Septoria leaf spot

Fungal <strong>leaf</strong> <strong>spot</strong>s<br />

<strong>Septoria</strong> <strong>leaf</strong> <strong>spot</strong><br />

Pathogen: <strong>Septoria</strong> spp.<br />

Hosts include: Artemisia, Baptisia,<br />

Campanula, Chrysanthemum,<br />

Coreopsis, Delphinium, Dianthus,<br />

Echinacea, Gaillardia, Heuchera,<br />

Lamium, Lathyrus, Lupinus, Lychnis,<br />

Monarda, Potentilla, Ratibida, Rudbeckia,<br />

Stachys, Veronica and Viola.<br />

Lesions on<br />

Heuchera.<br />

Symptoms: Tan to brown <strong>leaf</strong> <strong>spot</strong>s.<br />

Small, black fruiting bodies (pycnidia) may be<br />

visible in the lesions. Lesions on Rudbeckia and<br />

Echinacea are purple. Lesions may be more<br />

<strong>Septoria</strong> pycnidia are visible in lesions.<br />

Microscopic view<br />

of pycnidia on <strong>leaf</strong><br />

surface. Spores are<br />

released through the<br />

central opening in these<br />

volcanolike structures.

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<strong>Septoria</strong> <strong>leaf</strong> <strong>spot</strong> – continued<br />

Purple <strong>leaf</strong> lesions caused by <strong>Septoria</strong> rudbeckiae. Rudbeckia<br />

and Ratibida are the only hosts of this particular species of<br />

<strong>Septoria</strong>. At right, a closer look at severe purpling on rudbeckia<br />

foliage.<br />

severe on older foliage.<br />

Spread: The disease may be introduced on<br />

infected material. Spores are splash-dispersed<br />

to nearby foliage. Disease can also be spread<br />

by workers moving through wet foliage.<br />

Management: There are many species of <strong>Septoria</strong>.<br />

Each is relatively host-specific, affecting<br />

only a few plant genera. Remove and destroy<br />

infected plant material. Avoid overhead irrigation<br />

or carefully time it to limit the duration of <strong>leaf</strong><br />

wetness. Protectant fungicides can be used to<br />

manage <strong>Septoria</strong> <strong>leaf</strong> <strong>spot</strong>.