Effects of using indaziflam and activated carbon seed technology in efforts to increase perennials in Ventenata dubia-invaded rangelands

Authors: Davies, Kirk; Boyd, Chad; BAUGHMAN, OWEN - The Nature Conservancy; Clenet, Danielle

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2023
Publication Date: 3/17/2023
Citation: Davies, K.W., Boyd, C.S., Baughman, O.W., Clenet, D.R. 2023. Effects of using indaziflam and activated carbon seed technology in efforts to increase perennials in Ventenata dubia-invaded rangelands. Rangeland Ecology and Management. 88:70-76. https://doi.org/10.1016/j.rama.2023.02.007.
DOI: https://doi.org/10.1016/j.rama.2023.02.007

Interpretive Summary: Reestablishing perennial vegetation dominance in ventenata-invaded rangeland is often needed to increase ecosystem goods and services. We evaluated the multiple year effects of indaziflam, a newer preemergent herbicide, on ventenata and co-existing vegetation. We also investigated if activated carbon pellets with seeds incorporated within would protect seeded grasses from indaziflam non-target damage and thereby increase perennial grasses. Indaziflam controlled ventenata for three years and increased perennial grass abundance at a site that had more residual perennial grass prior to treatment, but not at a site that had very little residual perennial grass. Activated carbon pellets did not increase perennial grasses, likely due to limited emergence and establishment because of below average precipitation and inadequate seed-soil contact from broadcast seeding. Our results suggest that indaziflam is an effective treatment for controlling ventenata for multiple years and releasing perennial vegetation. Further tests of activated carbon pellets are needed. These results are of interest to land managers, weed specialists, and other researchers.

Technical Abstract: Reestablishing perennial vegetation dominance in ventenata (Ventenata dubia)– and other annual grass–invaded rangelands is critical to restoring ecological function and increasing ecosystem goods and services. Recovery of perennial dominance in ventenata-invaded rangelands is challenging and constrained by a lack of established best management practices; however, preemergent herbicides can, at least temporarily, reduce ventenata. Indaziflam is a preemergent herbicide that has longer soil activity than other commonly used preemergent herbicides that needs evaluated to determine if it offers multiple-year control of ventenata and to determine its effects on residual perennial vegetation. Some ventenata-invaded rangelands may not have enough residual vegetation to occupy the site after ventenata control, but longer soil activity with indaziflam likely limits establishment of seeded species. However, incorporating seeds in activated carbon pellets, which can limit herbicide damage, may be a strategy for establishing perennial vegetations simultaneously with indaziflam application. We evaluated 1) applying indaziflam to control ventenata and 2) broadcast-seeding perennial grass seed incorporated in activated carbon pellets with a simultaneous indaziflam application at two sites for 3 yr post treatment. Indaziflam controlled ventenata for the 3 yr sampled. Perennial grasses increased with indaziflam at the site that had more residual perennial grasses before treatment. At the other site, perennial forbs increased with indaziflam. Indaziflam offers multiple-year control of ventenata; however, plant community response depends on composition before treatment. Seeding perennial grass seeds incorporated in activated carbon pellets while indaziflam controlled ventenata did not increase perennial grass abundance. Though this was likely associated with low establishment due to below-average precipitation post seeding and because broadcast seeding is often an ineffective seeding method, we cannot rule out nontarget herbicide damage. Further evaluations of activated carbon technologies used in conjunction with indaziflam are needed to determine if this can be an effective management strategy.