Downy brome (Bromus tectorum L.), an invasive winter annual grass, may be increasing in extent and abundance at high elevations in the western United States. This would pose a great threat to high-elevation plant communities and resources. However, data to track this species in high-elevation environments are limited. To address changes in the distribution and abundance of downy brome and the factors most associated with its occurrence, we used field sampling and statistical methods, and niche modeling. In 2007, we resampled plots from two vegetation surveys in Rocky Mountain National Park for presence and cover of downy brome. One survey was established in 1993 and had been resampled in 1999. The other survey was established in 1996 and had not been resampled until our study. Although not all comparisons between years demonstrated significant changes in downy brome abundance, its mean cover increased nearly fivefold from 1993 (0.7%) to 2007 (3.6%) in one of the two vegetation surveys (P = 0.06). Although the average cover of downy brome within the second survey appeared to be increasing from 1996 to 2007, this slight change from 0.5% to 1.2% was not statistically significant (P = 0.24). Downy brome was present in 50% more plots in 1999 than in 1993 (P = 0.02) in the first survey. In the second survey, downy brome was present in 30% more plots in 2007 than in 1996 (P = 0.08). Maxent, a species–environmental matching model, was generally able to predict occurrences of downy brome, as new locations were in the ranges predicted by earlier generated models. The model found that distance to roads, elevation, and vegetation community influenced the predictions most. The strong response of downy brome to interannual environmental variability makes detecting change challenging, especially with small sample sizes. However, our results suggest that the area in which downy brome occurs is likely increasing in Rocky Mountain National Park through increased frequency and cover. Field surveys along with predictive modeling will be vital in directing efforts to manage this highly invasive species.

We evaluated the efficacy of the biological control agent, red-headed leafy spurge stem borer, against the nonnative invasive plant leafy spurge. Our three treatments were release of the biological control agent into uncaged plots, release of the biological control agent into plots caged to prevent agent escape, and control plots caged to prevent agent entry. These treatments were replicated three times at six sites in the western United States. We measured leafy spurge biomass for 1 or 2 yr following release. We also measured the percentage of leafy spurge stems showing evidence of red-headed leafy spurge stem borer oviposition for either 1 or 2 yr following agent release, depending on the site. Red-headed leafy spurge stem borer did not demonstrably reduce leafy spurge biomass in our study. Moreover, compared to the release year, evidence of red-headed leafy spurge stem borer oviposition declined with time, suggesting the agent population was diminishing. This suggests the agent is incapable of building large populations capable of controlling leafy spurge at the sites we studied. However, after being released, populations of biological control agents sometimes go through long lag phases and then begin rapid population increases, so we cannot completely dismiss the possibility that red-headed leafy spurge stem borer might become effective given more time.

Smooth brome and Kentucky bluegrass are introduced cool-season perennial grasses known to invade grasslands throughout North America. During the fall of 2005 and spring of 2006, we implemented a restoration study at six native prairie sites in eastern South Dakota that have been invaded by smooth brome and Kentucky bluegrass. Treatments included five herbicide combinations, a fall prescribed burn, and an untreated control to determine the potential of each for renovation of invaded native grasslands. Herbicide treatments tested were sulfosulfuron, imazapyr, imazapic + sulfosulfuron, and imazapyr + imazapic, and were applied in late September 2005 and mid-May 2006. Untreated control plots averaged 64% (± 3.1) smooth brome cover and 38% (± 5.5) Kentucky bluegrass cover after the third growing season. Smooth brome cover in herbicide treated plots ranged from 6 to 23% and Kentucky bluegrass cover ranged from 15 to 35% after the third growing season. Smooth brome cover was 20% (± 2.9) and Kentucky bluegrass cover was 19% (± 4.0) in burned plots after the third growing season. Spring and fall treatments had similar native plant cover after three growing seasons. Spring and fall application of 0.33 kg ai ha−1 imazapyr and 0.10 kg ai ha−1 imazapic + 0.16 kg ai ha−1 imazapyr had ≤ 10% smooth brome cover and increased native species cover after three growing seasons. Herbicides were effective at reducing cover of smooth brome and Kentucky bluegrass, and can be incorporated with other management strategies to restore prairie remnants.

