Dripping Sap Diseases

Q: I am having trouble with our willow tree. I found at least 4 of these dripping holes or knots.  What should I do?  Here is a photo.   Jim

Expert Reply:

Slime Flux on Elm and Willow

I have researched diseases of Laurel Leaf Willow.  In the photos you provided,  it seems that an injury to the bark, or the removal of a branch is related.  Both injuries seem to be almost healed, but could still provide the opportunity for sap to ooze out.  

There is a disease called Slime Flux that affects trees.  Does the wet area have an unpleasant odor?  Or does it just smell like sap? If there is no odor, is it just sap leaking from the old wounds.  

If it has an odor, it could be Slime Flux; here is some information about this disease.

Bacterial Wetwood (Slime Flux):

Bacterial wetwood, also called slime flux, is a major bole rot of trunk and branches of trees. Slime flux has been attributed to bacterial infection in the inner sapwood and outer heartwood area of the tree. The bacterial infection is normally associated with wounding or environmental stress. The bacteria, Enterobactor cloacae, is determined to cause wetwood in elm, but numerous other bacteria have been associated with this condition in other trees such as cottonwood, willow, ash, maple, birch, hickory, beech, oak, sycamore, cherry and yellow-poplar.

Symptoms of Slime Flux:

A tree with slime flux is water-soaked and “weeps” from visible wounds and even from healthy looking bark. The “weeping” may be a good thing as it is having a slow, natural draining effect on a bacterium that needs a dark, damp environment. A tree with this bole rot is trying its best to compartmentalize the damage. This bacteria alters wood cell walls, causing moisture content of the wood to increase. One interesting thing is that the weeping liquid is fermented sap which is smelly, alcohol based and toxic to new wood.

Control:

Several sources say not to bore holes to drain the rotting wood as it will further spread the bacterium. There is some debate about this practice. Actually, nothing can stop further rot except the tree’s ability to isolate the spot by growing good wood around the diseased portion. Using an insecticide will not help prevent the rot going on inside. You do see secondary insects feeding on sap and the rotting remains but they do not affect the disease process. It is not thought they spread the infection. Don’t waste your money spraying for insects.
Larger, reasonably healthy trees seem to outgrow the problem. A weaker tree may have  flux for a year or two; the problem may seem to go away for a year or two; and then the problem reappears. Improving the health and vigor of the tree helps reduce the chances of the problem becoming severe.

There is not anything that can be sprayed on the trunk to stop this oozing. If you are careful and do not cut around the entire trunk you may want to try  cutting out the infected bark tissue with a diamond shape to allow the sap to drain.

First mix up a bucket of 10% bleach water (one part bleach in nine parts water). Use a strong, sharp knife to cut out the infected bark. Dip the knife blade in the bleach water to disinfect it after every cut to prevent spreading the disease. Cut the bark down to hard wood. Be sure to cut out any discolored bark. Once you’ve got it down to the wood and all cleaned out, soak the open wound with the bleach water. At this point, leave the wound alone. Don’t paint, cover or wrap it. Leave it open and exposed to the air.  This may work for the wound at the base of the trunk.

Dryness is your friend here. Keep an eye on the wound. If you get some foaming ooze at the edge of the wound, just repeat the process.

You never want to remove more than one third of the circumference of the bark on a stem when you’re cutting out the bark. Cutting off more than that will do more harm than good (girdling). If the infection requires you to cut off more than half, you’re better off to remove the branch completely, or just leave the tree alone to fend for itself.

The disease never really goes away, it just fades in and out of the picture. The important thing is to keep your tree as healthy and happy as you know how to make it. Water the tree deeply, but don’t keep it wet all the time. We tend to think that Willows need lots and lots of water, but they withstand drought much better than we give them credit for. Let the soil dry slightly several inches down, and then soak it deeply again. Fertilizer in April is okay, just don’t overdo it, and don’t fertilize after May. Too much fertilizer, or too late in the season,  can result in lank, weak, disease-prone growth.