Creeping Jenny and Southern Blight

Creeping Jenny

• A European and southwestern Asian native, creeping Jenny arrived in the United States during the 19th century. It now flourishes along ponds and streams and in moist forest soils across the eastern states. Standing 2 to 4 inches high, the plant pairs modest, bright yellow flowers with round, 3/4-inch green leaves. Leaf root nodes anchor its slender stems to the soil. The plant may spread as much as 1 foot per month in warm weather. Creeping jenny survives winter temperatures to minus-40 degrees in U.S. Department of Agriculture Plant Hardiness Zone 3. (Reference 2, par. 10; Reference 4, Description; Distribution; History of Introduction in New England; Habitats in New England; Refernce 5, Zone; Reference 6)

Southern Blight Fungi

• The soil-borne fungal species responsible for Southern blight include Sclerotium rolfsii, Sclerotium delphinii and Pellicularia rolfsii. Flowing water and contaminated tools or transplanted, diseased plants all spread the organisms. The fungi remain inactive, however, until exposed to several consecutive days of high temperatures and sporadic rainfall.

Symptoms

• Southern blight infestation surfaces as leaf yellowing, partial to complete wilting and stems rotting at the soil line. Fine white webs -- fungal strands called mycelium -- grow along the bases of the stems and on the surrounding mulch or soil. Around the mycelium are what appear to be small white seeds that gradually deepen to light brown. These sclerotia are hardened, inactive mycelial masses. They remain dormant until hot, wet weather activates them. Solid crusts of sclerotia develop where infestations are heavy. While southern blight may destroy a plants entire above-ground system, it seldom affects the roots. Creeping Jenny and other perennials typically recover to reappear the year after infection.

Management

• Removing and destroying diseased plants and replacing the top 8 inches of infested soil reduces mycelium-producing sclerotia. Clearing away the soil to a 6-inch radius around plants is sufficient. Simultaneously adding organic material and drainage-improving amendments discourages the fungi even more. A black plastic covering on sites receiving two or more hours of daily sun during the summer's hottest months also destroys the sclerotia. Sanitizing garden tools in a 1:9 bleach and water solution immediately after use and pre-planting examination of new plants for symptoms check the disease. Thiophanate methyl- and mancozeb-based fungicides provide effective, non-organic control.