Rhizomania Root Madness
Beet Necrotic Yellow Vein Virus (BNYVV)
Pathogen
Virus
Hosts
Sugar beet
Symptoms
Excessive lateral rootlet growth (bearding) on the main tap root and browning of the vascular tissue at the root tip. Foliar symptoms appear as pale green and erect leaves in patches within the crop and these also visibly wilt when under high soil moisture deficit especially where soil is poorly drained or compacted.
Development
The causal virus is transmitted by the soil-borne fungus Polymyxa betae. The disease is spread by movement of soil containing the infected vector.
Favourable Factors
Excessive rain or irrigation, humid soil conditions and poor soil structure. It can persist in the soil within the fungal resting spores for many years.
Importance
First identified in Northern Italy in 1952 and was not recognised in the UK until 1987 but strict soil hygiene restrictions prevented its spread for many years which allowed breeders sufficient time to develop resistant varieties. Rhizomania is now widespread in the UK. Can reduce sugar yields by as much as 50 - 60%.
Control
All varieties on the UK Recommended List offer resistance to this disease
Strict crop hygiene practices
There is no chemical control treatment
