Occurrence and impact of Apocynum venetum rust (Melampsora apocyni) in Altay, Xinjiang

The rust caused by Melampsora apocyni is one of the main factors limiting Apocynum venetum industrialization. We investigated the occurrence of A. venetum rust in two wild (Yanhu, Honggou) and two cultivated (the sixth and seventh years) sites in 2016 and analyzed the correlation between the disease and meteorological factors and habitat. The results showed that the severity of rust disease increased gradually with the length of the plant growing season. The incidence of rust disease on A. venetum in Yanhu and Honggou reached a peak on July 18 and August 3, with a disease incidence was 86.47% and 87.60%, respectively. At the end of the growing season, the disease incidence decreased gradually to 75.97% and 53.78%, respectively. In the cultivated population, the incidence of rust disease on A. venetum in the sixth and seventh years reached a peak on August 7 and July 23, with a disease incidence of 25.52% and 31.49%, respectively. The disease index in the wild A. venetum population was 31.39~46.18, which was 6.51~6.95 times that in cultivated A. venetum. The area under the disease progress curve (AUDPC) in the wild A. venetum population was 651.74~1 522.31, which was 4.37~9.69 times that in cultivated A. venetum. The occurrence of rust disease in wild A. venetum was significantly positively correlated with rainfall and total vegetation coverage and negatively correlated with plant diversity (P<0.05). The occurrence of rust disease in cultivated A. venetum was significantly positively correlated with A. venetum coverage and negatively correlated with plant diversity (P<0.05).