Date of this Version
Weed Technology. 1996. Volume 10:392-403
The productivity and native species diversity of Great Plains grasslands have been substantially reduced by past management that facilitated the establishment of invasive exotic weeds and displacement of native species. Management strategies are needed to rapidly restore the productive capacity and biological diversity of these degraded grasslands. Critically important phases of the grassland restoration process are the reintroduction and establishment of native species. Weed interference is the primary constraint to successful establishment of native plants. The goal of our research is to develop strategies that use multiple technologies, including herbicides, to expedite grassland revegetation with native grasses and forbs. Imidazolinon eherbicides( AC 263,333, imazapyr, and imazethapyr) were used successfully to improve establishment of native perennial grasses (big bluestem, switchgrass, little bluestem) and selected forbs (blackeyed-susan, purple prairieclover, Illinois bundleflower, trailing crownvetch, and upright prairie coneflower) on cropland and as components of a strategy to revegetate leafy spurge-infested rangeland with native tallgrasses. Imazethapyr at 70 or 110 g ai/ha applied at planting resulted in stands of big bluestem and little bluestem that were similar or superior to stands established where atrazine was applied. Seedling grasses were susceptible to imazapyr at two of three study sites. Imazapyr at 560 g ai/ha plus sulfometuron at 100 g ai/ha applied in fall was the optimum treatment for suppression of leafy spurge and exotic cool-season grasses and establishment of big bluestem and switchgrass on degraded rangeland sites. Establishment of selected forbs was improved by PRE treatment with AC 263,222 or imazethapyr at 70 g ai/ha. This research provides evidence that the imidazolinone herbicides can be important components of integrated weed management strategies designed to reverse deterioration of grasslands by reestablishing native species, improving grassland productivity and decreasing the prevalence of exotic weeds. Nomenclature: Atrazine,6 -chloro-N-ethyl- N'-( 1-methylethyl)- 1 ,3,5-triazine-2,4-diamine; imazapyr, (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)- 5-oxo-lH-imidazol-2-yl]-3-pyridinecarboxylic acid; AC 263,222, (±)-2-[4,5-dihydro-4- methyl-4-(1-methylethyl)-5-oxo-lH-imidazol-2-yl]-5-methyl-3-pyridinecarboxylaici d; imazethapyr, 2-[4,5-dihydro-4-methyl-4-( 1 -methylethyl)-5-oxo- I H-imidazol-2-ylI-5-ethyl-3-pyridinecarboxylic acid; sulfometuron, 2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoaicci d; leafy spurge, Euphorbia esula L. #3 EPHES; big bluestem, Andropogon gerardii Vitman 'Pawnee' # ANOGE; little bluestem, Andropogon scoparium (Michx.) Nash 'Camper' # ANOSC; switchgrass, Panicum virgatum L . 'Trailblazer,#' PANI; blackeyed-susan, Rudbeckia hirta L. var. hirta # RUDHI; purple prairieclover, Dalea purpurea Vent.; Illinois bundleflower, Desmanthus illinoensis (Michx.) MacMill. ex B.L. Robins # DEMIL; trailing crownvetch, Coronilla varia L. # CZRYA; upright prairie coneflower, Ratibida columnifera (Nutt.) Woot. & Standl. # RATCO.