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Mysterious White Foamy Growth on Maple Trunk: Not Slime Flux

A homeowner sees a hard, white, foam-like substance 6–8 inches long on a maple trunk. Initially thought to be bacterial slime flux (wetwood), photos show it's dry, hard, and strip-like—more like spray foam.

Expert Assessment

The growth doesn't match slime flux (which is wet and odorous), insect galleries, or animal damage. It could be a fungal fruiting body (a type of mushroom) or an unusual bark abnormality.

Recommended Steps

If the tree is otherwise healthy, simply remove the growth and monitor for recurrence.
No treatment needed unless the tree shows decline.
Consult a local arborist if it reappears or spreads.

Reference on slime flux: University of Arkansas Fact Sheet.

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