Fusarium head blight has plagued eastern Canadian farmers for decades. Over the years the disease has spread into Western Canada, and the Canadian Grain Commission has found the fungus as far west as northern British Columbia.
The right management practices will reduce fusarium levels most of the time. But even farmers who do everything correctly are at the mercy of the weather.
“It is very much a disease that is driven by the environment. And now in Manitoba, it would probably be safe to say that if you have the right weather conditions, (there will be) fusarium head blight on your cereals (unless you protect with a fungicide),” says Dr. Jeannie Gilbert, research scientist with Agriculture and Agri-Food Canada (AAFC). Gilbert specializes in fusarium head blight and leaf spot pathogens.
Fusarium overwinters on crop residue. Wheat and corn are both susceptible and should not follow each other in the rotation if fusarium is present. Gilbert says seeding a crop like soybeans into wheat or corn stubble is a better option.
“There has been some suggestion that canola may not be such a good crop to (follow wheat). But it’s not a direct host of fusarium graminearum, and it would be preferable to do that than putting wheat back into your wheat residue, or wheat back into corn residue,” says Gilbert.
Other cereals, such as barley and oats, are also susceptible to fusarium. Oats may not look as diseased, but Gilbert says fusarium species have been isolated from kernels and high levels of deoxynivalenol (DON, also known as vomitoxin) have been detected in Manitoba oats at times. Fusarium graminearum is the only species that spawns the mycotoxin DON.
Two-row barleys are less susceptible to fusarium than six-row barleys, Gilbert says. There are also some newer wheat varieties such as 5602HR, Carberry, and Waskada, which are rated moderately resistant. Saskatchewan farmers haven’t seen as much fusarium, and susceptible varieties like Lillian have been grown regularly, Gilbert says.
“And while (Lillian) grows extremely well in years when you have no conditions for fusarium development, it will get very, very diseased in a year when you have rain.”
Richard Marsh, cereal specialist with Syngenta, says farmers with fusarium problems should consider a variety rated moderately resistant (MR) or at least IR for fusarium.
“We hope in the future that we’re going to have varieties with a lot more natural protection against fusarium.” Marsh says more varieties with even better fusarium suppression are in the pipeline.
Fusarium problems are different in Saskatchewan
Management strategies for Saskatchewan farmers will depend partly on which fusarium species has infected their fields.
Dr. Myriam Fernandez, a cereal pathologist with AAFC in Swift Current, and her colleagues survey fields for fusarium head blight every year. Fernandez says there is F. graminearum in the Indian Head area this year.
“But in Saskatchewan, the main FHB pathogen has been fusarium avenaceum.”
F. avenaceum doesn’t produce DON, and so is not monitored by export markets. However, F. avenaceum does produce other harmful mycotoxins. It will also attack cereals, pulses and even oilseeds. Saskatchewan also has other fusarium species, but so far they are at low levels, says Fernandez.
Between 1999 and 2002, AAFC researchers surveyed nearly 900 cereal fields in eastern Saskatchewan, looking for links between agronomic practices and fusarium.
High fusarium head blight levels, caused by F. avenaceum, were found in wheat and barley crops that followed pulse crops. However, F. graminearum levels dropped in cereals seeded into pulse stubble. Researchers think the higher levels of F. avenaceum in cereals following pulses may be linked to root and crown rot.
“Even in a dry year, you might not get FHB, but you will still get survival of the fusarium pathogen in the roots and the crowns… So in the following year, if conditions are right for FHB, you’re going to still get FHB.”
The surveys suggested links between tillage and fusarium. Fields under reduced tillage seemed to have more fusarium.
“The more residue you have on the ground, the more fusarium survival there is going to be,” says Fernandez.
Fernandez cautions that researchers weren’t able to pinpoint cause and effect relationships in the surveys. For example, though cereals seeded into canola stubble had fusarium head blight, Fernandez can’t say what caused the FHB.
“We have not been able to completely understand the mechanisms. It could be factors related to the crop and to the survival of the different pathogens in the residues and in the roots. And it could be due to the glyphosate. It could be due to the high nitrogen levels in the crop because people tend to apply more nitrogen in the canola crop compared to people who practice wheat after wheat.”
Fungicide application timing is crucial
Syngenta released Fuse, a new fungicide, in limited quantities this year. Fuse is a Group 3 fungicide that suppresses fusarium and controls several cereal leaf and rust diseases.
Marsh says farmers should apply Fuse at the early flowering stage. The main stem will usually flower before the tillers, making it difficult to time application.
“You have to make a bit of an estimation as a grower or an agronomist. Probably go with main stem because… main stems give you your biggest yield,” says Marsh.
Often plants are at different stages of maturity across the field. Marsh says many people will scout for flowering plants. Once plants are starting to flower, they’ll try to spray within 12 to 24 hours.
Farmers need to make sure the fungicide covers the entire head. Effective forward-backward facing nozzles help ensure good coverage, but driving too fast can reduce coverage. Marsh says there are new nozzles coming out designed specifically for controlling fusarium that also allow farmers to drive a little faster than older models. Calibrating the sprayer and correcting the boom height also help ensure good coverage.
Marsh says fungicides won’t stop fusarium 100 per cent. Rotation, residue management, variety selection, seed care, and using clean seed are important management practices.
“If you don’t do those first five steps correctly, coming in with a foliar fungicide, you’re probably not going to be very happy with the results. You have to have an integrated management plan.” †