Rhizomania is one of the most common sugar beet diseases. It is caused by the beet necrotic yellow vein virus which is transmitted to sugar beet by a rootlet parasite (Polymyxa betae). In particular, it causes anarchical proliferation of root hairs to the detriment of the tap root that can result in major losses in sugar yield.
The disease was first observed during the 1950s in the north of Italy. It spread quickly throughout Europe and the rest of the world. The severity of the damage and absence of a means of control give grounds for fears that at some point it may be necessary to stop growing sugar beet in the worst affected regions. In the early 1980s, the first variety resistant to Rhizomania came on the market: developed by SES, Rizor saved sugar beet in the affected regions.
In 2008, Rhizomania tolerant varieties caught up with the yield in sugar/ha of non-tolerant varieties with the result that in many countries thereafter only Rhizomania tolerant varieties were sown. At present, Rhizomania is present throughout the whole world. In Europe, almost all sugar beet growing regions are affected by the disease, including Scandanavia. In Britain, Rhizomania is endemic but the use of varieties with resistance is becoming widespread.
Rhizomania symptoms often appear in patches in fields:
1. In foliage
• from June onwards: wilting, particularly during the hottest hours of the day
• towards the end of summer: pale green foliage
• the new leaf blades produced are narrow; their leaf stalks are long and upright
• very occasionally: yellowing and necrosis of the leaf veins
2. In the root (at the end of the growing period)
• girdling of the lower part of the root
• development of dense, dark root hair to the detriment of the tap root
• inside the root, the vascular rings turn brown and die
• occasionally: development of perpendicular lateral roots
Depending on the sensitivity of the variety, the amount of inoculum present in the soil, the type of virus, climatic conditions (the disease is favoured by a warm, humid climate) and the period of infection, an outbreak can cause extremely serious damage: reduction of the sugar content, loss of yield, increase of the land tare and reduced extractability.
At present, there is no chemical treatment for Rhizomania. The only effective means of controlling it is the use of a variety of seed that has resistance to the disease. Implementation of agronomic measures is also advisable: adequate drainage, maintenance of soil structure, sparse irritation, avoidance of soil movement as far as possible, etc.
Across Europe, official tests have again demonstrated that SESVanderHave is at the leading edge of the Rhizomania resistance sector: confirming that our varieties produced some of the highest financial return in this sector.