Invasive species negatively impact vegetation communities. Invasive European common reed [Phragmites australis (Cav.) Trin. ex Steud. ssp. australis] is rapidly spreading throughout North American wetlands. As such, the suppression of P. australis populations is a goal of many managers, as its removal should provide an opportunity to restore native vegetation communities. In Ontario, managers applied a glyphosate-based herbicide to more than 400 ha of P. australis in ecologically significant coastal marshes, representing the first time this tool was used over standing water to suppress an invasive species in Canada. Using a before–after–control–impact monitoring design, we evaluated the efficacy of glyphosate-based herbicide at removing P. australis along a water-depth gradient and assessed the recovery of the vegetation community for 2 yr after treatment in relation to reference conditions. We found that herbicide suppressed more than 99% of P. australis 1 yr after treatment and worked effectively along the entire water-depth gradient (10 to 48 cm). However, the post-treatment vegetation community remains distinctive from reference marsh 2 yr after treatment. In many plots where P. australis was removed, nonnative European frog-bit (Hydrocharis morsus-ranae L.) is now dominant, likely aided by high lake-water levels.

PRE and POST herbicide options were evaluated to control perilla mint, a potentially deadly plant for livestock. The germination requirements of seed from weedy populations were also investigated to better understand and predict emergence timing. POST applications of aminocyclopyrachlor blends, glyphosate, picloram+2,4-D, aminopyralid+2,4-D, and 2,4-D alone provided superior control of perilla mint when applied in the early reproductive growth stage. Picloram+2,4-D and aminocyclopyrachlor+chlorsulfuron also provided soil residual activity and the most effective PRE control followed by pendimethalin and aminopyralid+2,4-D. Seed from weedy populations tend to germinate in a range of night/day soil temperatures from 10–15 C to 25–30 C. Therefore, application and activation of the most effective PRE treatments should be made before these temperatures occur in areas where weedy perilla mint populations are found.

Over-the-top applications of metriflufen {2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoic acid} at 0.6 to 2.2 kg/ha were highly toxic to johnsongrass [Sorghum halepense (L.) Pers.], but caused little visual injury to soybeans [Glycine max (L.) Merr. ‘Hill’]. Directed applications of metriflufen at 0.8 to 3.4 kg/ha provided equal and, in a few comparisons, better control of johnsongrass than did some rates of the herbicide applied over-the-top. Application of metriflufen at 0.8 and 1.7 kg/ha in directed sprays resulted in higher soybean yields than did comparable treatments applied over-the-top; yields of directed vs. over-the-top applications of metriflufen at 3.4 kg/ha resulted in statistically equal soybean yields. The research suggested that metriflufen entered johnsongrass plants through shoots and leaves and also through roots. Johnsongrass control was excellent following applications of metriflufen at 1.7 and 2.2 kg/ha without soybean injury and with greatly increased soybean yields. Results following over-the-top applications of metriflufen at 1.1 kg/ha to ‘Hill’, ‘Tracy’, ‘Lee 68’, ‘Bragg’, and ‘Forrest’ soybeans at three different stages of morphological development did not demonstrate any appreciable differences in the response of the cultivars to the herbicide.

We evaluated herbicide treatments for control of umbrella dracaena, locally invasive in central Florida. Biannual treatments of imazapyr (3.2 and 6.4 g ai L−1), metsulfuron (0.08 and 0.16 g ai L−1), and imazapyr (0.8 g ai L−1) plus glyphosate (19.9 g ai L−1) reduced cover to < 3% at 12 mo, but no treatment eliminated the plant. In contrast, a single treatment on individual potted plants in greenhouse trials was highly effective with ≥ 98% necrosis/chlorosis at 6 mo and no regrowth at 9 mo posttreatment for most treatments. Management of umbrella dracaena will require more than two herbicide treatments with imazapyr, metsulfuron, glyphosate, or a combination of these herbicides if eradication is to be achieved. Because it is currently problematic and localized in one specific area in about 40 ha, it should be a high management priority before it spreads throughout Florida and possibly other states.

Coral ardisia (Ardisia crenata) has been present in Florida for more than 100 yr as an ornamental and has become invasive in hammocks of natural areas. This plant forms dense understory cover, often greater than 90%, which can suppress native plant recruitment and growth. Results from herbicide trials at two sites in Florida indicate that a single foliar treatment applied as a spot application of triclopyr amine, triclopyr ester, glyphosate, imazapic, dicamba, triclopyr amine + imazapic, or triclopyr ester + fluroxypyr reduced Ardisia crenata to less than 13% at 12 mo after treatment (MAT). A single treatment of imazapic (2.4 g ae L−1) or imazapic (2.4 g ae L−1) + triclopyr (10.8 g ae L−1) reduced cover of mature plants to less than 0.5% and seedlings to less than or equal to 4% at 12 MAT. Native plant cover was less than 5% prior to treatment indicating that dense infestations of Ardisia crenata may suppress native vegetation. In the dense infestations of Ardisia crenata observed in this study, nontarget damage was not a concern due to the rarity of native plants. However, applicators should use caution applying triclopyr and imazapic when small shrubs and trees are present in the treatment area. Additional follow-up treatments will be required for control of seedling and possible resprouts at 12 MAT.