The sweep net is moved vigorously through the foliage in 180o arcs at several locations in each field. To obtain meaningful, representative estimates of leafhopper abundance, at least 25 sweeps should be taken from each of four locations in each field. This type of resistance is fairly reliable and will reduce the amount of damage that occurs from a given infestation level of the leafhopper. In severe cases, insecticide treatment may be required even with resistant varieties. Research has shown that economic damage has already occurred once the chlorotic symptoms are visible.
Economic damage is that which equals or exceeds the cost of an insecticide treatment.
Therefore, alfalfa growers are urged to begin sampling their fields in late May and June and to continue on at least a weekly schedule through the remainder of the season. It is not a wise plan to wait until the damage appears before making a decision to manage this insect. The following tables provide guidance for managing the potato leafhopper in alfalfa that is up to 12 inches tall. They provide a range of hay values and treatment costs. If leafhopper numbers equal or exceed the numbers in the table for the appropriate alfalfa height, hay value and treatment cost, an insecticide application should be considered to reduce the leafhopper infestation and protect the crop from further damage.