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AG NOTES - ISSUE #498
Rhizoctonia Root and Crown Rot Management Strategies
Rhizoctonia root and crown rot has been gradually increasing in incidence and severity for many years. Many factors have contributed to this trend. Selected management strategies can minimize or nearly eliminate Rhizoctonia as a threat to beet crop profitability. Lessons learned in Michigan and Western growing states can point Minnesota and North Dakota growers in the right direction when combating Rhizoctonia.
Root and Crown Rot Symptoms
- Yellowing of tops and sudden leaf wilting
- Petioles of outer leaves become blackened and rotted at the point of attachment to the crown
- When severe, all petioles are blackened, wilt and become prostrate on the soil surface
- Below ground, a dark brown gray rot starts near the crown and spreads over the root
- Root surface may crack and have sunken lesions
- Rot progresses inward to decay the entire root
- Disease often progresses down the row
Factors Increasing Rhizoctonia Severity
- More than a decade of wet summers
- Rotation with susceptible crops
- Soybean
- Dry edible beans
- Corn? (May be susceptible in region - currently under investigation)
- Shorter rotations
- Susceptible varieties planted for many years
| CROP |
R. SOLANI AG 2-2IV |
R. SOLANI AG 2-2IIIB |
| Sugarbeet |
+++ |
+++ |
| Bean Crops |
++ |
+++ |
| Wheat |
- |
- |
| Corn |
- |
? |
| - = nonhost, + = slightly aggressive, ++ = moderately aggressive, +++ = severely aggressive |
? + May be susceptible under investigation |
Rhizoctonia Control Strategies
- Long crop rotations, 4 years or more
- Grow wheat the year before sugarbeet
- Don't grow soybeans or edible beans the year before sugarbeet
- Use resistant varieties
- Don't cultivate or rotary hoe unless necessary for weed control
- Keep soil out of crowns during cultivation
- Never "hill" beets with soil to kill weeds in fields with Rhizoctonia
- Apply Quadris in a timely manner
Using Disease Severity, Variety Resistance Level and
Quardris for Rhizoctonia Management
| SEVERITY OF RHIZOCTONIA |
VARIETY TYPE |
QUADRIS 7-INCH BAND* |
| Light |
Susceptible |
Yes (2/3 full rate) |
| Moderate |
Moderately resistant
Most resistant |
Yes (2/3 full rate)
No |
| Severe |
Most resistant |
Yes (full rate) |
* A wider band reduces effective rate
A narrower band allows use of lower rate
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| From: Steve Poindexter, Michigan State University Extension |
Quadris: Timing & Placement
- Apply at 9.5 - 15.5 oz/A in a 7-inch band, 22-inch rows
- Quadris is ineffective if applied after infection takes place
- Apply at the 4-8 leaf stage as soil temp approaches 65°F
- Too early or too late = inadequate protection
- Band applications more effective than broadcast
- Effective when infection starts at crown - but not when infection starts below the surface soil
Know the Problem
Be certain your problem is Rhizoctonia. Quadris will not control other diseases. Contact your Agriculturist for help.
Be sure to heed all pesticide use label restrictions. Refer to the handout titled "Specifications for Proper Pesticide Use". Your Agriculturist has copies.
NEVER, EVER mix Quadris with any herbicide application.
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