Home & Garden: The many causes of oozing trees | PostIndependent.com

Home & Garden: The many causes of oozing trees

Curt Swift
Free Press Gardening Columnist
Pinon oozing with pitch.
Curt Swift |

What is that ooze running down the trunk of my tree?

The oozing of sap is called “fluxing.”

Is it frothy flux, bacterial wet wood, pitch from the pinon pitch mass borer, alcoholic flux, the result of boring insects, a fungal root problem, or the result of stress?

All those conditions are common in our area trees. Frothy flux is a foamy, bubbly frothy substance common to globe willows and other members of the willow family, including poplars. Bacterial wet wood, aka slime flux, is common to many of our trees regardless of genus or species. Pitch mass borer is an insect which feeds in wounds on pinons, causing sufficient irritation for the tree to produce a gum that looks and feels like pink bubblegum.

In some cases the ooze is unnatural, being caused by the fermentation of sugars by bacteria. Slime flux and alcoholic flux are two of these bacterial-caused fluxes. Alcoholic flux is the term we use when oozing is from lenticils on twigs and branches. While not causing any real problem for the tree, trees suffering from this problem look strange with bubbly foam oozing from spots along the branches. Washing the infected area down with a forceful stream of water from your hose often takes care of this problem.

Slime flux, however, is a different story as the problem is deep inside the tree. The complex of bacteria and possibly yeast (single cell fungi) results in a buildup of pressure inside the tree which can split the tree open. In most cases the pressure simply forces the ooze out of pruning wounds and cuts in the bark. Sometimes fluxing is a natural process used by the tree to protect it from attack by insects.

Trees often ooze resin when under stress. I have even seen resin running out of the stomates of pine needles and from twigs and cones due to high internal water pressure. The natural ooze of resin from stomates of bristlecone pine needles is one of the characteristics used to identify this tree. Conifers have resin ducts in their bark which are designed to protect the tree from invasion by insects and fungi.

These ducts supply the resin necessary to “pitch” the insect out of the tree and keep it from gaining entry. If you cut into a healthy conifer, resin will appear almost immediately at the edge of the cut. If a tree is healthy it has lots of resin and the internal water pressure necessary to force the resin out of the bark when cut or wounded. Ips and Mt. Pine Beetle are able to invade weak trees more successfully than more healthy trees due to the tree’s inability to “pitch” them out. Continued resin flow is critical to the continued health of these trees.

Oozing resin can be the sign of a healthy tree but the presence of resin can also led to invasion by the black turpentine beetle. Hence the reason for my recommendation of a trunk spray to help protect the tree from attack by this insect.

GJ Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com.

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