Potato leafhopper (PLH) resistant alfalfa varieties with the glandular haired trait have been commercially available for four years. Potato leafhopper is considered the most significant insect pest of alfalfa in Wisconsin and the upper Midwest. PLH injury to alfalfa can result in leaf yellowing (“hopperburn”), plant stunting, loss of yield and forage quality, and reduced alfalfa stand persistence. During the 2000 growing season we established field trials at the Arlington and Marshfield Agricultural Research Stations in a continuing effort to evaluate the efficacy of glandular haired varieties under Wisconsin conditions and agronomic practices, as new “generations” of varieties with improved resistance are released. In particular, the Arlington study was designed to evaluate the extent to which current treatment thresholds recommended in Wisconsin for PLH management in alfalfa need to be adjusted for glandular haired alfalfa cultivars advertised to be resistant to PLH. Our experience thus far indicates that commercial glandular haired varieties currently available exhibit various levels of partial resistance, but not complete resistance, to PLH. Consequently, effective management of this pest in the near term will likely require a combination of plant resistance and insecticide application as needed.