ABSTRACT
Common names: Black chaff, leaf streak, bacterial stripe, or bacterial blight of cereals and grasses
Symptoms Infected leaves show narrow, water-soaked streaks (yellowish in barley and triticale), necrotic at the center with a rust-colored margin (in wheat). On young leaves, generally, small, water-soaked leaf spots appear that later develop into longitudinal yellow to brown streaks (Smith, 1917; El Banoby and Rudolph, 1989; Duveiller and Maraite, 1993b). Leaves may wilt. In wet weather, small droplets of yellowish bacterial slime can be observed on the lesions (Jones et al., 1917) (Photo 2.1). Symptoms often develop in the middle of the leaf, where dew remains longer in the morning. Seedlings hardly show any symptoms. Glumes and seeds show “black chaff” symptoms, with purple-black discoloration of the surface. Symptoms take 10-14 days to appear. Streaks are more usual on triticale than on wheat. Culms, leaves, rachis, glumes, and awns may become infected, and symptoms on wheat have been reported to vary with the environment, variety, disease severity, and interaction with fungi (Bamberg, 1936; Boosalis, 1952). On the stem, brown to black stripes may be formed. On the chaff of many hosts, water-soaked spots are formed that later develop into brown to black spots. Ears may show brown discoloration and distortion. Seeds may be black and shriveled. The heavily infected crops show water-soaked to yellow-brown streaks, wilting, and complete necrosis of leaves.
