“The soft rot bacterium that causes seed piece decay is very common, and it has an extensive host range. It survives in soil and surface waters. Soft rot in potatoes is caused by Pectobacterium carotovorum subsp. carotovorum,” says Dr Eugenia Banks, potato specialist with the Ontario Potato Board in Canada.
She points out that temperature and moisture fluctuations play a critical role in the initiation and development of potato seed piece decay caused by soft rot.
Dr Banks suggests ten planting practices that potato growers should take note of in an effort to reduce soft rot to a minimum:
1. Soil temperature should be close to 8 C at planting.
2 . The temperature difference between soil and seed pulp at planting should be no more than 6 C.
3. Planting warm, freshly cut seed into cold soils can lead to poor emergence.
4. Planting seed pieces immediately after cutting into hot, dry soil results in poor wound healing and favours the development of soft rot.
5. Planting cut seed immediately after cutting in a wet soil either cold or warm also results in poor emergence.
6. Planting wet, pre-cut seed kept in storage with poor ventilation and high humidity can result in poor stands.
7. Cold seed planted in warm soils often sweats after planting. The film of moisture around the seed piece promotes soft rot.
8. Avoid bruising seed.
9. Seed cutters not calibrated properly can increase wedge and sliver pieces that are blind. Seed cutters not properly sharpened do not cut cleanly making suberization difficult.
10. Clean seed cutters thoroughly and sanitize with an appropriate disinfectant. Clean the cutters periodically, at the very least when switching to a new lot of seed tubers.
Dr Banks points out that there are no seed treatments specific for soft rot control, although seed treatments for Fusarium dry rot may help to reduce soft rot incidence.
Source: Dr Eugenia Banks, Ontario Potato Board
Cover photo: Courtesy and credit Eugenia Banks