Evaluation of prothioconazole and carboxin for resistance management of Fusarium fujikuroi associated with rice bakanae in Jiangsu Province, China

Abstract BACKGROUND Rice bakanae disease (RBD), primarily caused by Fusarium fujikuroi , is a seed‐borne fungal disease causing significant economic losses worldwide. Fungicide resistance in F. fujikuroi to carbendazim, prochloraz, and phenamacril is widespread in China, necessitating new management strategies. This study evaluated the potential of prothioconazole (PTC) and carboxin (CBX) for RBD control and resistance management. RESULTS In 2024, 171 F. fujikuroi strains were collected from Jiangsu Province and identified based on their morphological characteristics and translation elongation factor 1‐ α sequences. The resistance frequencies of these strains to carbendazim, prochloraz, and phenamacril were 47.37%, 49.12%, and 26.32%, respectively. Phenotypic profiling identified eight resistance types, with 1.17% of strains resistant to all three fungicides, 34.50% showing dual resistance, and only 14.04% fully sensitive. The mean half‐maximal effective concentration values of PTC and CBX for inhibiting mycelial growth against the 171 F. fujikuroi strains were 0.0370 ± 0.0010 and 10.9753 ± 0.5877 μg mL −1 , respectively, with no cross‐resistance to the three conventional fungicides. A 1:2 mixture of PTC and CBX showed synergistic inhibition of mycelial growth in vitro . In two‐year field trials (2024–2025), seed soaking with the PTC:CBX (1:2) mixture at 0.075 a.i. g L −1 provided more than 92% control efficacy against RBD, outperforming six registered fungicides. CONCLUSION F. fujikuroi populations in Jiangsu show high resistance to conventional fungicides. The PTC:CBX (1:2) mixture offers an effective and practical resistance management strategy for RBD. This study provides foundational data for integrated RBD management strategies in China. © 2026 Society of Chemical Industry.