A Survey of Phytophthora spp. in Eastern Indian Nurseries and Their Sensitivity to Six Oomycete-Targeted Commercial Fungicides

A survey of the flori-horticultural nurseries in eastern India found Phytophthora nicotianae to be the most widespread Phytophthora species associated with different foliar symptoms of nursery plants and identified the presence of P. palmivora in eastern Indian nurseries for the first time. The survey also led to the first worldwide finding of P. nicotianae on Dipteracanthus prostratus (Poir.) Nees; Ocimum tenuiflorum L. (syn. Ocimum sanctum L.); Philodendron xanadu Croat, Mayo & J. Boos; and Pyrostegia venusta (Ker-Gawl.) Miers and P. palmivora on Episcia cupreata (Hook.) Hanst., as well as the first report from India of P. nicotianae on Spathiphyllum wallisii Regel; Anthurium andraeanum Linden ex André; and Adenium obesum (Forsk.) Roem. & Schult. Sensitivity to commercial fungicides Glazer 35WS, Rallis India (metalaxyl, FRAC code 4); Ridomil Gold, Syngenta (mefenoxam + mancozeb); Revus, Syngenta (mandipropamid, FRAC code 40); Aliette Bayer (fosetyl-Al, FRAC code 33); Acrobat, BASF (dimethomorph, FRAC code 40); and Amistar, Syngenta (azoxystrobin, FRAC code 11) was analyzed, showing EC 50 values ranging from 0.75 to 16.39 ppm, 0.74 to 1.45 ppm, 2.43 to 17.21 ppm, 63.81 to 327.31 ppm, 8.88 to 174.69 ppm, and 0.1 to 1.13 ppm, respectively, with no cross-resistance of the isolates to the fungicides. The baseline information produced about these Phytophthora spp. from ornamental and horticultural host associations could help prevent the pathogens from becoming primary drivers of new disease outbreaks and their large-scale distribution beyond their natural endemic ranges.