Insects and Diseases of Trees in the South

by Anonymous

NECTRIA CANKER

Nectria canker of hardwoods, caused by Nectria galligena and N. magnoliae, is frequently found on yellow birch and black walnut. Common hosts also include bigtooth aspen, sassafras, northern red oak, red maple, beech, Carolina poplar, paper birch, and sweet birch. A closely related canker disease is also found on yellow-poplar and magnolias. The range of this disease includes the Lake States, the Northeast, and the southern Appalachians.

Target-shaped canker of Nectria on sassafras and yellow-poplar.

Older Nectria cankers are easily recognized in forest stands because of their typical “target” shape. “Target” cankers have rings, each of which represent a year’s growth. Younger cankers tend to be grown over by bark and callus tissue attempting to heal the wound. Such cankers are difficult to recognize, but close examination of the affected area may reveal tiny red bodies, which are the fruiting bodies of the Nectria fungi. Mortality rarely occurs from this disease, but stems may break at canker locations during high winds.

Control of Nectria canker is the same as for Strumella canker—the removal of infected trees during thinning operations.