Bacterial Blight

Barley
bacterial streak and black chaff - Xanthomonas campestris pv. translucens

Oats
halo blight - Pseudomonas syringae pv.coronafaciens
stripe blight - Pseudomonas syringae pv.striafaciens

Rye
bacterial blight - Xanthomonas translucens

Wheat
bacterial stripe and black chaff - Xanthomonas translucens
basal glume rot and bacterial black point - Pseudomonas atrofaciens
bacterial leaf blight - Pseudomonas syringae pv. syringae

Biology

Bacterial blight, caused by several different species of bacteria, can cause head and foliar diseases of barley, oats, rye and wheat.

The disease-causing bacteria overwinter on crop residue, seed, fall sown cereals and perennial grasses. Spring infection may result from any of these sources. Bacteria are spread by splashing rain drops, plant to plant contact and insects.

The disease is favoured by cool, wet weather. Warm dry weather checks bacterial diseases and new emerging leaves may be relatively free of bacterial infection.

Damage Description

• Barley
  Bacterial streak begins as small pale green spots that become water soaked. These join to form transparent stripes. Later, the stripes turn yellow or brown. A milky exudate may be present on the leaves under wet conditions. When dry, this exudate turns into small thin flakes that are easily removed from the leaf surface.
  This disease may superficially resemble fungus stripe. However, the fact that all barley plants are uniformly infected in a given location rules out fungus stripe since stripe is seed-borne and is normally scattered throughout the crop.
  
  
• Oats
  Halo blight begins as small light green oval spots with dark water-soaked centres. The spots join to form irregular brown blotches.
  
  Stripe blight produces elongated spots with no pale margins. These spots also have water-soaked centres and turn brown later in the year.
  
  
• Wheat
  Bacterial stripe produces dark green, water-soaked lesions that later turn brown. Near heading, upper leaves develop water-soaked spots that grow to whitish streaks or blotches (white blotch).
  
  Black chaff appears on the kernels as dark stripes on the glumes. These often join and the glumes turn black. These symptoms occur on both wheat and barley. These diseases are sometimes confused with melanosis of wheat that is caused by copper deficiency.
  
  Basal glume rot appears mostly on the inner side of the glumes as a light brown color. As the disease develops, the grain may develop a black spot at the germ end, known as bacterial black point.
  
  Bacterial leaf blight appears on the flag leaf when bright sunny weather follows a rainy period. This disease occurs occasionally on winter wheat.
  
  
• Rye
  The bacterial disease symptoms appear very similar to those described for barley but exudate on the leaves is not as common.

• Use seed from crops that are free of bacterial disease.
• Do not use cereals in the crop rotation for three or four years. Rye should not follow wheat or rye, and barley should not follow barley.