Verticillium Wilt Suspected in 'Bloodgood' Japanese Maple with Trunk Fungus

My 9-year-old 'Bloodgood' Japanese maple had a section of shriveled, dead leaves this summer. My husband pruned that part out. Now in September, another section is dying, and there's a white fungal growth on the trunk extending about a foot upward. Can we save the tree? Will it spread to other plants?

Likely Diagnosis: Verticillium Wilt

The symptoms—sudden branch dieback, often on one side or in sections, progressing over a season—are classic for Verticillium wilt, a soilborne fungal disease (Verticillium dahliae) that plugs the tree's vascular system. Japanese maples are highly susceptible.

Key Signs

• Wilting, browning leaves on individual branches
• Greenish-brown streaking in sapwood (visible if you cut into affected wood)
• Progressive dieback over months or years
• Often triggered by stress (drought, heat, root damage)

The White Trunk Growth

The "white fungus" on the bark is likely saprophytic fungi colonizing dead bark—a secondary invader, not the primary killer. Check if it's firmly attached or peels off easily. If the bark underneath is dead (brown, not green), the cambium in that area has been killed by the wilt.

Management Options

There is no cure for Verticillium wilt. The fungus persists in soil indefinitely. However:

• Prune out dead wood well below visible symptoms, sterilizing tools between cuts (10% bleach or 70% alcohol)
• Water deeply during drought to reduce stress
• Mulch properly (2–3 inches, not against trunk)
• Avoid high-nitrogen fertilizers which promote susceptible succulent growth
• Consider soil solarization if replanting in the same area

Spread Risk

The fungus spreads via soil, water, and contaminated tools—not airborne spores. Nearby shrubs and trees can be infected if they're susceptible species (maple, redbud, smoke tree, catalpa, and many others). Resistant species include conifers, birch, beech, oak, and honeylocust.

When to Remove

If the tree loses >50% of its canopy or becomes hazardous, removal is wise. Replace with a resistant species. Have an arborist confirm the diagnosis before investing in extensive treatment.