The problem of Gymnosporangium rusts on juniper plants.

摘要

Several rust species from genus Gymnosporangium were described on junipers as to date they were occurring occasionally. In recent years juniper and pear rust, caused by G. sabinae, has spread in Poland. The spread of rust caused by other species from genus Gymnosporangium, i.e. G. confusum, G. cornutum or G. clavariforme, could not be excluded. Identification of rust currently threatening junipers is of considerable importance for horticultural practice. In the spring of 2008 rust symptoms were observed on hawthorns. Symptoms were detected on flowers, fruits and shoots, which were deformed and grew rank. On infected organs aecia developed, in which aeciospores were formed from spring on flowers and on other infected organs - until late autumn. Based on the symptoms and microscopic characteristics the cause of rust on hawthorns was found to be G. confusum. The disease was commonly found on Crataegus monogyna as well as C. oxyacantha in different regions of the city Poznan. In the group of 242 examined plants symptoms were not found on 71 trees (29.3%), they were usually young and non-flowering trees.