Now that planting is pretty much finished, many producers were able to finish their first harvest of alfalfa over the past week or so. This is the time that potato leafhoppers migrate northward and begin to establish populations in alfalfa. When the crop reaches “sweepable height” (~6 inches), take 10 sweeps, which is equal to 1 sample. When the average number of leafhoppers per sample is equal or greater to the height of alfalfa (in inches), treatment may be warranted. For example, if the alfalfa is 6 inches tall and the average number of leafhoppers is 6 or higher, economic threshold is reached. If the average is lower, re-sampling should be done in a few days. In glandular-haired, leafhopper-resistant alfalfa, the economic threshold is 3X the normal threshold, or three leafhoppers per inch of growth (18 leafhoppers for 6 inch tall alfalfa, for example). However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding. After the first cutting, growers can then use 3X times the normal level threshold. More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available athttp://ohioline.osu.edu/ent-fact/pdf/0033.pdf.