Chemical control of disappearing root rot of ginseng caused by Cylindrocarpon destructans
The ability of fungicides to control disappearing root rot of ginseng (Panax quinquefolium L.), caused by the fungus Cylindrocarpon destructans (Zinssmeister) Scholten, was examined. Of 15 fungicides screened for toxicity to the fungus in vitro, the most toxic were Benlate (benomyl), Thiram (thiram), Orbit (propiconazole), Crown (carbathiin and thiabendazole), UBI-2584 (tebuconazole), and ASC-66835 (fluazinam). Orbit, Benlate, and ASC-66835 applied as fungicidal drenches significantly reduced the incidence of disappearing root rot in 1-year-old and 2-year-old ginseng gardens, by up to 77%. Thirteen species or genera of fungi were isolated from endosperms of ginseng seeds produced in Ontario. Cylindrocarpon destructans was isolated from 5.4% of 1,304 endosperm halves plated on isolation medium. Benlate applied to stratified seed did not significantly reduce the number of emerged plants and significantly decreased the number of plants that became diseased in the first six weeks after seeding. The results provide new opportunities for integrated management of the disease.