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Managing Bacterial Blight in Dry Beans (07/13/17)

Recent thunderstorms in Northeast ND and Northwest MN have created a favorable environment for bacterial blight in dry beans.

Managing Bacterial Blight in Dry Beans

Recent thunderstorms in Northeast ND and Northwest MN have created a favorable environment for bacterial blight in dry beans.  In response to last year’s bacterial blight epidemics, Amanda Beck a Ph.D. student in the plant pathology department working for dry bean pathologist Julie Pasche, evaluated a many products (new and old) against the most common bacterial blight disease in our region ‘Common Blight’.  We emphasize that this is only one year of data, and are reticent to make recommendations based on this data alone, but it is important to share it with the dry bean community.

Information about the treatments.  The treatments used in these trials are a combination of plant growth enhancers, copper-based products or peroxide based products.  In some cases, we have very limited additional information about the products.  However, product information is available online and can be found relatively quickly using an internet search tool.

Trials Information.  Each of the trials were conducted on NDSU Agriculture Experiment Station sites.  ‘Early’ treatments [Wakeup Summer (Early) and eA300 (Early)] were applied only once and in late June.  In Oakes and Prosper, the remaining chemical treatments were applied twice, with the first application occurring in mid-July (July 18th and July 20th) and the second in approximately 2-3 weeks later (August 1st and August 6th). Treatments were applied only once in Fargo (August 9th).  In all trials, plots were sandblasted to mimic wounding from thunderstorm damage, and inoculated with the pathogen during late flowering.  Oakes was under irrigation.  Disease severity was calculated by visually examining leaf tissue and plot damage.

Results.  Disease severity was moderate in Fargo and very high in Proposer and Oakes (Table 1).  Reduced disease severity was observed from all products in at least one location.  ‘Early’ applications were generally less effective at managing disease (numerically or statistically) than a two spray program beginning in July.  On average, the lowest disease severity was observed on plots applied with Oxidate or Kocide 3000, however, a high level of variation in disease control among products existed in each of the trials, and other products were comparable in specific trials.

No yield differences in any of the trials were observed.  However, a rust epidemic occurred in Fargo, and a white mold epidemic occurred in Oakes.  Both of these diseases confounded yield data.  Consequently, it is unclear if the reductions in disease severity from bacterial blight with these chemical treatments would have protected yield.

Conclusions.  Limited data exists on many of these products and these trials represent only one year of data. Consequently, this information should be interpreted with caution.  In other parts of the U.S. such as Eastern Colorado and Western Nebraska, a 2-4 spray program is used to actively manage bacterial blights.  Historically, a multi-application bacterial blight program has not been commonly used in our region because it was not cost effective.  However, we will continue to evaluate chemicals and timing for bacterial blights in order to re-evaluate bacterial blight management.

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Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

 

Amanda Beck

NDSU Plant Pathology Graduate Student

 

Julie Pasche

NDSU Plant Pathology Professor

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