Field experiments were conducted in 1986 and 1987 to determine the efficacy of various herbicides applied in the spring or fall for redvine population reductions. Spring applications of dicamba and picloram reduced redvine populations 4 mo after application. These treatments also reduced soybean density. A sequential spring followed by fall application of dicamba reduced redvine stem counts 32 to 45% the following year. Spring or spring followed by fall applications of clopyralid and hexazinone were not effective in reducing redvine populations. A fall application of clopyralid, dicamba, Dowco 433, glyphosate, or imazapyr reduced redvine regrowth 78 to 97% the following year. Dicamba at 2.2 kg ae ha-1, 3.4 kg ae ha-1 glyphosate, and 0.28 kg ai ha-1 imazapyr increased soybean yield the following year because of reduced redvine competition and lack of herbicide injury. Redvine populations were unaffected by fall applications of fosamine, hexazinone, and picloram, or clomazone applied in the spring or in the fall followed by a sequential spring application. A sequential spring followed by fall treatment of 1.1 + 1.1 kg ha-1 dicamba or 0.14 + 0.14 kg ae ha-1 clopyralid reduced trumpetcreeper population 49 to 58% the following year.

Amitrole (3-amino-s-triazole), asulam (methyl sulfanilylcarbamate), glyphosate [N-(phosphonomethyl)glycine], and fosamine [ethyl hydrogen (aminocarbonyl)phosphonate] were effective in reducing the amount of shoot regrowth from field horsetail (Equisetum arvense L.) 3 months after treatment. The order of effectiveness was amitrole > glyphosate > asulam > fosamine. The advantage of adding surfactant to the spray formulation or applying herbicides to wet foliage was rate dependent for all herbicides except fosamine. Spray retention was increased by application to wet foliage and by the inclusion of surfactant in the formulation. Spray retention increased as spray volume and plant size increased and as plant growth became prostrate. A scanning electron microscope study of the shoot surfaces showed an abundance of silica-containing structures and the presence of epicuticular wax. Certain surfaces of the scale leaves did not have these characteristics, indicating that redistribution of spray to these areas may result in greater penetration with subsequent increases in herbicide performance.

Over 20 experiments comparing glyphosate [N-(phosphonomethyl)glycine], dicamba (3,6-dichloro-2-methoxybenzoic acid), fosamine [ethyl hydrogen (aminocarbonyl)phosphonate], and 2,4-D [(2,4-dichlorophenoxy) acetic acid] for control of field bindweed (Convolvulus arvensis L. # CONAR) were conducted from 1976 to 1982 at various times of the year and different stages of weed growth. In three of the studies, 1.7, 3.4, and 5.0 kg ae/ha of glyphosate gave 54, 72, and 80% control, respectively, 1 yr after application. Control with glyphosate at 3.4, 2,4-D at 1.1, dicamba at 1.1, and fosamine at 13.7 kg ae/ha in the 20 studies was 71, 55, 57, and 73%, respectively, 1 yr after application. Glyphosate, 2,4-D, and fosamine gave good control at any time of the year if weed growth was lush. Dicamba gave good control anytime if growth was good and in the fall regardless of growing conditions. Control with mixtures of dicamba and picloram, picloram and 2,4-D, or glyphosate and picloram was higher than with the other herbicides. Dicamba at 1.1 kg/ha, applied after August caused some injury to wheat planted the same fall. Herbicide combinations with picloram at 0.28 kg/ha applied after June injured wheat planted in the fall.

Sustainable invasive weed management must address treatment effects on desired vegetation. Our objective was to determine the influence of clopyralid plus 2,4-D, glyphosate, and fosamine, at various application rates and timing, on the density and biomass of Russian knapweed and desired plant groups growing in association with this invasive weed. In a randomized complete block design with four replications, three herbicides by three herbicide rates by three herbicide application timings and a nontreated control were factorially applied to two sites located along the Missouri River riparian corridor in Montana. Clopyralid plus 2,4-D, glyphosate, and fosamine were applied during the spring rosette stage of Russian knapweed (June), the bud to bloom stage of Russian knapweed (July), or the flowering stage of Russian knapweed (August). Herbicide rates were considered low, medium, and high based on label rates of clopyralid plus 2,4-D, glyphosate, or fosamine. Density and biomass of all species were sampled 3 yr after treatment. Russian knapweed biomass decreased from 125 to about 25 g/m2 using clopyralid plus 2,4-D, irrespective of rate or timing of application. Russian knapweed density was reduced by about half by this mixture of herbicides. Nonnative grass density and biomass were maintained, whereas native grasses increased using clopyralid plus 2,4-D at medium or high rates. Neither glyphosate nor fosamine provided substantial Russian knapweed control or increases in grasses. Too few forbs were present to analyze their response to the treatments. We believe that herbicides must be combined with revegetation in areas lacking a diverse mixture of desired species capable of capturing resources made available by controlling Russian knapweed.

The invasive biotype of common reed has taken over wetlands and can spread into roadsides, turf, and ornamental sites. Additional control options are needed for managing this biotype in noncrop areas and other sites. In container trials, fosamine, glyphosate, and imazapyr all provided excellent control of common reed. Triclopyr suppressed common reed, with increasing rates improving the growth reduction. Chlorflurenol, primisulfuron, and sulfosulfuron did not suppress common reed growth. In field trials, glyphosate and imazapyr were more effective than fosamine, providing 82 and 93% control, respectively, the following April after either June or September applications. The optimum window of application for glyphosate may therefore include both summer and fall applications, wider than the commonly accepted window of only fall treatments. Fosamine provided greater suppression of common reed when applied in September (68% control) compared to June applications (43% control).