Succulent plants continue to be very popular in production. At
a recent greenhouse visit, Echeveria plants were yellowing,
shriveling, and dying from Fusarium infection.
Often when individual plants start dying on greenhouse benches, common root pathogens, including Pythium and Phytophthora, are suspected. When the Echeveria stems and roots were examined, symptoms were not typical of Pythium infection, which usually causes more of a “soft rot” of the crown and roots. The leaves and stem had more of a “dry rot” appearance where the leaves were yellowed, turned brown to black, shriveled, were leathery, and stayed intact (Images 1 and 2). Beneath the plant canopy on the stem at the soil line, white clusters of Fusarium spores and hyphae could be seen (Image 3). Fusarium spores are somewhat sticky and are easily spread by water-splashing, wind, and worker activity on contaminated tools and hands. Fusarium is a good colonizer of weakened tissues, particularly from drought stress. Soils that go through repeated cycles of excessive drying and re-wetting will stress the roots and foliage, which can be readily infected by Fusarium. The species of Fusarium was not determined on this plant sample. Most often, the cause of the stem rot is Fusarium oxysporum. Some F. oxysporum isolates are very host specific; however, many are not.
Read more at e-gro.org