Over winter survival of volunteer potatoes in Michigan

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

The 2009 season has been challenging for many growers in the state. Several thousand acres will not be harvested in areas throughout Michigan. This can be whole fields or parts of fields. The appearance of a new strain of late blight has also complicated matters regarding the integrated management of late blight for next season. Even normal agricultural harvest practices can result in volunteer problems for the following season, but this may be worsened by the challenges of 2009. In Michigan, Chris Long has reported that up to 200,000 tubers/A can be returned to the soil after harvest.

Volunteer potatoes act as hosts for a number of important pests and diseases, including Colorado potato beetle, several potato viruses, Paratrichodorus allius (the nematode that transmits tobacco rattle virus, the causal agent of corky ringspot disease) and Phytophthora infestans the late blight pathogen. For this reason, it is important that even at this late stage of the season growers should attempt to destroy tubers left in the soil. Potato tubers are susceptible to cold injury, and in the past tubers left in the soil after harvest would be killed by the freezing soil temperatures of the Michigan winters. However, new data from all over Michigan indicates that soil temperatures have not become sufficiently cold for long enough to completely kill off tubers since we started monitoring in 2000.

Integrated pest management for 2010 begins now

  • Growers should disc fields to leave tubers on the surface of the soil.
  • Where possible, roll the tubers to crush them during the winter.
  • Clearly mark where tubers are left in the soil for intensive scouting for 2010.
  • Culls should be spread on waste or earmarked ground where potatoes will not be grown.
  • Do not form cull piles larger than one ton as tubers in the center of larger piles do not freeze.

The increased risk of winter survival of volunteer and cull potatoes in Michigan increases the chances of them acting as a source of infection for the establishment of late blight epidemics.

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