Magnolia Canker Disease

Nectria Canker

• Nectria canker is a common canker disease amongst magnolia trees. The spores of this fungal disease lie dormant in mature cankers and dead tissue throughout the winter months. Active during the rainy periods of spring and early summer, the fungal spores are transported onto the magnolia’s healthy tissue by wind and rain. A fairly weak disease, nectria canker spores can only infect the magnolia tree through its open wounds and scars. Any entry point to the tree’s tissue suffices, including wounds caused by pruning, weather injury and insects.

Symptoms

• The infected magnolia experiences a series of symptoms that result in the tree’s gradual loss of vigor. Shortly after infection, the magnolia develops discoloration at the disease’s points of entry. The magnolia develops miniature white- to orange-colored fungal bodies that develop into cankers. The cankers grow and spread in efforts to girdle the infected areas. Although nectria canker infections generally do not kill the established magnolia, branches and stems can be killed from the canker’s girdling growth. Distressed magnolias and sapling magnolias can also be killed from severe nectria canker infections.

Treatment

• Nectria canker is a slow-growing disease that can quickly be controlled if treated upon first symptoms. Prune the magnolia’s dead and diseased areas with sharp, sterile pruning shears. Remove infected branches and stems completely with flush cuts. Prune away cankers on the trunk and base of the tree. Cut the wood back to its healthiest area. Always sterilize your shears between each cut to prevent spreading infection throughout the magnolia tree.

Prevention

• Preventative steps will greatly reduce the magnolia’s potential for canker infection. Provide the magnolia with regular irrigations and fertilization to promote vigorous, healthy development. Never allow the magnolia’s soil to dry out completely. Follow the fertilizer’s instructions carefully to prevent over-fertilizing the tree. Mulch the young magnolia’s planting area just before the dormancy period to protect the tree from winter injury and freezing damage. Reserve pruning sessions for dry periods when nectria canker spores are left active and unable to travel.