Imidazolinone Herbicides Improve Restoration of Great Plains Grasslands

Abstract

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. Imidazolinone herbicides (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.

Restoring Tallgrass Prairie Species Mixtures on Leafy Spurge-Infested Rangeland

“…Sideoats grama yields may have been low because this mid-grass is not as productive and may not have been as competitive as the planted tallgrasses. Low yields of switchgrass may reflect its susceptibility to imazapic as reported by Masters et al (1996). At Tilden, indiangrass yields were greatest where imazapic was applied with glyphosate, whereas there was no difference in big bluestem yields where glyphosate was applied with or without imazapic (Table 4).…”

Frequency Grid: A Simple Tool for Measuring Grassland Establishment

“…Plots with initial frequencies as low as 30% (12 plants m-2) produced lower yields the first year after establishment but, by the second year after establishment, yields were equivalent to plots with higher initial frequencies of occurrence. These results, when combined with the previous research by Cornelius (1944), Launchbaugh (1966) We have used the frequency grid to determine seeding rates that are needed to establish grasses when pre-or post-emergence herbicide treatments are used to control weeds (Vogel 1987, Masters 1997 and to assess rangeland and pasture improvement strategies (Masters et al 1996, Masters and Nissan 1998). Data derived from these studies has been used to register herbicides for use in non-cropland, rangeland, and pastures.…”

Roadside Landscapes – A potential environmental resource

“…Site preparation is the first and most critical step for effective weed control. Weed interference is the primary obstacle to establishment of seeded wildflowers, prairie forbs, and grasses (SCHRAMM, 1978;MARTIN et al, 1982;JORDAN et al, 1988;DICKENS, 1992;LYONS, 1992;HOWELL and KLINE, 1993;MASTERS et al, 1996). Projects should begin by conducting a weed inventory and test germinating a soil sample (6) .…”