Life cycle and appearance of Glume blotch

Phaeosphaeria nodorum or Septoria nodorum survives as perithecia containing ascospores and pycnidia containing conidia on crop residues and winter wheat seedlings. Ascospores germinate at any temperature above freezing when water is available. Conidia require a minimum of 5 °C for germination. Primary infection is mostly by ascospores or conidia on the oldest leaves, but seed transmission is also possible. The germ tubes can infect the leaves of the plants directly or through stomata. The lesions become visible after five to seven days. On the lesions, new pycnidia are formed. The conidia that are produced in these pycnidia emerge in a pink slimy substance. The conidia are released at high relative humidity (RH). The optimum temperature for germination of the conidia is between 20 and 25 °C.

The ascospores are responsible for wind dispersal of the fungus over longer distances, but inside an infected crop the conidia cause secondary infection by splash dispersal. Splashing rain water helps the fungus to reach the upper leaves and ears. Seed infection is enhanced by wet weather conditions during heading.

How to prevent Glume blotch

• Remove crop debris
• Use clean seed
• Be careful with overhead irrigation
• Be careful with chemicals that limit stem elongation when the lower leaves are infected and frequent rain is expected
• Be aware that in a crop with dense foliage, splash dispersal is more efficient so the disease will spread faster

Prevent plant diseases by optimizing plant potential and crop resilience.