Black and pale swallowwort (BSW and PSW, respectively) are perennial, herbaceous vines in the Apocynaceae that are native to Europe. The species are becoming increasingly abundant in the northeastern United States and southeastern Canada and are difficult to manage. However, we know little about the demographic parameters of these species. We determined the survival, annual rate of vegetative growth, and fecundity of mature clumps of these swallowwort species. We selected four PSW sites (three of which comprised both old-field and forest habitats) in central New York and three BSW old fields in southeastern New York. BSW is largely restricted to higher light habitats in its introduced range. In each habitat, we followed the growth of 30 to 32 randomly selected clumps of similar size (2 to 5 stems clump−1 in the initial year) for 3 to 4 yr. Yearly survival was 99.6 ± 0.3% [mean ± standard error] for PSW and 100 ± 0% for BSW. In old fields, vegetative expansion varied from −0.01 ± 0.1 to 4.6 ± 0.4 stems clump−1 yr−1 for BSW and −0.02 ± 0.2 to 2.1 ± 0.5 stems clump−1 yr−1 for PSW. In forests, PSW growth was lower with vegetative expansion ranging from −0.01 ± 0.1 to 0.8 ± 0.2 stems clump−1 yr−1. Fecundity of PSW in 2007 and 2008 (130 ± 10 viable seeds stem−1 yr−1) was similar to BSW (100 ± 10 viable seeds stem−1 yr−1). Fecundity of PSW in forests was generally lower than PSW in old fields, but it varied greatly among sites (0 to 170 viable seeds stem−1 yr−1). We found that stem growth and fecundity did not vary with clump size (stems per clump). Since vegetative expansion and fecundity rates were high in old-field habitats, but were generally low or nonexistent in forest habitats, we suggest that management of these two invasive vines be focused in higher light environments to reduce overall seed production and its subsequent spread to surrounding areas.

Cogongrass invades forests through rhizomatous growth and wind-dispersed seeds. Increased density and abundance of woody vegetation along forest edges may strengthen biotic resistance to invasion by creating a vegetative barrier to dispersal, growth, or establishment of cogongrass. We evaluated differences in dispersal of cogongrass spikelets experimentally released from road edges into tallgrass-dominated and shrub-encroached longleaf pine forests (Pinus palustris). Average maximum dispersal distances were greater in the pine–tallgrass forest (17.3 m) compared to the pine–shrub forest association (9.4 m). Spikelets were more likely to be intercepted by vegetation in pine–shrub forests compared to pine–tallgrass forests. Results suggest that dense woody vegetation along forest edges will slow spread from wind-dispersed cogongrass seeds.

Bridal creeper has become a serious environmental weed in southern Australia. Historically the invaded areas had low soil nutrient levels. However, our field surveys indicate that soils in bridal creeper–invaded areas have higher phosphorus and iron levels than soils in nearby native reference areas regardless of the proximity to agriculture or other disturbances. A glasshouse experiment was undertaken to determine the influence of increased nutrients on plants that co-occur with bridal creeper in order to (1) assess the impact of changed soil conditions and (2) predict the response of dominant species following the biological control of bridal creeper. The relative growth rate (RGR) of bridal creeper, two native shrubs (narrow-leaved thomasia [Thomasia angustifolia] and bluebell creeper [Billardiera heterophylla]), and an invasive exotic grass (annual veldt grass [Ehrharta longiflora]) were determined in three soil types: soil collected within a bridal creeper stand, soil collected from a nearby reference area, and a potting mix with nutrient levels higher than that recorded in the field. The plant species were chosen due to their association with bridal creeper. For example, the native species narrow-leaved thomasia was identified in a previous survey as the most abundant shrub at the invaded site where the soil was collected. The two other species, bluebell creeper and annual veldt grass, were identified from a previous seedbank trial as being abundant (in the seedbank) and able to readily germinate in invaded areas. When grown in either the bridal creeper–invaded soil or reference soil, bluebell creeper had significantly lower RGRs than narrow-leaved thomasia and annual veldt grass. However, as all these species showed increases in RGRs between reference soil and bridal creeper soil, this study indicates that for at least these three species the impact of increased nutrients may not be a barrier to the recovery of invaded areas following the control of bridal creeper.

