Scouting for diseases: Septoria leaf spot

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.   

Pathogen:
Septoria spp. (view photos)

Hosts include:
Artemisia, Baptisia, Campanula, Chrysanthemum, Coreopsis, Delphinium, Dianthus, Echinacea, Gaillardia, Heuchera, Lamium, Lathyrus, Lupinus, Lychnis, Monarda, Potentilla, Ratibida, Rudbeckia, Stachys, Veronica and Viola.

Symptoms:
Tan to brown leaf spots. Small, black fruiting bodies (pycnidia) may be visible in the lesions. Lesions on Rudbeckia and Echinacea are purple. Lesions may be more severe on older foliage.

Spread:
The disease may be introduced on infected material. Spores are splash-dispersed to nearby foliage. Disease can also be spread by workers moving through wet foliage.

Management:
There are many species of Septoria. Each is relatively host-specific, affecting only a few plant genera. Remove and destroy infected plant material. Avoid overhead irrigation or carefully time it to limit the duration of leaf wetness. Protectant fungicides can be used to manage Septoria leaf spot.

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