In June and July 2016, a cobweb disease epidemic appeared on fruiting bodies of P. eryngii var. tuoliensis on mushroom farms in Changchun (Jilin Province, China), which resulted in 1% economic loss. First, the surfaces of the fruiting bodies were covered with white, coarse, and cobweb-like mycelia. Later, the cap and stipe became rotten. Finally, they were covered with masses of conidia, which can spread rapidly through the air-conditioning systems to cause disease in adjacent ones. Based on morphological characteristics, molecular data (sequence analysis of the internal transcribed spacer region, elongation factor 1-α gene and the second largest subunit of RNA polymerase II gene) and pathogenicity test, the causal agent was identified as C. varium. This fungus has been reported to cause cobweb disease on types of important mushroom, including Agaricus bisporus, Flammulina velutipes, Pleurotus eryngii and Hypsizygus marmoreus, among others. This is thought to be the first report of C. varium causing cobweb disease on cultivated P. eryngii var. tuoliensis.