Effects of Cultural Practices and Temperature on Fusarium Root and Crown Rot of Container-Grown Hostas

Fusarium root and crown rot of hosta plants grown in containers is caused primarily by Fusarium hostae. In an effort to develop an integrated strategy for managing this disease at nurseries, the effects of wounding, container mix content, watering schedule, and temperature on disease development were investigated. Plants were not wounded or were wounded by severing the roots, severing the roots and making incisions in the crown, or severing the roots and removing a small piece of the crown. Plants were inoculated by dipping roots and crowns into a suspension of conidia from one of two isolates of F. hostae. In addition, some plants were inoculated by wounding crowns with a scalpel dipped in a conidium suspension. Disease development was examined on plants grown at different temperatures (18, 25, or 32°C), grown in different container mixes (100% Canadian sphagnum peat, 100% aged and processed pine bark, or a mixture of 50% peat and 50% bark), and watered on different schedules (which kept the container mix wet, moist, or dry). Significant levels of disease occurred only on plants that were wounded when inoculated. Fusarium root and crown rot was more severe when both the roots and crowns were wounded than when only the roots were wounded. Disease symptoms developed when crowns of plants were wounded with a scalpel infested with conidia, suggesting that contaminated tools used for vegetative propagation may transfer F. hostae. Disease development also was affected significantly by container mix content, watering schedule, and temperature. In separate experiments, disease was most severe on plants grown in 100% aged pine bark, in dry container mix, or at 18 to 25°C. Disease development was significantly less when plants were grown in 100% peat, in wet container mix, or at 32°C. These results suggest that altering or manipulating cultural practices used to produce hostas in containers at nurseries can reduce the impact from Fusarium root and crown rot.