Blog Post

Spring control of Rhizoctonia in PNW potatoes

Black scurf on a potato

PACIFIC NORTHWEST: Now’s the time to take control of Rhizoctonia canker, or as some growers know it, black scurf. You’ve bought disease-free seed, but Rhizoctonia is already in the soil waiting to infect your crop. This can cause all sorts of grief to start your season, including slowed-down emergence, a reduced stand and/or weakened plants. As the disease progresses, it can stunt plants, cause the formation of aerial tubers and even turn leaves a purplish color.

Underground cankers can girdle stems, stolons and roots, causing a loss in water and nutrient uptake and a reduction in tuber set. And then there’s that black scurf that doesn’t wash off – it really makes fresh potatoes and seed potatoes look less attractive.

black scurf 2

About that “dirt” that doesn’t wash off; Take the time to wash a few handfuls of your seed before you plant it. Whether you find black scurf or not, we recommend using a seed treatment like CruiserMaxx® Potato insecticide/ fungicide and applying a fungicide like Quadris® in-furrow. This is the standard for controlling Rhizoctonia in the PNW.

Keep in mind a consistent set of uniformly sized tubers under every hill results in higher yields and quality, and total yield is an important factor when choosing a product to control Rhizoctonia.

And that black scurf you don’t want? There’s another good reason to get this disease under control early in the season, helping lessen the amount of “dirt” that doesn’t wash off when you harvest your crop.

All photos are the property of Syngenta unless otherwise noted.

Reporting from Magic Valley, ID



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