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Plant Disease Clinic

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Fact Sheets

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Agronomic Crops

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Streptomyces Soil Rot [Image: Photo of soil rot on plant roots] [Image: Photo of sweet potatoes with lesions] This soilborne disease can cause a rot of the feeder roots that effectively prunes the root system (Fig. 1), leading to reduced vine growth and yield. It also causes distinctive lesions and indentations on storage roots. In some cases, shallow black corky lesions develop on the surface of the root; in others, the lesions may cause the root to crack. The disease is more severe in dry soil and in soil with a pH above 5.2. Jewel is very susceptible and may not produce any yield of marketable roots in severely infested fields. Beauregard and Hernandez are resistant and can produce good yields, but may have some lesions on the storage roots in severely infested fields (Fig. 2).