White Oak

(Quercus alba — also applicable to white oak hybrids)

White Oaks are long-lived and more tolerant of Colorado’s alkaline soils than red oaks, making them strong landscape choices. While generally resilient, they can experience scale, gall insects, borers, and environmental stress.

Seasonal Pest & Disease Calendar

Problem Type Active Season
Kermes scale Insect/scale Spring crawlers; visible year-round
Gall wasps Insect Spring–Summer
Two-lined chestnut borer Insect/borer Summer
Oak lace bug Insect Summer
Anthracnose / leaf spot Fungus Spring–Summer
Chlorosis Abiotic Spring–Summer
Environmental scorch Abiotic Summer–Fall

Pest & Disease Guide (Homeowner-Friendly)

Kermes Scale

Common symptoms
  • Honeydew and sooty mold
  • Yellowing leaves
  • Scale bumps on twigs
Treatment & management
  • Treat crawler stage
  • Horticultural oil
  • Prune infested areas

Gall Wasps

Common symptoms
  • Galls on leaves or stems
  • Distorted foliage
Treatment & management
  • Usually cosmetic
  • No treatment needed

Two-Lined Chestnut Borer

Common symptoms
  • Upper canopy thinning
  • D-shaped exit holes
Treatment & management
  • Reduce drought stress
  • Preventive treatments if needed

Oak Lace Bug

Common symptoms
  • Stippled leaves
  • Leaf browning
Treatment & management
  • Rinse foliage
  • Encourage predators

Anthracnose / Leaf Spot

Common symptoms
  • Leaf blotches
  • Early leaf drop
Treatment & management
  • Usually cosmetic
  • Remove infected leaves

Chlorosis

Common symptoms
  • Yellow leaves with green veins
  • Poor growth
Treatment & management
  • Iron treatments
  • Improve soil conditions

Environmental Scorch

Common symptoms
  • Brown leaf edges
  • Early color change
Treatment & management
  • Deep watering
  • Mulch base

When to Worry vs. When It’s Cosmetic

When to Worry (action recommended)

  • Top-down dieback
  • Borer exit holes
  • Heavy scale infestation
  • Severe chlorosis with dieback
  • Persistent honeydew buildup

These conditions may require professional evaluation and treatment.

Mostly Cosmetic (monitor only)

  • Minor gall formation
  • Light lace bug damage
  • Occasional leaf spot
  • Mild seasonal chlorosis

These typically improve with proper watering and care.