Indaziflam and imazapic comparisons for reducing annual grass fuels in forage kochia (bassia prostrata) green strips.

Authors: Harmon, Daniel - Dan; Clements, Darin - Charlie

Submitted to: Society of Range Management
Publication Type: Abstract Only
Publication Acceptance Date: 11/8/2022
Publication Date: 2/7/2023
Citation: Harmon, D.N., Clements, D.D. 2023. Indaziflam and imazapic comparisons for reducing annual grass fuels in forage kochia (bassia prostrata) green strips. Society of Range Management. 76:64.

Interpretive Summary: Green-stripping is the practice of establishing fire resilient vegetation to reduce the occurrence and or size of wildfires. “Immigrant’ forage kochia is an ideal candidate for green strips because it remains green and succulent throughout the summer and can be readily established by arial seeding. The effectiveness of a green strip relies on very little dry fuel occurring in the green strip. Thus, cheatgrass must be suppressed to keep fuel levels low. Suppressing cheatgrass (fuels) requires a competitive perennial plant that utilizes soil resources in the soil seedbed zone, leaving insufficient soil resources for cheatgrass to germinate, establish and produce seed. Forage kochia, being a deep tap rooted evergreen shrub, is not as effective at utilizing seedbed soil resources and suppressing cheatgrass occurrence compared to shallower fibrous rooted perennial grasses. This can often lead to a dense cheatgrass interspace and understory in forage kochia stands. We examined the effectiveness of two pre-emergent herbicides, Imazapic and Indaziflam applied within a forage kochia stand occupied by cheatgrass. Both herbicides were effective at controlling cheatgrass, however Imazapic plots experienced forage kochia plant damage and mortality, whereas we observed no negative effects on forage kochia from Indaziflam applications. Multiple application rates, surfactant additive and decreased water volume were examined with Imazapic use. We observed and recorded forage kochia plants throughout the growing season and recorded plant vigor and mortality. The reduction of cheatgrass improved plant vigor, yet experienced a level of mortality in Imazapic treated plots. Reducing annual grass fuels in green strips is an important tool in an integrated range wildfire management program. Our results find that pre-emergent herbicides can be very effective at achieving this.

Technical Abstract: Green-stripping is the practice of establishing fire resilient vegetation to reduce the occurrence and or size of wildfires. “Immigrant’ forage kochia is an ideal candidate for green strips because it remains green and succulent throughout the summer and can be readily established by arial seeding. The effectiveness of a green strip relies on very little dry fuel occurring in the green strip. Thus, cheatgrass must be suppressed to keep fuel levels low. Suppressing cheatgrass (fuels) requires a competitive perennial plant that utilizes soil resources in the soil seedbed zone, leaving insufficient soil resources for cheatgrass to germinate, establish and produce seed. Forage kochia, being a deep tap rooted evergreen shrub, is not as effective at utilizing seedbed soil resources and suppressing cheatgrass occurrence compared to shallower fibrous rooted perennial grasses. This can often lead to a dense cheatgrass interspace and understory in forage kochia stands. We examined the effectiveness of two pre-emergent herbicides, Imazapic and Indaziflam applied within a forage kochia stand occupied by cheatgrass. Both herbicides were effective at controlling cheatgrass, however Imazapic plots experienced forage kochia plant damage and mortality, whereas we observed no negative effects on forage kochia from Indaziflam applications. Multiple application rates, surfactant additive and decreased water volume were examined with Imazapic use. We observed and recorded forage kochia plants throughout the growing season and recorded plant vigor and mortality. The reduction of cheatgrass improved plant vigor, yet experienced a level of mortality in Imazapic treated plots. Reducing annual grass fuels in green strips is an important tool in an integrated range wildfire management program. Our results find that pre-emergent herbicides can be very effective at achieving this.