Summary

Rhizoctonia root rot is caused by the soil fungus, Rhizoctonia solani. The disease causes a dark black or brown rot that envelops the root and crown of sugarbeets.

Outbreaks occur in favorable conditions with abundant rainfall and high spring or summer temperatures. Poor soil structure consisting of tightly compacted soil increases the spread of the fungus. Infection typically occurs in the crown when contaminated soil is deposited onto the crown during cultivation or by wind or rain.

The strain of Rhizoctonia solani that causes Rhizoctonia root rot is fairly common and can attack a wide range of hosts such as corn or beans. Planting these crops in rotation with sugarbeets greatly increases the risk of infection.

Symptoms appear late in the growing season, spreading in patches or down the rows in the field. The damage is characterized by permanent wilting of the foliage and dark rot spots on the root or crown.

In severe cases, Rhizoctonia root rot causes significant economic devastation through major losses in yield, reduction in sugar content, an increase in soil tare and poor industrial quality.

Complete immunity from a Rhizoctonia outbreak is not possible, however several things can be done to minimize the risk of infection.

Adopt the following agronomic measures:

  • Extend Rotation. A three to five year buffer between sugarbeet crops in the same field is ideal.
  • Avoid susceptible crops. This means supplementing corn, beans and sugarbeet crops with non-host crops.
  • Exercise careful weed control
  • Use caution cultivating as it can result in the spread of contaminated soil to the beet tops.
  • Maintain good soil structure. Use appropriate fertilizers, sow a cover crop in the winter and avoid the use of heavy machinery in wet or unfavorable conditions.
  • Minimize soil compaction. Use wide tires.

In the United States, some fungicides are available to help combat the fungus. Growers should consult their agriculturalists and chemical representatives for more information on managing the disease after planting.

Varieties with resistance to both Rhizoctonia and Rhizomania continue to provide growers a higher level of tolerance and the opportunity to grow this valuable crop.

Seedex, Inc. is a leader in dual Rhizoctonia-Rhizomania tolerant varieties. These consistent Seedex varieties blend a high degree of resistance, excellent yield performance and the strong emergence that Seedex is known for.

Contents

Rhizoctonia Root Rot
1. Introduction, Damping Off, and Epidemiology
2. Symptoms and Economic Importance
3. Disease Control and Dual Resistant Varieties
4. Summary

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