Alcoholic Flux Treatment: Tips For Preventing Alcoholic Flux In Trees

Alcoholic Flux Treatment: Tips For Preventing Alcoholic Flux In Trees

By: Jackie Carroll

If you’ve noticed frothy-like foam seeping from your tree, then it has likely been affected by alcoholic flux. While there is no real treatment for the disease, preventing alcoholic flux may be your only option to avoid future outbreaks. Keep reading to learn more frothy flux info.

What is Alcoholic Flux?

Alcoholic flux is a stress-related disease that affects sweet gum, oak, elm and willow trees. It usually occurs after a period of very hot, dry weather. The disease is caused by a microorganism that ferments the sap that seeps or bleeds from cracks and wounds in the bark. The result is a white, frothy ooze that has a sweet, fermenting odor similar to beer.

Alcoholic flux is sometimes called frothy flux or foamy canker because of the white ooze that looks and feels like melted marshmallows. Fortunately, this ooze only lasts for a short time in summer.

Frothy Flux Info and Prevention

Anything that promotes the overall good health of the tree aids in preventing alcoholic flux. Symptoms usually occur after a period of extremely hot, dry weather, so water the tree deeply during dry spells. Apply the water slowly to encourage absorption to a depth of 18 to 24 inches (45 to 60 cm.). Water the entire area under the canopy of the tree and cover the root zone with mulch to cut down on water evaporation and keep the roots cool.

A good annual fertilization program helps keep trees healthy and able to resist disease. For mature trees, this means at least one feeding a year, usually in late winter or early spring as the leaves begin to bud. Young trees benefit from two or three smaller feedings over spring and summer.

Wounds and cracks in the bark make it easier for the microorganism to enter the tree. Also, you should prune damaged and diseased limbs back to the collar. Use alcohol, a 10 percent bleach solution or a household disinfectant to clean the pruning tools between cuts so that your tools don’t spread disease to other parts of the tree.

Take care when using a string trimmer around the tree, and mow the grass so that debris flies away from the tree rather than toward it to avoid chips in the bark.

Alcoholic Flux Treatment

Unfortunately, there is no effective alcoholic flux treatment, but the symptoms only last a short while in a healthy tree. In severe cases, the layer of wood under the bark may become rotten and mushy. If the tree doesn’t recover properly, it should be cut down.

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Slime flux

Slime flux, also known as bacterial slime or bacterial wetwood, is a bacterial disease of certain trees, primarily elm, cottonwood, poplar, boxelder, ash, aspen, fruitless mulberry and oak. A wound to the bark, caused by pruning, insects, poor branch angles or natural cracks and splits, causes sap to ooze from the wound. Bacteria may infect this sap causing it to darken and stain the bark, eventually taking on a foamy appearance and unpleasant odor. This slimy ooze becomes toxic to the bark and eats into the tree. Additionally, the fermented sap attracts insects like flies, ants, and maggots.

Wisconsin DNR Forestry News

Recently, there were two reports of a white, frothy substance on the bases of otherwise healthy- looking, mature pine. There are two different possible explanations for this interesting and unusual phenomenon.

Frothy foam at tree base, from distance. Photo by Gary Vander Wyst .

Frothy foam at tree base, close up. Photo by Gary Vander Wyst.

The first is the formation of a crude soap mixture through “stemflow mixing.” As rainwater trickles down tree stems (called stemflow), it collects dust particles (e.g., salts) and plant residues (e.g., acids) that have accumulated on the bark surfaces. As the downward-flowing solution of dissolved acids and salts encounter bark plates, furrows, and ridges, the solution is agitated and aerated, resulting in the formation of suds which collect diffusely at the tree base. Occasionally a light coating of suds is visible higher on the stem. Stemflow mixing has no known affect on tree health.

Alcoholic flux. Photo by Mark Diesen.

The second possible cause of foam formation is the fermentation of sap by microbes, known as alcoholic flux. When wounds and cracks in the cambial area exude sap, microbes such as yeasts may ferment the sap, producing alcohol and gases. This milky colored, alcoholic froth then exudes from the crack/wound to the bark surface, sometimes forming a bubbly stream that smells of fermentation and persists for only a short time. Alcoholic, frothy flux typically originates at a specific location on the tree and is associated with wounds or cracks that may independently cause strength loss or wood defects.

The fluid temporarily bleeding from a tree during warm weather is the external symptom of more serious internal damage. Left unchecked, white-flux bacteria rot the cambial layer, limiting the tree's wound-healing ability.

To reduce a tree’s risk of white flux, avoid wounding it when you mow or trim weeds and keep it adequately watered during dry, hot weather. Gauge when to water by inserting a tile spade -- available from a garden supply center -- into the soil near the tree. Scoop out a soil sample. If the entire sample feels dry or slightly moist, water the tree. If only its top is wet, increase watering time so moisture reaches the lower roots. To control a minor infection, cut out the wounded, frothing area and let it heal. Removal is the only option for trees with severe white flux.

