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Curvularia Blight on Lolium perenne on Turfgrasses in Argentina

Lolium perenne L. is commonly used alone or in association with blue-grass and fescues in sport fields, parks, and gardens. During 2003, symptoms of an unknown disease were observed on L. perenne turfgrass in western Buenos Aires. Initial symptoms were indefinite yellow and green dappled spots that extended downward from the leaf tip, turned brown and finally gray, causing leaf death. Segments of symptomatic leaf tissues were surface sterilized and placed on 2% potato dextrose agar in petri dishes. After 4 days at room temperature, blackish brown colonies developed with dark brown septate conidiophores. Conidia were 21 to 29 × 9 to 13 μm, 3-septa, curved at the third cell from the base that is longer and darker than the others. Cells at each end are subhyaline and intermediate cells are medium brown. These characteristics are consistent with Curvularia lunata (Wakker) Boedijng (1). Pathogenicity tests were performed in five plastic trays with substrate of natural soil and sand (1:1 [v/v]) where the turfgrass (L. perenne cv. El Cencerro) was seeded. Plants were inoculated by spraying a suspension of 2 × 10⁶ conidia per ml of sterile distilled water. Controls were sprayed with sterile distilled water. The trays were covered with transparent plastic bags, sprayed periodically with water, and incubated at 25°C in a greenhouse for 20 days. The first symptoms were observed 3 days later. After 9 days, 24% of the grass surface area showed blight lesions. C. lunata was consistently reisolated from affected tissues. Control plants remained symptomless. To our knowledge, this is the first report of C. lunata affecting L. perenne in Argentina.

Reference: (1) M. B. Ellis and I. A. S. Gibson Cochliobolus lunatus (conidial state: Curvularia lunata). Page 474 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1975.