barley scald

Barley scald is a foliar disease caused by the fungus Rhynchosporium secalis. It appears as elongated, water-soaked lesions on leaves, typically starting at the leaf tip and spreading downward along the leaf blade. The affected tissue turns brown or tan with a darker border, and in wet conditions the lesions may coalesce, causing entire leaf sections to die. The disease reduces photosynthetic area, weakens grain fill, and can cut yields by 10 to 40 percent depending on variety, timing of infection, and growing conditions.

The fungus overwinters on infected crop residue and spreads via spores carried by wind and splash from rain. Infection occurs most readily when leaf wetness persists for 24 to 48 hours and temperatures sit between 15 and 20 degrees Celsius. Spring barley is generally more vulnerable than winter barley because it is sown later and grows through a period of higher rainfall. Susceptible varieties show symptoms as early as the three-leaf stage, though the most damaging infections occur during stem elongation and heading.

Management and prevention

Varietal resistance is the first line of defense. Modern barley cultivars show a range of resistances to Rhynchosporium secalis, and resistant varieties significantly reduce disease pressure without chemical intervention. Crop rotation (avoiding barley or susceptible cereals for two to three years) reduces inoculum carryover. Fungicide applications, typically azoles or strobirulins, are effective if applied at the flag leaf stage or earlier; timing is critical because applications after head emergence offer little benefit to grain quality or yield.

The disease takes its name from the scalded appearance of affected leaf tissue. In some regions it is called leaf scald or leaf spot to distinguish it from other barley diseases. It is most common in maritime and temperate climates with regular spring and early summer rainfall; it causes little damage in dry years or in arid regions. Agronomists monitor fields during tillering and stem elongation to catch early infections and decide whether fungicide use is economically justified.