Wilkinson and Kane (3) previously reported diseased zoysiagrass infected by Gaeumannomyces graminis (Sacc.) Arx & Olivier var. graminis in the spring in Illinois. Emerald zoysiagrass (Zoysia japonicum Steud. × Zoysia matrella (L.) Merr var. tenufolia (Willd. ex Thiele) established by sod in a home lawn for one year in Austin, TX, developed irregular, chlorotic, and, subsequently, necrotic patches 30 cm in diameter and larger in late summer of 1999. Patches were restricted to areas of the lawn receiving full sun. The lawn was fertilized, mowed at 2.5 cm, and watered daily during active growth. A thatch layer in excess of 1.9 cm was present. Tillers within diseased patches were removed easily from stolons. Crowns were rotted and colonized by dark brown septate hyphae (4.5 µm wide) and olivaceous brown lobed hyphopodia (25 × 21 µm). Diseased tillers were desiccated and newly developed leaves were chlorotic. Stolons were also chlorotic and developed water-soaked lesions adjacent to crowns. Diseased roots appeared light brown and brittle with strands of dark brown septate runner hyphae along the surface of the root axis and olivaceous brown growth cessation structures within the cortical tissue. Overall, symptoms were more severe on crowns and nodes than roots. A Gaeumannomyces fungus was isolated from root, sheath, and bud tissues. Taxonomy of the fungus was consistent with the description of G. graminis var. graminis by Walker (1,2). Diseased plants were washed free of soil and other debris and maintained in a moist chamber for 14 days. Perithecia were formed on leaf sheaths. Morphology of perithecia, asci, and ascospores was consistent with Walker's description of perithecia, asci, and ascospores of G. graminis var. graminis (2). Leaf buds and root tissue, colonized by G. graminis var. graminis, were plated directly onto potato-dextrose agar containing streptomycin sulfate and rifampicin (100 ppm, respectively). Colonies of sparse white, slightly aerial mycelium turning olive brown with age and producing lobed hyphopodia, developed from plated plant material. Hyphae at the margin of colonies curled back, characteristic of G. graminis var. graminis. Symptoms reported here are similar to those described by Wilkinson and Kane (3); however, the season and prevailing environmental conditions were different.
References: (1) J. Walker. Trans. Br. Mycol. Soc. 58:427, 1972. (2) J. Walker. Mycotaxon 11:1, 1980. (3) H. T. Wilkinson and R. T. Kane. Plant Dis 77:100, 1993.
