As demonstrated by terms like rhinorrhea, which is basically a runny nose, some conditions sound worse than they are. In the case of fusarium head blight (FHB), a cereal disease affecting small grains and corn, the nasty name fits like a glove.
In her research work on plant pathology for The Grain Research Centre (CEROM) in Quebec, agronomist Dr. Sylvie Rioux has worked extensively on FHB and seen its effects.
“It’s caused by a range of fusarium species, but easily the most damaging one is Fusarium graminearum (F. graminearum),” said Dr. Rioux. “Apart from causing yield losses and grade reductions, F. graminearum’s main damage comes from the presence of mycotoxins in the grains. These toxins — among which the best known is vomitoxin or DON (deoxynivalenol) — are produced by the pathogenic fusarium species which infect cereal ears in the field.”
Mycotoxins are harmful to both animals and humans. Whether producers are focusing on feed or food, the harm to end use marketability can be devastating. And while outbreaks of the disease — which is promoted by wet weather and high temperatures — are more frequent in Eastern Canada than in the Prairies, in 2016 it turned up in many places where it hadn’t been seen before.
Hitting them where it hurts
Fusarium head blight can do severe economic damage. Rioux quoted a paper from 2004 that estimated the annual cost of fusarium head blight losses in Manitoba at $50 million. “In Quebec,” she said, “there was an outbreak in 2003 that cost $11 million to the harvest insurance program of the Quebec government for compensating grain producers.”
More recently, an economic impact study conducted by Alberta Agriculture and Forestry in May 2015 looked at the effect at the farm level when Canada Western Red Spring (CWRS) wheat becomes infected with fusarium.
The study, by senior economic analyst Richard Heikkla, found that with just 0.4 per cent fusarium damaged kernels in a sample (0.4 per cent disease prevalence), the total revenue loss from a downgrade from No. 1 to No. 2 is about $52 per acre. When the wheat is downgraded further to No. 3 or feed wheat, the economic impact increases to $62 or $65 per acre, respectively. And these are just the losses with a low-level infection.
With the stakes so high, reducing the severity of the disease is critical. While the best ally to control FHB is dry weather, Mother Nature doesn’t always co-operate.
“Because the inoculum comes from crop residues left on the ground, contaminated crop residues from the previous year are a major source of inoculum,” said Rioux. “Rotation with a non-host crop (soybean, canola, pea, clover, alfalfa, etc.) the year preceding the cereal is important, especially in reduced tillage or no-till systems. When it is impossible to plant cereal on a non-host previous crop, plowing is recommended to reduce fusarium inoculum.”
The problem arises when the theory of crop rotation meets the reality of the marketplace.
“A few crops are much more profitable than others these days, so we’ve become very specialized,” said Dr. Randy Kutcher, a plant pathologist with the Crop Development Centre at the University of Saskatchewan. “Rotating three to five crops might be optimal for combating FHB; however for durum growers a lentil-durum rotation is common, while in other areas canola and wheat are often rotated, so you can get a huge inoculant build-up.”
Apart from rotation, Rioux recommends using varieties that are more resistant to FHB to reduce disease severity for a minimal cost.
The third line of attack is fungicides. Of course, there’s a reason it’s No. 3.
“You want all of your wheat heads at the same stage when you spray to have the best chance for control, but that’s hard to achieve,” said Kutcher. “If you have seedling emergence issues or hilly land with high and low spots, it’s very hard to accurately time a fungicide application.
Also, if it’s wet and rainy during flowering you can’t spray, even though there’s a higher risk for disease in those conditions.
Although all of these control methods can reduce FHB, none of them alone are effective enough to reduce it to an acceptable level (<2 ppm DON in grain) in years that are very favorable to the disease.
“Fusarium head blight can’t be eradicated,” said Rioux. “The best we can do is to try and control it by combining different approaches.”
It’s a scary sounding name, and with a prognosis like that for fusarium head blight, the name says it all.
Find the Alberta government’s paper on the impact of fusarium, “Economic Cost of Fusarium: Farm-Level and Regional Economic Impact of Fusarium in Alberta” by searching for “Economic Cost of Fusarium.”).