Dahlia Diseases: A Guide for Young Gardeners
Dahlias are beautiful flowers that can add a splash of color to your garden from midsummer to autumn. They come in a wide range of sizes, colors, and shapes, so you’re sure to find one that you love.
But even though dahlias are relatively easy to grow, they can be susceptible to certain diseases. In this article, we’ll discuss the most common dahlia diseases and how to prevent and treat them.
Common Dahlia Diseases
The most common dahlia diseases include:
- Powdery mildew: This fungal disease is easy to spot by the white, powdery growth that appears on leaves. It can affect the appearance of the plant, but it’s rarely fatal.
- Botrytis blight: Also known as gray mold, this fungal disease causes brown, water-soaked spots on leaves and stems. As the disease progresses, the spots enlarge and develop a fuzzy, gray or tan mold. Botrytis blight is often a problem in humid weather conditions.
- Wilt: Fusarium wilt and verticillium wilt are two fungal diseases that cause wilted, yellowing leaves. The plant may eventually turn dark brown or black and die. Fusarium wilt is most severe when the soil is warm, while verticillium wilt often appears when the weather turns warm after a cool period.
- Stem rot: This deadly disease causes stems to become mushy and rotted. It’s most common in dahlias that are planted in poorly drained, soggy soil.
- Viral diseases: Viral diseases are often transmitted by thrips, which are tiny insects that burrow into the stems and buds of plants. Symptoms of viral diseases include lines, rings, a mottled appearance, and streaks of dark and light green. Infected plants are usually discarded, as thrips are notoriously difficult to control.
Dahlia Disease Control
Most common dahlia diseases are caused by damp, humid conditions, overwatering, or poorly drained soil. The best way to prevent disease is to:
- Plant dahlias in well-drained soil.
- Avoid overwatering.
- Water at the base of the plant and avoid wetting the foliage.
- Keep plants spaced apart so that air can circulate freely.
- Remove any diseased plant material from the garden and dispose of it properly.
Treating Dahlia Diseases
Some dahlia diseases, such as powdery mildew and gray mold, can be treated with fungicides. Fungicides can also be used as a preventive measure. However, many dahlia diseases are fatal, and the best recourse is to start fresh with new, disease-resistant tubers.