How to Care for Columbines With Black Spots on the Leaves

Columbine blooms in spring or early summer.

Columbines are graceful, bell-shaped flowers that are right at home in wildflower meadows and cottage gardens. Many of the hybrids are valuable assets to formal perennial beds as well. Columbine is susceptible to viral leaf spot diseases, particularly the necrotic spot virus, and there is no cure. Infected plants must be removed and destroyed. Thrips spread the disease as they feed on the plants, and controlling thrips is an important part of controlling the disease.

Things You'll Need

• Hand trowel
• Garbage bag
• Blue sticky traps
• Insecticide

Instructions

1. Dig up columbine plants infested with viral leaf spot disease. Place them in a plastic bag and dispose of them immediately. Don't compost the plants.

2. Clean up the garden area, removing and disposing of fallen leaves and flowers.

3. Control weeds by cultivating and pulling them. Dispose of them in plastic bags. Weeds aid in the spread of disease by harboring insects and disease viruses.

4. Control thrips to prevent the spread of viral necrotic spot virus. Place blue sticky traps near the columbine plants to monitor for thrips, and treat the plants for thrips as long as you continue to capture them on the traps.

5. Spray with an insecticide labeled for use against thrips. Carefully follow the application instructions and recommended spraying intervals. Pay particular attention to the undersides of the leaves.

Tips & Warnings

• Thrips are common pests in nurseries and greenhouses. Inspect plants carefully before purchasing them to avoid introducing the pest into your garden. Thrips are tiny and nearly impossible to see without a magnifying lens. Look for spots of shiny excrement on the leaves. When you hold an infested plant over a sheet of white paper and give it a gentle shake, the tiny, dark-colored insects will fall onto the paper.

• Read insecticide labels before use, and carefully follow the instructions and safety precautions. Store insecticides in their original containers and out of the reach of children.

References

• University of Massachusetts Extension: Impatiens Necrotic Spot Virus and Tomato Spotted Wilt Virus
• Pennsylvania State University Extension: Impatiens Necrotic Spot Virus
• University of Florida IFAS Extension: Thrips
• The Flower Gardener's Bible; Lewis Hill et al.