Mum Powdery Mildew Symptoms: Treating Powdery Mildew On Chrysanthemums

If your chrysanthemum plants grow in a sunny, well-drained site in your garden and get adequate water, they probably are blooming and healthy. However, when that’s not the case, your plants may suffer from fungal diseases, including powdery mildew. Powdery mildew on chrysanthemums is one of those diseases that can usually be avoided with good cultural care. Read on for information about mum powdery mildew symptoms and effective chrysanthemum powdery mildew control.

White Spots on Mums

Chrysanthemums are popular garden flowers. They are hardy perennials that thrive in mild or even cool climates. The species flowers are yellow, and the name comes from the Greek words for gold and flower. Today, however, chrysanthemum blooms come in a large range of shapes and colors including white, purple, and red.

If you see white spots on mums that look like pale powder, don’t just hope they will go away. These are mum powdery mildew symptoms.

Powdery mildew is a fungal disease. The ashy growths can show up on leaves, flower parts, or on stems. The leaves pucker and distort, and many will ultimately shrivel and die. In severe cases, the entire plant is covered.

Often, you’ll first see the white spots on lower leaves. In time, the disease spreads upward. You might spot tiny black round spheres inside the white spots late in the season.

Powdery mildew attacks plants during hot, humid weather. Standing water is not necessary as long as humidity is high.

Chrysanthemum Powdery Mildew Control

You can go a long way toward preventing powdery mildew on chrysanthemums by planting the shrubs correctly. Space the plants far enough apart to allow for good air circulation. Be sure they get sufficient water in dry weather and are planted in sunlight.

If you see powdery mildew on chrysanthemums in your yard, you can fight the fungal disease with fungicides. Regular foliar fungicide applications will control this disease.

When you see the first symptoms, apply fungicides with one or more of the following list of active ingredients:

  • Copper
  • Azoxystrobin
  • Pyraclostrobin
  • Fludioxonil
  • Triflumizole
  • Myclobutanil
  • Triadimefon
  • Propiconazole
  • Sulfur
  • Potassium Bicarbonate
  • Thiophanate Methyl
Teo Spengler

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.