Biological activity and systemic translocation of the new tetrazolyloxime fungicide picarbutrazox against plant‐pathogenic oomycetes

Abstract BACKGROUND Picarbutrazox is a new tetrazolyloxime fungicide discovered in 2014 by Nippon Soda. It is mostly used to protect against Phytophthora spp. and Pythium spp. However, little is known of its inhibition spectrum, protective and curative activity, and systemic translocation in plants. RESULTS While picarbutrazox did not show obvious antifungal activity, it exhibited significant activity against oomycetes, including Phytophthora spp. , Pythium spp. and Phytopythium spp. . The effective concentration for 50% growth inhibition (EC 50 ) values of picarbutrazox against 16 oomycetes ranged from 3.1 × 10 −4 and 7.27 × 10 −3 μg mL −1 . Furthermore, picarbutrazox could markedly inhibited the mycelial development, sporangia production, zoospore release, and cyst germination of Phytophthora capsici , with EC 50 values of 1.34 × 10 −3 , 1.11 × 10 −3 , 4.85 × 10 −3 , and 5.88 × 10 −2 μg mL −1 , respectively. Additionally, under greenhouse conditions, the protective and curative activities of picarbutrazox at 200 mg L −1 (100%, 41.03%) against the P. capsici infection in peppers were higher than those of the reference fungicide dimethomorph at 200 mg L −1 (77.52%, 36.15%). High‐performance liquid chromatography analysis confirmed that picarbutrazox showed excellent systemic translocation in pepper plants. CONCLUSION The results showed that picarbutrazox markedly inhibited the important plant oomycete pathogens including Phytophthora spp. , Pythium spp. and Phytopythium spp. . It also displayed excellent protective, curative and systemic translocation activity. Picarbutrazox thus has significant potential for preventing and controlling diseases caused by oomycetes. © 2024 Society of Chemical Industry.