Slime Flux (Wet Wood) on Maple Trees: A Bacterial Condition

Slime Flux (Wet Wood) on Maple Trees: A Bacterial Condition

Black, vertical streaks on a maple trunk that appear wet, follow bark cracks, and may emit a foul odor are classic symptoms of slime flux (wet wood). This condition occurs when bacteria enter a wound (from pruning, mower damage, etc.) and ferment internal sap, creating pressure that forces dark, smelly liquid out through the bark.

Key Points

• Slime flux itself does not kill the tree; the bacterial fermentation actually inhibits wood-decay fungi.
• Flow may be intermittent, worsening in summer heat.
• Insects (flies, wasps) are attracted to the fermenting sap.

Management

• No cure exists, but reduce tree stress: water during drought, mulch properly, avoid further wounds.
• If odor or insects are problematic, periodically flush the area with water or a dilute bleach solution (1:10).
• Do not install drain tubes—they spread bacteria and create new wounds.

The tree can live many years with this condition if kept vigorous.