The Korea National Arboretum (KNA) in Pocheon, Korea has diverse plant species including Rosaceae species of high ecological and landscape significance; however, no fungal disease surveys have been conducted. Thus, we investigated rust occurrence and identification across diverse plant species of the subtribe Malinae (Rosaceae) and examined host diversity (or specificity) of rusts in this study, as well as in the literature and databases. We collected rust (aecial stages) samples from the leaves of nine Malinae species on June 20, July 7, July 21, or August 8, 2025. We also identified rust samples by analyzing the sequences of internal transcribed spacer and large subunit rDNA regions, as well as aeciospore characteristics. We revealed that Gymnosporangium asiaticum occurred in six host species of five genera (Aria, Chaenomeles, Crataegus, Pseudocydonia, and Pyrus) in subtribe Malinae; Gymnosporangium yamadae occurred in three species of the genus Malus in the subtribe. Literature and databases further revealed that G. asiaticum occurred in plant species of nine genera (Aria, Chaenomeles, Crataegus, Cydonia, Malus, Photinia, Pourthiaea, Pseudocydonia, and Pyrus); G. yamadae occurred in plant species of only the genus Malus in Malinae. This is the first comparative study of rusts caused by G. asiaticum and G. yamadae at KNA; it provides basic information on the occurrence of two different rusts and may facilitate the development of appropriate rust management strategies.