To identify the causative plant factors and develop a rapid screening method based upon their chemical identity or biochemical mode of action. To identify cultivars of cereals and forages for the greatest resistance to grasshoppers as evidenced by highest mortality and lowest rates of growth and reproduction. Determine the physiological response of grasshoppers (regulation of digestive enzyme secretion and uptake of the products of digestion), and the biological and environmental factors which affect the expression of the resistance factors in cereals. Incorporate these data into a model of grasshopper population growth and outbreak potential.