Symptoms of ascochyta leaf scorch (spot) in cereals

Unlike many other foliar diseases of cereals, ascochyta leaf scorch (spot) is sporadic and rarely severe. Learn about the causal pathogen’s life cycle and the characteristic symptoms in wheat, barley, oats, rye and triticale.

The pathogen that causes ascochyta leaf scorch (spot) in cereals – Didymella exitialis (Ascochyta spp.) – has many similarities to septoria diseases, although it is of relatively minor importance.

D. exitialis is thought to overwinter as pycnidia and mycelium on crop debris, much like the septoria pathogens.

The fungus often invades damaged leaf tissue, such as that caused by liquid urea or nitrogen.

Disease symptoms are on lower leaves early in the season and on upper leaves later on.

Symptoms are often seen later in the season, towards the end of grain filling, when they are unlikely to cause any yield loss.

It probably contributes to leaf death in the same way as the septoria diseases. However, a distinctive lesion distinguishes ascochyta infections from septoria tritici blotch.

The lesions are usually elliptical and, although chlorotic at first, soon become a buff-to-brown colour, often splitting longitudinally. Initially, lesions have a dark-brown margin with a papery white centre.

Symptoms become less distinct with time, appearing very similar to those caused by septoria nodorum. However, pycnidia are generally black, whereas pycnidia associated with septoria nodorum are typically light in colour.

In the UK, airborne ascospores of the fungus are typically found in late summer and have been implicated in late summer asthma.