Cereal yields blighted by disease

Extremely high levels of ear blight in cereals are being blamed for poor grain size and yields, with early indications showing wheat yields are anywhere between 10% and 50%. But mycotoxin levels may not be as bad as first feared.

North Kent grower Fred French started cutting his first wheat on Monday afternoon (6 August) and yields were 10-15% down. “We were cutting Cordiale at 18% moisture on some early gravelly ground,” he said. “Bushel weights look very variable, but I’d set the yield monitor to 74-75kg/hl.

“Running across the field we were averaging 7.5t/ha to 8.5t/ha. That’s 1-1.5t/ha less than we would expect from a first wheat on this ground.”

A grower near Winchester, Hampshire, who has cut about 140ha has described it as a disaster.

“We have harvested some Claire and Gallant, with a mixture of early and late drilled, and both have been slashed by 50% from last year in terms of yield,” he said.

Mycotoxins in a minute 

 Mycotoxins are toxic substances produced by a fungus that can affect animal and human health.

What causes them?

In wheat, fusarium mycotoxin contamination is produced in the field as a result of infection with fusarium head blight (FHB). It is not always the same species, but Fusarium graminearum is among the most common mycotoxin- producing species.

What is DON and ZON?

The key mycotoxins produced by F graminearum are deoxynivalenol (DON) and zearalenone (ZON).

Head blight can also be caused by Microdochium nivale and M majus, but these do not produce mycotoxins while they do reduce yields.

“Bushel weights are extremely low and have been rejected for milling in some cases, despite us spending more than ever on our fungicide programme.

“We had huge potential six weeks ago, and even now it looks good from a distance, but on closer inspection the ears are still standing straight, where they normally would have gone over.

“There are some ears with absolutely nothing in whatsoever, with many ears carrying small and shrivelled grains. Some may even struggle to make feed quality and I can see there being a two-tier market for feed wheat this year.”

Andrew Watts, NFU combinable crops board chairman, said rejections and claims for poor-quality wheat were likely to be rife this year, so farmers should sample all their loads before fulfilling contracts.

Instead of just hoping wheat loads would be accepted by end users, farmers should sample stores carefully, and speak to merchants about where best to place different quality supplies, said Mr Watts.

Initial reports from Kent confirmed lower bushel weights, particularly in early Gallant, where samples were 67-70kg/hl.

“We have now received about 1,000t of that variety and they [bushel weights] have picked up a little and are now more like 73-74kg/hl,” said John Smith, store manager at Weald Granary.

“Grains look pinched, but screenings are still not high, coming in at 2% or less. The yield loss is coming from the lighter grains, which I believe is likely to be 4-5% down on last year, but Hagbergs and proteins are holding up, so milling quality is being reached,” added Mr Smith.

  Fera sampling

Results derived from 300 FERA samples from around the UK this week demonstrated the high levels of ear disease in wheat crops.

  • Huge 96% of samples carrying fusarium symptoms
  • Higher-than-normal levels of mycotoxin-producing fusarium graminearum and culmorum (28% and 10% respectively)
  • Toxicity likely to be high
  • Lower risk in the North
  • Growers urged to use risk assessments and DON testing

NB: figures from the 52% of isolates completed so far.


Mycotoxins have so far been higher than normal, but also comfortably within limits for milling quality. “We had one random sample produce a DON reading of 700 parts/bn, but most have been 100-200 parts/bn,” he said.

But there seems to be some confusion in the industry over exactly what it faces this year in terms of ear disease, said Simon Edwards, professor of plant pathology at Harper Adams.

“The dominant pathogen that is causing disease symptoms in the ear is Microdochium, which was previously included within the fusarium group, however they are a different species,” explained Prof Edwards.

Microdochium does not produce mycotoxins and typically does not result in huge yield penalties. However, this year is different, pointed out Prof Edwards.

“Like most ear diseases, the susceptible period is through flowering and this year the ear emergence and flowering was extended due to the cool, wet weather and infection was taking place throughout.

“To get effective fungicide control the earwash has to be applied just before or at the point of infection, which was extremely difficult this season,” said Prof Edwards.

“Which is why we have such high levels of Microdochium and the result is whole spikelets being taken out.”

The final consequences will include poor bushel weights due to small grains and also reduced germination. Prof Edwards expected this to have a big effect on malting barley and seed crops.

“Winter barley on the whole has escaped the high levels of infection, with most areas having gone through the flowering period before the worst of the wet weather hit,” he said.

“But in spring barley there could be quality issues where grown for malting and crops will struggle with germination scores.”

Fungicide performance on microdochium 

Microdochium, when considering fungicide control, is not particularly sensitive to current chemistry.

“Tebuconazole and metconazole are far less effective against microdochium compared with fusarium and there would be a higher risk of poor ear blight control,” said Simon Edwards, professor in plant pathology at Harper Adams University College.

“Strobs in the past were very effective against microdochium, but it looks like resistance has built up in the background since the last bad year in 1998.

“Control has been compromised by the extended flowering period and lack of spray days, but in our trials where prothioconazole was used at three-quarter rate, we have achieved 50% ear blight control. It is as good as could be expected.”

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