Effects of root inoculation and fungicide soil drenches on sclerotinia blight of coneflower

Greenhouse studies showed that root inoculation had significant effects on sclerotinia blight (Sclerotinia sclerotiorum) of coneflower (Echinacea sp.) . Seedling wilt and root rot symptoms caused by S. sclerotiorum were most s evere when inoculum was placed in direct contact with seedling roots, and d iminished as the distance of the inoculum from the roots increased. When co lonized agar disks, colonized oat grains and sclerotia as inoculum sources were evaluated on E. angustifolia, grain inoculum was the most virulent and sclerotia the least. An in vitro bioassay was conducted and a logistic dos e-response model was developed for the fungicides benomyl, vinclozolin, ipr odione and dicloran. The first three fungicides were further evaluated in g reenhouse experiments. Benomyl was the most effective in controlling S. scl erotiorum in both bioassay and greenhouse evaluations. The same three fungi cides were evaluated in two field experiments in Alberta, where all were ef fective in reducing disease incidence.