RALEIGH, N.C. — Sweetpotato black rot, caused by the fungal pathogen Ceratocystis fimbriata, was found in two commercial sweetpotato storage facilities in January of 2021. Afflicted sweetpotatoes exhibited symptoms of firm, circular lesions ranging from grey to greenish black in color consistent with the disease.
Growers and packers should remain vigilant as sweetpotato black rot can develop and spread under storage conditions. To limit disease outbreaks during storage, prevention is the best method of control. Reusable storage bins should be clear of debris prior to use and properly sanitized. During storage, a storing temperature of 55˚F should be maintained.
Growers and packers can also consider using effective fungicides postharvest and in the field during the next growing season. The fungicides Mertect (thiabendazole) and Stadium (azoxystrobin, fludioxonil, difenoconazole) are effective against black rot and have a postharvest label to use in sweetpotato. The fungicide Mertect can also be applied to seed to protect 2021 plantings from black rot. While both fungicides can be used for domestic markets, they may have restrictions related to maximum residue levels allowed in particular export markets.
If you think you may have sweetpotato black rot at your storage facility and need assistance with diagnostics or management, please contact your local Extension agent and send physical samples and/or photos to the Plant Disease and Insect Clinic. For additional management options, please refer to those listed in our disease factsheet.
–Madison Stahr and Dr. Lina Quesada-Ocampo, N.C. State University