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Sclerotium rolfsii

Symptoms & Signs   Sclerotium rolfsii (fungus) often referred to as Southern Blight (in the Southern U.S.) causes a crown rot disease of Ajuga, Hosta, Iris and other ornamentals. This disease can cause severe damage and is difficult to eradicate. Typically restricted to warm, humid states in the Southern U.S. crown rot appeared in many Midwest (Iowa) gardens in the mid 1990s. How severe the disease may be in Colorado remains to be seen. More than likely, in dry landscape situations the disease will not be a problem. However, in the nursery, greenhouse or in humid landscape microclimates, the disease has the potential to cause damage. Growers receiving perennials from other States may want to check plants for telltale signs and symptoms. Symptoms: Lower leaves of infected plants begin to wilt and may turn yellow or brown. Signs: Tiny white strands or threads called mycelium (body of the fungus) may be present at the base of the plant. Look closely for small tan spheres, about the size of mustard seeds. These are called sclerotia and serve as the over wintering and reproductive structures of the fungus. The sclerotia may be confused with fertilizer pellets, but are usually smaller in size and grow at the base of the plant.

Susceptible Herbaceous Perennial plants Susceptible Herbaceous Perennial plants: (this is not a complete listing) Latin name Common name Ajuga bugleweed Anemone windflower Aquilegia columbine Arrhenatherum Oat grass Asplenium Dragontail fern Caladium Fancy-leaved caladium Campanula Bellflower Chrysogonum Golden star Convallaria Lily of the valley Dicentra Bleeding heart Digitalis Fox glove Hemerocallis Day lily Hosta Plantain lily, Hosta Lysimachia Loosestrife Phlox Phlox Ranunculus Buttercup Vinca Periwinkle Viola Pansy, violet

Management Management of the disease will occur only through: Immediate removal and destruction of infected plants Use of pasteurized potting media Adequate drainage and avoidance of over irrigation Use of pathogen free stock There are a few fungicides labeled for control of this disease. They are used to suppress S. rolfsii. Contrast (flutolanil) Terraclor, Defend, Pennstar, Revere, and PCNB (all contain PCNB) Since phytoxoicity may result to PCNB, test it on a small scale before attempting larger-scale treatments. If a chemical is used, be sure to follow manufacturers directions.

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