First confirmation of sugar beet as a host plant for <i>Reptalus quinquecostatus</i> (Hemiptera: Cixiidae) nymphs

Planthoppers transmit pathogens to various economically important crops. In Central Europe, the sugar beet, Beta vulgaris L. ssp. vulgaris var. altissima (Döll) (Amaranthaceae: Caryophyllales) and potato production are threatened by diseases associated with the γ-proteobacterium "Candidatus Arsenophonus phytopathogenicus" and the phytoplasma "Candidatus Phytoplasma solani". Infections cause yellowing and wilting, reduce sugar yield in sugar beet, induce rubbery taproots in potato, and can lead to plant decline. In Austria, the cixiid Reptalus quinquecostatus (Dufour) is considered a main vector of these pathogens. While several plant species have been reported as feeding or shelter plants for adult R. quinquecostatus, no reproductive host plant supporting nymphal development has previously been confirmed. In this study, we investigated whether sugar beet is a potential host plant for the development of R. quinquecostatus. Host plant trials were conducted using potted sugar beet plants placed outdoors in insect cages. Four cages were infested with a total of 15 adult Reptalus spp. (10 females and 5 males) per cage to allow oviposition. Egg masses and nymphs were observed in 75% of the cages during the trial period. After 366 ± 3.46 (SD) d, 4 adult R. quinquecostatus emerged from 2 out of 4 cages. Our findings provide the first experimental evidence that sugar beet can function as a reproductive host plant for R. quinquecostatus.