Two dry years in a row doesn’t mean Manitoba sunflower growers can skip scouting for moisture-loving diseases.
Producers should always be on the lookout for sclerotinia and rust, Holly Derksen said at the recent Manitoba Special Crops Symposium.
“When we do have a wet year, those are ones to watch for,” said Derksen, a plant pathologist with Manitoba Agriculture, Food and Rural Initiatives.
Scouting for rust is especially important because it’s a disease that can be treated.
“Rust is not generally a huge issue, but it is one we actually have fungicides for,” she said.
If rust appears on the upper four leaves of a sunflower with a one per cent or greater severity at any point before petals start to fall off, it’s time to spray, Derksen said.
“I don’t think it happens very often where we get to the stage where disease is that high, but it’s something growers can look for,” she said. “Because like most diseases, by the time you see it, it’s too late.”
Unlike other crops affected by rust, sunflowers don’t need to wait for spores to blow into an area for infection to occur. Sunflower rust can complete its entire life cycle on the sunflower plant, infecting each year if there’s not proper rotation.
A more serious threat to sunflowers in Manitoba is sclerotinia.
“Sclerotinia is our biggest yield robber in terms of diseases in sunflowers,” Derksen said.
The fungal disease can cause head rot, as well as basal and mid-stock rot, and thrives in damp conditions.
“If the last two years were any indication, the drier years are definitely very beneficial for sunflower growers, because we don’t have a lot of control options for a lot of our diseases in sunflowers,” said Derksen. “When it’s a wet year, sunflower guys can get pretty hard hit and not be able to do much about it.”
Two fungicides for sunflower head rot did hit the market two years ago, but without a bad sclerotinia year to test them out on, Derksen said most producers have yet to make use of them.
“But we’re not going to have dry years every year, so eventually we will be able to really test these fungicides and see how they perform,” she said.
However, sprayed fungicides won’t help producers treat basal rot. Derksen said that requires a different mentality and a long-term plan.
Biofungicides, which attack the disease in the soil and deactivate it before it can attack the plant, need to be applied in off years before a sunflower crop is planted to be effective, she said.
But in order to know what your land needs next year, the pathologist said it’s important to keep a close eye on what your crop is doing this year, and which diseases are affecting it.
“Don’t just go out and scout once, go out and continually scout,” she said. “I know sometimes later in the year you’re past the point where you can do anything about it… but it’s still important for your future management, things like rotation and tillage.”