Managing secondary Broadleaves after Cheatgrass control

Authors: Harmon, Daniel; Clements, Darin

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/19/2026
Publication Date: 3/25/2026
Citation: Harmon, D.N., Clements, D.D. 2026. Managing secondary Broadleaves after Cheatgrass control. Meeting Abstract. 26:4.

Interpretive Summary:

Technical Abstract: The integrated mitigation process for restoring the immense acres of landscape lost to the exotic and invasive annual grass, cheatgrass (Bromus tectorum), and associated wildfires often includes the use of pre-emergent herbicides to control cheatgrass prior to restoration seeding efforts. The purpose of herbicidal cheatgrass control is to increase available soil resources such as available soil moisture and soil nitrate in the absence of cheatgrass competition. This increased soil resource window of opportunity with reduced cheatgrass competition only last for one to two years after the fallow year. This provides one or two at best seeding opportunities to establish competitive perennial grasses that will resist the return invasion of cheatgrass once the herbicide is not active anymore. The most common pre-emergent herbicide for use before a seeding effort is imazapic, Plateau, which is active in the soil for about 12 to 15 months (the fallow year). After pre-emergent application in early fall (September) the herbicide strength or effectiveness degrades from microbial activity over time breaking down the herbicide in the soil. This often means that 9 months after application around May or June if any precipitation events occur, lower successional secondary summer germinating broadleaf weeds can survive and establish with the herbicide strength weaker and in the absence of cheatgrass competition. These secondary broadleaf weeds can use up soil resource gains that are the intended goal for controlling the cheatgrass prior to seeding. We will present when and what broadleaf weeds can be expected to be an issue after pre-emergent herbicide cheatgrass control and some possible herbicide treatments for those broadleaf weeds as to maintain the increased soil resources to increase the chance of successfully establishing perennial grasses. We will introduce our newest broadleaf weed herbicide control research project that began in 2025 and what and where we are testing this project.