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| Alternaria leaf spot | |||||
| IPM scouting in herbaceous perennials > alternaria leaf spot | |||||
| Pathogen: Alternaria spp. Hosts: Several species are pathogenic on perennials. Together, they have a wide host range, including Aster, Calendula, Coreopsis, Dianthus, Gypsophila, Helianthus, Iris, Ligularia, Pelargonium, Platycodon, Shasta and Stokesia. Symptoms: Dark-colored leaf spots. Lesions may have concentric rings within them. Spots may coalesce, resulting in blight-ing of foliage. Petals of some plants may be infected. Dianthus flower buds can be rotted. Spread: Spores are produced on the plant surface and are spread by splashing water or air movement or by moving infected plant material. Management: Maintain adequate plant spacing to allow for good aeration to reduce humidity levels around plants. Alternaria spp. require leaf wetness for germination and infection; reduce durations of leaf wetness with good timing of overhead irrigation. Regular fungicide applications will likely be necessary to reduce losses on especially susceptible hosts. |
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| This information was developed from A Pocket Guide for IPM Scouting in Herbaceous Perennials by Jan Byrne and Raymond A. Cloyd. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2981). | |||||
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