Common bacterial blight is caused by the pathogen Xanthomonas axonopodis pv. phaseoli (syn.=X. campestris pv. phaseoli). The pathogen can be found on the leaves of many plants, but only causes disease on a dry bean. Infection occurs when bacterial cells are deposited onto leaves by splashing water, aerosols, or from contaminated seed, and multiply to form large populations. The bacteria gain entry into plants through natural openings and wounds. Infection occurs most readily during warm (greater than 85ºF), wet weather, especially hard, wind-driven rains. Bacteria are disseminated within and among fields by splashing water, aerosols, and on contaminated equipment and workers. The pathogen survives between susceptible hosts in and on weeds, infested crop debris and contaminated seed.
Common bacterial blight symptoms first appear as flaccid, small water-soaked spots on the underside of leaflets. These spots enlarge and merge, becoming dried and brown. A narrow, bright lemon-yellow border of tissue encircles the lesion. Infected pods develop circular water-soaked spots, and yellow masses of bacteria may appear at their center. Later, the spots dry and become reddish-brown, sunken lesions. Early pod infection causes shriveled seeds, and the bacteria may cause yellow to orange discoloration under the seed coat of infected seeds. A stem girdling or joint rot occurs above the cotyledonary node of plants grown from infected seeds. Yield losses can range from 20 to 40% during certain year. The disease also reduces seed size and quality.
No biological control strategies have been commercialized for common bacterial blight.
Plant certified seed of recommended varieties less susceptible to common bacterial blight. Avoid overhead irrigation and reuse of irrigation water where possible. Avoid working in fields when plants are wet. Promptly and thoroughly incorporate infested bean debris into the soil after harvest, and rotate beans with non-host crops such as small grains for at least two years. Practice strict sanitation of weeds and volunteer beans early in the following season.
Antibiotic seed treatment and preventative bactericide applications can reduce spread of the common bacterial blight pathogen, but chemical controls are most effective when integrated with sound cultural practices.
Product List for Common Bacterial Blight:
Pesticide |
Rate per Acre |
Application Frequency |
Remarks |
|
Copper fungicides: not all formulations listed |
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|
Basicop |
32-64 oz |
7-10 |
- |
|
Champ DP |
0.66-2.0 lb |
7-14 days |
Apply preventatively beginning when plants are 6”in height |
|
Copper Count N# |
64-96 fl oz |
5-10 |
- |
|
Cuprofix Disperss |
1.5-3.5 lb |
7-14 days |
Apply preventatively beginning when plants are 6”in height |
|
Kocide 2000 |
0.75-2.25 lb |
7-14 days |
Apply preventatively beginning when plants are 6”in height |
|
Kocide 3000 |
0.5-1.25 lb |
7-14 days |
Apply preventatively beginning when plants are 6”in height |
|
Nu Cop 50 WP |
1-3 lb |
7-14 days |
Apply preventatively beginning when plants are 6”in height |
|
Top Cop+S |
64 fl oz (37.1) |
- |
1 day PHI |
|
Tri Basic Copper# |
32-48 fl oz |
7-10 |
Maximum of 6 times |
|
Streptomycin: not all formulations listed |
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|
Agri-Strep 500 |
13 oz (6.6) |
- |
Slurry seed treatment (50,000 ppm) |
|
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: Dry Bean, Disease, Common Bacterial Blight
Date: 04/01/2007