Catalpa

(Catalpa speciosa – Northern Catalpa; Catalpa bignonioides – Southern Catalpa)

Catalpa is a hardy, fast-growing ornamental tree known for its huge heart-shaped leaves, showy white flowers, and long bean-like seed pods. In Colorado, Catalpa is generally resilient but can experience issues with leaf spots, canker diseases, borers, mildew, and environmental stress in compacted soils.

Seasonal Pest & Disease Calendar

Problem Type Active Season
Catalpa sphinx caterpillar Insect/defoliator Summer
Scale insects Insect Spring crawlers; visible year-round
Verticillium wilt Fungus Spring–Fall
Leaf spot (various fungi) Fungus Spring–Summer
Powdery mildew Fungus Summer–Fall
Cytospora canker / Nectria canker Fungus Spring–Fall
Environmental stress (drought/compaction) Abiotic Summer–Fall

Pest & Disease Guide (Homeowner-Friendly)

Catalpa Sphinx Caterpillar

Common symptoms
  • Heavy defoliation in mid–late summer
  • Large striped larvae
  • Rapid leaf loss (tree usually recovers)
Treatment & management
  • Hand-pick if reachable
  • Professional treatment if severe
  • Trees often releaf later in season

Scale Insects

Common symptoms
  • Sticky honeydew
  • Black sooty mold
  • Hard or cottony bumps on twigs
  • Yellowing leaves
Treatment & management
  • Treat crawler stage in late spring
  • Horticultural oil in late winter
  • Prune infested branches

Verticillium Wilt

Common symptoms
  • Sudden one-sided wilting
  • Brown or green streaks under bark
  • Progressive dieback
Treatment & management
  • No cure—manage stress
  • Prune out affected limbs
  • Deep watering and mulch improve survival odds

Leaf Spot (Various Fungi)

Common symptoms
  • Brown/black blotches on leaves
  • Early leaf drop
  • Worse in wet springs
Treatment & management
  • Rake up fallen leaves
  • Improve airflow
  • Fungicides rarely needed

Powdery Mildew

Common symptoms
  • White, powdery coating on leaves
  • More common in shaded, humid sites
  • Reduced growth if severe
Treatment & management
  • Prune to improve airflow
  • Avoid overhead watering
  • Fungicide only in severe cases

Cytospora / Nectria Canker

Common symptoms
  • Sunken bark areas
  • Discolored sapwood
  • Branch dieback
Treatment & management
  • Prune out infected limbs to branch collar
  • Sanitize tools
  • Improve vigor—no chemical cure

Environmental Stress

Common symptoms
  • Leaf scorch
  • Yellowing
  • Sparse canopy
  • Early leaf drop
Treatment & management
  • Deep water every 2–3 weeks
  • Reduce soil compaction
  • Mulch 2–4" under canopy

When to Worry vs. When It’s Cosmetic

When to Worry (action recommended)

  • Rapid one-sided wilting (possible Verticillium wilt)
  • Heavy sphinx caterpillar infestations defoliating the tree
  • Multiple cankers with progressing branch dieback
  • Large-scale scale infestation with sooty mold
  • Early-season defoliation year after year

These may require professional evaluation and targeted treatment.

Mostly Cosmetic (monitor only)

  • Light mildew in shaded areas
  • Minor leaf spotting in wet years
  • Occasional late-summer caterpillars
  • Slight scorch during heat waves
  • Early leaf drop in drought

Catalpa is naturally tolerant and often rebounds well with proper watering and minimal stress.