Around 73% of the GB winter wheat area was at moderate risk and 17% at high risk of fusarium infection during the flowering period, according to AHDB-funded monitoring work.

The summary risk results for 2016, produced by researchers at ADAS, are in contrast to the relatively low fusarium infection risk reported in 2015.

Infection of crops by fusarium species increases the risk of mycotoxins entering the food and feed chain.

Due to the highly local nature of infection risk, growers are being reminded to follow mycotoxin management guidelines and to calculate field-level mycotoxin risk scores for recording on the grain passport.

Risk level estimates for 2016

Risk levels were estimated based on crop growth stage information, gathered by an established network of independent agronomists covering 30 counties in England and Scotland, and daily rainfall data.

Analysis of regional fusarium infection risk data revealed that of the winter wheat area in Great Britain (GB):

    10% (189,000ha) ­– with an estimated tonnage of 1.4Mt – was at low risk
    73% (1,320,000ha) – with an estimated tonnage of 10.1Mt – was at moderate risk
    17% (304,000ha) – with an estimated tonnage of 2.3Mt – was at high risk
    <1% (3,000ha) – with an estimated tonnage of 26,000t – was at very high risk

Rainfall is a major factor in determining risk. Due to the localised nature of showers, a significant variation in infection risk level was reported across GB.

All GB regions had crops at both low and moderate fusarium infection risk. The largest areas of moderate and high-risk crops were located in the southern and eastern regions.

Areas with the highest risk levels had a significant amount of crops in flower as the weather turned more unsettled from mid-June onwards.

Dr Dhan Bhandari, who manages grain quality research at AHDB, said: “Flowering started at the beginning of June, when conditions were generally settled.

“The weather turned during the peak flowering period, which happened from the middle to the end of June.

“This exposed relatively large areas of winter wheat to conditions which favour fusarium infection.”

Regional risk charts

Weekly regional risk charts have been published throughout the main flowering period on cereals.ahdb.org.uk/monitoring.

The final summary information breaks down risk further, displaying infection risk data mainly at the county level.

The charts reveal the proportion of winter wheat crops flowering and estimates of whether they were at ‘very high’, ‘high’, ‘medium’ or ‘low risk’ of fusarium infection.

Areas identified with the largest areas of high-risk crops were located in Cambridgeshire, Kent, Norfolk, Shropshire and Staffordshire. In these areas, crops were often exposed to over 40mm of rain during the flowering period.

A small proportion of crops were classified as being at very high risk of fusarium infection. These were located in Derbyshire and Nottinghamshire, which saw heavy rainfall (up to 26mm) falling on 14 to 15 June.

Accounting for rain

Dr Bhandari said: “Our fusarium infection risk reports provide an indication of potential infection risk levels.

“However, the best indicator of risk will always be based on field-level rainfall data recorded during the flowering period for the crop in the ground.”

Infection risk can be mitigated to some degree by a T3 spray and the majority of the wheat area received a well-timed spray at the start of the flowering period.

Dr Bhandari continued: “As always, there are exceptions where the weather derails the best laid plans and interrupts spraying.

“Further rainfall, particularly after ripening, will also allow for secondary infection.

“But the important thing is to record what happened on the mycotoxin risk assessment and let the results guide your management decisions.”

Fusarium head blight

The final summary report also includes observations of fusarium head blight (FHB) incidence in the field.

Symptoms were first reported at the end of June and continued to increase. For example, as of 12 July around 35% of ears inspected in the eastern region showed signs of FHB, which was an increase on the previous week.

FHB can be caused by fusarium and microdochium species. Data from five untreated winter wheat plots, published by CropMonitor, show that no stem-based infection occurred due to mycotoxin producing fusarium species (9 May to 6 June). Infection symptoms were only associated with microdochium species, which do not produce mycotoxins.

Harvest 2016

As part of harvest preparations, many growers will prioritise the order in which crops are cut.

Dr Bhandari said: “This is a wise strategy, particularly during this changeable weather period we seem to be locked into, as it can help protect the quality of crops where a premium needs to be secured.

 “As part of your harvest plan, map out the potential mycotoxin risk across your farm. Group crops with similar agronomy that have been exposed to similar amounts of rain during the critical fusarium infection and spread periods.

“Where FHB symptoms have been spotted in crops, adjust combines to minimise the retention of light fusarium-damaged grains and chaff.

“Crucially, at every opportunity, segregate crops according to their risk score. Once mixed, your power to control grain quality can diminish significantly.

“Once safely in the shed, calculate the final risk score and record it on your grain passport.”

Growers are also advised to check end-user requirements to determine whether mycotoxin testing is required and to plan their approach to grain sampling carefully.

To access AHDB Cereal & Oilseeds full range of harvest resources, visit cereals.ahdb.org.uk/harvesttoolkit