Walnuts (Juglans regia L.) are a major food crop in Beijing. Recently, walnut anthracnose has become a serious problem in walnut plantations of Beijing, and the diversity of pathogens that cause this disease is poorly understood, making targeted treatment difficult. This study investigated incidences of walnut anthracnose in seven districts of Beijing (Changping, Fangshan, Haidian, Huairou, Mentougou, Miyun and Pinggu). A total of 377 isolates of Colletotrichum spp. were obtained from walnut anthracnose infected leaves and fruits. Morphological observation and multigene phylogenetic analysis of the genes ACT, CAL, CHS-1, GAPDH, ITS and TUB2 revealed that the isolates consisted of six species, C. aenigma, C. fructicola, C. gloeosporioides, C. siamense, C. liaoningense and C. sojae. Among these, C. gloeosporioides was the dominant species, and, for the first time, C. liaoningense and C. sojae were found to cause anthracnose in walnuts. Sensitivity tests showed that prochloraz and SYP-14288 had the strongest inhibitory effect on mycelial growth. These findings have clarified the species that cause walnut anthracnose in these seven districts of Beijing, which provides a scientific basis for diagnosis and control of walnut anthracnose.

Pseudostellaria heterophylla, an important traditional medicinal plant in China, has suffered increasing yield and quality loss due to leaf spot disease in recent years. In this study, the causal agent was conclusively identified as Sclerotiophoma versabilis through detailed morphological characteristics and multi-locus phylogenetic analyses based on the internal transcribed spacer regions (ITS), the 28S large subunit of the nrDNA (LSU), RNA polymerase II (rpb2), and ß-tubulin (tub2) sequences. Pathogenicity tests fulfilled Koch’s postulates, thereby resolving previous taxonomic inconsistencies regarding this disease. The effects of environmental and nutritional factors on mycelial growth, conidial germination, and infection were systematically evaluated. Optimal mycelial growth occurred at 20–25 °C, pH 6–8, under continuous light. Optimal mycelial growth occurred at 20–25 °C, pH 6–8, under continuous light, while conidial germination was maximized at 20–25 °C and pH 6–7 under continuous light. Starch and glycine were identified as the most favorable carbon and nitrogen sources for the fungal mycelial growth, respectively. Infection assays indicated an incubation period of approximately 3 d and maximal disease development at moderate temperatures under low-light conditions, with 6 d-old cultures exhibiting the greatest infectivity. Microscopic observations revealed that S. versabilis penetrated host tissues directly or via stomata without forming specialized infection structures. These findings integrate taxonomic resolution with ecological and infection biology analyses, providing mechanistic insight into the environmental drivers of leaf spot epidemics and a scientific basis for disease-risk assessment and management in P. heterophylla production systems.