Got Nature? Blog

Question: What Should I Do About The Dark Streaks On Bark Of Mulberry Trees?

Question: We have a large 60+ foot mulberry tree in our back yard that is located by our pond. This is the first year I have seen these dark streaks on the bark of the tree. Should I have concerns?

Answer: From the photos, it looks like wet wood/slime flux is affecting your tree. It is a bacterial infection on trees and in most cases is not a serious issue, but unfortunately, there is nothing to be done about it. Many years ago they used to drill holes to try and allow gases and liquids drain from an area with the slime flux but through research and experience this practice is not recommended.

“Slime flux (also known as wet wood) is a dark, foul-smelling and unsightly seepage of sap from tree trunks (fig. 1). The disease is not usually a serious problem but the appearance can be alarming. Slime flux is caused by common surface-inhabiting bacteria or yeast fungi that enter the trunk through wounds associated with improper pruning, stem breakage, injections, cracks from freeze injury or weak limb crotches. The bacteria and yeast may live on sap nutrients within injured trees for many years without any outward evidence.”

This article from the Purdue Landscape Report titled Slime Flux of Trees shares more about this disease.

Resources
Purdue Landscape Report
Find an Arborist video, Trees are Good-International Society of Arboriculture (ISA)
Tree Pruning Essentials, Publication & Video, The Education Store, Purdue Extension resource center
Tree Pruning: What Do Trees Think?, The Education Store
Tree Installation Process and Practices, The Education Store
Tree Pruning for the Landscape, Webinar, Purdue Extension – Forestry and Natural Resources YouTube channel
Tree Wounds and Healing
Why Is My Tree Dying?, The Education Store
Tree Risk Management, The Education Store
What Are Invasive Species and Why Should I Care?, Got Nature? Blog Post, Purdue Extension – FNR
Purdue Plant & Pest Diagnositc Lab (PPDL)
Subscribe – Purdue Extension-FNR YouTube Channel