Corticum & Lawn Fungus

Corticum Fungi

• Corticum or corticium describes a genus of fungi species, most frequently associated with the turfgrass disease known as red thread. According to Houston B. Couch of the Virginia Polytechnic Institute and State University, corticum is likely the first known fungal pathogen of turfgrass, with the first reported case of red thread occurring in Australia in 1854. Fungi belonging to the corticum genus were once thought to be the only pathogens of red thread, but recently scientists have confirmed that Limonomyces roseipellis can cause red thread as well.

Red Thread

• Red thread is most easily recognized by the titular deep red, thread-like growths that break out over infected grass. The earliest symptoms of this disease, however, are intermittent dead patches that appear water soaked as the diseases progresses. The thread-like fungal mycelium that break out over the top of blades of grass is an indication that the disease has progressed to an advanced stage. Infected regions of the lawn typically only span 20 inches in diameter, though there can be more than one infection area in a single lawn.

Preventative Treatments

• As is usually the case with plant fungal diseases, preventative steps are the most effective means of treating the disease. Lawns that are not given sufficient amounts of nitrogen through fertilizer and other soil amendments are believed to be more susceptible to infection by red thread. Red thread infection is more common on bentgrass, bermudagrass and Kentucky bluegrass, so planting more disease-resistant grasses in lieu of these susceptible varieties can help prevent infection, particularly if you live in the kind of cooler, more humid climates that favor the disease.

Chemical Controls

• Mercury fungicides were once a mainstay of red thread management, but these fungicides were outlawed long ago due to health and environmental concerns. Today, control is best achieved using fungicides containing fenarimol, triadimefon, cadmium succinate, vinclozolin, anilizine and propiconazole. State and federal regulatory agencies are constantly re-evaluating chemical fungicides and removing some fungicide compounds due to health and environmental concerns -- some states also band fungicide chemicals that are legal in other states, so some or more of these fungicide formulations may not be available to you. Always follow the manufacturer's printed application instructions exactly.