Avoid Pruning Oak Trees in Summer – Oak Wilt Causes

Avoid Pruning Oak Trees in Summer – Oak Wilt Causes

Oak trees have long been an American favorite. They're one of the best shade trees out there, and many varieties grow fast!

If you love oak trees as much as us, you’ve likely dreaded the deadly oak wilt disease.

Well, pruning oak trees in summer increases their risk of oak wilt. Read on to learn why.

Why You Should Avoid Trimming Oak Trees in Summer

Sap beetles – such as the picnic beetle, dusky sap beetle and strawberry sap beetle – buzz around your yard from April to August and are most active in June and July.

These beetles are attracted to the sap that seeps from wounds and holes in trees, like those from storm damage and pruning. They also love the sweet smell of oak wilt. 

After munching on a tree with oak wilt, these beetles fly to unaffected trees with pruning cuts or holes. Carrying oak wilt spores, those bugs unknowingly infect another tree – most often from April through mid-July. That’s why they're nicknamed the oak wilt beetle.

Because of this added risk, Davey experts avoid pruning oaks from April through August. Just to be safe.

Some tree trimming companies still do trim oak trees during this timeframe, which unnecessarily puts your trees and wallet in danger.

The Worst Case Scenario – What Happens Next

If one tree gets oak wilt, all oak trees in your yard are at risk.

You have to remove the infected tree and treat the other oak trees with a fungicide to protect them. And, your arborist may recommend a mechanical intervention since oak wilt most commonly spreads between root systems.

As you may have guessed, these treatments add up – as Emily in Akron, Ohio recently learned.

Last June, Emily had three red oaks pruned by a local tree company. This spring, Emily was devastated when her 100-year-old oak returned with fewer leaves and soon died.

The local tree care company didn't mention that pruning oaks in summer could lead to oak wilt. If Emily had known, she would have invested in a TCIA-accredited company with professional arborists to avoid these hefty removal and treatment costs.

Keep an Eye Out for Oak Wilt Symptoms

If your oak was pruned from April through July, watch it for signs of oak wilt.

Now, in early August, is when you’ll start to see symptoms, such as the wilting, browning or excessive shedding of green leaves and branch dieback.

If you see these warning signs, scrape off 1-2 inches of bark on a branch that has wilted leaves or premature leaf drop. Under the bark, look for streaking, which is a tell-tale sign of oak wilt.

Suspect oak wilt? Click to learn more about identifying and controlling this deadly disease.

  • The Tree Doctor November 3, 2017 >Hi Lorna. Yes, this applies to pin oak. But if the tree has oak wilt, it would not still be alive. What you described sounds like your tree may have anthracnose or another foliar disease. It’s best to have an arborist evaluate the tree when the symptoms start next year. Hope this helps, Lorna.
  • Lorna Hobart November 1, 2017 >Does this also apply to pin oak? The tree has not been pruned. It looks healthy in Spring but late summer the leaves start curling, browning. I am in an over 55 community. Each small yard has one tree and mine definitely looks different from the others.
  • Brian Tedrick September 14, 2017 >Thanks advice the tree is beautiful red color don't want to see anything happen to it my neighbor ask me cut some limbs over his drive way low hanging
  • chris Walker August 6, 2016 >Great article, thanks for sharing it.
  • Mike Hale August 5, 2016 >I am a salesman arborist in the Akron office of Davey Tree, I have 2 lab confirmed cases in the ravenna area and 2 more samples being cultured. Please do not prune your Oak trees now! Wait until late fall or winter when transmitting insects are not flying and the trees are going dormant for winter. If you live in the Summit or Portage County area please call our office (330) 928-4911 if you see symptoms in your Oak trees.
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