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Bacteria Wetwood


Bacteria Wetwood

Usually appear in

Spring to Autumn

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Caused By:-     Various Bacteria, Fungi and Yeast


Bacterial Wetwood is a bacterial disease called Slime Flux which attacks many trees such as apple, ash, aspen, beech, birch, cottonwood, elm, fir, hickory, maple, mulberry, oak, plum, cherry poplar, sycamore and willow.
Oak is often affected and Clematis may also be affected.
It is believed that these bacteria, that normally reside harmlessly in the soil or on the stem surface, gets into a wound on the tree which starts to seep sap and stain the bark. The wound to the bark may be caused by many things such as pruning, insects, branch rubbing against each other, cracks and splits especially in the spring. As this sap is very high in sugars the bacteria thrives and eventually enters deep into the stem tissues of the wood and cambium of the tree causing it to ooze more. As the bacteria grows the gasses given off causes more pressure in the infected area and forces out more sap.
Several common bacteria, yeasts and fungi including species of Enterobacter, Klebsiella and Pseudomonas are found in the Slime Flux. Due to the conditions created by the bacteria fungi is much rarer and it is the bacteria that causes the damage.
As the sap putrefies it becomes foul smelling, it does not stop insects from colonising the slime bringing more bacteria, and fungi.
Even bees may be seen collecting the sap from the Slime Flux which may be foaming caused by the fermenting bacteria and yeasts.
These insects are a consequence of the Slime Flux and can be ignored.
This fermentation also produces alcohol and other substances which are toxic to the tree and may well kill it.
On woody climbers such as Clematis, symptoms are wilting and yellowing of the leaves or a failure to come into leaf in the spring. The slimy ooze may be apparent at the base or in a puddle on the soil. The condition is usually fatal.
Picture by Joseph O'Brien, USDA Forest Service,
See also Bleeding Canker, Horse Chestnut Bleeding Canker.


It can be difficult to prevent the stem damage that leads to the development Slime Flux. However, protecting plants from strong winds and frosts, and taking care when digging and working around them, should help. Pruning at the correct time will also limit the chances of getting Slime Flux.
Fortunately, it may be possible to save some affected plants. The bacteria may attack only a branch and yellowing and wilting of the foliage, particularly in spring and early summer may be limited which can be pruned out. Care should be taken as most of the plant can wilt if main stems are affected.
Keeping plants healthy will let the plants natural defences limit any damage and prevent the bacteria from getting a foothold. Therefore mulching and proper fertilising will help the tree to cure itself.
Slime Flux infected plant material should be burnt. Although it is usually safe to replant the same area it would also be prudent to replace some of the soil.
On tree trunks the wound, if caught early enough, the bark and infected area could be cut back slightly and disinfected household bleach solution and allow the trees natural defences to repair the damage. The excess sap should be wiped or washed from the tree to discourage insect's feeding a strong smelling bleach will discourage the insects from coming to the infected area. With prompt and continuous treatment, the tree should survive.
An old practice is to use drain tubes placed into the wood can help release pressure in those trees where Slime Flux is in the inner core. The slime oozes out the tube instead of somewhere else. There is some debate about this practice.

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