Gummosis is the exudation of a gummy-like substance typically found on fruit trees.  The gum is an amber-colored sappy substance produced as a result of stress on the tree. Gummosis is a specific term for a wide range of potential problems.

Causes of Gummosis

• Environmental stress
  • Freeze damage on trees can cause the trees to produce gum.
  • Over-fertilization can cause trees to grow too fast, causing small splits in the bark where gum will leak out. Therefore, we always recommend you fertilize based on a soil test. It is better than guessing, trust us.
• Mechanical Injury
  • The most common example of mechanical damage we see is from a string trimmer or a lawnmower. However, these issues can be solved with a nice mulch boundary around the tree.
  • Other examples of mechanical damage could include hail, wind, or animals.
• Disease
  • Fungal diseases like cytospora canker or Phytophthora can cause gum formation as well.
    • Cytospora canker causes lesions on branches and trunks of trees. The outer bark of infected areas can turn yellow, brown, red, gray, or black and will appear sunken.
    • Phytophthora root rot will cause the tree to look drought-stressed. identified by cutting away the bark on affected areas, revealing red-brown coloration. (healthy wood will be white on most trees)

      

  • Bacterial Canker
    • Bacterial canker will often start on the leaves giving a tattered appearance, eventually, the disease has moved into the wood it can cause cankers and black lesions on fruit.
• Insects
  • Boring insects in the tree can cause a gummosis reaction. The gum produced by a boring insect can usually be identified by sawdust (frass) mixed in the gum. Furthermore, there should be a small hole behind the gum.
    • However, boring insects are usually a sign of an already stressed tree (drought or overwatering, extreme temperatures, improper planting, poor site, etc.) and could mean there are more underlying problems.

What does this mean for your tree?

First, you need to determine that issue is causing the gummosis, then suggestions can be made for treatment or mitigation. Wellnitz Tree Care can come to assess trees with gummosis problems and give you answers as to what is causing the problem and options. If you have a gummosis problem, give us a call or send us an email.