“With any rust the younger the crop is when infected the greater the potential for yield reduction. That’s why one of the main control methods is early planting.”
– PAM DE ROCQUIGNY
Farmers checking their wheat crops for leaf rust, tan spot and septoria can add stripe rust to the disease watch list.
Jason Voogt, agronomy manager with Cargill in the eastern half of Manitoba, has found the fungus in four spr ing wheat cultivars – AC Domain, Harvest, Kane and Glenn– in the south-central part of the province.
Str ipe rust has the potential to cause significant yield losses. The good news is since first showing up in the province in 2000 it hasn’t done much damage, even though says Brent McCallum, a plant pathologist with Agriculture and Agri-Food Canada in Winnipeg, most spring wheats grown here are rated intermediate to susceptible.
AC Domain’s resistance to stripe rust is rated “good” in the 2010 edition of Seed Manitoba.
Leaf rust has also been found in AC Domain in south-central Manitoba.
AC Barrie’s tolerance to both stripe and leaf rust is rated “poor”.
Stripe rust was bad in 2005 around Regina and southeast Saskatchewan, McCallum said. It remained cool that year and the disease was able to build up and move around.
“Other than that, we haven’t seen economic damage so far due to stripe rust,” he said.
“When the weather gets hot, the stripe rust will tend to die out and the leaf rust will tend to increase,” he said. “So it will probably switch around in a little while (if it warms up).”
Stripe rust, like leaf rust, is easily controlled by several different fungicides, said Pam de Rocquigny, provincial cereals specialist with Manitoba Agriculture, Food and Rural Initiatives (MAFRI).
“With any rust the younger the crop is when infected the greater the potential for yield reduction,” she said. “That’s why one of the main control methods is early planting.”
Unfortunately this year stripe and leaf rust are showing up earlier than normal, probably because of early, strong southerly winds that can blow in spores from the southern United States, the wet weather and stressed crops.
With rust it’s important to protect the flag leaf, which is responsible for producing the plant food required to fill wheat heads. A lot of spring wheat has reached the flag-leaf stage or beyond already.
It’s relatively easy to distinguish stripe rust from leaf rust, McCallum said. Stripe rust, as its name implies, runs in lines parallel to the leaf views and is a yellow-orange colour.
Leaf rust is scattered on the leaf surface and is a darker-orange colour.
While the new wheats Kane and Glenn appear susceptible to stripe rust, it’s unlikely they’ll contract leaf rust, McCallum said. Both are rated “very good” for resistance to the disease.
In an interview June 18, MAFRI plant pathologist Vikram Bisht said he hadn’t found any rust in wheat fields near Pilot Mound, al though tan spot and septoria were present.
He said sunflower rust has also been found in fields in western and central Manitoba.
Voogt said a lot of his customers with tan spot and rust in their wheat have already applied a fungicide. Others with few signs of disease are monitoring crops in anticipation of spraying to protect them against fusar ium head blight.
Last week MAFRI rated the risk for the disease at moderate to high in much of the south-central region.
Voogt also said the risk for sclerotinia in canola is high in many areas. He found apothecia – the mushroom-like bodies that produce disease spores – in a spring wheat field near Morden two weeks ago. Edible beans were grown in the field last year.