Pear rust in the conditions of north-eastern Forest-Steppe of Ukraine

Abstract

Studies were conducted during 2017‒2019 based on the training laboratory of horticulture and viticulture of the Sumy National Agrarian University in the conditions of the North-Eastern Forest-Steppe of Ukraine. It was found that the pear was massively affected by rust. This is a fungal disease that was rarely found in fruit orchards of the North-Eastern Forest-Steppe of Ukraine.
 Rust infected pear trees very rarely in previous years. Only single spots were found on the leaves of the pear. Since 2015, the development of the disease has noticeably accelerated from year to year. There was a massive rust damage of the pear in the region in 2019. The prevalence of the disease reached 100 % in almost all varieties. Mostly the leaves were affected, not to a large extent the shoots of the pear. On the fruits of the external signs of the disease were not detected.
 During the years of research, weather conditions were optimal for the spread of fungal diseases. Only the aecial stage of the fungus was observed on the pear. The aecial stage of the pathogen is the most harmful. Affected pear leaves fall prematurely. Studies were conducted on pear varieties Lymonka, Petrovska, Medova, Osinnia Yakovlieva, Chyzhovska, Noiabrska, Bere Desiatova, Uliublenytsia Klappa, which showed different degrees of rust damage. The disease manifested itself most significantly (5 points) on the varieties, Uliublenytsia Klappa and Bere Desiatova. Not one of the varieties did not show high resistance to the pathogen. The pear of the Chyzhovska variety was less affected, with a defeat score of 3 (18.8 %) in 2017 and 4 (32.3 % and 44.1 %) in 2018‒2019.
 It is known that the life cycle of the rust pathogen Gymnosporangium sabinae (Dicks.) G. Winter occurs on two plants: pear and juniper. The pathogen from juniper goes on the pear and vice versa. Pear trees do not become infected from each other. On the territory adjacent to the fruit garden of Sumy National Agrarian University, a survey of plantings of different types of juniper was conducted. There were no visible signs of the disease on the juniper. At the same time, pear trees were highly infected with the pathogen. Perhaps the spores of the fungus can spread far through air currents. But at the same time, possible changes in the life cycle of the pathogen in the conditions of this region. Clarification of this circumstance requires deeper further research.