Development of Rye Leaf Diseases and Possibilities for Their Control

Diseases of rye (Secale cereale), an important crop in Latvia, might be a risk factor for rye production. The aim of the study was to determine features of rye leaf diseases, to estimate the risk of rye diseases under conditions of Latvia, and to compare various schemes of fungicide treatment that possibly might be useful for integrated disease control. Field trials were carried out from 2009 to 2012 in two locations in Latvia - State Stende Cereals Breeding Institute and State Priekuïi Plant Breeding Institute. Sixteen trials (two cultivars each year, two sites, and four years) were established during the investigations. Each trial was one-factor design with three variants of fungicide treatment: control (without fungicides), standard treatment during heading (GS 51-55), and DSS (Decision support system). Leaf scald caused by Rhynchosporium secalis and brown rust, caused by Puccinia recondita, were found to be the most important rye diseases during the study. Average additional yield achieved by fungicide application was 8%. Number of rainy days (more than seven, starting from GS 31) was not a sufficient threshold for the control of rye diseases. It was necessary to make assessment of the disease development in the the field. Fungicide application might be necessary if symptoms of leaf scald appear on the youngest leaves after beginning of stem elongation (GS 31-32).