Disease Control

NOTE: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 25 and Fungicides and Bactericides Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Prevention is essential for disease control in sweet potato. The most important diseases are root diseases which become systemic; once infected it is not possible to cure the plant. Vegetative propagation is an ideal vehicle for disease perpetuation. Start with healthy propagating stock and inspect frequently in the production cycle. Planting stock should be produced and stored separately from commercial sweet potatoes. Careful handling and proper curing at harvest are primary disease prevention measures. Application of fungicides and bactericides are not as effective as proper curing in controlling post-harvest diseases. Practice good sanitation of farm equipment, storage bins, and storage rooms. 

Rhizoctonia Root Rot and Stem Canker

azoxystrobin (Quadris): 0.4 to 0.8 fl oz/1000 row feet; PHI 14d, REI 4h, Group 11. Apply in-furrow or banded applications over row. Rotate with a fungicide with a different mode of action.

pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A. May cause crop injury under certain conditions. Do not apply as tank mix with anything other than water. See label for precautions.

thiabendazole (Mertect 340F): 107.0 fl oz/100 gal water or 8.0 fl oz/7.5 gal water); REI 12h, Group 1. Dip the seed roots in the suspension for 1 to 2 minutes and plant immediately. Do not use treated seed roots as food or feed.

Black Rot (Ceratocystis fimbriata)

One of the most significant diseases of sweet potato, black rot is the common name for the decay of fleshy roots and symptoms on sprouts and vines. Successful control of black rot depends on selection of healthy seed roots, fungicide treatment, crop rotation, proper curing, and effective sanitation.

thiabendazole (Mertect 340F): 107.0 fl oz/100 gal water  or 8.0 fl oz/7.5 gal water; REI 12h, Group 1. Dip the seed roots in the suspension for 1 to 2 minutes and plant immediately. Do not use treated seed roots as food or feed.

Soft Rot (Rhizopus)

Careful handling and proper curing at harvest are primary disease prevention measures. Application of fungicides and bactericides are not as effective as proper curing in controlling post-harvest diseases. Practice good sanitation of farm equipment, storage bins, and storage rooms.

dichloran (Botran 75 W): 1.0 lb/100 gal water; REI 12h, Group 14. Apply at bedding as a root dip or postharvest spray. Do not plant tomatoes as follow-up crop. See label for details.