Combining Management Techniques for Short-Term Reduction of Introduced Old World Bluestems in South Texas Rangelands

Abstract

Several ecotypes within a group of introduced, warm-season, perennial bunchgrasses labeled Old World Bluestems (OWB) have become invasive throughout much of Texas. Specifically, Kleberg bluestem (Dichanthium annulatum Forssk.) and yellow bluestem (Bothriochloa ischaemum L.) in South Texas have become a dense monoculture that reduces biodiversity of both plants and wildlife while also being poor fodder for domestic livestock. Reduction of Kleberg and yellow bluestem is desired, but there has been limited research on effective combinations of grassland management practices. We conducted two 4 × 5 factorial experiments at six locations across Bee, Kleberg, and San Patricio counties in South Texas. Primary treatments (summer fire, glyphosate and native reseeding, or nicosulfuron + metsulfuron methyl, and a control [no treatment]) were combined with secondary treatments (plowing, plowing and native reseeding, mowing, or fertilization, and a control [no treatment]). In both experiments, herbage mass was not different among primary treatments at any sample collection date, whereas plowed treatments had reduced herbage mass until the spring (Experiment 1) or summer (Experiment 2) after treatments were completed. Plowing reduced canopy cover until the summer after treatment when canopy cover was not different among treatments in both experiments. Among primary treatments, only glyphosate herbicide application reduced canopy cover. All management practices applied in this study either had negative effects or provided only short-term (1–1.5 yr) reduction in OWB. Treatments that were most effective in reducing OWB cover and herbage mass included plowing, mowing, and glyphosate application and were also detrimental to desirable plant species so may not be desirable to land managers. Limited success of treatments applied in this study reinforces the challenge to reduce the invasive tendencies of introduced forage species such as OWB.