Alfalfa variety trials were planted in 1997 at two locations in New York: Ithaca in Central New York and Clarendon in Western New York. Varieties in these trials were either resistant or susceptible to potato leafhopper (PLH), Empoasca fabae (Harris), the most damaging insect pest of alfalfa in the Northeast. In the seeding year, the Ithaca trial was severely damaged by PLH and the Clarendon trial was moderately damaged by PLH. Sweep data in 1998 at Clarendon indicated that the PLH population was above threshold only at Harvest 2 (22 July).