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Tracing and Saving Diseased Elms

OPENING flagging on elmOnce a tree has Dutch elm disease, treatment becomes much more difficult as infected areas must be physically cut out of the tree using a process known as ‘tracing’. Tracing has been used as an effective treatment for Dutch elm disease that can save trees, but it’s difficult, costly to the client, and there’s no guarantee the tree won’t die anyway.

Long story short: treat trees for Dutch elm disease before they get infected.

In some cases, elms infected with Dutch elm disease can be saved, but only if the fungus is completely removed from the tree. This process has been effective for nearly thirty years but the health of the tree, the progression of the disease, and the aesthetics of what’s left of the tree after tracing must be considered before starting the process.

Download our Tracing Quick Guide Here

Four Steps in This Dutch Elm Disease Treatment

1 Tracing Elm07

Step 1: Find the Fungus

  • Finding the fungus in the tree is the first step to saving elms by tracing. On the branches that are ‘flagging’ (limbs with yellow, wilted leaves), use a chisel and hammer to cut exploratory windows into the bark.
  • The tree responds to the Dutch elm disease fungus with a staining of the water-conducting tissue under the bark. Keep cutting windows until there is only clear wood.
  • NOTE: if the staining is within 10’ (3m) of the ground, the fungus has reached the roots and the tree may not be saved with this process.

2 Tracing and Saving Diseased elmsStep 2: Remove Diseased Branches

  • Prune off the diseased branch where it connects to the main trunk.
  • Do this for every branch showing flagging symptoms. Be sure to leave a proper branch collar when removing limbs.

OLYMPUS DIGITAL CAMERAStep 3: Tracing

  • The Dutch elm disease fungus grows in a five to eight inch (13-20cm) wide band down to the roots. Removing the bark will kill the fungus by exposing it to air.
  • Using a chainsaw or a chisel and mallet, remove a narrow strip of bark on the trunk.
  • As the fungus can be up to 10 feet (3m) beyond the staining, continue to remove a strip of bark up to 10 feet (3m) past the stain.

4 HPIM0188Step 4: Post-Tracing Protection

  • Tracing only removes the fungus growing in the tree. It will not defend the remaining tree from getting Dutch elm disease again.
  • Protecting the remaining tree with Arbotect is an important step in protecting this tree from future Dutch elm infections.