Linden

(Tilia cordata – Littleleaf Linden, Tilia americana – American Linden/Basswood)

Lindens are popular shade and ornamental trees in Colorado, prized for their heart-shaped leaves, fragrant flowers, and strong structure. They are generally hardy but susceptible to Japanese beetles, aphids, leaf scorch, Verticillium wilt, and environmental stress, especially in hot, dry urban sites.

Seasonal Pest & Disease Calendar

Problem Type Active Season
Aphids (several species) Insect Spring–Fall
Japanese beetle Insect/defoliator Summer
Leaf miners Insect Summer
Verticillium wilt Fungus Spring–Fall (symptoms peak Summer)
Anthracnose / Leaf spot diseases Fungus Spring infection; visible Spring–Summer
Environmental leaf scorch Abiotic Summer
Salt/infrastructure stress Abiotic Winter–Spring

Pest & Disease Guide (Homeowner-Friendly)

Aphids

Common symptoms
  • Sticky honeydew dripping from canopy
  • Sooty mold on leaves and surfaces
  • Curling or distorted foliage
Treatment & management
  • Water-spray to remove aphids
  • Encourage predators
  • Systemic insecticide if severe

Japanese Beetle

Common symptoms
  • Skeletonized leaves
  • Brown, lacy foliage mid-summer
  • Clusters of feeding beetles
Treatment & management
  • Professional systemic treatments
  • Hand-pick beetles early morning
  • Reduce lawn watering (grub control)

Leaf Miners

Common symptoms
  • Brown blisters inside leaves
  • Tunneling patterns
  • Early leaf drop
Treatment & management
  • Typically cosmetic
  • Prune affected areas
  • Treat only if widespread

Verticillium Wilt

Common symptoms
  • Sudden wilting on one side
  • Leaf yellowing/browning
  • Streaking in sapwood
Treatment & management
  • No chemical cure
  • Remove affected limbs
  • Improve watering and reduce stress

Anthracnose / Leaf Spot

Common symptoms
  • Tan/brown blotches
  • Early leaf drop in wet springs
  • Distorted leaves
Treatment & management
  • Usually cosmetic
  • Rake leaves
  • Improve airflow

Environmental Leaf Scorch

Common symptoms
  • Crispy brown leaf edges
  • Yellowing between veins
  • Appears after hot, dry winds
Treatment & management
  • Deep water every 2–3 weeks
  • Maintain mulch ring
  • Supplement irrigation in heat

Salt / De-icer Damage

Common symptoms
  • Browning on roadside-facing side
  • Thin canopy in spring
  • Stunted growth
Treatment & management
  • Redirect runoff
  • Flush soil in spring
  • Apply mulch buffer

When to Worry vs. When It’s Cosmetic

When to Worry (action recommended)

  • Large sections of canopy wilting or browning
  • One-sided dieback (possible Verticillium)
  • Heavy honeydew dripping constantly
  • Full-canopy Japanese beetle damage
  • Repeated yearly leaf scorch

These warrant professional assessment or treatment adjustments.

Mostly Cosmetic (monitor only)

  • Light leaf spotting
  • Minor honeydew
  • Occasional leaf miner damage
  • Early fall color from drought
  • Small scorch patches

These often resolve with improved watering and routine care.