Root rot of American ginseng(Panax quinquefolium) caused by Ditylenchus destructor is a novel disease found recently in Beijing area.The effects of three soil treatments(fumigating with chloropicrin,chloropicrin+lvfeng organic manure and nematicide fosthiazate) on the number of rhizospheric nematodes,survived plants,root yield and root rot of 3-year ginseng plant were compared.The effects were also investigated at the second year after treatment.The results indicated that the number of parasitic nematodes in rhizosphere of treated soil reached the peak value in late June to early July as the soil temperature raised in the growing season.Compared with the regular treatment,the number of plant parasitic nematodes was reduced while non-plant parasitic nematodes increased.The number of non-plant parasitic nematodes in the soil treated with chloropicrin+lvfeng organic manure was 2 times than that treated with chloropicrin only.The ratio of non-parasitic to parasitic nematodes of three treatments was higher than the control.Percent of survived plants was 94.8%-96.4% and diseased root was decreased obviously.The control efficacy was more than 89% at the first year after treatment.The survived plants and plot yield of ginseng increased significantly and the control efficacy was around 40% at the second year.The best of the three treatments was by chloropicrin+organic manure.
