During surveys conducted in 2020, severe symptoms associated with death and decline were observed on more than 30-year-old Metasequoia glyptostroboides (Chinese redwood) trees in the shelter forests along the Yangtze River in Jingzhou City, Hubei Province, China. A previous study showed that Phytophthora acerina was one of the causal agents of the decline of the Chinese redwood. In this study, a total of 147 fungal isolates were obtained from the diseased roots and xylem of trunks of declining M. glyptostroboides trees. Through morphology and multilocus phylogenetic analysis, these isolates were identified as eight species belonging to the genera Fusarium and Neocosmospora, including F. fujikuroi, F. irregulare, F. odoratissimum, F. reticulatum, N. falciformis, N. keratoplastica, N. solani, and N. tonkinensis. Single inoculation and coinoculation with P. acerina assays of these Fusarium and Neocosmospora species were then performed to test pathogenicity on 3-year-old seedlings of M. glyptostroboides. Lesions (i.e., on seedling stems) caused by species of the genera Neocosmospora and Fusarium were smaller than those caused by P. acerina. Coinoculation of F. fujikuroi and P. acerina, as well as the coinoculation of F. reticulatum and P. acerina, caused larger lesions than inoculation with P. acerina alone. All these species of Fusarium and Neocosmospora were shown to have the potential to be pathogenic to M. glyptostroboides. This study provided evidence that the decline of M. glyptostroboides in Jingzhou is a disease complex.

The red turpentine beetle, Dendroctonus valens LeConte, is an important phloem-feeding pest of pine forests in China. RNA interference (RNAi) is a conserved, sequence-specific gene-silencing mechanism induced by double-stranded RNA (dsRNA), and has become an important molecular tool for screening and evaluating potential targets for pest management owing to its high efficiency, target specificity, and relative environmental safety. In this study, six candidate genes were selected, including mesh and ssk responsible for gut barrier formation, actin involved in cellular structure maintenance, iap involved in apoptosis regulation, hsp70-2 responsible for stress response, and v-atpaseE involved in ion transport and cellular homeostasis. The effects of dsRNA microinjection on gene silencing and mortality were then evaluated in both larvae and adults of D. valens. Following dsRNA treatment, all six candidate genes were significantly downregulated in both larvae and adults, with v-atpaseE showing the strongest transcript suppression in larvae. Survival analysis revealed target-dependent lethal effects: v-atpaseE caused rapid larval mortality, reaching 100% by day 3, whereas ssk caused the strongest adult mortality, reaching 100% by day 5, and mesh also induced substantial adult mortality. In contrast, actin, iap, and hsp70-2 produced weaker or slower lethal effects. These results indicate that dsRNA injection can induce effective gene silencing in D. valens and that the resulting phenotypic responses differ among target genes and between life stages. Taken together, v-atpaseE and ssk represent the most promising candidate targets for further development of RNAi-based management strategies against D. valens.