Timing of Seeding After Indaziflam Control of Annual Grasses to Limit Nontarget Damage

Invasive annual grasses are a widespread problem negatively impacting western US rangelands. Restoring perennial dominance to invaded rangelands is a management priority. Indaziflam effectively controls invasive annual grasses for multiple years and promotes coexisting perennial vegetation. However, in rangelands without abundant coexisting perennial vegetation, seeding perennial vegetation is likely necessary after annual grass control to reestablish perennial dominance. When to seed after indaziflam application in the annual grass–dominated sagebrush steppe is largely unknown. The manufacturer recommends waiting for at least 24 mo before seeding after indaziflam application, but plant-back times may need to be longer if toxicity has not abated. To investigate plant-back times after indaziflam application in the annual grass–invaded sagebrush steppe, we seeded eight perennial species 2, 3, and 4 yr after indaziflam application. The density of seeded perennial grasses was greater in areas seeded 4 yr after indaziflam application compared with shorter plant-back times, but similar between areas seeded 2 and 3 yr after indaziflam application. Annual grass control was dissipating by the fifth growing season after indaziflam application, further suggesting that indaziflam toxicity had abated. The influence of time since indaziflam application on nongrass species was inconclusive, suggesting that plant-back times after indaziflam application vary among species. Our results reaffirm that indaziflam is effective for longer-term annual grass control in sagebrush steppe and suggest that seeding of grasses after its application may need to be postponed for at least 4 yr to limit nontarget damage.