Management of Phytophthora palmivora disease in Citrus reticulata with chemical fungicides

Over 200,000 ha of citrus are grown in Vietnam, and many orchards have been impacted by Phytophthora disease, leading to tree decline and death. Phytophthora palmivora has recently emerged as a serious problem in mandarin (Citrus reticulata) orchards in northern Vietnam, and producers are looking for management solutions. Therefore, we evaluated the efficacy of a range of commercial fungicides and biological agents on the growth of P. palmivora in vitro and for P. palmivora disease management in 6-month-old C. reticulata seedlings and in a 2-year-old C. reticulata orchard. In the in vitro experiment, potassium phosphonate, metalaxyl-M, mancozeb, and Trichoderma viride strongly inhibited the growth of P. palmivora. For diseased seedlings, the percentage recovery of seedlings 50 days after being treated with metalaxyl-M was 70.9%, potassium phosphonate, 69.1%, and mancozeb 57.1%. The percentage recovery of mandarin trees declining from P. palmivora in the orchard 6 months after the first application of potassium phosphonate was 50.0%, metalaxyl-M 45.9%, and mancozeb 30.6%.

DOI: 10.1007/s10327-020-00953-z