Rehabilitation of downy brome–infested shrublands is challenging once this invasive grass dominates native communities. The effectiveness of imazapic herbicide in reducing downy brome cover has been variable, and there is uncertainty about the impacts of imazapic on native species. We used a before-after-control-impact (BACI) field experiment and greenhouse studies to (1) determine if imazapic herbicide applied at 132 g ai ha−1 (8 oz/ac−1) and seeding with two native shrub species (Wyoming big sagebrush [Artemisia tridentata] and Mexican cliffrose [Purshia mexicana]) reduced downy brome cover and promoted shrub establishment, (2) assess potential effects of imazapic on nontarget plant species and plant community composition, and (3) determine if imazapic affected downy brome or seeded shrub species when applied at different developmental stages. Seeding shrubs, alone, or in combination with imazapic application, did not significantly increase shrub density, possibly because of droughty conditions. In the field, imazapic reduced downy brome cover by 20% and nontarget forb cover by 25% and altered plant community composition the first year after treatment. Imazapic was lethal to downy brome at all growth stages in the greenhouse and reduced shrub germination by 50 to 80%, but older shrub seedlings were more tolerant of the herbicide. We conclude that a one-time application of imazapic combined with seeding shrubs was only slightly effective in rehabilitating areas with high downy brome and thatch cover and resulted in short-term impacts to nontarget species. These results highlight the need to treat downy brome infestations before they become too large. Also, removing thatch prior to treating with imazapic, although likely lethal to the native shrubs we studied, could increase the effectiveness of imazapic.

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.

Smooth brome (Bromus inermis) is an introduced, cool-season perennial, sod-forming grass that has been shown to invade both native cool-and warm-season grasslands throughout North America. During the fall of 2005 through spring 2007, we implemented a smooth brome removal study at five sites in eastern South Dakota. Sites were selected to represent a range of soil and environmental conditions. Seven fall herbicide treatments, five spring herbicide treatments, an untreated plot that was planted with a native seed mix, and an untreated control that received no herbicide or seed addition were applied at each location in fall 2005/spring 2006 and fall 2006/spring 2007. Based upon first-year results, three fall herbicide treatments and two spring herbicide treatments were added in fall 2006/spring 2007. Sites were seeded with a native plant mix within 2 wk following spring herbicide treatment. Smooth brome cover in untreated plots ranged from 73 to 99% at the conclusion of the study. Smooth brome cover on herbicide-treated plots ranged from 0 to 84% on 2005/2006 plots and 0 to 98% on 2006/2007 plots after three growing seasons. Native plant response varied by site and treatment, possibly due to competition from exotic weeds. Although several herbicides show promise for control of smooth brome, future response of native plants will be important in determining the proper timing and herbicide combination.

A total of 24 pre-and posttreatment plant frequency data sets were analyzed from 15 Wisconsin lakes treated with granular 2,4-D BEE herbicide for the control of Eurasian watermilfoil (Myriophyllum spicatum). Six data sets from four untreated control lakes were analyzed for comparison. The data sets included the results of line-transect aquatic plant surveys and point-intercept aquatic plant surveys. The results from these two survey methods were analyzed separately. Analysis of pre-and posttreatment changes in frequency of occurence for 46 species of aquatic plants indicated Eurasian watermilfoil was the only species to show significant declines in all the surveys. At application rates of 112 kg ha−1, Eurasian watermilfoil declined an average 65.9% among the line-transect surveys; and 58.0% among the point-intercept surveys. At application rates of 168 kg ha−1, Eurasian watermilfoil declined by 94.4% and 76.5% among line-transect and point-intercept surveys, respectively. Among the control lakes, Eurasian watermilfoil increased an average of 77% in year 1 and 24% in year 2. Northern watermilfoil (Myriophyllum sibiricum), a closely related native plant, underwent declines in frequency at the higher 2,4-D application rate (20.0%) but showed an increase (88.9%) at the lower rate among the line-transect surveys. Northern watermilfoil exhibited declines at both rates among the point-intercept surveys (48 and 50%, respectively); however, the plant also exhibited declines in the control lakes in year 2. Most other native aquatic plant species were unaffected or showed increases following treatment with 2,4-D BEE. The high degree of selectivity to Eurasian watermilfoil found in this survey of operational treatments with 2,4-D BEE suggests that this herbicide is an important tool for restoring plant communities that have been degraded by Eurasian watermilfoil.

On the west coast of North America and in Australia, there have been parallel cases of sequential invasion and replacement of the shoreline plant American sea-rocket by European sea-rocket. A similar pattern has also occurred in New Zealand. For 30 to 40 yr, from its first recording in 1921, American sea-rocket spread throughout the eastern coastlines of the North and South Islands of New Zealand. European sea-rocket has so far been collected only on the North Island. From its first collection in 1937, European sea-rocket spread to the northern extremity of the island by 1973, and by 2010, it had reached the southernmost limit. In the region where both species have occurred in the past, American sea-rocket is now rarely found. This appears to be another example of congeneric species displacement.