Cylindrocladium Root Rot, Cylindrocladium scoparium Morg.

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.-Sycamore seedlings and other southern hardwood species are susceptible to Cylindrocladium root rot, especially in nurseries where seedlings are grown close together (fig. 21a).

Identifying the Disease.-Infected seedlings may be killed by this disease or will exhibit a combination of symptoms: damping-off, root rot, hypocotyl rot, leaf spots, leaf blight, stem lesions, twig dieback, and wilting. Affected roots turn black, shrivel, and die (fig. 21b). Aboveground symptoms are favored by warm, moist conditions such as those that exist during summer irrigation by overhead sprinklers.

Figure 21a. - Sycamore seedling survival in the center and right rows is poor due to root rot, compared to that of the two rows on the left.

Identifying the Fungus.-The fungus produces pinpoint-sized, brown microsclerotia on dead roots, leaves, and stem lesions. Tiny white tufts of conidia appear on surface lesions. Yellow-orange perithecia (0.4 mm) may form on dead leaves and bark under moist conditions.

Biology.-Conidia produced on stem and leaf lesions are spread by wind and splashing rain to other susceptible seedlings. Microsclerotia released into the soil may survive for years, and, during moist conditions, germinate to infect roots.

Figure 21b. - Sycamore seedlings with root damage (left), normal roots (right).

Control.-To prevent spread of inoculum and minimize conditions that favor the fungus, avoid overhead watering in the summer. Plant seedlings further apart to promote vigorous growth and reduce seedling susceptibility. Remove diseased seedlings, and improve soil drainage on moist sites. High-hazard sites may require soil fumigation in the fall or spring to reduce inoculum in the soil.