The environmental protection agency (EPA) has renewed the specific exemption section 18 emergency label, originally obtained in 2016, for the use of Mertect (thiabendazole) postharvest to control black rot (caused by the fungus Ceratocystis fimbriata) in sweetpotatoes. The renewed label is intended for use in 2020 and will expire on April 3rd, 2021.
While Mertect has been approved for domestic use, the European Union recently lowered the maximum residue level (MRL) for thiabendazole in sweetpotato to 0.01ppm.
Due to this, thiabendazole should not be used on any sweetpotato roots intended for export to the European Union until residue data is available for sweetpotato and the MRL is revised. Information regarding current MRLs can be found here.
For any questions, please contact your county Extension Agent or the NC State University Vegetable Pathology Lab. Thiabendazole is an effective tool to be used by sweetpotato packers and growers to control black rot, but should be used as a complement to cultural practices.
For more information on sweetpotato black rot please see our disease fact sheet.