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​Common Tree Diseases in Wisconsin

Tree Disease Signs & Symptoms

Our Certified Arborists believe that early disease detection can be an important part of protecting your trees. By providing our tree disease gallery as a resource for our clients, we hope to help your trees as soon as the signs of damaging diseases appear. While this tree disease gallery is a useful resource for beginning the process of accurate tree care, it is important to have your tree diagnosed by a tree care professional. Contact our Certified Arborists if you suspect that your trees are being affected by one of the tree diseases below and we will start a custom plant health care plan for your trees.

Apple Scab

  • Fungal disease of ornamental crabapple and apple trees
  • Leaves will develop small brown to olive green spots
  • Most common in spring and early summer


  • Fungicide treatment 2-3 times per year
  • Annual treatment is necessary

More About Apple Scab

Tree Fungus Treatment
Tree Fungus Treatment


  • Fungi that affects Pines and Spruces
  • Browning can develop slowly, over several years, or rapidly, depending on spring weather conditions
  • Fungi attacks needles as they emerge and is especially affective with moisture from rains or heavy dews


  • Can be controlled through a protective fungicide spray program
  • Spray treatment protects the new growth that arrives in spring; it can take a least 3 consecutive years of treatment to have aesthetic beauty return

More About Needle Cast

Dutch Elm Disease

  • Fungus that is transmitted from one Elm to another
  • Symptoms typically arise in late spring or early summer
  • Leaves on outer branches will curl (wilt) turn gray-green or yellow and then brown


  • Trunk injection
  • Sanitation pruning of recently infected branches may help

More About Dutch Elm Disease

Tar Spot

  • Black spots on maple leaves
  • Will not kill your tree, just a cosmetic issue
  • Easily spread from tree to tree each year

More About Tar Spot


  • Caused by fungi infecting newly emerging leaves in spring
  • This disease will not result in the death of your tree
  • Systemic fungicides can be used to combat the disease

More About Anthracnose

oak wilt

Oak Wilt Disease

  • Dull green/bronze leaves
  • Careful to not injure/trim Oak trees from April – July as that is the most common time of infection from the spore-carrying beetles.
  • Remedies must be acted upon quickly in order to save the oak trees.

More About Oak Wilt