Preemergent herbicide protection seed coating: A promising new restoration tool

Authors: HOLFUS, CORINNA - Oregon State University; Rios, Roxanne; Boyd, Chad; MATA-GONZALEZ, RICARDO - Oregon State University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2021
Publication Date: 3/19/2021
Citation: Holfus, C.M., Rios, R.C., Boyd, C.S., Mata-Gonzalez, R. 2021. Preemergent herbicide protection seed coating: A promising new restoration tool. Rangeland Ecology and Management. 76:95-99. https://doi.org/10.1016/j.rama.2021.02.005.
DOI: https://doi.org/10.1016/j.rama.2021.02.005

Interpretive Summary: Activated carbon-based pellets containing native plant seeds have previously been used to impart herbicide resistance to desired seeds when simultaneously applying pre-emergent herbicides, however, the shape and size of these pellets is not ideal for drill seeding equipment. We investigated a new methodology (“vortex coating”) for coating individual seeds of bluebunch wheatgrass and tested the degree of herbicide protection provided by this method. Our lab results indicate that for pots sprayed with the pre-emergent herbicide imazapic, pots containing vortex coated seeds had higher emergent seedling density and larger seedlings than those containing uncoated seeds, however, seedlings of coated seeds in sprayed pots were smaller than those in unsprayed pots (containing either bare seed or coated seed), suggesting that herbicide protection was not complete. These results suggest that vortex coating may be a viable technique for imparting herbicide protection to desired seeds, but field studies will be needed to confirm this result.

Technical Abstract: Invasive annual grasses such as cheatgrass (Bromus tectorum L.) outcompete native grasses, increase fire frequency, and impact the functionality and productivity of rangeland ecosystems. Preemergent herbicide treatments are often used to control annual grasses but may limit timely restoration options due to negative effects on concurrently planted desired seeded species. We tested the efficacy of activated carbon-based herbicide protection coatings applied to individual bluebunch wheatgras (Pseudoroegneria spicata [Pursh] A. Love) seeds for protecting seedlings from injury associated with pre-emergent herbicide (imazapic) application in a laboratory environment. Emergence of coated seed averaged 57% ± 5% compared with bare seed, which had 14% ± 10% emergence with imazapic application. Seedling height for coated seed averaged 7.56 ± 0.6 cm compared with 2.26 ± 0.4 cm in uncoated bare seed in the presence of imazapic. Coated seeds produced 87% more plant biomass than uncoated seeds. Our laboratory results suggest that treating individual seeds with an activated carbon-based coating dramatically reduces negative effects of pre-emergent herbicide on desired seeded species. Field studies are needed to confirm these results in an applied restoration context.