Leaf and Glume Blotch of Wheat

Disease

Leaf and Glume Blotch of Wheat

Parastagonospora nodorum

fungi

In a Nutshell

    Water-soaked and small chlorotic lesions on the lower leavesLater tan-brown oval leaf blotches with yellow marginsEnlarged gray lesions with tiny brown fruiting bodies on heavily infected leavesDark brown to dark purple lesions on the glumesSeedlings grow with brown shoot tips

Hosts: %1$s

· Triticale · Wheat · Rye · Barley

Symptoms

Water-soaked and small chlorotic lesions appear on the lower leaves of the plant. The disease emerges from the lower leaves up to the flag leaf. Later, the lesions become tan-brown, oval- or irregular-shaped leaf blotches with yellow margins. As the disease progresses, tiny brown fruiting bodies in the enlarged gray lesions can be seen using a magnifier or a microscope. Badly affected leaves die back from the tip as the blotches converge. After flowering, wet weather can lead to lesion development on the glumes. Symptoms often start at the tip, but whole areas may be covered with dark brown to dark purple lesions with ash gray areas ( “glume blotch”). Severe infections may result in lightweight, shriveled kernels. Infected seeds show irregular emergence and seedlings have brown shoot tips.

Trigger

This foliar disease is caused by the fungus Parastagonospora nodorum, which survives on wheat straw, infested seeds or on alternative host crops. The fungus is dispersed through water and requires about 12 to 18 hours of leaf wetness for infection. Older leaves near the soil are the first affected. Then, the fungus is dispersed via wind or rain-splashes to the upper parts of the plant and to neighboring crops. Late season infections could lead to glume blotch if the disease is moving up the canopy. It causes shriveled grains and reduces yield. Spores are spread by wind and can cover long distances to infect the seedlings in other fields later in the season. This leads to earlier infection of the following crops and to irregular emergence. The life cycle of the fungus is stopped at temperatures below 7°C. Optimal growth range is between 20°C and 27°C.

Biological Control

Sorry, we don't know of any alternative treatment against Phaeosphaeria nodorum . Please get in touch with us in case you know of something that might help to fight this disease. Looking forward to hearing from you.

Chemical Control

Chemical treatment of the disease may be effective to reduce the risk of an outbreak but may be inviable in smaller farms. If fungicides are needed, products containing difenoconazol, triadimenol or fluquinconazol can be applied. The application method varies depending on time of occurrence and cultivation type.

Preventive Measures

    Use seeds from healthy plant material or from certified pathogen-free sourcesUse tolerant or long straw varieties available in your areaUse late maturing wheat varieties or plant later in the seasonUse an optimal sowing density at plantingUse growth regulators at moderate levels and a balanced fertilizationEnsure soil potassium levels are adequate for healthy plantsCheck your plants or fields for any sign of disease after emergenceEnsure a moderate application of herbicidesPerform crop rotation with non-host cropsPlow deep to bury plant residues under the surfaceRemove straw and other plant debris from fieldRemove volunteer plants




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