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UNIVERSITY OF IDAHO by Phillip Nolte, University of Idaho extension professor Cheap Insurance Using seed piece treatments IT SEEMS AS THOUGH ALMOST everything continues to get more expensive. Recently, those of us in agriculture have watched prices of fertilizer and other inputs fluctuate in price from expensive to outrageous and back to merely expensive again. Another expensive input for the potato producer is seed potatoes. How do we get the most “bang for the buck” from the seed we can’t do without? Naturally, the purchase and use of certified seed is a good place to start. Certified seed has been produced by a dedicated seed grower and has been subjected to an entire battery of inspections. Like I said, a good start. What else might be recommended? Unfortunately, there are a number of important diseases that can come in with the seed, and management practices to consider that avoid problems. Several of the most important of these seed-borne diseases are Fusarium dry rot, Rhizoctonia (stem canker and black scurf), late blight and silver scurf. There are other diseases, but all of the ones included here can be managed by using an effective seed piece treatment. Not only are these diseases the source of potential problems, there is also the matter of dealing with the risks inherent when cutting tubers to make seed pieces. We all know we aren’t supposed to damage our potatoes, and most growers go through a lot of trouble to avoid bruising and other types of injury during harvest and handling. It almost goes against the grain then, when we cut seed tubers to make seed pieces. Making tubers into seed pieces creates some of the most serious wounds that tubers will ever suffer! It’s still good advice after cutting to continue treating seed pieces gently to avoid further damage, but there may be other practices that could be beneficial— like the aforementioned seed piece treatments. Use of a seed piece treatment makes sense on several levels. From the strictly physiological side of things, the application of a seed treatment can help speed up the healing process by drying out the newly cut surface and improving www.potatogrower.com 27 oxygen exchange, which is necessary for wound healing. The drying can also help prevent an attack of soft rot bacterium by creating an environment less favorable for the pathogen. From the disease control angle, most seed treatments also contain active ingredients that combat the diseases mentioned above. Two of the diseases referred to, dry rot and late blight, attack the freshly-wounded tissues of the cut seed pieces. Late blight can also infect the newly developing sprouts on the non-cut areas of the tuber. For either of these two diseases, an effective fungicide in the seed treatment can prevent infection, seed decay and the spread of disease. The other two diseases, Rhizoctonia and silver scurf, are not associated with the cut portion of the seed piece, but rather with the intact, undamaged skin of the former tuber. Both diseases are activated in the soil, where they began growing on the surface of the seed piece. Rhizoctonia then spreads to the newly developing sprouts, where it causes the stem cankers that we are all familiar with. The silver scurf fungus forms spores on the seed piece that somehow gets spread to the daughter tubers. Rhizoctonia can prune stems and stolons below ground and change the grading profile of the crop. Both Rhizoctonia and silver scurf are responsible for blemishes that are mostly cosmetic, but the presence of either disease can downgrade the appearance of the crop and cost a lot of money, especially in markets where appearance is paramount. I guess I’ve always thought that using seed piece treatments on cut seed was a form of cheap insurance. It just makes good sense to spend a little time and effort protecting the foundation of your crop as well as one of your most expensive inputs. PG