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Three steps to reduce root rot
April 14, 2005

Three steps can significantly reduce the incidence of root rot in dry beans, says Jim Percich, U of M plant pathologist.

1. Rotate with non host crops. U of M research indicates that root rot pathologens don't colonize buckwheat, oat, rye and soybeans.

2. Use deep tillage to disrupt compacted soil layers. In U of M trials, moldboard tillage increased dry bean yield by 50% over chisel plowing. Chiseling 6-8 inches deep caused the formation of cap action layer that inhibited soil drainage and interfered with root growth and development. The increased yield obtained from moldboard tillage was a result of enhanced root growth and reduced root rot severity (28% reduction) resulting from less penetration resistance and improved drainage. More extensive root development reduces plant susceptibility to moisture and nutrient stress. Enhanced drainage shortens periods of soil saturation that favor root rot development. Irrigation may exacerbate root rot severity in plants growing above the impedance layer by increasing the number and duration of episodes when soils are saturated.

The combined use of moldboard tillage and biocontrol seed treatments (B. subtilis and Rhizobium) at the Central Lakes Agricultural Center and in a grower's field significantly increased average yields 20 and 27%, respectively, as well as enhancing edible bean root development and decreasing disease severity when compared to chisel tillage.

3. Apply biological seed treatment consisting of the Bacillus subtilis (Kodiak or Subtilixâ) and Rhizobium tropici. They reduced root rot and increased yield 10 to 30% compared to untreated seed. If you use biological seed treatment, don't also treat the seed with Captan and Streptomycin.

In U of M lab and field research, Captan and Streptomycin significantly reduced the effectiveness of biological seed treatments (B. subtilis and Rhizobium) and did not increase yield compared to biological seed treatments. However, the insecticide Lorsban had no effect on the biological seed treatments.

At a glance

*          Rot doesn't colonize buckwheat, oat, rye and soybean.

*          Breaking up compaction layer reduces rot by improving drainage.

*          Biological seed treatments increased yields 10-30%.


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