Risk assessment for fusarium mycotoxins in wheat

Assess the risk of fusarium mycotoxins and record the score on the grain passport.

Some fungal species can grow on crops and foodstuffs and produce toxic chemicals. Of widely varying toxicity to humans and animals, these chemicals are called mycotoxins. To keep mycotoxin levels below set limits, it is important to follow best practice – which includes the completion of a risk assessment.

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Paper version of the mycotoxin risk assessment

Excel version of the mycotoxin risk assessment

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Which fungal species are associated with cereal mycotoxins?

In cereals, mycotoxins can result from fungi that either develop from field-borne infections (fusarium mycotoxins and ergot alkaloids) or in stored crops (ochratoxin A).

Which fungal species are associated with cereal mycotoxins?


The need for accurate risk assessment

There are legal limits for fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZON) in wheat intended for human consumption and guidance limits for feed grain.

The owner (farmer, merchant or processor) is legally obliged to ensure grain is safe for human consumption. 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.

Crop assurance schemes are designed to help farmers comply with food laws. They include an audit of the risk assessment and an AHDB risk assessment score is required on the grain passport.

What are the limits for mycotoxins?

Access the combinable crops grain passport

For traceability purposes, document the actions required when performing a risk assessment.


Completing the mycotoxin risk assessment

The final risk assessment score for a field of wheat is calculated by adding together scores for a number of key risk factors:

  • Region
  • Previous crop
  • Cultivation
  • Varietal resistance rating to fusarium ear blight
  • T3 fungicide application
  • Total rainfall during flowering
  • Total rainfall pre-harvest

Calculate this score at harvest and enter it on the grain passport.

Check purchaser requirements to determine whether mycotoxin testing is required.

Pre-flowering risk factors

Region

DON and ZON levels in wheat tend to be highest in southern and eastern England. Higher humidity in coastal areas may increase risk.

Details (see risk map) Risk
High 4
Moderate 2
Low -2
Very low -4

Previous crop

Crop residue on the soil surface is the major source of inoculum. The greatest risk is after grain maize or forage maize. Rotations should aim to minimise wheat sown after maize.

Details  Risk
Maize 6
Other 0

After maize, sugar beet and grass are potential inoculum sources.

Always aim to remove inoculum sources (e.g. straw).

Cultivation

Complete burial of debris by ploughing is most effective at reducing the risk, while risk is highest with direct drilling. Intensive non-inversion tillage (three or more passes with discs or tines) is more effective at reducing risk than reduced non-inversion tillage (one or two passes).

Details  Risk
Direct-drilled 4
Standard non-inversion tillage 3
Intensive non-inversion tillage 2
Ploughed (soil inversion) 0

Wheat variety

The risk assessment includes varietal resistance based on the AHDB Recommended List (RL) rating for fusarium ear blight.

Details  Risk
RL rating 1–5 1
RL rating 6–9 0
RL rating unknown 1

Other factors

  • Untreated infected seed*
  • Poor seedbeds
  • Warm, dry weather from sowing to about GS31 encourages the build-up of fusarium inoculum
  • Microdochium is more prevalent in cooler conditions
  • Various broad-leaved and grass weeds, crop debris, as well as some insects, can provide a source of fusarium

*Seed treatment is the main method of controlling seedling blight. Information on the effectiveness of seed treatments against fusarium seedling blights is available from the fungicide performance section of the AHDB website.

Foliar fungicide activity and seed treatment options for wheat

At-flowering risk factors

T3 ear fungicide

Using an appropriate dose of an approved T3 ear fungicide with activity against fusarium and/or mycotoxin production reduces the risk.

Details  Risk
<50% dose 0
50–74% dose -2
≥75% dose -3

Fungicide programmes for wheat

Fungicide programmes for barley

Rainfall at flowering

Wet weather promotes fusarium development. The score is based on total rainfall during flowering (GS59–69 – full ear emergence to end of flowering).

Details  Risk
>80 mm 9
40–80 mm 6
10–40 mm 3
<10 mm 0

Pre-harvest risk factors

Rainfall pre-harvest

Wet weather promotes fusarium development. The score is based on total rainfall from GS87 (dough development stage/start of ripening stage) to harvest.

Details  Risk
>120 mm 12
80–120 mm 9
40–80 mm 6
20–40 mm 3
<20 mm 0

Other factors

  • Lodging, resulting in humid conditions conducive to mycotoxin production
  • Delays in harvesting by more than two weeks
  • Damaged grain

Post-harvest management

Avoid delays at harvest for crops at high risk of mycotoxins, especially where grain is intended for human consumption.

Set combine, especially the fan speed, to minimise retention of light fusarium-damaged grains and chaff that contain the highest concentrations of mycotoxins. Dry and cool grain as soon as possible.

Harvest and store grain from localised patches of weathered or lodged crops separately.

It is important to understand and manage the quality of your grain. As part of this, accurate sampling is required to guide management and provide a robust record of all the grain that leaves the farm.

When ear blight levels are high nationally, the risk of DON and ZON occurrence in crops will increase.

Although mycotoxin risk in barley is lower than in wheat, it should be considered, especially when it is commonly grown in the rotation with maize with minimum tillage.

An introduction to grain sampling

Grain sampling before storage

Mycotoxin risk map



Mycotoxin rainfall risk tool for cereals

Covering thousands of sites across England, Scotland and Wales, our map-based tool shows how much rain has fallen during the critical winter wheat flowering and pre-harvest periods. Use this information to help calculate (DON) risk assessment scores required on the combinable crops grain passport.

Use the mycotoxin rainfall risk tool for cereals


Further information

The following resources will help you assess and manage mycotoxin risk. They will also help you to obtain composite and representative samples for testing for DON and ZON (where required by the end-user).

UK Codes of Practice produced by the Food Standards Agency

Contaminants monitoring

A robust foundation to instil confidence

A robust foundation to instil confidence

An article from Crop Production Magazine

Agrochemical residues, mycotoxins and other major contaminants in cereals and co-products have been monitored independently since mid-1980s. Find out about our research that aims to help ensure the safety of the UK grain and its end-products.

Monitoring of contaminants in UK cereals used for processing food and animal feed

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