EFFECTS OF SAGEBRUSH REMOVAL AND LEGUME INTERSEEDING ON RANGELAND GRASSHOPPER POPULATIONS (ORTHOPTERA: ACRIDIDAE)

Abstract

AbstractGrasshopper density and species composition were determined from 1982 to 1985 in four 75-ha pastures in the northern mixed prairie region near Miles City, MT. Treatment in two pastures consisted of sagebrush removal and interseeding alfalfa and cicer milkvetch. Two pastures were not treated. The treated pastures were grazed only half as long as the untreated pastures but with twice the number of steers. Forage yield decreased in all pastures from 1983 to 1985 because of below-average precipitation and grasshopper density increases. In one pasture, 10% of the legume seedlings were destroyed by grasshoppers. The annual rates of increase in total grasshopper presence were similar in treated and untreated pastures. However, Melanoplus sanguinipes (F.), which eats forbs and is a strong flyer, increased more in treated than untreated pastures; six additional abundant species, all of which were grass feeders, did not increase more in treated pastures. Thus, treatments did not markedly affect total grasshopper population trends but did influence species composition and provided additional food plants for some species.