Predicting crop disease problems is like taking a shot in the dark at a moving target.
“For disease to develop, we need certain weather, certain hosts, and certain pathogens, so it can really be like looking into a crystal ball,” said Stephen Strelkov, a professor and researcher at the University of Alberta.
“As a result, there are multiple issues that may be vying for attention.”
But when asked to give their best educated guess, three Alberta plant pathologists all targeted one disease that producers should watch out for this summer — fusarium head blight.
“If I were to name one disease that producers should be thinking about and preparing for, it would be fusarium head blight,” said Kelly Turkington, research scientist with Agriculture and Agri-Food Canada.
“It caused some real problems last year, and what that means is you have lots of infested residue in many areas of the Prairies that carries the fusarium pathogen.”
In 2016, fusarium shot up significantly in both incidence and severity, with almost one-quarter of all crop samples in Alberta testing positive for the disease — up from about six per cent in 2015. But the disease is also expanding its reach into other regions of the province from its typical epicentre of southern Alberta, said Michael Harding, research scientist with Alberta Agriculture and Forestry.
“Fusarium head blight is the one that’s probably experiencing the biggest change across the province and moving into areas where it previously hadn’t really been an issue,” said Harding.
“It is expanding into new areas regardless of the season, and the seasons where we have the really conducive environmental conditions, it’s becoming more and more severe.”
An expensive disease
Years where producers saw high fusarium levels — such as last year — produce inoculum that stays in the soil for the following growing season, triggering another outbreak if conditions are warm and wet.
“It becomes a bit of a cycle,” said Strelkov. “There’s more severe disease, so there’s more infected residue, and then that’s available again to cause further infections. It can start to increase more rapidly as time goes by as you have more and more disease present.
“Fusarium head blight was a pretty big issue last year, so it definitely might be an issue again this year.”
And in wet seasons, the losses can be devastating for farmers. Since the early 1990s, when the disease caused its first severe outbreak in the Canadian Prairies, estimated losses have ranged between $50 million to $300 million annually in Canada.
“It will cause a reduction in yield as little as five per cent upwards of 30 per cent, depending on the level of disease,” said Turkington.
Fusarium also produces mycotoxins that limit the end-use markets for the grains, added Harding.
“In cases where you get a lot of mycotoxin in the grain, it can be difficult to find a market for it.”
But the thing that “really hits producers’ pocketbooks” is the downgrading that comes with fusarium-damaged kernels, said Turkington.
“You can quickly go from a No. 1 to a No. 2 to a No. 3 depending on the type of wheat.”
Last year, conditions were “very conducive” to fusarium, and producers saw a lot of downgrading, said Harding.
“When we get a wet season, we can have quite a bit of damage and financial loss,” he said.
“In cases where graminearum becomes common or well established, we start to see more fusarium-damaged kernels and more downgrading and, therefore, more financial loss.”
And when high levels of mycotoxins are combined with downgrading, “the grain almost becomes unmarketable,” added Turkington.
Managing fusarium head blight can be a “tough nut to crack” too, said Harding.
“It’s really difficult to throw one single management tool at it and see any effect,” he said.
“There isn’t one thing you can do — like spray a fungicide or use a crop rotation or grow a resistant variety — to manage the disease. It’s challenging to manage it. You have to pile on as many management tools as necessary to try and get ahead of the disease.”
Extending your crop rotation, treating your seed, choosing fields with low levels of disease, and using a resistant variety will all help, but once the seed is in the ground, options are limited.
“At that point, you’ll want to look at spraying a fungicide and ensure that you get the most out of that fungicide as possible,” said Turkington.
“The key thing with fusarium is waiting until you have full head emergence. You get that product on all of the plant tissue ideally that you want to protect.
“It will certainly help to improve the level of control, which can be a challenge with fusarium head blight.”
But at best, fungicides will offer about 50 per cent control of the disease, and “once you see disease in your field, it’s too late to spray with a fungicide,” said Turkington.
So producers need to be on the lookout for it.
“You need to scout for it and you need to be aware of how much fusarium graminearum you have in your region or on your farm,” said Harding.
“If you’re in an area where it’s already common, you know to expect it. But fusarium graminearum is moving. If you’re a producer who hasn’t had to deal with fusarium graminearum before, that situation could change.”