Grasshopper feeding mode differentially affects grass species cover in a northern mixed grassland

Authors: Branson, David

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2025
Publication Date: 12/12/2025
Citation: Branson, D.H. 2025. Grasshopper feeding mode differentially affects grass species cover in a northern mixed grassland. Journal of Economic Entomology. Online 00:1-4. https://doi.org/10.1093/jee/toaf339.
DOI: https://doi.org/10.1093/jee/toaf339

Interpretive Summary: Livestock grazing can influence grassland plant composition, but there is increasing evidence that grasshopper feeding mode also plays an important role in rangeland systems. Blue grama can increase with intensive cattle grazing in the northern Great Plains, as the growing tissue is less exposed to feeding by cattle. The results from this study show that blue grama is less resistant to grass feeding grasshoppers than cattle grazing. As cool season grasses such as western wheatgrass produce more livestock forage, grass feeding grasshoppers could assist in reducing the dominance of less productive blue grama that can result from intensive cattle grazing. Grasshopper densities in this study were lower than densities where control efforts might be considered and ~15 times lower than in a severe outbreak in the study area. The 50% decline in blue grama cover is noteworthy, as similar grasshopper densities often don't impact forage for cattle after accounting for plant regrowth. The two grasshopper species in this experiment can be major contributors to grasshopper outbreaks. The results are relevant for understanding grasshopper impacts on rangeland ecosystems and the justification underlying grasshopper control on rangeland.

Technical Abstract: Little research has examined if consistent insect herbivory over multiple years affects plant composition in grassland ecosystems. We conducted a seven-year manipulative cage-based experiment at a northern mixed-grass prairie site in eastern Montana examining changes in the basal cover of native grasses in response to herbivory by two grasshopper species with different feeding modes. The objective was to examine if relatively low but sustained levels of herbivory over seven years affects basal cover of the dominant grass species western wheatgrass and blue grama. Blue grama cover was approximately 50% lower at the end of the 7-yr experiment in the grass feeding Ageneotettix deorum treatment relative to controls without herbivory and a larger mixed grass and forb feeding Melanoplus sanguinipes. The results appear to be driven by plant preference and feeding behavior, as A. deorum fed on blue grama more frequently than M. sanguinipes. Although vertebrates typically have stronger impacts on rangeland plant composition, blue grama appears less resistant to herbivory by grass feeding grasshoppers than cattle grazing in this mixed grass prairie system. The results point to the need for further research on the relative importance of grasshopper feeding mode on rangeland function and productivity.