A little known canola disease that appeared in Alberta a few years ago
is turning up in more places this year.
But pathologists say the increase in fusarium wilt appears to be due to
a rare combination of dry weather and susceptible seed varieties and it
is not expected to become a perennial scourge like sclerotinia and
black leg.
“When you have a heavy year for sclerotinia, there are a lot of fields
infected, and so the total yield loss across the country can be huge,”
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said Ralph Lange, a pathologist with the Alberta Research Council and
an expert on fusarium wilt.
“With fusarium wilt, at least so far, we haven’t seen that.”
That’s small consolation to Jack Lesanko, who farms near Sturgis in
east-central Saskatchewan.
He seeded 60 acres to Pioneer’s 45A55, a Roundup Ready Argentine canola
with a high-yield potential in the black soil zone.
“The crop looked good all year until about 21/2 weeks ago,” Lesanko
said.
“The plants had podded out and then they just wilted up to nothing.
There is just pepper in them.”
He is upset that Pioneer and the marketer, Proven Seed, don’t appear to
have information on the variety’s resistance to the disease.
Thom Weir, the Saskatchewan Agriculture agrologist at Yorkton, Sask.,
said he has had reports of 30 infected fields in the area so far.
“The majority of them appear to be one variety. So there appears to be
significant difference in varietal susceptibility to it.”
He has seen adjoining fields where one was significantly damaged and
the other virtually untouched, depending on the variety seeded.
Bruce Harrison, Proven Seed canola product manager, said he has only
recently received calls about the disease from several farmers in
east-central Saskatchewan and northwestern Manitoba.
The company is taking samples and sending them to labs for
identification.
But generally, the situation “caught us off guard,” he said.
“If you looked back when this product was registered, and even today
… fusarium is not a consideration in the registration process.”
Lange said the problem is not limited to one variety. There is a range
of resistance and susceptibility in existing varieties and the industry
must start to screen them to give growers more information.
Lange was one of the first to diagnose the disease in 1999, along with
Lorraine Harrison, an Alberta Agriculture plant pathologist from Grande
Prairie.
Lange’s monitoring this year shows disease reports from all three
prairie provinces, probably due to the weather.
“There are two types of fusarium involved here. One is fusarium
avenaceum and the other is fusarium oxysporum,” he said. Both are
widely found.
“This year we are really seeing oxysporum coming to the forefront,” he
said.
“Wilt disease tends to be worse, sometimes a lot worse, when plants are
under moisture stress.”
The disease causes the plants to turn yellow, then reddish brown to
purple. The stain is usually on one side of the main stem and branches.
“If you take a jackknife and cut into the water-conducting tissue,
there is a black streaking. What seems to be happening is it’s cutting
off the nutrient and water supply to the plant so the pods dry down and
shrivel.”
There is no way to control the disease and variety selection appears to
be the only solution.
“The real issue now is we need to establish field nurseries where we
can test varieties as they come through the registration system – that,
and indoor screening trials,” he said.
“When we get these running reliably and scaled up, then we can start
running large numbers of different varieties through and get answers
for people and also help out with the breeding process.”
He is developing screening protocols and expects a full program can
begin in a couple of years.
“Then the breeders can take over.”
