Dahlia Diseases (2024)

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Informational table showing disease name, symptoms, pathogen/cause, and management of Dahlia diseases.

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Updated:

July 5, 2023

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Disease	Symptoms	Pathogen/Cause	Management
Aster Yellows	Leaf-like tissue forms where flower parts should be located. Flower-like parts remain green or light green.	Phytoplasma	Destroy infected plants. Control leafhoppers.
Bacterial Stem Rot	Blackened stems have a soft, wet, interior and a foul odor.	Erwinia carotovora	Promptly destroy infected plants
Gray Mold	In wet weather, masses of gray spores form on brown spots on buds, leaves or stems.	Botrytis cinerea	Maintain low relative humidity. Apply a fungicide to protect healthy plants.
Powdery Mildew	Dry, white, mealy, fungal growth occurs on the upper surface of leaves.	Golovinomyces cichoracearum (formerly Erysiphe)	Apply a fungicide when the fungus is first observed.
Storage Rot	Tubers decay into a soft smelly mass.	Various fungi and bacteria.	Avoid wounding the tubers. Let the tuber surfaces dry and remove soil before storing. Store tubers in a cool, dry location.
Verticillium Wilt	Single branches or the entire plant wilts and dies. Vascular tissue in affectes stems is black, dark brown, or greenish-brown.	Verticillium	Plant in pathogen-free potting mix.
Virus	Conspicuous rings and line patterns may be present or a mosaic of light and dark green may occur on leaves.	Impatiens necrotic spot virus	Discard infected plants. Do not save tubers from affected plants. Control thrips since they vector the virus.