The Rule of Thumb for Sunflower Disease: The Lighter the Lesion, the Bigger the Losses

Phomopsis of sunflowers. The lesions are a light brown colour. Sclerotinia infection is lighter; phoma is much darker. Photo Credit: Sam Merkell

Sunflowers may rival flax for the honour of “prettiest crop,” but this brightly flowered food and oilseed crop has another rather dubious distinction — disease magnet.

From the very ominous sounding phoma black stem, to the insidious sclerotinia, Real Agriculture caught up with Sam Markell, extension plant pathologist with North Dakota State University to talk about all the disease that are trying to kill your sunflowers.

Head rot of sunflowers. Photo credit: Samuel Markell, NDSU

Head rot of sunflowers. Photo credit: Samuel Markell, NDSU

“You can’t manage sunflower diseases if you don’t know what you’re looking at,” Markell says, citing proper identification as the first step in managing disease. From there, understanding the yield-robbing potential of each disease is also really important — while phoma lesions look awful because they are so black, it’s actually the lighter phomopsis and sclerotinia that rob the most yield.

Filmed at CropConnect at Winnipeg, in this video Markell runs through your best options for disease control (hint: rotation first!), plus how to best to protect sunflowers from a rust epidemic.

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