Net blotch of barley

Net blotch is a major fungal disease affecting barley, caused by the pathogen Drechslera teres (anamorph of Pyrenophora teres). It is recognized as one of the most significant constraints to barley production globally, causing both economic losses and reductions in grain quality.

The disease primarily attacks the barley plant, manifesting symptoms on leaves, leaf sheaths, and occasionally on the stems and spikes. The pathogen survives between growing seasons primarily on infested barley stubble and crop residues, as well as through infected seeds.

Symptoms are distinct and characterized by small, dark, necrotic spots that expand longitudinally and transversely, creating a netted pattern of dark brown or black lines. These lesions are often surrounded by a chlorotic yellow halo. As the infection progresses, leaves die back rapidly, which severely hampers the plant's photosynthetic capacity.

The development of net blotch is favored by mild, wet weather conditions, with temperatures ranging from 15°C to 20°C being optimal for fungal growth. Frequent rainfall or prolonged dew periods significantly accelerate the spread of conidia, which are dispersed by wind and splashing rain to healthy plant tissues.

Effective management strategies rely on an integrated approach. This includes:

• the use of resistant cultivars;
• crop rotation to reduce inoculum levels in the soil;
• removal of crop debris through tillage;
• seed treatment with fungicides;
• timely application of foliar fungicides during the vegetative growth stages to protect the flag leaf.