Gymnosporangium sabinae (Dicks.) G. Winter, the causal agent of European pear rust, is a heteroecious rust fungus with a demicyclic life cycle-it produces teliospores and basidiospores on junipers, spermatia and aeciospores on pears. Environmental factors and agrotechnical methods influence the progress and duration of each stage, which is why the specifics and mechanisms of each stage of development are to be studied to predict the spread of the disease and its potential severity. A wide-range study of European pear rust in Latvia started in 2008-the impact of agroecological factors on the biology of G. sabinae was studied. It was concluded that pears' infection depends on basidiospores' development and release, which is mainly influenced by favourable meteorological conditions-precipitation of at least 10 mm and an average air temperature not below 10°C. The pathogen develops on shoots in the same way as on leaves. However, the development on shoots is slower overall, and the pathogen cannot overwinter there.