Slime Flux

The unsightly seepage of sap seen on tree trunks this time of year is likely a bacterial disease commonly called slime flux or wet wood.  It occurs in apple, birch, elm, maple, mulberry, oak, poplar and willow. This oozing of sap is termed fluxing.  The infected wood is frequently discolored or appears water soaked (wet wood). As fluxing continues, large areas of the bark become soaked.  Grass may be killed where the flux runs down the trunk onto the grass. 

Many different microorganisms grow in the flux producing a foul or alcoholic smell.  As these microorganisms develop in the nutrient rich tree sap, extreme gas pressures are commonly reached up to 60 pounds per square inch. This pressure forces sap from the trunk through cracks in branch crotch unions, pruning wounds, lawn mower wounds, other injuries and occasionally unwounded bark. This sap composed of nutrients, fatty acids, bacteria and gasses is a readily available source of nutrients for insects of various types. Bees and wasp can usually be observed feeding on the ooze.

There are no curative measures for effectively controlling slime flux.  Preventative measures such as avoiding moisture stress, proper pruning and adequate fertilization may help invigorate trees.  Trees should be watered during periods of drought. To prevent wounds through which bacteria can enter, avoid unnecessary damage to the tree and do not disturb the soil around base of the trees.  Most importantly, trees should be fertilized annually based on the results of a reputable soil analysis to increase tree vigor.

Fortunately, damage to the tree is primarily aesthetic.  Trees rarely die as a result of slime flux.  In fact, trees infected with slime flux are very resistant to decay by other microorganisms.  Unfortunately, slime flux soaked wounds do not close properly as the seeping fluids kill tree tissues involved in wound closure. A solution of 10% sodium hypochlorite (1 part household bleach to 9 parts water) will help surface disinfect the area around the damaged area. This will help discourage insect attraction and help restrict damage to the bark below the damaged oozing area.