Plum rust – a new disease in the Moscow oblast

In 2023–2024, we conducted research studies to investigate the distribution of plum rust caused by the Tranzschelia pruni-spinosae (Pers.) Dietel fungus across the Moscow Oblast. The results showed that the ‘Pamyat Timiryazeva’ plum variety was most aff ected by this disease, with the amount of leaf lesions reaching 90 %. The Utro variety was found to be least prone to the disease, with the amount of leaf lesions reaching 5.5%. In the ‘Opal’ and ‘Tulskaya Chernaya’ varieties, the disease aff ected from 20 to 21.8% of plum foliage, respectively. The ‘Shater’ cherry plum variety was not aff ected by rust, although being located in close proximity to plum trees signifi cantly aff ected by the disease. Primary symptoms of plum rust in the conditions of the Moscow Oblast appeared in the second decade of July–fi rst decade of August in the form of yellow-green spots on the upper surface of leaves. These spots further formed pale brown raised dots (pustules) on the corresponding areas on the underside of leaves, in the sites of fungal spore development, becoming more noticeable by the end of the vegetation period, when their color turned dark brown/black. Identifi cation of the primary symptoms of plum rust was complicated by the presence of leaf spots of other species that had started to develop earlier (clasterosporiosis, red spot, etc.).