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.