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Black chaff (wheat) and bacterial blight (barley) (caused by a bacterial pathogen:
Xanthomonas campestris pv. translucens, Xct) were common problems in southcentral and eastern
Idaho in the early and middle 80’s and were the most frequently diagnosed diseases
of wheat and barley in 1986. However, they have been much less prevalent up to 1996.
The symptoms to look for are dark green, water-soaked tissue or dark brown or
black spots or streaks on the lower leaves. The water-soaked tissue is almost
guaranteed to be due to bacterial infection, whereas the dark spots could be caused
by Xct or another leaf pathogen such as Cochliobolus (syn. Helminthosporium), the
cause of spot blotch, or Rynchosporium, the cause of scald.
Yield losses can approach 40% in the most severely diseased wheat fields although
they are usually less than 10%. There are no effective control measures at this
stage other than avoiding excessive irrigation. Increasing the amount of water
applied by sprinklers during an irrigation and reducing the number of irrigations may
be of some benefit if that can be accomplished without stressing the crop.
If you find wheat or barley with symptoms of black chaff and bacterial blight, please
contact Bob Forster. Additional
information on these diseases may be found in CIS 784 (Black chaff of wheat and
barley) and in the Compendium of Wheat Diseases and Compendium of Barley
Diseases.
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