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Zinnia Diseases

Name: Zinnia Diseases
SKU: ART-3967

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

Updated:

July 7, 2025

Zinnia blossom

Disease	Symptoms	Pathogen/Cause	Management
Alternaria Leaf Spot	Large reddish brown or purple spots, at first round to oblong but becoming irregular in shape, developing a gray or tan center that may drop out, leaving a hole. Severely affected leaves turn brown, dry, and become brittle.	Alternaria zinniae	Apply a fungicide. Whenever possible, water in a manner that keeps the leaves dry to inhibit this seedborne disease.
Aster Yellows	Leaf-like tissue forms where flower parts should be located. Flower-like parts remain green or light green. Often, flowers on only one side of the composite inflorescence show symptoms. Sepals may be very large or dwarfed.	Phytoplasma	Destroy infected plants. Control leafhoppers.
Bacterial Leaf Spot	Spots reddish brown to dark brown, angular in shape, and with a prominent yellow halo form on leaves.	Xanthomonas campestris pv. zinniae	No sprays are effective. Whenever possible, water in a manner that keeps the leaves dry to inhibit this seedborne disease.
Powdery Mildew	White fungal growth forms on the upper surface of leaves and may form on flower petals.	Golovinomyces cichoracearum (formerly Erysiphe)	Apply a fungicide to protect plants.