Effects of crop rotation and soil tillage on suppressing the syndrome “basses richesses” vector Pentastiridius leporinus in sugar beet

The planthopper Pentastiridius leporinus (Hemiptera: Cixiidae), is the most important vector of syndrome “basses richesses” (SBR) in sugar beet; it leads to severe economic losses. Planthoppers have probably adapted recently from reed grass ( Phragmites australis ) to sugar beet - winter wheat crop rotations. So far, no reliable vector control strategies are available. In this study, field assays were performed to test different soil tillage methods and crop rotations as potential management options. Barley, spring wheat, maize, bare soil and winter wheat (control) were grown using different soil tillage treatments (ploughing and cultivator) after sugar beet harvest. In five of seven field trial sites, reduced tillage did not differ from ploughing and, in two trial sites, it resulted in even higher numbers of emerging planthoppers. In nearly all field sites, consistent and significant reductions (up to 98.9%) of emerging adults were detected in the bare soil and maize treatments when compared to winter wheat. The survival and development of first instar nymphs were then studied on wheat, barley, and maize seedlings in the laboratory to confirm the field observations. The lowest survival was found in nymphs feeding on maize seedlings (4.2%), while 29.2% survived on barley, and 66.7% on wheat, over a period of 300 days. Almost 90% of nymphs in the maize treatment died after eight days. These results suggest that maize is a poor host for P. leporinus first instar nymphs. A combination of soil tillage and late sown specific spring crops are discussed as options for P. leporinus control.