By Emmanuel Byamukama
Figure 1. Bacterial leaf streak symptoms on winter wheat leaves.
Bacterial leaf streak (BLS) was found in several winter wheat fields scouted this week. This continues to be the main disease currently observed in winter wheat, whether a fungicide was utilized. The BLS severity ranged from mild (Figure 1) to severe (Figure 2) especially for wheat on wheat fields planted with a susceptible cultivar. For the majority of fields observed with BLS, there were scattered clusters of a few plants with BLS seen. Just one field had wide spread BLS throughout the entire field (Figure 3).
Figure 2. Winter wheat plants with severe bacterial leaf streak symptoms.
Causal Agent and Symptoms
Bacterial leaf streak is caused by a bacterium called Xanthomonas translucens pv undulosa. The bacteria survive mainly on seed but can also survive on plant debris, volunteer cereals, and other wild hosts. Pathogen spread amongst plants is achieved by plant to plant contact, insects, and rain splash. The bacteria enter the leaf through natural openings of the plant or wounds caused by high winds. Symptoms start as small regular brown to dark brown water soaked lesions limited within the veins (Figure 1). These later coalesce to form larger lesions and can cause the leaf to start dying from the tip (Figure 2). The lesions are transparent when held against the light. Symptoms start to develop after flag leaf growth stage under wet and warm weather.
Figure 3. A winter wheat field with plants yellowing due to bacterial leaf streak. This field had wheat residue (non-rotated) and was planted with a BLS susceptible cultivar.
Click here to see more...