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44 POTATO GROWER | FEBRUARY 2019 Managing Fusarium dry rot with seed treatments Treat It Right Diggin' In Diggin' In SEED | By Syngenta Dry rot is one of the most important causes of post-harvest potato loss nationwide. Prevention of the fungus, which is caused by several species in the genus Fusarium, begins with a proper seed treatment. The pathogen typically infects a tuber via a cut or bruise before slowly spreading throughout the tuber. The first symptoms of Fusarium dry rot are usually dark lesions on the surface of the tuber, while the skin covering the affected area wrinkles as the underlying tissue dries up. Internally, the affected tissue will appear light to dark brown or black as the fungus kills the cells. Although the fungus primarily enters the tuber through injuries sustained in the seed-cutting phase, it can also spread in seed storage, commercial storage, equipment and conveyor systems, or via infected soil during cultivation. The risk of disease spread is high during storage phases, which is done at cooler temperatures, meaning the fungus tends to spread slowly and take longer for symptoms to appear. However, once you bring out potatoes for cutting and planting, the latent infection manifests in the form of rotted centers. The chances of spreading Fusarium during handling and cutting are very high. "Generally, seed is stored very cold; you don't see the extent of spread in a storage facility," says Kiran Shetty, technical product lead for Syngenta. "But once the potatoes start to warm when they're brought out for cutting and planting, the latent infection that was in the potato starts to cause a dry rot. If the conditions are right, the dry rot will turn into a soft rot. If you plant a seed piece with Fusarium, very likely the Fusarium will spread and you might not get any emergence out of that particular seed piece." In preparation for long-term storage of your seed potatoes, there are few things to consider: • Check for warm spots in the storage. These areas of rot can quickly spread to surrounding tubers. • Maintain a constant holding temperature within the potato pile. • When removing potatoes from storage, handle them with great care and avoid bruising. This care should continue throughout post-storage operations until the seed is cut, treated, transported and planted. It is imperative to use an effective seed treatment when preparing for planting. CruiserMaxx Vibrance Potato, one of Syngenta's newest seed treatments registered for use in the United States, contains two modes of action to fight Fusarium spread. CruiserMaxx Vibrance Potato also reduces the silver scurf and Rhizoctonia spread in the early stages of plant establishment and subsequent growth and development. Following are some general guidelines to reduce or eliminate Fusarium problems being carried into the next production season: While the spread of disease symptoms is often low during storage, the latent disease can spread quickly once seed potatoes are brought out of storage for cutting and planting.