Preventing Oak Anthracnose and Oak Wilt

By Hillary HeathDiseases, Prevention, SeasonalComments are off

Oak Anthracnose and Oak Wilt are two commonly confused diseases that occur in Oak trees. Fall and Winter are the best times to prevent these common problems.

The diseases look very similar but cause very different problems in the tree. Oak Anthracnose kills new foliage and twigs, but Oak Wilt blocks water and nutrients in the xylem tissue of the tree. Listed below are ways to spot both diseases, prevention measures, and ways to cure your trees.

Oak Anthracnose is a leaf spot disease caused by fungus. The most susceptible trees are in the White Oak family and anthracnose can kill all the foliage and many twigs on the tree in a new growing season. The plant tissues infected the year before by anthracnose produce spores that are then rain splashed onto the new growth in the spring. Necrotic (brown/dead), deformed, leaf tissue and irregularly shaped spots begin to appear. These spots will form along the veins of the leaf and will have a distinct margin between the healthy and dead tissue. The spots most commonly occur on the lower inside branches where it is more humid. Oak Anthracnose, when treated properly can be cured with no permanent damage.

Oak Wilt is most severe in trees in the Red Oak family. This disease is also caused by fungus and leads to necrotic leaves. Browning of the leaves begins at the margins of the leaf, resembling drought. The fungus that causes Oak Wilt infects the xylem tissues, making the tree unable to carry water and nutrients from the roots to the crown, killing the foliage. The fungus produces a sweet smelling mat of fungal spores under the bark of the tree, this attracts sap feeding insects which carry the spores from tree to tree. You will notice the leaves begin to wilt on the branch extremities and the upper portions of the tree and then will spread inward. A Red Oak tree can completely wilt in 2-6 weeks if left untreated and can die within a year.

The best way to prevent both of these diseases is to practice proper tree maintenance. Rake and remove leaves in the fall and prune trees in the fall to make sure air continues to circulate in the humid spring months when new growth comes in. Make sure when planting trees you have proper tree spacing to promote air circulation through the trees. Prune your trees only during dry weather, this will keep fungal spores from spreading out of infected trees or into fresh cuts on healthy trees. Fertilize your trees regularly with a nitrogen fertilizer, your Certified Arborist can recommend the right fertilizer for your needs. A regularly fertilized Oak tree can build up a resistance to Oak Wilt and Anthracnose.

The only way to treat these diseases is with a fungicide application done by an arborist. Only an arborist can diagnose your tree and recommend whether removal of the tree is necessary.

If you suspect there is something wrong with your Oak trees, call Heath Tree Service today and one of our Certified Arborists will evaluate your needs. 404.261.5000.