Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Bean, Snap (Phaseolus vulgaris) -- Rust
 
Cause: The fungus Uromyces appendiculatus (formerly U. phaseoli) causes rust. It has had minor importance for many years. When present, the disease is widespread in the major bean-growing areas of the Willamette Valley. It is not known to occur in Idaho. Disease is favored by moderate temperature and high humidity or moisture.
Symptoms: In June, white blisters (pycnia) develop on leaves' upper sides. In 2 to 3 weeks, the lower side of the blister (aecia) turns white and produces a white powder (aeciaspores). In July, brown powdery spots (uredinia) appear on upper and lower leaf surfaces and petioles. If infection is severe, many leaves die and the crop is reduced. In August to September black powdery spots (telia) appear on upper and lower leaf surfaces and petioles. Leaves die, and the crop is reduced. Rust also attacks all other aboveground green portions of the plants.

Snap bean plants with rust.

Snap bean leaf with white blisters (pycnia) on the upper side.

Snap bean leaf with aecia on the lower side.

Snap bean leaf with uredinia.
 
Cultural control:
  1. Plant resistant cultivars.
  2. Rotate with nonhost crops.
  3. Eliminate volunteer beans in other fields.
  4. Encourage decomposition of old bean debris.
Chemical control:
  1. Dust with sulfur products (325 mesh or finer) containing at least 80% sulfur. Apply first as soon as lesions or spots appear. Apply at 20 to 36 lb/A, depending on the plants' size. Continue dusting at 7-day intervals until blossom time. Early dusting is especially important apply sulfur before any rust is noticeable. Controlling rust by dusting is difficult if the disease becomes established in a planting.
  2. Chlorothalonil products such as:
    1. Bravo Ultrex at up to 2.7 lb/A. Do not apply within 7 days of harvest. Do not graze treated area or feed treated plant parts to livestock. 12-hr reentry.
    2. Echo 720 at 1.375 to 3 pt/A on 7-day intervals when disease threatens. Preharvest interval is 7 days. 12-hr reentry.
  3. Endura at 8 to 11 oz/A. To limit the potential for development of resistance, do not make more than two (2) applications of Endura per season. The preharvest interval is 7 days. 12-hr reentry.
  4. Folicur 3.6F at 4 to 6 fl oz/A on 14-day intervals. Do not apply within 7 days of harvest. 12-hr reentry.
  5. Headline at 6 to 9 fl oz/A prior to disease development on 7- to 14-day intervals. Do not make more than two (2) application of Headline or other Group 11 fungicide before alternating to a labeled fungicide with a different mode of action. Preharvest interval is 7 days for pods, 14 days for forage and hay. 12-hr reentry.
  6. JMS Stylet-Oil at 3 to 6 qt/100 gal water. Do not spray if temperature is below 50°F, above 90°F or when plants are under heat or moisture stress. Good coverage is essential. 4-hr reentry.
  7. Orius 3.6F at 4 to 6 fl oz/A on 14-day intervals. Do not apply within 14 days of harvest. 12-hr reentry.
  8. Quadris at 6 fl oz/A on 7- to 14-day intervals. Do not apply more than two (2) foliar applications rotating to chemistry with a different mode of action. May be applied the day of harvest. 4-hr reentry.
  9. Rally 40WSP at 4 to 5 oz/A on 7 to 10 day intervals. Application can be made on day of harvest. 24-hr reentry.
Biological control:
  1. Sonata at 2 to 4 qt/A on 7- to 14-day intervals for disease suppression. Can be applied up to and on the day of harvest. 4-hr reentry.
Content edited by: Cynthia M. Ocamb on January 1, 2009
 
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