Bur oak blight management

Forests and savannas

Bur oak blight is common in summer and early fall after wet springs and summers. Most bur oaks can handle bur oak blight though and will look healthy the following spring. In May and June, if bur oaks have dieback and epicormic shoots, they are likely stressed by something other than bur oak blight.

During regularly scheduled management we suggest removing bur oaks with significant dieback. Not only are these stressed oaks more susceptible to various pests and diseases, but we have seen increased bur oak blight on stressed bur oaks. We recommend reforesting with a variety of trees appropriate for the site, including bur oak, and protecting them from deer browse, cattle rubbing, and other disturbers.

Despite bur oak blight, bur oak is an excellent species for Minnesota's future. In all cases, promoting tree species diversity is a wise choice to make forests resilient to weather, diseases, and insects.

Yard trees

The same bur oak as above, but photographed in June 2017. Bur oaks susceptible to bur oak blight often look healthy the following spring.

Just because a bur oak has bur oak blight does not mean you should cut it down. In most cases, the tree will leaf out just fine the following year. In fact, we are aware of bur oaks that have sustained severe bur oak blight every year for well over a decade without apparent harm. If a bur oak has significant branch dieback, and if you want to remove it, do so from August through March to avoid possible aboveground oak wilt infection to neighboring oaks.

Fungicide treatment

Unstressed bur oaks that get bur oak blight almost always survive without any treatments. We have observed that many bur oaks showing branch dieback, that also get severe bur oak blight, have sustained root damage in the past (for example, from construction) or have root disease. In those cases, we do not consider bur oak blight the problem. Arborists report widely varying levels of success at treating bur oak blight with the fungicide propiconazole or the plant growth regulator paclobutrazol. Therefore, at this time, we recommend you first consider if there was previous root damage, root disease, or some other problem. If there is, then treating bur oak blight might not make sense. Consider treatments for bur oak blight as experimental, since results vary so widely.

If you treat your bur oak for bur oak blight, you shouldn't need to treat your tree again for several years. We recommend you'd only treat again after the oak has had severe bur oak blight for a couple of years in a row.

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