Cattleya × hybrid is one of the most important orchids in Taiwan. Yellow to brown blights were first observed on the leaves of this orchid located in Changhua County, Taiwan in July 2018. This symptom often presented on the basal leaves or occasionally, on leaf tips. The disease incidence was up to 30 in some greenhouses. Fungal isolates were obtained from symptomatic tissues after the diseased tissues were surfacesterilized using 1 NaClO. Ten fungal isolates were analyzed. The isolates were identified as Neoscytalidium sp. based on their morphology (Crous et al. 2006). The analysis showed that the fungal colonies had aerial hyphae. The colonies also turned black after 6 days of incubation at 28 °C on PDA medium with 12-h light daily. These isolates could produce 0- to 1-septate arthrospores and non-septate conidia from pycnidia. The arthrospore sizes were estimated to be 13.11 ± 2.36 × 4.30 ± 0.50 μm. The conidia sizes were 15.64 ± 1.32 × 5.17 ± 0.56 μm. Ten isolates were chosen to complete Koch’s postulate with wound inoculation (1 mm depth). The test was carried out by inoculating a 3-mm disc on host healthy leaves; 3 mm PDA discs were used as controls.
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