Scytinostroma Root Rot, Scytinostroma (=Corticium) galactinum (Fr.) Donk

Leininger, T.D; Solomon, J.D.; Wilson, A. Dan; Schiff, N.M. 1999. A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury of Sycamore. Gen. Tech. Rep. SRS-28. Asheville, NC: USDA Forest Service, Southern Research Station. 44 p.

Importance.-Seedlings of sycamore and other southern hardwoods such as sweetgum, white oak, and nuttall oak are very susceptible to Scytinostroma root rot. The pathogen may kill young seedlings within a month to a year after infection. Fortunately, the disease is not common in southern sycamores.

Identifying the Disease.-The fungus causes a white rot of roots in the collar and lateral roots of the taproot. Lateral roots may decay and, in severe cases, separate from the taproot. Infected seedlings may be dwarfed, have thin crowns, yellowing or dead leaves, and exhibit reduced vigor or decline prior to death. Dead leaves usually remain on the plant after death.

Figure 37. - White mycelial mats on roots and root collars of young sycamore (top) and cottonwood (bottom) trees.

Identifying the Fungus.-Scytinostroma galactinum produces thick, white fungal mats on the surfaces of the root collar and roots below the collar (fig. 37). Fungal mats are visible below the soil line when soil is removed from the base of a tree. Fruiting bodies of this fungus are I very small and inconspicuous, forming from fungal mats on the roots and root collar.

Biology.-Scytinostroma galactinum infects trees through wounds at the root collars of seedlings. Lateral and feeder roots often are killed. The fungus can then survive on dead roots and stumps and spread to living roots. Spores from fruiting bodies also may produce hyphae that infect seedlings.

Control.-Sycamore seedlings and saplings are most susceptible to this disease. Care should be taken to prevent the mechanical wounding of the root collar and lateral roots of seedlings. Removal of diseased seedlings will help minimize the fungus’ spread to healthy seedlings, but no controls are feasible in natural stands.