Investigation and characterization of red thread and pink patch on warm-season turfgrasses in Hainan Province, tropical China

Red thread caused by Laetisaria fuciformis and pink patch caused by Limonomyces roseipellis often occur on many cool-season turfgrass species in temperate regions throughout the world. Incidences of L. fuciformis causing red thread on seashore paspalum (Paspalum vaginatum) and Li. roseipellis causing pink patch on hybrid bermuda grass (Cynodon dactylon × C. transvaalensis) have been reported as new diseases in Hainan Province, a Chinese island with a tropical climate. Field investigations were carried out at 14 golf courses and three college lawns in six cities of Hainan Province from April 2011 to April 2013. Red thread disease was observed on four warm-season turfgrasses throughout the period in all six cities, while pink patch was found on two warm-season turfgrasses in three cities. A total of 21 red thread isolates and five pink patch isolates were collected from these infected turfgrasses. These isolates were identified based on morphological and culture characteristics as well as nucleotide sequences from partial mitochondrial small subunit ribosomal RNA (mtSSU) and nuclear large subunit ribosomal RNA (nuLSU) genes. The optimal temperature for hyphal growth was either 25 or 28 °C for red thread isolates and 28 °C for pink patch isolates. The growth rate of all isolates was significantly less when cultures were grown under continuous light compared to the 12 h light/12 h dark or 24 h dark regimes. Arthroconidia production was optimized under the 12 h light/12 h dark regime. Selected fungal isolates were tested for pathogenicity by inoculating on ‘Seaspray’ seashore paspalum, ‘Princess 77’ bermuda grass (Cynodon dactylon), and ‘Lanyin No 3’ japanese lawngrass (Zoysia japonica) under controlled environmental conditions. All tested L. fuciformis and Li. roseipellis induced foliar blight in the turfgrass species.