Summary

Rhizomania is one of the most common sugarbeet diseases. It’s caused by the Beet Necrotic Yellow Vein Virus (BNYVV) and is transmitted through a soil parasite, a protist called Polymyxa betae. The disease causes the aimless development of random roots, which is how Rhizomania got its name (Greek for “crazy root”). These frivolous roots fail to absorb nutrients resulting in sugar loss and overall crop loss.

Rhizomania was first recorded domestically in 1983, however the abundant number of Rhizomania observations nationwide that year likely means it has been in the United State much longer. Since the late 2000s, the quality of Rhizomania-resistant varieties has increased dramatically to the point where it’s production is comparable to conventional varieties. As such, the majority of varieties planted today carry some type of Rhizomania resistance.

Symptoms of Rhizomania often appear in patches in fields and include:

In Foliage:

  • Wilting of the foliage, usually during the hottest part of the day in June
  • A pale, greenish-yellow color in the foliage (called Blinkers) during the later summer months
  • Newly produced, narrow leaf blades with long and upright leaf stalks
  • A yellowing and necrosis of leaf veins. While this symptom is the reason for the name Beet Necrotic Yellow Vein Virus, it’s very rare to witness actual vein decay. The virus traditionally affects and remains in the roots, hence the name “crazy root”.

In Roots:

  • Girdling of the lower part of the root
  • Random development of dense, dark root hair. These rootlets eventually dry up and turn from white to brown. As a result, new roots are continuously forming. This simultaneous growth and discoloration has been called a “salt & pepper beard.”
  • Browning and death of vascular rings inside the root
  • The formation of perpendicular lateral roots

Outbreaks of Rhizomania can cause severe damage ranging from the loss of sugar content, the loss of yield, an increase in tare or reduced extractability. The severity of the outbreak depends on several factors including the amount of the parasite/virus present, the duration of the infection and the climactic conditions. The Polymyxa betae/BNYVV complex prefers wet and warm climates with soil temperatures ranging from 59º to 77º F.

No chemical treatment for Rhizomania exists. The only defense for growers is planting varieties with Rhizomania-resistant genetics. Measures to reduce favorable conditions for the disease are also beneficial such as harboring adequate drainage, maintaining soil structure, minimizing soil movement, etc.

Testing across the United States has shown the success of Seedex varieties. Seedex, Inc. continues to be a pioneer in the field of Rhizomania research, producing some of the greatest financial returns in the United States.

Contents

Rhizomania
1. Introduction, Domestic Rhizomania, Geographical Distribution, and Epidemiology
2. Symptoms and Economic Impact
3. Disease Control and Resistant Gene Management
4. Summary

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