Potentilla

Seasonal Pest & Disease Calendar

Pest & Disease Guide (Homeowner-Friendly)

1. Aphids

Symptoms

• Curled or distorted new growth
• Sticky residue (honeydew)
• Ants on stems/branches

Treatment

• Strong water spray to knock them off
• Prune out the worst curled tips early
• Usually cosmetic unless growth is heavily stunted

2. Spider Mites

Symptoms

• Fine yellow “stippling” on leaves
• Leaves look dusty/bronzed; webbing may appear in heavy infestations

Treatment

• Hose foliage (especially undersides) during hot spells
• Avoid drought stress—deep water
• Miticides only if severe and spreading

3. Powdery Mildew

Symptoms

• White/gray powdery coating on leaves
• Most common mid–late summer

Treatment

• Improve airflow and sun exposure
• Avoid excess nitrogen
• Fungicides optional (mostly cosmetic for established shrubs)

4. Leaf Spot / Foliar Blight

Symptoms

• Small brown/black spots that can merge into blotches
• Premature leaf drop late season

Treatment

• Rake/remove fallen leaves
• Water at soil level (avoid overhead irrigation)
• Thin lightly for airflow

5. Rust (Leaf Rusts)

Symptoms

• Yellow/orange spots on leaf tops
• Orange “dusty” spores/pustules often on leaf undersides

Treatment

• Remove heavily infected leaves (don’t compost if it’s bad)
• Improve airflow; avoid wet foliage
• Fungicides rarely needed for homeowners

6. Root / Crown Rot

Symptoms

• Wilting despite watering
• Poor growth, thinning canopy
• Roots/crown dark, soft, or decayed

Treatment

• Fix drainage first (raise bed, amend soil, correct irrigation)
• Let soil dry between waterings
• Replace plants in chronically wet sites (no spray “cure”)

7. Winter Dieback

Symptoms

• Dead tips/branches in spring, delayed leaf-out
• Worse in exposed windy sites or after dry winters

Treatment

• Spring prune back to green wood
• Winter water during warm/dry periods
• Mulch 2–3" (keep off the crown/stems)

Treatment Timing Calendar – Potentilla (Colorado Front Range)

March–Early April ( )

• Prune out winter dieback; lightly thin for airflow
• Start checking tender tips for aphids

Late April–May ( )

• Aphids peak on new growth
• Treat only if heavy distortion/stunting is building

June ( )

• Begin mite scouting as heat ramps up
• Deep water during dry spells (avoid daily light watering)

July–August ( )

• Spider mites + powdery mildew + leaf spots show up
• Treat mites early if stippling is spreading
• Fungicides only if appearance matters

September–October ( )

• Rake and remove fallen leaves (big disease reducer)
• Water before the ground freezes

Winter ( )

• Winter water during warm dry stretches
• No pesticide treatments needed

When to Worry vs. When It’s Cosmetic

When to Worry (Action Needed)

• Repeated heavy bronzing/stippling and leaf drop from mites
• Decline + wilting with wet soil (possible root/crown rot)
• Significant dieback year after year (site stress)

Mostly Cosmetic (Monitor Only)

• Mild powdery mildew late summer
• Light leaf spotting late season
• Small aphid pockets on a few tips