US (LA): Southern blight challenges growers

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Louisiana’s warm, humid weather provides a conducive environment for plant pathogens to quickly establish and spread. As a result, an important plant disease called southern blight has started to show up in Louisiana vegetable and ornamental production.

Southern blight is caused by the soilborne fungus Athelia rolfsii (Sclerotium rolfsii). The pathogen has a wide host range and is known to cause disease on various economically important vegetables (cucurbits, eggplants, peppers, potatoes, tomatoes) and ornamental plants.

The fungus attacks the lower stem of plants at or near the soil line during warm and wet conditions. Initial symptoms appear as wilting and yellowing of leaves. The lower stem becomes necrotic, and the whole plant eventually turns brown and dies.

Closer examination of the base of a diseased plant reveals a lesion that girdles the stem. As the disease progresses, white fungal growth (mycelium) and small, mustard seed-like, tan-colored sclerotia appear at the base of infected plants. Sclerotia turn reddish to dark brown as they age. The mycelium and sclerotia extend on the soil surface around the infected plant.


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