Time to stop pruning oaks

[Lee Borgersen]

                  Time to stop pruning oaks

04/05/2016
 

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The safe period to prune oak trees is over, according to the Minnesota Department of Natural Resources. With recent warm temperatures, oaks are now at high risk of becoming infected with oak wilt.

"Beetles that carry the oak wilt fungus are attracted to sap on fresh cuts on oaks," said Brian Schwingle, DNR forest health specialist. "Therefore, oaks should not be pruned when these beetles are active, which is right now."


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Current oak wilt risk level can be found on the DNR oak wilt Web page at www.mndnr.gov/treecare/forest_health/oakwilt.

Oak wilt symptoms start in the tree's outer crown and move inward. Trees in the red oak group (northern red and pin oaks; black oaks) can die within weeks of becoming infected, while white oaks can take years. Bur oaks take from a year to several years to die from oak wilt.

According to Schwingle, oak wilt spreads from infected trees to healthy trees  training-087in two ways: by disease-carrying-beetles attracted to fresh wounds or cuts and through the fungus moving between connected roots of oaks.

To prevent the spread of oak wilt, follow these guidelines:

Trim oak trees during the winter (November through February).
Avoid wounding or cutting oak trees when beetles are active in spring and summer.
Immediately treat cuts or wounds with pruning paint from spring through autumn.
Cut down diseased oaks in the winter.
Destroy infected wood or treat wood on site by debarking, chipping or tarping the wood.
To tarp diseased wood properly, cover split wood with plastic and bury the edges for at least twelve months to kill the oak wilt fungus and any insects.
Before removing diseased oaks from spring through autumn, sever root connections between healthy and diseased oaks. Work with an experienced, professional arborist or forester. Learn more about oak wilt control at www.mndnr.gov/treecare/forest_health/oakwilt/whatcanido.html.[/color]]www.mndnr.gov/treecare/forest_health/oakwilt/whatcanido.html.

                                 
 


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