Verticillium wilt

Verticillium wilt, caused by two similar fungal pathogens, Verticillium albo-artrum and Verticillium dalhiae, can infect over 300 kinds of annual, perennial and woody ornamental plants worldwide. Elm and maple trees are particularly susceptible to this pathogen. Both Verticillium spp. are soil-borne fungi that typically infect plants through wounds in the roots. Once infected, the fungus spreads throughout the plant by mycelium growth or via spores transported in the plant sap, eventually restricting water movement and causing branch dieback. Depending on the size of tree, they can be killed within a year or over time. Fungal spores can survive in the roots, trunk, or soil for long periods of time.

Wilt diseases typically have similar symptoms, with sudden wilting of individual branches. Trees infected with Verticillium wilt will often have chlorotic or partial defoliation of leaves prior to branches wilting. Growth of infected trees may also be reduced or stunted, small twigs may dieback and crowns may appear sparse. In branches with advanced infections, the sapwood will often have bands or streaks of light to dark brown (elms) or light to dark green (maple).

Control

Avoid planting trees in soil where plants were known to have died from Verticillium wilt, as the fungal pathogen can live for years in the soil. Remove trees with severe infections, burning or burying wood. There are no chemical control options for Verticillium wilt.