Oak Wilt

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Prevention

Once an oak is infected it cannot be saved. There are rather expensive chemical treatments available for individual high-value oaks that are not yet infected, but the treatment is neither guaranteed to prevent oak wilt and must be repeated over time.

The best way to deal with oak wilt is prevention. Avoid wounding oaks from April to August. Don’t prune during that time. Be careful with the lawnmower and weed-whacker. If possible, put off construction activities around oaks until the late summer.

Oak Wilt Risk Status

Oak wilt is fatal for all the species in the red oak group; those oaks with pointy-tipped leaves. The white oak group is less vulnerable; those oaks with round-tipped leaves. Oak wilt can be recognized by rapid wilting and loss of leaves beginning at the top of the tree. The entire tree usually dies within a few weeks.

Oaks killed last year will display spore mats with pressure pads that rupture the bark, usually evidenced by a slight swelling and a vertical crack. These are the trees that are particularly dangerous.

If you suspect your trees are infected with Oak Wilt or need more information, please call the professional Arborists at South Metro Land and Landscape for a free consultation today.

More Information

https://extension.umn.edu/plant-diseases/oak-wilt-minnesota

https://www.cityofeagan.com/oak-wilt

https://www.ci.apple-valley.mn.us/241/Oak-Wilt


Other problems for Oak Trees in Minnesota

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Anthracnose

Anthracnose is a fairly common disease among a variety of shade trees, including the oak family. It is caused by the fungus Apiogromonia Quercina. While the symptoms may appear to be serious, the damage is usually minimal and rarely kills a tree on its own. The best defense against Anthracnose in most varieties of shade trees is to simply cleanup and remove the fallen leaves from your yard each Fall and Spring, preventing the spread of the fungal spores.



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Armillaria root rot

Armillaria root root (Armillaria mellea) is a fungal root rot. Symptoms range from stunted leaves to dieback of twigs and branches. The most effective ways of management focus on limiting the spread of the fungus, planting resistant species, and removing infected material. Besides rotting around the trunk and root flare, the most distinctive sign of infection is the honeycolored mushroom that grows from the roots and the base of the plant.

Trees will die from Armillaria root rot when the infection girdles the base of the trunk, eventually causing the trunk to fail or trees fall over due to loss of roots.

More information

https://extension.umn.edu/plant-diseases/armillaria-root-rot


Two-lined chestnut borers

One of the most important insect causes of oak mortality is the two-lined chestnut borer (Agrilus bilineatus). Stressed and weakened trees attract the insect, as well as environmental extremes, construction injury to roots, road salt injury, storm damage, defoliation from leafmining insects, and impacts from other diseases.

Symptoms include dieback at the ends of branches, sparse or discolored foliage, or leaves that wilt suddenly, turn brown, and remain attached to the branches. The two-lined chestnut borer larvae feed under the bark and destroy critical tissue responsible for delivering nutrients and water.

The best defense against the two-lined chestnut borer is again, prevention. Healthy, non-stressed trees will not attract the adults, and vigorous trees are able to put up a good defense against a borer invasion. Removing and proper disposal of infested wood before the beetles emerge in mid-May.

More information

https://extension.umn.edu/tree-and-shrub-insects/metallic-wood-boring-beetles

https://hort.extension.wisc.edu/articles/two-lined-chestnut-borer/

https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5350723.pdf

An adult two-lined chestnut borer

An adult two-lined chestnut borer