Effects of Sagebrush Removal and Herbivory by Mormon Crickets (Orthoptera: Tettigoniidae) on Understory Plant Biomass and Cover

Abstract

The effects of herbivory by the Mormon cricket, Anabrus simplex Haldeman (Orthoptera:Tettlgoniidae), and removal of sagebrush (Artemisia tridentata Nutt.) on understory plant biomass production and cover were determined. Averaged over a 3-yr period, 50–75% removal of sagebrush resulted in an ≍20% increase in summer understory biomass production; understory plant cover was not affected by sagebrush removal. Mormon crickets, at densities of four and eight crickets per square meter during a 5-wk period, did not significantly affect understory plant biomass production but did reduce forb and total vegetative cover. Mormon cricket herbivory and sagebrush removal were independent with respect to their effects on understory vegetation. Furthermore, the incomplete removal of sagebrush did not affect the feeding ecology of Mormon crickets. Analysis of cricket crop contents suggested that sagebrush was fed upon predominantly; there was little dietary overlap between crickets and cattle. As long as some sagebrush is left intact (e.g., 25%), sagebrush control programs are unlikely to influence Mormon cricket diet selection or damage potential. Cover estimates, which are commonly used by ranchers and rangeland managers to estimate forage availability, provide deceptive assessments of cricket effects, ultimately perhaps leading to an undeserved reputation as a rangeland pest.