Treating styroblock containers in hot water (68°C) with a very dilute bleach and detergent solution effectively reduced populations of Fusarium and Cylindrocarpon spp., two potential root pathogens of containerized conifer seedlings. However, the treatment did not significantly reduce levels of Phoma (another potential pathogen) nor saprophytic Penicillium and Alternaria spp. The treatment also eliminated Fusarium and Cylindrocarpon spp. from pieces of seedling roots which had penetrated walls of container cells. This cleaning technique will be used in the future at the Champion Timberlands Nursery, Plains, Montana.