Articles

Marigold Diseases

Name: Marigold Diseases
SKU: ART-4110

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

Updated:

July 7, 2025

A field of Marigolds

Disease	Symptoms	Pathogen/Cause	Management
Alternaria Leaf Spot	Purplish spots form on leaves and stems.	Alternaria	Avoid overhead irrigation. Apply a fungicide registered for use on this crop.
Bacterial Leaf Spot	Small (2-5 mm) circular dead spots form on leaves and petioles. Spots have purple margins.	Pseudomonas syringae pv. tagetis	Destroy infected plants. Avoid overhead irrigation.
Botrytis Flower Blight	Flower parts brown and die. Gray masses of spores form on the infected tissue when wet.	Botrytis cinerea	Avoid overhead irrigation. Apply a fungicide registered for use on this crop.
Fusarium Wilt	Seedlings are killed. In older plants, black streaks darken the vascular tissue up one side of the plant. Plants wilt. Roots of the greatly reduced root system are rotted. During wet weather, salmon-colored spore masses form on infected stems.	Fusarium oxysporum	Plant in potting mix free of pathogens. Destroy infected plants.
Leaf Burn	The tips and margins of leaves turn yellow and die.	Excess boron, manganese, or molybdenum	Measure and apply micronutrient solutions carefully. Manganese should not be above 55 ppm, molybdenum above 24 ppm, or boron above 3 ppm.
Septoria Leaf Spot	Oval to irregular gray to black spots with tiny dots peppering their surface (fungal fruiting structures) form first on lower leaves and then spread upward.	Septoria tageticola	Avoid overhead irrigation. Apply a fungicide registered for use on this crop.