Frequent rains may have delayed alfalfa harvest but they haven't slowed the buildup of potato leafhopper populations. Potato leafhopper is a small, bright green insect that can be seen hopping out of your way as you walk in an alfalfa field. This sap-sucking insect can cut alfalfa yields in half and even kill seedlings when populations are high and left unmanaged. The primary cause of yield loss is shorter or stunted stems; however, leaf yellowing or hopperburn is the telltale symptom of this pest.