Alberta may still be winning the battle of keeping rats outside its borders, but it’s lost the battle against another scourge from the east. Until last spring, the province could claim to be fusarium free, but last fall, the Canadian Grain Commission found fusarium in 18 per cent of durum and 11 per cent of Hard Red Spring wheat from District 2, in the centre-south. In District 1, farther east, eight per cent of durum and 10 per cent of Hard Red were infected.
Worse still, the CGC recently tightened grade tolerances for fusarium in wheat and durum. Wet weather this year will have provided ideal conditions for the fungal disease and plant pathologists now say that in the south, farmers have to assume fusarium is in the ground and work to control it.
“We’ve had favourable weather for fusarium, with showers and warmth during flowering,” says Alberta Agriculture plant pathologist Ron Howard. “And we have lots of spores around. So we have the conditions for disease – pathogen, host and environment.”
Grain growers in central and northern Alberta can still buy time by using seed with no detectable fusarium and avoiding bringing in seed or straw from irrigated areas or the eastern Prairies, where fusarium is endemic.
Fusarium overwinters on seed or stubble of infected crops and produces infective spores during summer. With just a little moisture, spores can be carried to grain heads, including in nearby fields. At flowering, the spores can infect the floret, causing infected spikelets to bleach prematurely and produce light, shrivelled kernels. In corn, fusarium causes stalk rot and ear rot.
If you have to assume fusarium is in your area, there’s no single strategy to manage it. Durum is the most susceptible wheat and barley the least, but all cereals can be affected, even the few varieties that have “good” resistance. Winter wheat sometimes escapes infection because it ripens early, but not always.
Variety selection is just one part of fusarium management. Corn and tight cereal rotations, yours or your neighbours’, can increase the risk of infection. It takes at least two years to break down crop residue enough to reduce inoculum levels.
At harvest, you can set the combine to blow out lighter, possibly fusarium-infected kernels of wheat, but this doesn’t work for barley or oats. Also, it may increase the inoculum left in the field.
Fusarium can be difficult to see in fields, says Howard. He advises checking wheat at late-milk to early-dough stage when the heads are still green. “Then, you can see the dead glumes white against the dark background of healthy heads that are still green,” he says. “Later, the dead spikelets disappear in the mature heads. After harvest, fusarium may discolour the first node above the ground, but you need lab analysis to confirm the symptoms are fusarium.”
Howard is organizing a province-wide survey of fusarium levels. Applied Research Associations, ag fieldmen and others are assessing infection in wheat and collecting samples of infected heads and later collecting samples of cereal and corn stubble. Howard is hoping for around 700 samples.
“We hope to get a handle on inoculum levels to know where we have the disease,” he says. “We need lab results, so we’ll probably know the situation by the end of the year.”
The Southern Applied Research Association (SARA) is running some trials of fusarium management, looking at variety selection, irrigation management and fungicide treatments.