets. As the crop ripens, symptoms become less visible. At harvest, fusarium ear blight can result in shrivelled grains with a chalky white or pink appearance, although this is not always the case. There is little correlation between fusarium-damaged grains and mycotoxin occurrence. Therefore, the presence of ear blight symptoms is not a good indicator of mycotoxin risk.

Life cycle of fusarium and microdochium

Primary infection by fusarium is from infected seed, soil, crop debris and volunteers or host weed species. Spores – from seedling blight or foot rot lesions – that are splashed up the plant or move from leaf to leaf are the main source of ear blight infection. For some fusarium species, spores are also wind-spread, although this is not an important infection source. Ear blight infection occurs during flowering. It infects the grain and completes the life cycle.

Environmental conditions affect disease development and fusarium species have different temperature requirements. For example, M. nivale seedling blight is most severe under cool, wet soil conditions, whereas F. graminearum seedling blight is most severe under warmer, drier soil conditions. Warm, wet, humid conditions during flowering favours infection by fusarium species, causing ear blights and seed-borne infection. Further rainfall and humid conditions allow secondary infection to occur, allowing further fungal growth and mycotoxin production.


Most cereal crops develop fusarium symptoms each year. F. culmorum and F. graminearum are the most commonly found species in the UK that cause ear blights. Although infection by fusarium species can cause poor establishment and lower yields, the most important issue is the production of mycotoxins in the grain by some species (see mycotoxin section below). However, the presence of ear blight is not a good indicator of likely mycotoxin risk. Mycotoxins are present at lower levels in barley and oats compared to wheat. The overall risk of DON exceeding legal limits in wheat is low and in barley and oats is very low.


F. graminearum and M. nivale cause the most significant seedling losses in UK wheat. However, crops usually compensate from the loss of a few plants through tillering. F. graminearum is more common in a maize-producing area, whereas M. nivale is more generally distributed. Severe foot rotting in wheat is very rare in the UK because badly infected seed is not used and seed treatments are effective, and losses are generally very small.

High levels of ear blight can occur, especially when conditions are conducive (e.g. wet) during flowering, but yield losses are rarely serious. Seed saved from these crops can suffer from poor establishment, unless the seed is treated with a product effective on fusarium.

The mycotoxins DON and ZON are frequently detected in wheat but average concentrations are usually below the legal limits. Limits are most frequently exceeded in wet harvest years.


Seedling blight in barley due to fusarium species is rare, but may occur where there are very high infection levels and seed is sown into cold seedbeds. Losses are generally not as high as those seen for wheat.

Early sown spring barley is at more risk of M. nivale seedling blight infection.

Ear blight and mycotoxin risk is also lower in barley than in wheat, but should be considered if barley is commonly grown in rotation with maize with minimum tillage. Developed for wheat, the AHDB fusarium mycotoxin risk assessment tool is also useful for assessing risk in barley.

DON, ZON, HT-2 and T-2 levels in barley have been routinely low with legal limits rarely exceeded.


Oats are more resistant to fusarium infection than wheat and barley, and it is difficult to see the symptoms in this crop. Symptoms can include premature plant death or bleaching of spikelets.

F. langsethiae is the predominant species that infects oats and produces the mycotoxins HT-2 and T-2. There is good evidence that at least 90% of mycotoxins are removed during dehulling. Previous Food Standards Agency surveys of fusarium mycotoxins in retail oat products have identified that exposure to these toxins from oat products in the UK diet is very low.


Mycotoxins are toxic chemicals produced by specific fungi that can grow on a variety of different crops and foodstuffs. Different fungal species produce mycotoxins of widely varying toxicity to humans and animals. Fusarium species are not the only group of fungi to produce mycotoxins, they are also produced by ergot alkaloids and ochratoxin A (the latter during crop storage).

F. avenaceum, F. culmorum and F. graminearumare the main mycotoxin-producing species, and these all produce similar symptoms. F. poae and F. langsethiae do produce mycotoxins but are not such an important source. M. nivale and M. majus do not produce mycotoxins.

Mycotoxins formed before harvest are stable and likely to remain during storage but not increase.

Legal limits

Although legal limits exist for fusarium mycotoxins in UK cereals, the risk of exceeding them is low. Risk varies between regions and years depending on climate and the intensity of host crops in the region. Levels of mycotoxins are generally much lower in the UK than in mainland Europe and rarely exceed GB and EU limits.

There are rules and strict limits in place for fusarium and other fungal toxins in certain foods to protect consumer safety. Maximum levels (MLs) are established in:


There are legal limits for fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZON) in wheat, barley, and oats intended for human consumption and guidance limits for grain for feed. The owner (farmer, merchant or processor) is legally obliged to ensure the grain is safe for human consumption. This means that all sellers must be able to demonstrate due diligence in determining the levels of mycotoxins that are present.

Depending on end use, processors may require a lower limit at intake than the legal limit for unprocessed cereals to ensure finished products conform to legal limits.

Table 1. GB limits for mycotoxins (ppb) in grain*

  • Legal (L) limits for grain intended for human consumption
  • Guidance (G) limits for grain intended for animal feedstuffs

The guidance values, which cover key mycotoxins for livestock, were published by the EU. Although not laid down in GB legislation, the technical content remains applicable as a general guidance tool.

Note: On 1 July 2024, new reduced maximum levels for DON came into force (only apply to NI and EU countries).

End-use DON ZON
Unprocessed wheat and barley (L) 1,250 100
Unprocessed oats (L) 1,750 100
Flour (L) 750 75
Finished products (L) 500 50
Infant food (L) 200 20
Feed grains (G) 8,000 2,000
Complete feedstuffs for pigs (G) 900 250
Complete feedstuffs for piglets and gilts (G) 900 100
Complete feedstuffs for calves, lambs and kids (G) 2,000 500

T-2 and HT-2

T-2 and HT-2 mycotoxins are produced by fusarium species that are favoured by drier conditions, such as F. langsethiae. Therefore, risk factors are different to those for DON/ZON. Currently, there are no legal or indicative limits for T-2 and HT-2 in GB. On 1 July 2024, the European Commission published REGULATION (EU) 2024/1038 as regards maximum levels for the combined concentration of T-2 and HT-2 in food. These MLs apply to EU Member States and Northern Ireland.

Commission Recommendation 2013/165/EU, which set out the indicative levels for T-2 and HT-2, did not form part of retained legislation at the point of EU exit and were always voluntary to encourage gathering and monitoring of data. However, they provide a useful guide for industry to initiate investigation into adverse results and to also monitor any trends that may emerge to support the identification of potential mitigation to reduce levels to As Low As Reasonably Achievable (ALARA).

For businesses moving goods from Great Britain to Northern Ireland, information on the Windsor Framework is available on the GOV.UK website.

The Windsor Framework (policy paper)

Table 2. EU maximum levels for the combined concentration of HT-2 and T-2 (ppb) in unprocessed cereals (only apply to NI and EU countries)


HT-2 and T-2
Unprocessed wheat (I) 50
Unprocessed barley (I) 200
Unprocessed oats with husk (I) 1,250


  • Legal limits – maximum levels for specific mycotoxins in cereals and cereal products, as defined by European Commission regulations and applied at the point of sale
  • Guideline limits – guidance as to the acceptability of feed and feedstuffs
  • Indicative levels – guidance on when to investigate high levels to identify mitigating actions


The risk of fusarium diseases can be minimised throughout the season: from rotation planning, to deciding which field to harvest first.

Use our risk assessment to manage potential mycotoxin risks

Pink grains indicate possible fusarium infection

Ear blight infection can cause bleached ears