Distribution and development of European pear rust in Latvia and relationshipbetween severity and yield


Abstract: Pear (Pyrus communis L.) is the second most common pome fruit crop in Latvia. Acritical situation with the severity of disease – European pear rust (caused by Gymnosporangiumsabinae) – has been observed in gardens of Latvia, where plant protection products are not usedat all or in very limited amounts. Therefore the disease becomes more and more common. Theagent of pear rust is an obligatory parasite with incomplete development cycle, which requiresboth pear and juniper. In case of strong infection disease features could be found not only on pearleaves, but also on branches and fruits. The disease can cause significant crop losses, as well asgradual destruction of trees. Therefore the aim of study was to determine the incidence level ofEuropean pear rust infection in Latvia and to analyze peculiarities of disease development. Forthe detection of European pear rust incidence 33 pear orchards in different regions of Latvia wereevaluated, whereas disease development was investigated for three years at the pear collection ofthe Latvia State Institute of Fruit-Growing. Severity of pear rust was scored using scale of points(0-5) indicating average number of infected leaves per tree. European pear rust severity resultsshowed significant difference over the years of evaluation. The incidence and spread of thedisease was increasing during more humid growth periods. There were no resistant cultivarsamong the tested ones, only variability of susceptibility. Results showed that high severity of pearrust infection has significant influence on pear yield.

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