How to Manage Pests
UC Pest Management Guidelines
Leaf Scald of Barley
Pathogen: Rhynchosporium secalis
(Reviewed 2/07, updated 2/07)
In this Guideline:
Lesions first appear on foliage as dark, pale or bluish gray spots. These spots expand into oval lesions with bluish gray centers and dark brown margins. The lesions enlarge and coalesce, giving the appearance of rapid scalding. Entire leaves may be covered and killed if the disease is severe. Lesions normally occur only on leaves, but when conditions favor severe disease, they also develop on spikes.
Leaf scald of barley affects only domestic and wild barleys (Hordeum spp.). It is most severe in years of higher than normal rainfall. The fungus survives between seasons primarily on barley residue and volunteer barley plants, and to a lesser extent on some grasses and barley seed. Infection, development, and spread occur during cool, 40° to 77°F (4° to 25°C), rainy weather. Spores are formed in a thin layer of slime on the surface of lesions and are spread short distances by splashing or wind-driven rain. Spores that land on plant surfaces germinate and infect the leaf if the surfaces remain wet for at least 24 hours. If infected seeds are planted, coleoptiles can be infected after the seeds germinate. The optimum temperature for coleoptile infection is about 60°F (16°C).
Control measures include crop rotation (to any crop other than barley), removal/disposal of barley residue from the surface of the soil, and destruction of volunteer barley and grass hosts. Also, avoid early plantings (Oct. to Nov.) because when conditions favor disease development late plantings (Dec. to Jan.) are less damaged. Use clean seed and resistant cultivars (see BARLEY CULTIVAR TABLE).
UC IPM Pest Management Guidelines:
R. M. Davis, Plant Pathology, UC Davis