Rhizoctonia canker and black scurf are caused by the fungus, Rhizoctonia solani. The fungus can be spread from the soil, or infected seed and seed pieces.
The fungus can cause reddish-to-dark brown lesions or cankers on sprouts, roots, stolons, and underground stems. Sprouts can be girdled by cankers, and killed before they emerge. Girdling cankers on stolons can pinch off small tubers. Stems seem to become more resistant to infection after emergence. But severe infections can result in cankers on above-ground stems. Severe stem cankers can disrupt water movement in the plant, resulting in yellow leaves and wilting.
Black scurf (fungal masses) can form on the surface of mature tubers. The scurf is not easy to remove, and tubers with a lot of scurf may be rejected for the fresh market.
Control Options for Rhizoctonia canker and black scurf on Potatoes
| Material | Application per Acre | REI | PHI | MOA | Eff. | Notes |
|---|---|---|---|---|---|---|
|
thiamethoxam + fludioxonil + difenoconazole (Cruiser Maxx Potato Extreme) |
0.31 fl oz/100 lb seed | 12 h | - | IRAC 4A; FRAC 12, 3 | G | It will suppress seed-borne Rhizoctonia around developing sprouts. Avoid using seed from infected or heavily scurfed tubers, even with fungicides. Combine with a soil-applied product (in-furrow) to control soil-borne Rhizoctonia. |
|
thiamethoxam + fludioxonil (Cruiser Maxx Potato Insecticide and Fungicide) |
0.19 to 0.27 fl oz/100 lb seed | 12 h | - | IRAC 4A; FRAC 12 | G | It will suppress seed-borne Rhizoctonia around developing sprouts. Avoid using seed from infected or heavily scurfed tubers, even with fungicides. Combine with a soil-applied product (in-furrow) to control soil-borne Rhizoctonia. |
|
thiamethoxam + fludioxonil + difenoconazole + sedaxane (Cruiser Maxx Vibrance Potato) |
0.5 fl oz/100 lb seed | 12 h | - | IRAC 4A; FRAC 12, 3, 7 | G | It will suppress seed-borne Rhizoctonia around developing sprouts. Avoid using seed from infected or heavily scurfed tubers, even with fungicides. Combine with a soil-applied product (in-furrow) to control soil-borne Rhizoctonia. |
|
manxozeb (Dithane F-45 Rainshield (seed treatment)) |
See Label | 24 hr | - | M3 | G | It will suppress seed-borne Rhizoctonia around developing sprouts. Avoid using seed from infected or heavily scurfed tubers, even with fungicides. Combine with a soil-applied product (in-furrow) to control soil-borne Rhizoctonia. |
|
fludioxonil (Maxim 4FS) |
See Label | 12 hr | - | 12 | G | It will suppress seed-borne Rhizoctonia around developing sprouts. Avoid using seed from infected or heavily scurfed tubers, even with fungicides. Combine with a soil-applied product (in-furrow) to control soil-borne Rhizoctonia. Use Rate: 0.08 fl oz product/100 lb seed. |