Alcoholic flux is not related to bacterial wetwood, although the two disease can be mistaken for each other. Microorganisms invade the tree through cracks and feed on sap in tree bark and in the layer of wood just under the bark. As they, feed they ferment the sap, causing gas to build up. The gas pressure pushes the frothy, fermenting sap through the bark in small bubbles.

  • There is no cure for this disease, but cultural practices can help extend the life of your tree.
  • Fertilize in the spring with a balanced fertilizer and irrigate regularly to avoid stressing your tree.

Frothy Flux Info - What Is Alcoholic Flux And How To Prevent It - garden


A single wound or bark crack located on the trunk or a large branch may be observed that is actively oozing or bleeding. The oozing liquid is usually clear and may be sour-smelling in the case of slime flux, or frothy (Figure 1) and “fermented-smelling” in the case of alcoholic flux.

The bleeding is often vigorous, and the liquid stains the bark below dark brown or black, whereas the bark above remains completely unaffected (the stain often resembles a comet with a long “tail” extending below the bleeding wound) (Figure 2).

Differential diagnosis

Flux problems can affect any tree species, but appear most commonly on mulberry, elm, and oak. The flux point occurs singly, may be isolated on an otherwise-healthy trunk, branch, or stub, is often associated with pruning wounds, and is usually not too close to the ground (usually above one meter in height or so).

In addition, the volume of the fluxing liquid is usually substantial, wetting the bark for some distance below (in contrast to canker diseases that produce only a few droplets of liquid or none at all).

Importantly, there will be no entry holes or other evidence of insect infestation, thus differentiating the fluxes from beetle-vectored infections such as foamy bark canker of oaks or the Fusarium infection carried by the polyphagous shothole borer (these two insects also invade trees en masse, creating multiple weeping points).


The two flux problems are thought to have different causes. Slime flux is associated with bacterial wetwood (Figure 3), a condition in which the heartwood and parts of sapwood become soaked with liquid containing high levels of bacteria. The bacteria ferment the liquid, increasing its pressure until it oozes out through a bark crack or wound.

The differences in bacteria and the location of infection (wood vs. cambium) likely cause the two liquids to differ in smell and appearance.


Despite their prominence, both types of flux are thought to be minor problems in landscape trees (in contrast to within some fruit or nut trees, where they can be more serious). Neither disease affects tree structure, and slime flux only occasionally causes branch dieback.

Foamy flux is typically also benign, as it usually dries up with the onset of cool weather in late fall. Importantly, no treatment has been shown to consistently result in tree improvement, and chemical treatments are ineffective.

Slime flux has occasionally been treated with scribing (excision) of the margins of the bleeding canker, but this is supported only by anecdotal evidence. On the other hand, such “surgery” may risk interfering with the tree's own process for compartmentalizing and sealing-over the damaged area. Because of this concern, installation of drainage tubes is also no longer recommended.

Instead, provide appropriate cultural care—which may mean providing water—and avoid wounding the tree. The bark staining can often be washed off with water.

Additionally, continue monitoring the tree, as other problems (such as Phytophthora or other canker diseases like Armillaria) could occur on the same tree and should not be allowed to go unnoticed as they can resemble the flux diseases, but are distinguishable upon closer examination.

Visit the UC IPM Website for more information about bacterial wetwood (or slime flux) and alcoholic (“foamy”) flux.

What Lies Beneath

Leaking trees can be caused by three things: chronic slime flux associated with wetwood short-lived, spring sap-flows and foamy, alcoholic "white flux." The key to separating these sources of tree leakage rests with understanding both the origin of the leakage and the colonization of the fluids by various microorganisms.

I've Been Slimed

The exact nature of slime flux and the associated wetwood deep inside the tree is not clearly understood. Wetwood is discolored water-soaked wood that may include both the heartwood and sapwood of the xylem. The affected wood has a high concentration of solutes which draws water through osmosis from the unaffected sapwood. The resulting "wet wood" has a much higher moisture content than even the sapwood making the affected zone anaerobic.

Numerous species of bacteria have been isolated from wetwood. Many are naturally found in the soil and enter the tree primarily through root injury which can be “natural” such as drought or freeze damage, or unnatural through physical injury. The bacteria thrive in the anaerobic conditions of the wetwood and as they digest the wood fiber, they release various gases including methane.

The gasses build pressure to a point where fluids are forced out of openings in the tree such as old wounds. The colorless fluid has a foul odor and seeps down branches or trunks. It can become colored (yellow, red, etc.) primarily by yeast fungi that colonize the seeping fluid.

The slimy, fluxing fluid is called bacterial slime flux because of its connection to bacterial activity. However, the chicken or the egg causality question between bacteria and wetwood has never been clearly answered.

It remains unknown if the high solute concentration that draws water into the wood is simply due to the presence of bacteria, or if bacterial digestion of living sapwood cells releases solutes, or if the concentrated solutes are just a natural occurrence as living sapwood dies. In fact, some wetwood has very low levels of bacteria. Conversely, research aimed at determining if bacteria isolated from wetwood can induce the condition has proven inconclusive.

