Articles

Coreopsis Diseases

Name: Coreopsis Diseases
SKU: ART-3395

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

Save for later Print

Updated:

June 26, 2025

Skip to the end of the images gallery

Closeup of a coreopsis flower

Skip to the beginning of the images gallery

Disease	Symptoms	Pathogen/Cause	Management
Aster yellows	Flowers develop green, elongate, or stunted petals and an excessive number of flower heads. The affected plants are usually stunted and yellowed.	Phytoplasma	Maintain good leafhopper control and eliminate nearby weeds that harbor aster yellows.
Bacterial leaf spot	Irregular brown blotches and spots develop on leaves.	Pseudomonas cichorii	Water in a manner that keeps leaf surfaces dry, and water when the leaves will dry quickly. Remove infected plants. Apply a bactericide to protect plants.
Botrytis blight	Lower leaves die and become covered with white to gray, fluffy fungal growth that soon becomes a mass of gray spores.	Botrytis cinerea	Water in a manner that keeps leaf surfaces and flowers dry, and water when the plants will dry quickly. Apply a fungicide to protect plants.
Crown rot	Plants wilt, brown, and die. White fungal growth webs at the base of the dying plant and become peppered with small, tan, round structures.	Sclerotium rolfsii	Remove infected plants. Mulch in a manner that does not hold moisture close to the stems.
Downy mildew	Black spots form on the upper leaf surface, and white, felt-like growth covers the underside of the leaf.	Plasmopara halstedii	Apply a fungicide to protect plants.
Fungal leaf spots	Purple to tan spots develop on leaves.	Cercospora, Septoria, Phyllosticta	Water in a manner that keeps leaf surfaces dry, and water when the leaves will dry quickly. Apply a fungicide to protect plants.
Powdery mildew	White fuzzy growth develops on the upper side of the leaves.	Sphaerotheca macularis	Apply a fungicide to protect plants.
Root rot	Plants turn yellow, wilt, collapse, and die.	Phymatotrichopsis or Rhizoctonia	Apply a fungicide to protect plants.
Rust	Orange-yellow masses of spores form on the underside of leaves.	Coleosporium inconspicuum	Apply a fungicide to protect plants.
Scab	Leaves have a coating of gray to brown spores.	Cladosporium coreopsidis	Water in a manner that keeps leaf surfaces dry, and water when the leaves will dry quickly. Apply a fungicide to protect plants.
Stem rot	Stems turn brown or tan and die as large portions of the plant collapse.	Alternaria sp., Rhizoctonia solani and Sclerotinia sclerotiorum	Remove infected plants. Cut plants back to the soil line in the fall. Mulch in a manner that does not hold moisture close to the stems. Apply a fungicide to protect plants.
Wilt	Plants wilt, turn brown, and die.	Verticillium albo-atrum	Remove infected plants. This fungus survives in the soil for very long periods of time, even in the absence of susceptible plants. Do not plant susceptible varieties.