A new natural planthopper vector of stolbur phytoplasma in the genus Pentastiridius (Hemiptera : Cixiidae)

A new disease of sugar beet called Syndrome des Basses Richesses, which app eared in Burgundy and Franche-Comte, France, in 1991, is of uncertain aetio logy. However, evidence for aerial transmission of the disease, symptom sim ilarity with yellow wilt and preliminary results of phytoplasma detection, support the hypothesis of a phytoplasma being associated to the disease. A search for a natural phytoplasma vector, was conducted in Franche-Comte in 1997 and 1998, in an area where sugar beet crops had been affected since 19 96. A cixiid, tentatively identified as Pentastiridius beieri, not describe d in the preceding years and not formerly reported as a phytoplasma vector, was present in sugar beet plots in high populations from June to August in 1997 and 1998. Individuals were captured and used for transmission experim ents to periwinkle and sugar beet seedlings. They were further tested for t he presence of a phytoplasma in their body, using PCR amplification of 16S rDNA of phytoplasmas. In 1997 and 1998, from 2% to 13.3% of the individuals carried a stolbur phytoplasma and insects which tested positive, appeared to have transmitted, through feeding, a stolbur phytoplasma to periwinkles and to sugar beets. This cixiid, whose vectoring capacity of stolbur phytop lasma to plants, is now clearly demonstrated, is available for experimental inoculations, in order to examine the role of phytoplasmas in the Syndrome des Basses Richesses, through the observation of symptom expression in phy toplasma-inoculated plants.