It is known that although the unsightly bacterial slime flux may last several months and recur for many years, it's mainly an aesthetics problem. Other than perhaps indicating a structural defect that should be investigated, it appears to have little impact on overall tree health. However, wetwood presents a significant problem for the wood products industry by seriously degrading lumber quality.

Saps Up!

Spring sap-flow occurs when sap simply seeps from relatively recent tree wounds, or from wounds that have failed to close. As the name implies, this occurs during heavy periods of sap flow in the spring meaning that it's often a fleeting condition that ceases once the wound closes. The sap can quickly become colonized by fungal yeasts which may give it strange colors including deep reds, oranges, and yellows.

It's important to note that despite the deceptive appearance that the colorful goo is oozing out of the tree like toothpaste, the sap issuing from the tree is actually clear in color. It only looks like something out of black water Hattie's shack after it is colonized at the surface by the yeast. This is an important distinction because the sap-flow is colonized under aerobic conditions whereas bacterial slime flux arises from anaerobic conditions.

Unlike bacterial slime flux, spring sap-flow does not indicate a possible structural degradation deep inside the tree. It's an important diagnostic point. As you can imagine, this would be an awkward conversation with a client: "I have good news and bad news. The good news is that after cutting-up your tree, we didn't find any wetwood it was just spring sap-flow. The bad news is …"

I now believe spring sap-flow that has been colonized by a colorful yeast was responsible for the peculiar bubbling ooze flowing down the Spring Grove dogwood. This is supported by a research paper that highlighted a connection between a particular "red yeast" and spring sap-flow from giant dogwood (Cornus controversa).

The researchers noted that the yeast produces a carotenoid which imparts an orange color to the bubbling brew. The bubbles arise as the yeast ferments sugar in the sap to produce alcohol. In fact, we saw bubbles in the ooze on the Spring Grove dogwood and noticed a sweet, fermentative odor which does not fit with the foul, sulfurous odors emitted from bacterial slime flux.

Alcoholic Trees

Frothy, white fluid issuing forth from a tree indicates a more serious condition. It's sometimes called alcoholic frothy flux because sugar in the sap leaking from affected trees is converted into alcohol by colonizing microorganisms. The frothing is produced by carbon dioxide released during fermentation. Of course, the effluent has a distinctive fermentative odor.

The flux is highly attractive to a number of insects in search of an adult beverage. These include flies as well as various wasps such as yellowjackets, paper wasps, and bald-faced hornets. There is nothing worse than a gag of drunk, belligerent hornets cruising around in their black jackets!

Alcoholic flux is associated with a number of conditions that cast a shadow on the overall health of affected trees. Chief among them is severe tree stress. Several years ago, I diagnosed alcoholic frothy flux on newly planted lacebark elms (Ulmus parvifolia) in parking lot tree islands. The islands were almost constantly irrigated for almost three weeks while the irrigation system was being balanced. Ultimately, around 75% of the trees had to be replaced.

Bacterial Wetwood and Alcoholic Flux

Bacterial Wetwood and Alcoholic Flux

Many times, the first time you see a tree “leaking” will be when insects such as Green June Beetles or Hackberry Butterflies are attracted to the fluid seeping out of the trunk and draw your attention to it.

Bacterial Wetwood, also known as Slime Flux, is a bacterial disease that can affect a variety of tree species, such as oak, elm, mesquite, maples, and others. Bacterial Wetwood occurs when bacteria infect the wood of a tree, usually through a wound in the trunk, limb, or root. The bacteria multiply in the anaerobic environment and may thrive in the tree for several years before pressure builds up and forces the bacteria out of the tree. Because the ooze from the tree contains bacteria, it may have a foul odor. Other microorganisms grow in the flux, contributing to the smell. Insects are often attracted to the odor and congregate around the “leak”.

Although chronic, this disease is rarely serious, and the flux may continue year-round or appear just seasonally. Because it is chronic, it can contribute to a general decline in the tree health but is not known to directly cause tree death.

Stressed trees, especially drought-stressed trees, are particularly susceptible to this disease. Since there is no “cure” for Bacterial Wetwood, providing proper cultural methods will greatly improve the general health of the tree.

*Fertilize the tree in the spring with MicroLife organic fertilizer, spreading it out under the entire canopy.

*Proper pruning cuts are essential, encouraging rapid callusing of the wound.

*Regular deep irrigation under the entire canopy will prevent drought-stress. Dry winters require irrigation as well.

*Avoid wounding of the trunk by string trimmers, etc.

*Do not use “weed and feed” products under the canopy of the tree.

*Do not allow mulch to contact the trunk of the tree.

Alcoholic Flux, also called Frothy Flux, is not related to Bacterial Wetwood but does cause the tree to “leak” a white frothy substance. It is caused by microorganisms that ferment the sap in cracks in the tree. The frothy sap has a pleasant fermentative odor and persists for only a short time in the summer.

Alcoholic Flux is stress related, with heat stress being the most common factor. To avoid this problem, follow the same recommendations for good cultural practices outlined above for Bacterial Wetwood.