Tips for scouting, controlling black dot

Tips For Scouting Controlling Black Dot Large

Research Triangle Park, NC, August 28, 2017

Because black dot infects potato plants relatively early in the season and symptoms generally do not appear until late in the growing season, potato growers must always be prepared.

In fact, potato growers should expect to encounter the disease and have a preventative disease control plan in place to most effectively manage black dot when it strikes.

“Black dot is caused by the soil-borne fungus Colletotrichum coccodes and can infect all parts of the potato plant,” said Tye Shauck, Technical Service Representative for BASF. “However, it is most common to get infections in the roots, stolons, tubers and stems.

“The fungus can survive in the soil for several years,” he said. “Additionally, black dot infections can occur from tuber-borne inoculum (from infected seed pieces) or airborne inoculum from windblown soil or sand.”

Be aware of the following black dot warning signs late in the season:

  • Yellow, wilted leaves
  • Yellow stems with small black dots ranging from the base of the stem to several inches above soil level
  • Blemishes or lesions on the surface of your potato tubers, as well as small black dots that develop in storage

Overall plant growth can be impacted by early infections in roots, stems and leaves, causing significant yield reductions in potatoes. In potato tubers, black dot infections can develop during storage and reduce quality.

What’s the most effective way to control black dot? Apply fungicide early in the growing season prior to infection.

“Many diseases, including black dot, have already damaged the crop by the time visual symptoms appear,” Shauck said. “Therefore, preventative fungicide applications around the time or growth stage when the pathogen is known to infect plants, is generally the most effective approach.”

Shauck suggests that growers apply Priaxor® fungicide 40 to 60 days after planting when the plants are in a vegetative growth state. The fungicide’s two active ingredients — pyraclostrobin (FRAC group 11) and fluxapyroxad (FRAC group 7) – work together to effectively control the disease.

Growers can learn more about Priaxor fungicide by visiting, or by contacting their local BASF representative.

Always read and follow label directions.
Priaxor is a registered trademark of BASF. © 2017 BASF Corporation. All rights reserved.


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