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Title: Indaziflam: A new cellulose biosynthesis inhibiting herbicide provides long-term control of invasive winter annual grasses

Author
item SEBASTIAN, DEREK - Colorado State University
item Fleming, Margaret
item PATTERSON, ERIC - Colorado State University
item SEBASTIAN, JAMES - Colorado State University
item NISSEN, SCOTT - Colorado State University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2017
Publication Date: 6/12/2017
Citation: Sebastian, D.J., Fleming, M.B., Patterson, E.L., Sebastian, J.R., Nissen, S.J. 2017. Indaziflam: A new cellulose biosynthesis inhibiting herbicide provides long-term control of invasive winter annual grasses. Pest Management Science. doi:10.1002/ps.4594.

Interpretive Summary: Indaziflam is an herbicide that kills plants by a unique method, namely, preventing proper formation of cell walls. Resistance to indaziflam has not yet developed. Indaziflam has previously been used for bare-ground applications such as roadsides and train tracks; this research investigated its usefulness in rangelands infested with invasive winter annual grasses. Grasses (monocots) were found to be more susceptible to indaziflam than broad-leaved plants (dicots). Microscopic analysis of the cell walls showed different and more drastic effects on cell walls of monocots compared to dicots. Field application of indaziflam and imazapic, another herbicide currently used for rangeland weed control, in rangeland sites showed superior invasive winter annual grass control, increased field biomass, and increased species richness up to two years after treatment with indaziflam compared to imazapic. The long-term control potential reduces the risk of development of resistance to indaziflam. Indaziflam’s increased activity on monocots could provide a new alternative management strategy for long-term control of multiple invasive winter annual grasses that invade >23 million hectares of US rangeland. Indaziflam could potentially be used to eliminate the soil seed bank of these invasive grasses, decrease fine fuel accumulation, and ultimately increase the competitiveness of desirable, perennial co-occurring species.

Technical Abstract: BACKGROUND: Indaziflam (Esplanade™, Bayer CropScience) is a cellulose biosynthesis inhibiting (CBI) herbicide that is a unique mode of action for resistance management and has broad spectrum activity at low application rates. This research further explores indaziflam’s activity on monocotyledons and dicotyledons, and evaluates indaziflam’s potential for restoring non-crop sites infested with invasive winter annual grasses. RESULTS: Treated Arabidopsis, downy brome, feral rye, and kochia were all susceptible to indaziflam in a dose-dependent manner. We confirmed indaziflam has increased activity on monocots (average GR 50 = 231 pM and 0.38 g·ai·ha-1 ) at reduced concentrations compared to dicots (average GR 50 = 512 pM and 0.87 g·ai·ha-1 ). Fluorescence microscopy confirmed common CBI symptomologies following indaziflam treatments, as well as aberrant root and cell morphology. Across five application timings, indaziflam treatments resulted in superior invasive winter annual grass control 2 YAT (84% ± 5.1 to 99% ± 0.5) compared to imazapic (36% ± 1.2). Indaziflam treatments significantly increased biomass and species richness of co-occurring species, 2 YAT. CONCLUSION: Indaziflam’s increased activity on monocots could provide a new alternative management strategy for long-term control of multiple invasive winter annual grasses that invade >23 million ha of US rangeland. Indaziflam could potentially be used to eliminate the soil seed bank of these invasive grasses, decrease fine fuel accumulation, and ultimately increase the competitiveness of perennial co-occurring species.