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TAKE-ALL ROOT ROT:
A Detrimental Root Disease of Bermudagrass Putting Greens By Maria Tomaso-Peterson, Ph.D and Aaron Tucker, MSc., Mississippi State University Cameron Stephens, Ph.D candidate, North Carolina State University
Al ab ama Tu rf Tim es > >> Spring 2021
T
ake-all root rot (TARR), as the name indicates, is a disease that affects roots, stolons, and rhizomes. This disease is widespread on ultradwarf bermudagrass greens throughout the transition zone and subtropical climates, including Alabama. However, TARR is also active in dwarf bermudagrass greens and sod production fields where bermudagrass putting green cultivars are grown. Until recently the causal agent of TARR was identified as Gaeumannomyces graminis var. graminis – or Ggg. We initiated research in 2012 in the Turfgrass Pathology lab at Mississippi State University (MSU) to get a better understanding of the ectotrophic rootinfecting (ERI) fungi associated with this disease — originally referred to as bermudagrass decline (BD). We identified three novel ERI fungi, G. nanograminis (Gn), Magnaporthiopsis cynodontis (Mc), and Candidacolonium cynodontis (Cc), that formed a complex with G. graminis infecting roots in bermudagrass (BG) putting greens. These fungi do not discriminate between Tifdwarf, 328, or other ultradwarf bermudagrasses. Parallel research conducted by Cameron Stephens and Dr. Jim Kerns at North Carolina State University (NCSU) identified a fifth ERI fungus, G. graminicola (Ggram), associated with rootrot and symptoms of TARR. ERI fungi colonize the outer surface of roots, stolons, and rhizomes and produce distinct structures, readily identifiable with the aid of a microscope. They are characterized by the formation of dark brown to black runner hyphae and growth cessation structures on the surfaces of roots, stolons, and rhizomes. Infection hyphae originate from lobed hyphopodia (Fig. 1). The foliar symptoms of TARR first appear as irregularshaped, chlorotic to white patches up to 3.0–ft in diameter. Foliar symptoms of chlorosis/necrosis progress upwards from the point of infection near the crown of the plant to the leaf tips. The chlorotic to white patches may be solitary or coalesce with neighboring patches to create large, irregular areas within a green. A general thinning with the patches or along the
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margin of the green may result if the disease is left unchecked (Figs. 2–3). These symptoms may be confused with other foliar diseases such as mini ring or nematodes.. Therefore, it is important to check the root system of affected plants. These roots, stolons, and rhizomes will appear dark brown to black. Black lesions may be observed on the stolons and roots. Overall, the roots will be very short, 0.5–in., brown, rotted, brittle and lack secondary roots and root hairs.
