DTR (hvedebladplet) [Pyrenophora tritici-repentis]
In straw and stubble residue the sexual Propagation period persists in the form of round brown
. Formation takes place between autumn and spring whereby the climax for the release of ascospores is in March/April as moisture must be present. It spreads only a few centimeters or decimeters. Over longer distances the asexual formed
conidiospores are wind carried. For epidemics to occur temperatures over
20° C are required. The spores are formed during moist warm nights and they spread on warm dry days by being wind carried. Other leaves are more prone to infection than younger ones.
Wheat, durum wheat, triticale, rye
Primary infection emanating from the straw and stubble residue causes round, light brown infected points on leaves near the ground. In secondary infection typical dark brown infected spots form surrounded by chlorotic
Irregular limited leaf spots appear which later join together, The dark infected supports are visible for a long time. The DTR tan spot disease can be clearly differentiated through the spores which stand individually on the upper surface of the leaf. A 30 time magnification is required to differentiate between Septoria nodorum, black fungus and alternaria.
Preventative field measures
• loose rotation, avoiding planting wheat following wheat
• plow in well straw and stubble residue
• promote soil life
• sew less sensitive types
• Fungicidal use at ES 32-37 upon first sporulation
• In case of high infective pressure: spray twice at an interval of three weeks.
• After leaf infection with DTR tan spot disease it is difficult to stop using fungicides