marigold leaf & flower blight (Alternaria)

Symptoms

Dark brown to black spots, often with concentric rings and a yellow halo, appear on the lower leaves first and enlarge until the leaf shrivels; the blight runs up the stem and into the flower buds and petals, which rot and turn brown. Worst in warm, wet, humid weather and on crowded plants.

Plants affected

• French marigold

Common questions

How do I recognise marigold leaf & flower blight (Alternaria) on French marigold?

Dark brown to black spots, often with concentric rings and a yellow halo, appear on the lower leaves first and enlarge until the leaf shrivels; the blight runs up the stem and into the flower buds and petals, which rot and turn brown. Worst in warm, wet, humid weather and on crowded plants.

Do I have to report marigold leaf & flower blight (Alternaria)?

No. marigold leaf & flower blight (Alternaria) is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is marigold leaf & flower blight (Alternaria) treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.