Master of Science (MS)
Plant, Enviromental and Soil Sciences
The potential usage and benefits of native perennial grasses (NPG) in urban plantings may be severely hindered during establishment by high weed pressure. Two studies were conducted with the objectives of examining the tolerance of several NPG to commonly available herbicides during vegetative establishment; and comparison of establishment vigor of NPG in Louisiana when weed control is implemented. The first study was conducted in greenhouse conditions to evaluate tolerance of broomsedge (Andropogon virginicus L.); blue grama (Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths); Virginia wildrye (Elymus virginicus L.); switchgrass (Panicum virgatum L.); little bluestem (Schizachyrium scoparium (Michx.) Nash); and Indiangrass (Sorghastrum nutans (L.) Nash) established 6 weeks from plugs to applications of pendimethalin; sulfosulfuron; imazapic; triclopyr; or fenoxaprop. Overall, fenoxaprop was the most injurious to NPG and slowed tillering on affected species compared to controls. Plants treated with imazapic, triclopyr, or sulfosulfuron varied in tolerance among species as well as timing of application relative to temperature. Pendimethalin was consistently the least injurious to NPG. In the second study, the same NPG species were evaluated for establishment vigor in Baton Rouge, Louisiana and Fort Polk near Leesville, Louisiana over a 12-month period with pendimethalin applied at initial planting in October 2011 and again in March 2012. At the Baton Rouge site, little bluestem and broomsedge had the highest canopy coverages of 97.7% and 100% and corresponding biomasses 156.8 and 244.8 g at the conclusion of the 12-month establishment period along with the lowest weed encroachment of 1.7%. Little bluestem and broomsedge also achieved the highest canopy coverages and biomasses at the Fort Polk site, but overall NPG establishment was slower compared to NPG establishment in Baton Rouge. Environmental factors such as soil texture, fertility, and rainfall between the two locations affected NPG establishment. Results indicate herbicide applications at least during the first year of NPG vegetative establishment may be necessary to reduce weed competition in order to establish NPG in disturbed urban sites. Species selection, herbicide selection and application, and site characteristics must be accounted for when establishing NPG in urban areas.
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Stagg, Jason Walter, "Herbicide Tolerance of Native Perennial Grasses During Vegetative Establishment in Disturbed Urban Sites in Louisiana" (2014). LSU Master's Theses. 3204.
Kuehny, Jeff S