Development of tan spot (Pyrenophora tritici-repentis) in winter wheat under field conditions

The pathogen that causes tan spot on wheat is Pyrenophora tritici-repentis (Died.) Drechs. (anamorph Drechslera tritici-repentis (Died.) Shoemaker). In recent years tan spot has become a potentially destructive disease of wheat in Lithuania and neighbouring countries. Three winter wheat cultivars (Aron, Tauras and Hereward) were grown during three seasons. Weather conditions were observed from April to August when the tan spot pathogen spreads. During the experimental years the weather conditions varied from season to season. A severe epidemic of tan spot occurred in 2004 when there was a sufficient amount of rain and the air temperature was close to optimal. The other two seasons were not extremely favourable for tan spot occurrence, especially in 2005, because of the lack of rain during the main growing period. Investigations of tan spot development patterns under field conditions enable wheat growers to better forecast tan spot and achieve better timing of fungicide applications.