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SPUDSMART.COM SUMMER 201522 ONE OF THE more pervasive tuber diseases in North America silver scurf has been increasing in incidence and severity in recent decades. This has resulted in economic losses that have been most clearly felt in the fresh sector where unsightly potato skins can lower the market value of the crop. Tracy Shinners-Carnelley is the director of research and quality enhancement for Manitobas Peak of the Market a grower-owned not-for-profit vegetable marketing agency. She spoke about silver scurf and the fresh market experience at Manitoba Potato Production Days held in Brandon Man. earlier this year providing some valuable tips for growers looking for ways to battle the disease. WHAT IS SILVER SCURF Caused by a fungal pathogen known as Helminthosporium solani silver scurf causes skin blemishes on potatoes that are tan to silver in appear- ance. These well-defined lesions can expand and join together as they spread across the tuber surface. According to Shinners-Carnelley silver scurf is one of those potato diseases that growers often dont know is there until the blemished tubers come out of the storage. Its also considered a superficial disease in that the fungus is usually confined to the epidermal layer of the tuber although it can damage internal tissue thats in direct contact with infected skins. The skins of scurf-infected potatoes may also thicken and crack after some time in storage causing internal tissues to lose water and shrivel. In those very severe situations you can see it having a greater impact on quality says Shinners- Carnelley. Usually though silver scurf doesnt affect a potatos edibility much provided the damaged portions are cut away before cooking. Why then is silver scurf a cause for concern Producers for the fresh market know that a potatos appearance is a major selling feature so anything that dampens consumer appetites obviously needs to be avoided. These days smooth and thinner-skinned yellow and red varieties of potato tend to dominate the produce aisles and its on these kinds of cultivars that silver scurf tends to show up the most and inflict the most economic damage. For example its hard not to detect silver scurf on a yellow-skinned potato after its infected especially once its been washed. According to Shinners-Carnelley customer expectations are very high these days and one of the assumptions is that potatoes they buy will be attractive and relatively blemish-free. So silver scurf does have the risk of being a very important disease for the fresh industry she says. CONTROL MEASURES Prevention is the key to controlling silver scurf since once a potato has been infected it cant be cured. With this in mind a sensible approach is to start with the seed since the primary source of this disease in potatoes is from other infected tubers. Its important to use seed that is relatively free from silver scurf says Shinners-Carnelley. When an infected seed tuber is planted the spores will form on the surface of that seed. Then throughout the season theyll move down through the soil either by rain or irrigation water to get into that zone where the daughter tubers are developing or they can also grow down the stolons to come in contact with the daughter tubers. The infection then takes place and it isnt necessarily that obvious at harvest time unless you look really really carefully at the tubers she adds. You dont really tend to see the impact of silver scurf until its given some time in storage. Its possible that seed from some sources may be contaminated with silver scurf. Its useful Controlling Silver Scurf This common disease that causes unsightly blemishes on potatoes can be a headache for fresh market producers. What options are available to growers for controlling silver scurf BY MARK HALSALL TRACY SHINNERS- CARNELLEY Silver scurf does have the risk of being a very important disease for the fresh industry. Varying degrees of silver scurf infection on potatoes.