Stem rust, Puccinia graminis, has caused enormous yield losses throughout history which have had significant consequences for oat and wheat production. Today in Sweden stem rust is only reported from rye, oats and wild grasses. Stem rust infections in wheat have become unusual due to the general use of resistant wheat varieties and also due to the eradication of barberry, Berberis vulgaris, the alternate host for P. graminis. According to international sources, new races of P.