Black chaff, also called bacterial stripe, is caused by the bacterium Xanthomonas translucens pv. translucens (syn. X. campestris pv. translucens). The bacterial streak/black chaff pathogen attacks many small grains and grasses worldwide, but generally is of little importance in the High Plains region. The disease is usually associated with sprinkler irrigation and/or humid, wet conditions in the High Plains. The pathogen is spread by seed, splashing rain, sprinkler and furrow irrigation, plant-to-plant contact, and spike-visiting insects such as aphids. The pathogen can survive between susceptible small grain crops in plant debris, pathogenically and epiphytically on other crops and weeds, and in seed.
Black chaff symptoms are most obvious after heading and include brown to black, water-soaked, and necrotic streaks and blotches. Glumes and leaves are often most symptomatic. Typically, upper portions of glumes are discolored, but can be totally darkened. Bands of healthy and necrotic tissue on awns are characteristic of black chaff. In wet weather, bacterial growth may appear as slime or viscous droplets on diseased tissues. Diseased heads mature late and may be sterile if infected before flowering. Damage caused to the plant can range from insignificant to severe; however, yield losses can be aggrevated under frequent or sprinkler irrigation
No biological control strategies have been developed for black chaff.
Plant high quality seed free of the black chaff pathogen. Varieties vary in their susceptibility to black chaff and resistant or tolerant varieties can effectively control the disease. Avoid frequent irrigation, especially by sprinklers, and reuse of irrigation water.
Seed treatment with copper bactericides may provide some disease control.
Product list for Black Chaff and Bacterial Streak:
Pesticide
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Mode of action
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Product per 100
pounds
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Remarks
|
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Copper and Copper/EBDC: not all formulations listed |
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Champ Flowable |
|
2 fl oz |
Seed treatment |
|
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Kocide 4.5LF |
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2 fl oz |
Seed treatment |
|
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ManKocide |
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4 oz |
Seed treatment; may provide superior suppression of copper tolerant bacteria |
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|
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Small Grains, Disease, Black Chaff, Bacterial Streak, Barley, Wheat, Oat, Triticale, Rye
Date: 3/8/05
