Crabapple Tree
(Malus spp. — ornamental crabapple varieties)
Crabapples are popular ornamental trees for spring flowers and colorful fruit, but they can be prone to apple scab, fire blight, cedar-apple rust, aphids, and other common apple-family issues in Colorado.
Seasonal Pest & Disease Calendar
| Problem | Type | Active Season |
|---|---|---|
| Apple scab | Fungus | Spring–Early Summer |
| Fire blight | Bacteria | Spring–Summer |
| Cedar-apple rust | Fungus | Spring–Summer |
| Aphids | Insect | Spring–Fall |
| Scale insects | Insect/scale | Spring crawlers; visible year-round |
| Spider mites | Mite | Summer |
| Environmental stress | Abiotic | Summer–Fall |
Pest & Disease Guide (Homeowner-Friendly)
Apple Scab
Common symptoms- Dark leaf spots
- Premature leaf drop
- Clean up leaves
- Improve airflow
Fire Blight
Common symptoms- Blackened twigs
- Shepherd’s crook tips
- Prune infected branches
- Sanitize tools
Cedar-Apple Rust
Common symptoms- Orange spots on leaves
- Defoliation
- Reduce nearby juniper source
- Treat severe cases
Aphids
Common symptoms- Leaf curl
- Honeydew
- Rinse foliage
- Encourage predators
Scale Insects
Common symptoms- Bumps on bark
- Canopy thinning
- Treat crawler stage
- Horticultural oil
Spider Mites
Common symptoms- Bronzed leaves
- Fine webbing
- Increase irrigation
- Rinse canopy
Environmental Stress
Common symptoms- Leaf scorch
- Poor flowering
- Deep watering
- Mulch base
When to Worry vs. When It’s Cosmetic
When to Worry (action recommended)
- Repeated fire blight
- Heavy defoliation from scab
- Declining canopy
These issues can reduce flowering and long-term vigor.
Mostly Cosmetic (monitor only)
- Minor spotting
- Light aphids
- Occasional mite damage
These usually improve with seasonal care and pruning.