First Report of Dollar Spot Disease on Seashore Paspalum Caused by Clarireedia monteithiana in Taiwan

In January 2026, straw-colored spots of blighted turf were observed on seashore paspalum (Paspalum vaginatum) putting greens and teeing grounds of the Kuo Hua Golf Club in New Taipei City, Taiwan, reducing the aesthetics and playability. A few days later, these expanded into irregular lesions and eventually bare patches as conditions persisted. Symptomatic leaves were excised from lesion margins, surface-disinfected with 1% NaOCl, rinsed twice with sterile distilled water, and blotted dry with sterile tissue. The cleaned samples were placed on half-strength potato dextrose agar (PDA) supplemented with 0.1% ampicillin and 0.1% streptomycin and incubated at 25°C in the dark for 3 days. Five distinct fungal colony morphologies were obtained from 12 isolates. The most common, fast-growing colonies (isolates DS1-1, DS1-2, and DS1-3) initially produced white floccose mycelia and later formed brown stromata after two weeks. To confirm their identity, the internal transcribed spacer (ITS) region, the DNA replication licensing factor (MCM7), and calmodulin (CAL) were amplified and Sanger sequenced with primers ITS1/ITS4 (Gardes and Bruns 1993; White et al. 1990), MCMF/MCMR (Hu et al. 2019), and CAL-228F/CAL-737R (Carbone and Kohn 1999), respectively. BLASTN results using NCBI database indicated that the three isolates showed 99.47% (558/561bp), 99.79% (483/484bp), and 100% (579/579bp) identity to the ITS (PZ575677-PZ575679), CAL (PZ714222-PZ714224), and MCM7 (PZ585362-PZ585364) genes of the Clarireedia monteithiana H7 T genome (GCA_026226035.1) respectively, and an ML-tree constructed from concatenated ITS–CAL–MCM7 sequences placed them within the same clade as C. monteithiana H7 T . Two isolates (DS1-2 and DS1-3) were tested for pathogenicity. Fungal inoculum was prepared by transferring mycelium from 10-day-old PDA cultures to autoclaved oats (oats:ddH 2 O:CaCO 3 = 50:20:1, v/v/v) and incubating at 25°C in the dark for 3 weeks. Five colonized oats were placed in the center of seashore paspalum plugs (12-cm diameter) maintained at 25°C with >80% relative humidity and a 12-h photoperiod; controls were inoculated with sterile uninoculated oats. Turf was trimmed to 1 cm height every 3 days. Within 5 days post-inoculation, white aerial mycelium emerged and covered the grass, forming approximately 6-cm-diameter lesions. Upon transfer to ambient conditions, mycelium receded rapidly, leaving bare patches consistent with initial field observations. The pathogen was reisolated from lesions, and the reisolates exhibited identical morphology on PDA and 100% ITS sequence identity (515/515 bp) to the original isolates, fulfilling Koch’s postulates. Accordingly, the molecular and morphological characterizations confirmed the causal pathogen as C. monteithiana. Dollar spot disease was first reported in the United Kingdom (Bennett 1937), and C. monteithiana has since been reported worldwide, including Japan (Tsukiboshi et al. 2021), and China (Hu et al. 2019), but has not previously been reported in Taiwan. C. monteithiana primarily infects C4 warm-season grasses, including seashore paspalum, which are widely cultivated under the tropical and subtropical climate of Taiwan (Salgado-Salazar et al. 2018). Although dollar spots were anecdotally observed, this is the first empirical report of dollar spot caused by C. monteithiana in Taiwan, and this identification represents a critical first step toward effective disease management.