Handling Seed Pieces

Other pages about wound healing:

Using sharp knives during tuber cutting will improve the healing process as a smooth surface heals better. Using clean knives will diminish the spread of any tuber rots from seed-piece to seed-piece and minimize the spread of pathogens. It is best to cut tubers that have been warmed for a few days after storage. It is important to heal the cut surface by storing seed-pieces at 55 to 65 F with relative humidity at 85 to 95%. Keep the storage area well-ventilated. Tubers to be cut should be between six and 10 ounces, and seed-pieces should be two to two and a half ounces with at least one eye. Grade out seed-pieces that are too large and re-cut them, and grade out "blinds," pieces with no eyes, and discard them. Do not store seed-pieces in sunlight or exposed to wind as they will dehydrate.

Use a fungicidal seed treatment after cutting. These treatments have not been reported to delay wound healing and some like mancozeb may promote it (Nolte et al., 1987). Common seed treatment products are mancozeb (MZ), Maxim and Maxim MZ, Tops 5 and Tops MZ, Moncoat, and Moncut. They are primarily effective against dry rot, stem canker and black scurf, and silver scurf. For the bacterial diseases, soft rot and common scab, one would need to add an streptomycin sulfate as an antibiotic (Dusteret A or LD). For more on these diseases, refer to the book "Compendium of Potato Diseases" and the "Potato Education Guides" web-site.

Allow two weeks for the healing process before planting, one week minimum. Timing is critical. Figure 2 shows the percentage of rot in seed pieces exposed to Fusarium spp. (dry rot) and Erwinia spp. (soft rot) at different times after cutting and storing at 68 F (Nolte et al., 1987). After four days, the suberin layer is sufficient to prevent soft rot while two weeks are needed to prevent dry rot on the seed-pieces. Planting directly into the soil ("fresh cut") will cause the wounds to heal more slowly and increase rot.

Planting should be done in soil that is at least 50 F at a six-inch depth. Cooler soils delay emergence allowing pathogens time to attack. Plant in soil that is cooler than the seed-piece. When the seed-piece is cooler than the soil the moisture in the soil will condensate onto the seed-piece causing slower healing from lack of oxygen and create anaerobic conditions that promote the soft rot bacteria to grow. It is not advisable to irrigate after planting until emergence. It is better to irrigate prior to planting so that the soil is about at 70% field capacity (see Nebraska Potato Eyes, summer, 2003, vol. 15, issue 2). Should the soil become dry and the pre-emergence herbicide needs to be activated by moisture, some irrigation can be applied after application two weeks after planting.


Seed piece with soft rot

Figure 1:Seed piece with soft rot

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Seed cut healing and rot

Figure 2:


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