Research on a new disease of sugarbeet in France: ‘Syndrome des Basses Richesses’
In France, a new disease of sugarbeet appeared in Bourgogne and Franche-Comté regions in 1991. This disease which was called ‘Syndrome des Basses Richesses’ is of uncertain aetiology. Symptoms are characterized by yellowing and curling of old leaves, leading to the new growth of central leaves which appear chlorotic, lanceolated and asymmetrical. Roots are of normal size but contain brown vascular bundles, and their sugar content suddenly decreases at the beginning of September. Since 1991, this disease has occurred with variable severity in these regions. Economic losses could be observed due to the poor sugar content of affected roots. Considering the apparent aerial transmission of the disease, the similarity of symptoms with yellow wilt (phytoplasma disease) and the detection of phytoplasmas in affected plants, it is strongly suspected that phytoplasmas are involved in the disease. However, the presence of detectable phytoplasma DNA in leaves and roots could not reliably be related to the expression of symptoms. In 1997 and 1998 in Franche-Comté, searches were made for potential phytoplasma vectors in an area where sugarbeet crops had been affected by the disease since 1996. Results revealed the presence of a cixiid, tentatively identified as Pentastiridius beieri (full determination is not yet finalized). High populations of this insect were observed in sugarbeet plots during summer. In addition, Stolbur phytoplasma (EPPO A2 quarantine pest) was detected in several individuals (and also in diseased sugarbeet). Experiments showed that P. beieri could transmit Stolbur phytoplasma to periwinkle and sugarbeet. So far, only Hyalesthes obsoletus was a known vector of Stolbur phytoplasma. Research will continue to better understand the aetiology and epidemiology of this new sugarbeet disease.
Sources
Gatineau, F.; Larrue, J.; Clair, D.; Lorton, F.; Richard-Molard, M.; Boudon-Padieu, E. (2001) A new natural planthopper vector of stolbur phytoplasma in the genus Pentastiridius (Hemiptera: Cixiidae).
European Journal of Plant Pathology, 107(3), 263-271.