• Evaluation of Herbicide and Disking to Control Invasive Bluestems in a South Texas Coastal Prairie

      Ruffner, Marvin E.; Barnes, Thomas G. (Society for Range Management, 2012-05-01)
      Conservation and restoration efforts of native grasslands are being hindered by invasive, exotic plants. Exotic bluestem grasses (Bothriochloa and Dichanthium spp.) have become increasingly invasive throughout the rangelands of the central and southern Great Plains, United States. Accordingly, the aim of this study was to evaluate the efficacy of glyphosate, imazapyr, and imazapyr + glyphosate treatments with or without disking to remove exotic bluestems from a south Texas coastal prairie. We evaluated three different control regimens: 1) herbicide treatments only, 2) herbicide treatments followed by two diskings (H + D), and 3) disking followed by herbicide treatments (D + H). Percent exotic bluestem, native grass, and forb cover were visually estimated at 0 (pre-treatment: May 2006), 20, 52, and 104 wk after treatment (WAT). The herbicide-only and H+D regimens were ineffective at controlling exotic bluestems. However, exotic bluestem cover in herbicide-treated plots of the D+H regimen was significantly lower (P<0.05) compared to control plots and most treatment plots of the herbicide-only and H+Dregimens up to 52 WAT. Control regimens did not notably facilitate an increase in native grass cover from pre-treatment levels, but native grass cover remained the highest, and increased the most, in some imazapyr-treated plots of the herbicide-only and D+H regimens, respectively. In the H+D and D+H regimens, disking resulted in a flush of forb cover (up to 50%) at 52 WAT; yet forb cover was <5% in these plots by 104 WAT. Exotic bluestem cover recovered back to, or was greater than, pretreatment levels among most treatment plots across all three control regimens at 104 WAT. This study suggests that follow-up control measures are needed to suppress the re-invasion of exotic bluestems after initial control efforts. Additional studies are needed to evaluate other strategies to control exotic bluestems in rangelands of the central and southern United States./Los esfuerzos de conservación y reforestación de pastizales nativos han sido obstaculizados por plantas invasivas y tóxicas. El pasto exótico bluestem grasses (Bothriochloa and Dichanthium spp.) se ha vuelto cada vez mas invasivo en los pastizales del centro y el sur delas Grandes Planicies de Estados Unidos, por consiguiente, el objetivo de este estudio fue evaluar la eficiencia de tratamientos a base de glyphosate, imazapyr, y imazapyr+glyphosate con o sin arado de disco para remover los plantas exóticas de bluestem de un pastizal delas planicies de las costas de Texas. Evaluamos tres diferentes regímenes de control: 1) aplicación u ́nicamente de herbicida; 2) aplicación de herbicida seguidos por las rastra de discos dos veces (H+D); y 3) rastra de discos seguido de la aplicación de herbicida (D+H). El porcentaje del pasto exótico bluestem, gramíneas nativas y cobertura herbácea fue estimado visualmente como 0 (pre-tratamiento: Mayo 2006), 20, 52, and 104 semanas después de la aplicación de los tratamientos (WAT). Los tratamientos solo herbicida y H+D no fueron efectivos para control del pasto exótico bluestems. Sin embargo, la cubierta de este pasto exótico en las parcelas bajo la aplicación de herbicida del re ́gimen D+H fue significativamente menor (P<0.05) comparado con las parcelas control y la mayoría de las parcelas tratadas solo con herbicida y H+D regímenes hasta 52 WAT. Los regímenes de control no facilitaron notablemente un incremento en la cobertura de pastos de niveles a comparación de los niveles antes de los tratamientos, pero la cobertura de los pastizales nativos permaneció como la más alta, y la que mas aumentó, en algunos parcelas tratadas con imazapyr o con solo herbicida y D+H regímenes, respectivamente. En los tratamientos H+D y D+H, y la rastra de discos resultaron en un aumento de la cobertura herbácea (de hasta 50%) en 52 WAT; sin embargo la cobertura fue <5% en estas parcelas por 104 WAT. La cobertura del pasto exótico bluestem se recuperó, o fue más grande que, los niveles presentados antes de los tratamientos entre la mayoría de las parcelas tratadas a través de todos los tres regímenes de control a 104 WAT. Este estudio sugiere que el seguimiento de las medidas de control es necesario para suprimir una nueva invasión del pasto exótico bluestem después de esfuerzos iniciales para controlarlo. Estudios adicionales son necesarios para evaluar otras estrategias para controlar el pasto exótico bluestem en pastizales de centro y sur de los Estados Unidos.
    • Saltcedar recovery after herbicide-burn and mechanical clearing practices

      McDaniel, K. C.; Taylor, J. P. (Society for Range Management, 2003-09-01)
      Mechanical clearing and herbicide-burn treatments were compared to evaluate saltcedar (Tamarix chinensis Lour.) control and recovery along the Rio Grande on the Bosque del Apache National Wildlife Refuge, Socorro, N.M. The herbicide-burn treatment included an aerial application of imazapyr (+)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid] + glyphosate [N-(phosphono-methyl)glycine] (0.6 + 0.6 kg ai ha-1 rate) followed 3 years later by a prescription broadcast fire that eliminated > 99% of the standing dead stems. Six years after initial herbicide application, saltcedar mortality was 93%. Mechanical saltcedar clearing entailed removing aerial (trunks and stems) growth by blading, stacking and burning debris, followed by removal of underground plant portions (root crowns) by plowing, raking, and burning stacked material. Saltcedar mortality 3 years after mechanical clearing averaged 70%, which was deemed unsatisfactory. Thus, root plowing, raking, and pile burning was repeated. Three years later, after the second mechanical clearing, saltcedar mortality was 97%. Costs for the herbicide-burn treatment averaged 283 ha-1, whereas mechanical control costs were 884 ha-1 for the first surface and root clearing and an additional 585 ha-1 for the second root clearing. Riparian managers should consider environmental conditions and restoration strategies prior to selecting a saltcedar control approach. Although control costs were significantly lower for the herbicide-burn treatment compared to mechanical clearing in this study, the choice of methods should always consider alternative control strategies for saltcedar. Frequently, combinations of methods result in more efficient, cost-effective results.