in areas where natural enemies of the grape leafhopper, Erythroneura elegantula Osb. are absent, or insufficient in numbers, chemical control may be necessary to prevent an increase in leafhoppers from causing serious economic damage. From an economic standpoint, determining the level of infestation allows not only prevention of serious damage to the vines, but also could save the cost of insecticide applications. This study of daily and seasonal periods when leafhopper damage occurred was conducted as a preliminary step in determining the economic level of leafhopper infestation.