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Bacterial Leaf Streak Showing up in Wheat (07/18/19)

Severe thunderstorms across the state have provided suitable conditions for infection by Xanthomonas translucens pv. undulosa, the causal agent for bacterial leaf streak.

Severe thunderstorms across the state have provided suitable conditions for infection by Xanthomonas translucens pv. undulosa, the causal agent for bacterial leaf streak. Although we can see the disease as early as tillering in wheat, we most readily observe the disease after flag leaves are out. Bacterial leaf streak will first cause water-soaked lesions that run parallel along the midrib of the leaf (Figure 1). Within these lesions, crystalline granules (bacterial ooze), yellow to white in color, can be observed during periods of prolonged leaf wetness. As the lesions mature, they will turn yellow and eventually brown (Figure 2), causing substantial damage to the leaves (Figure 3). Later in the season, the bacterial propagules can splash onto wheat spikes leading to the head disease black chaff (figure 4). When black chaff is observed, risk of kernel infection increases.

The best management option for bacterial leaf streak is using less susceptible varieties. Hard red spring wheat varieties vary in their susceptibility to bacterial leaf streak and varietal information can be found in the North Dakota Hard Red Spring Wheat Selection Guide. There are several plant protection products labeled for bacterial leaf streak, however, none of the products tested have provided consistent results. Yield loss from this disease can approach 40% and will largely depend on disease onset. Last year, routine yield losses around 5% were reported from several areas of the state.

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Andrew Friskop

Extension Plant Pathology, Cereal Crops

 

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