You’ll almost never find a plant pathogen making the kind of headlines that COVID-19 is making right now, but the news surrounding the pandemic makes for a lot of interesting parallels when it comes to how we communicate such scourges as Fusarium head blight (FHB) and pasmo, the latter being a flax disease that is prevalent in Canada.
The pandemic has brought with it a predictable pattern in human behaviour that goes something like this: initial fear about the pathogen/virus/disease, followed by frustration caused by the lack of a cure or reliable treatment, followed by a general malaise that sets in (which is when people let their guard down, opening the door for further spread).
As we learn to live with the threat of COVID-19 and make social distancing a habit, so we have learned to live with plant diseases that slowly creep their way into Canada and threaten the livelihoods of farmers in many parts of the country.
Fusarium head blight has become a big issue for us north of the border across Western Canada. Just like COVID-19 began in Asia and seemed a world away, at first people felt like FHB was more of a Manitoba issue. When it became clear that FHB, like every other plant disease, totally ignores provincial borders, research ramped up and we began looking for new sources of resistance.
We are undertaking a five-year project looking at how crop rotation impacts FHB. Currently growers rely on one group of chemicals — triazoles — to mitigate its effects. Since pathogens are known to become resistant to chemistry (think glyphosate resistance), we need multiple ways to combat FHB.
Three different chemotypes of Fusarium graminearum, the predominant species that causes FHB, have been discovered: 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and nivalenol (NIV). It’s believed 3-ADON is more aggressive than 15-ADON, causing more severe symptoms. Understanding chemotypes helps us better understand the pathogen and hopefully come up with new tools for mitigation in the future.
Like the virus that causes COVID-19, we don’t totally understand all the species that cause FHB. If we don’t understand the pathogen, it’s hard to figure out what to do about it. A major problem with FHB is its complexity — although Fusarium graminearum is predominant, there are other species involved and the disease can be viewed as multiple diseases. We don’t yet understand well enough what Fusarium species cause what and the environments in which they are most successful.
Breeding for resistance has been an ongoing process for decades. South of the border they’ve been dealing with FHB for longer than we have, but a treatment is still elusive. Fungicides reduce the severity of symptoms and amount of toxins produced, but in general, only by about 50%. Right now, mitigation methods like diverse crop rotation strategies are an additional weapon as research continues.
The same goes for pasmo, caused by the fungus Septoria linicola, which is widespread globally, including throughout the flax growing areas of Western Canada. Pasmo has been observed in almost all flax fields surveyed in Western Canada, with disease severity ranging from trace to 60% of the foliage affected. Yield losses in infected fields have ranged from 10-30%, according to the Flax Council of Canada.
Like with FHB, efforts are underway to find sources of genetic resistance to incorporate in future flax cultivars.
Until we have a proverbial vaccine, we must take the needed precautions to protect ourselves.