Identify potential problems before grasshoppers begin migrating into alfalfa. A general estimate of grasshopper age, abundance and encroachment into the field may suffice, particularly if treatment is restricted to border areas. Sampling around seed production fields, well in advance of the onset of bloom in alfalfa, may prevent serious losses later. This will also help avoid chemical application when pollinators are active. Threshold Levels and Management Effective control of small nymphs can be obtained with insecticides before damage is done to alfalfa.
Insecticides are generally much less effective on large nymphs or adults.
Seven to eight grasshoppers per square yard in the field proper, or 15 to 20 per square yard in field margins are usually considered to exceed economic threshold levels. Consult OSU Extension Facts F-7150 for specific insecticide recommendations.