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BASF Agricultural Solutions Danmark

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DTR (hvedebladplet) [Pyrenophora tritici-repentis]

Spread/Transmission

In straw and stubble residue the sexual Propagation period persists in the form of round brown

pseudothecia

. 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.

Incidence

Wheat, durum wheat, triticale, rye

Diagnosis

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

ring spots.

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.

Control

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 measures

• 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

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