Tree Pests & Diseases
Plum Tree Maintenance
Plum trees are attractive ornamentals and fruit trees, but they can be prone to black knot, canker, borers, aphids, leaf spot, and environmental stress in Colorado conditions.
- Species
- Plum Tree
- Botanical Name
- Prunus spp. — flowering and fruiting plums
- Group
- Ornamental Trees
- Tracked Problems
- 7
Seasonal Calendar
| Problem | Type | Active Season |
|---|---|---|
| Black knot | Fungus | Visible year-round; spreads Spring |
| Cytospora canker | Fungus | Spring–Fall |
| Peach twig borer / borers | Insect | Spring–Summer |
| Aphids | Insect | Spring–Fall |
| Shot hole disease | Fungus/Bacteria | Spring–Summer |
| Brown rot | Fungus | Spring–Summer |
| Environmental stress | Abiotic | Summer–Fall |
Pest & Disease Guide
Black Knot
Common symptoms
- Black branch swellings
- Dieback
Treatment & management
- Prune below infected tissue
- Destroy cuttings
Cytospora Canker
Common symptoms
- Gumming
- Sunken bark
Treatment & management
- Prune affected limbs
- Reduce stress
Borers
Common symptoms
- Flagging shoots
- Exit holes
Treatment & management
- Prune damaged shoots
- Timed treatment if severe
Aphids
Common symptoms
- Leaf curl
- Honeydew
Treatment & management
- Rinse foliage
- Encourage predators
Shot Hole Disease
Common symptoms
- Holes in leaves
- Brown spotting
Treatment & management
- Clean up leaves
- Avoid overhead irrigation
Brown Rot
Common symptoms
- Fruit rot
- Blossom blight
Treatment & management
- Remove infected fruit
- Improve airflow
Environmental Stress
Common symptoms
- Scorch
- Poor fruiting
Treatment & management
- Deep watering
- Mulch base
When to Worry
- Black knot spreading rapidly
- Heavy canker damage
- Repeated fruit loss
Mostly Cosmetic
- Minor spotting
- Light aphids
- Some summer scorch
Notes
These can shorten tree life and reduce performance.
These often improve with pruning and proper irrigation.
Related Resources
Related Services
Great Western Tree Care
When you want a professional opinion
The Root exists to help you understand your landscape. When a tree needs hands-on evaluation, a Great Western arborist can look at it in person.