Alternative Management Techniques for Controlling Microstegium vimineum on Stream and Riparian Restoration Sites

Microstegium vimineum (Trin.) A. Camus, also known as Japanese stiltgrass, is an invasive grass native to Asia that has widely colonized riparian woodland and wetland environments in the eastern U.S. Research was conducted on alternative management techniques for M. vimineum control on stream and riparian restoration sites in field and greenhouse settings in North Carolina. Aquatic-use herbicides were applied preemergence (PRE) and postemergence (POST) to M. vimineum populations that infested two stream restoration sites in the Piedmont and Upper Coastal Plain regions.;Herbicides applied PRE at standard recommended and lower than recommended rates were evaluated in the field. Both rates of flumioxazin, fluridone, imazamox, and imazapyr and the standard recommended rate of penoxsulam provided early reduction of M. vimineum stem density 6 weeks after treatment (WAT) and extended control of plant biomass 30 WAT. Bispyribac, carfentrazone, and the lower rate of penoxsulam provided effective stem reduction 6 WAT but not 30 WAT. Flumioxazin, fluridone, imazamox, and imazapyr applied at two rates controlled 98 to 100% of M. vimineum 6 WAT. These same treatments 30 WAT demonstrated 86 to 97% control in 2009 and 92 to 100% control in 2010. Bispyribac, carfentrazone and penoxsulam provided good control at 6 WAT; results 30 WAT were mixed.;POST herbicide field trials showed standard recommended rates and lower than recommended rates of diquat, flumioxazin, glyphosate, imazamox and imazapyr reduced stem density of M. vimineum 6 WAT and plant biomass 30 WAT. Bispyribac, fluridone, and the low rate of glyphosate were less effective. Diquat, flumioxazin, glyphosate, imazamox, and imazapyr significantly reduced M. vimineum plant cover 41 to 100% 6 WAT. Flumioxazin, imazamox, and imazapyr reduced cover of the invasive weed 90 to 100% 30 WAT. Bispyribac, fluridone, and penoxsulam treatments provided varying control 6 and 30 WAT.;POST synthetic auxin herbicide field trials included 2,4-D, aminocyclopyrachlor, aminopyralid, and triclopyr applied at 3 different rates to M. vimineum. Stem density was less in the herbicide treated plots compared to untreated control plots 6 WAT. Significant vegetation cover reduction resulted from all application rates of aminocyclopyrachlor and the highest rate of aminopyralid 6 WAT. Aminocyclopyrachlor applied at the higher levels reduced M. vimineum between 83 to 100% 30 WAT.;Greenhouse studies evaluated effects of POST herbicides on M. vimineum and four native riparian graminoid species to determine if lower than recommended rates could successfully control M. vimineum while not adversely affecting the graminoids. Five different rates of diquat and glyphosate were applied to M. vimineum, Carex vulpinoidea, Chasmanthium latifolium, Juncus effusus, and Panicum virgatum. Higher rates of diquat applications including 0.5 and 0.25 times recommended rate resulted in early leaf injury to M. vimineum 1 WAT while glyphosate injury occurred later 6 WAT; all five treatment rates significantly reduced the invasive plant. P. virgatum was most susceptible to diquat injury at every rate, but only to glyphosate at the half-recommended rate. C. latifolium was vulnerable to diquat injury 1 and 3 WAT, but showed signs of recovery 6 WAT. Half-recommended rate of glyphosate was the only rate that significantly damaged this species. C. vulpinoidea was effectively injured by diquat at half-recommended rates, but not at lower levels. Glyphosate-induced injury to C. vulpinoidea was significant at 0.5 and 0.25 recommended rates 6 WAT. Diquat applications to J. effusus resulted in sustained injury at the three highest rates throughout the three measuring periods. However, glyphosate treatments applied at all rates to J. effusus resulted in no significant plant damage at any time.