Sycamore

(Platanus occidentalis – American Sycamore; Platanus × acerifolia – London Planetree)

Sycamores and London Planetrees are widely planted in Colorado for their massive size, mottled bark, and excellent shade. While generally tough, they are prone to anthracnose, powdery mildew, borers, cankers, and drought-related stress.

Seasonal Pest & Disease Calendar

Problem Type Active Season
Anthracnose Fungus Spring infection; symptoms Spring–Early Summer
Powdery mildew Fungus Summer–Fall
Sycamore lace bug Insect Summer
Scale insects Insect/scale Spring crawlers; visible year-round
Borer insects Insect/borer Summer
Canker diseases Fungus Spring–Fall
Leaf scorch Abiotic Summer–Fall

Pest & Disease Guide (Homeowner-Friendly)

Anthracnose

Common symptoms
  • Browning and curling leaves
  • Twig dieback in spring
  • Early defoliation
Treatment & management
  • Remove fallen leaves
  • Improve airflow
  • Professional fungicide if severe

Powdery Mildew

Common symptoms
  • White powdery coating
  • Reduced vigor
Treatment & management
  • Improve airflow
  • Avoid overhead watering
  • Treat only if severe

Lace Bugs

Common symptoms
  • Yellow stippling on leaves
  • Leaf browning
Treatment & management
  • Rinse foliage
  • Encourage predators
  • Treat if heavy infestation

Scale Insects

Common symptoms
  • Honeydew and sooty mold
  • Bumps on bark
  • Branch dieback
Treatment & management
  • Treat crawler stage
  • Horticultural oil
  • Prune infested areas

Borers

Common symptoms
  • Exit holes
  • Sawdust/frass
  • Branch dieback
Treatment & management
  • Deep watering
  • Avoid bark injury
  • Preventive treatments if needed

Canker Diseases

Common symptoms
  • Sunken bark areas
  • Oozing sap
  • Branch dieback
Treatment & management
  • Prune infected limbs
  • Sanitize tools
  • No chemical cure

Leaf Scorch

Common symptoms
  • Brown leaf edges
  • Early leaf drop
  • Burned appearance
Treatment & management
  • Deep watering
  • Mulch base
  • Reduce heat exposure

When to Worry vs. When It’s Cosmetic

When to Worry (action recommended)

  • Repeated severe anthracnose defoliation
  • Large cankers on major limbs
  • Borer damage with canopy thinning
  • Heavy scale infestation
  • Rapid upper canopy dieback
  • Major limb failure risk

These issues often require professional arborist evaluation due to tree size and risk.

Mostly Cosmetic (monitor only)

  • Light anthracnose
  • Powdery mildew patches
  • Minor lace bug activity
  • Some drought scorch
  • Early leaf drop in extreme heat

These typically improve with proper watering and seasonal recovery.