Effects of Sheep Grazing Timing on Pyrenophora semeniperda (Black Fingers of Death) Infection of Cheatgrass Seeds in Soil Seed Banks
Faculty Mentor Information
Tshianeo Ndou, Boise State University; Dr. Kelly Hopping, Boise State University; and Dr. Allison Simler-Williamson, Boise State University
Presentation Date
7-16-2026
Abstract
Cheatgrass (Bromus tectorum) is an invasive annual grass that has transformed the landscape in the Great Basin by outcompeting native vegetation, increasing wildfire frequency and intensity, and reducing biodiversity. Targeted sheep grazing has been suggested as a possible strategy to suppress cheatgrass and restore invaded landscapes, but its effectiveness may depend on the intensity, frequency, and timing of grazing. In addition to reducing cheatgrass abundance, grazing may also influence naturally occurring fungal pathogens such as Pyrenophora semeniperda, a fungus that infects cheatgrass seeds in the soil seed bank before they germinate and that has been suggested as a possible biocontrol agent for this invasive grass. Here we examine how sheep grazing and grazing timing shifts fungal impacts of Pyrenophora semeniperda. To assess this, we collected soil seed bank samples from spring and summer grazed and ungrazed plots. Soil samples were air-dried, sieved, and cheatgrass seeds were extracted. The extracted seeds were then placed on moistened germination papers and incubated for two weeks to assess germination and infection by Pyrenophora semeniperda. From preliminary observations, we expect Pyrenophora seminiperda infection to vary among grazing treatments and sites, with the highest infection occurring in the Deer Creek site’s summer-grazed plots. Understanding how sheep grazing timing influences Pyrenophora semeniperda infections will improve our understanding of disease dynamics in the Great Basin and help inform future cheatgrass restoration and management strategies.
Effects of Sheep Grazing Timing on Pyrenophora semeniperda (Black Fingers of Death) Infection of Cheatgrass Seeds in Soil Seed Banks
Cheatgrass (Bromus tectorum) is an invasive annual grass that has transformed the landscape in the Great Basin by outcompeting native vegetation, increasing wildfire frequency and intensity, and reducing biodiversity. Targeted sheep grazing has been suggested as a possible strategy to suppress cheatgrass and restore invaded landscapes, but its effectiveness may depend on the intensity, frequency, and timing of grazing. In addition to reducing cheatgrass abundance, grazing may also influence naturally occurring fungal pathogens such as Pyrenophora semeniperda, a fungus that infects cheatgrass seeds in the soil seed bank before they germinate and that has been suggested as a possible biocontrol agent for this invasive grass. Here we examine how sheep grazing and grazing timing shifts fungal impacts of Pyrenophora semeniperda. To assess this, we collected soil seed bank samples from spring and summer grazed and ungrazed plots. Soil samples were air-dried, sieved, and cheatgrass seeds were extracted. The extracted seeds were then placed on moistened germination papers and incubated for two weeks to assess germination and infection by Pyrenophora semeniperda. From preliminary observations, we expect Pyrenophora seminiperda infection to vary among grazing treatments and sites, with the highest infection occurring in the Deer Creek site’s summer-grazed plots. Understanding how sheep grazing timing influences Pyrenophora semeniperda infections will improve our understanding of disease dynamics in the Great Basin and help inform future cheatgrass restoration and management strategies.