By Mark Sulc
We have heard of and observed increasing potato leaf hopper (PLH) damage in many areas across OH last week. PLH feed similar to aphids, by piercing and sucking on plants causing stunting, thinning and yellowing of alfalfa, often called hopperburn. To scout fields, use a sweep net—a single sweep sample is a set of 10 sweeps, and choose 5-10 different field locations. Treatment is needed if the number of PLH (adults and nymphs) caught a sweep sample is equal to the height of alfalfa. For glandular haired or PLH-resistant alfalfa, the threshold is multiplied by 3. For older, thinning alfalfa stands, thresholds can also be increased, while newer stands (e.g. new seedings or 1st year) are more vulnerable. See Ohio State University Extension Bulletin 545, Control of Insect Pests of Field Crops (https://agcrops.osu.edu/publications/control-insect-pests-field-crops-bulletin-545), for those insecticides labeled for potato leafhopper, or for all insecticides labeled on alfalfa.