5 Common Tree Diseases in Anchorage (And How to Save Your Birch or Cottonwood)
Is your tree looking sickly? Harsh Alaska winters, pests, and fungal infections can wreak havoc on Anchorage’s beloved birches, cottonwoods, and spruces. In this guide, Boreal Tree Care’s certified arborists break down the 5 most common tree diseases in Anchorage, how to spot them, and—most importantly—how to save your trees before it’s too late.
1. Birch Canker (Anchorage’s #1 Birch Killer)
Signs:
Sunken, dark lesions on bark
Dead branches in the upper canopy
Yellowing leaves in summer
Cause: Fungal infection (often Cytospora or Nectria) exacerbated by stress from drought or winter damage.
How to Save It:
✂️ Prune infected branches 6-8 inches below cankers (sterilize tools between cuts!).
💧 Deep-water during dry spells to reduce stress.
🌲 Preventative sprays in early spring (ask an arborist!).
“We’ve saved dozens of Anchorage birches with early canker intervention—don’t wait until the tree is 50% dead!” – Boreal Tree Care Team
2. Cottonwood Leaf Rust
Signs:
Orange/yellow pustules on leaves
Premature leaf drop (July-August)
Stunted growth
Cause: Fungus (Melampsora) thriving in wet, cool Anchorage summers.
How to Save It:
🍂 Rake and destroy fallen leaves to stop spore spread.
🌿 Apply fungicide in spring (copper-based formulas work well).
⚠️ Avoid overhead watering (damp leaves = rust party).
3. Spruce Needle Cast
Signs:
Purple/brown needles on lower branches first
Needles dropping prematurely
Thin, “see-through” canopy
Cause: Fungus (Rhizosphaera) attacking stressed Sitka or white spruces.
How to Save It:
✂️ Thin dense branches to improve airflow.
💦 Water deeply in fall before ground freezes.
🛡️ Preventative fungicide sprays in May-June.
4. Aspen Leaf Spot
Signs:
Black/brown spots with yellow halos on leaves
Early defoliation (by mid-summer)
Cause: Fungus (Marssonina) in warm, rainy periods.
How to Save It:
🧹 Remove infected leaves ASAP to break the cycle.
🌞 Prune for better sunlight penetration.
🌱 Fertilize in spring to boost immunity.
5. Root Rot (Silent Killer of Anchorage Trees)
Signs:
Mushrooms at the base
Thinning canopy
Bark peeling near soil line
Cause: Fungus (Armillaria) in poorly drained soils (common in Eagle River homes!).
How to Save It:
🚜 Improve drainage with mulch or grading.
⚠️ Avoid overwatering (soggy roots = rot buffet).
🆘 Call an arborist if >30% of roots are infected—it may need removal.
When to Call Boreal Tree Care
While DIY care helps, professional intervention is critical if:
40% of the tree is affected
You see fungal conks or carpenter ants (secondary invaders)
The tree leans near your home or power lines
Anchorage homeowners trust us for:
✅ Disease diagnosis & treatment plans
✅ Safe, expert pruning
✅ Tree removal (if beyond saving)
Act Now—Save Your Trees!
Spotted any of these symptoms? Schedule a free arborist assessment with Boreal Tree Care today. Let’s keep Anchorage’s urban forest healthy!
📞 Call (907) 531-8007 | 🌐 Get a Free Estimate
