Managing Tar Spot and Scale on Holly Bushes

Dual Problem Identified

The north-side holly shows yellow leaves with large black spots (likely tar spot, a fungal disease) and small white spots outlined in black (likely scale insects). The south-side holly remains healthy, suggesting a localized issue—perhaps more shade, poorer air circulation, or drainage differences.

Integrated Treatment

1. Fungicide: Apply chlorothalonil (Daconil) or Spectro 90 to control tar spot. Spray at bud break and repeat per label.
2. Insecticide: Use a systemic like imidacloprid (Bayer Advanced Tree & Shrub) as a soil drench. It provides up to 8 months of scale control.
3. Sanitation: Rake and destroy all fallen leaves to remove fungal spores and overwintering scales.
4. Cultural improvement: Prune to increase airflow. Ensure the north-side bush isn't staying wet longer.

Monitoring

Inspect new growth for signs of scale (bumps on stems) and reapply systemic if needed. With combined treatment, the holly should recover.