Kentucky bluegrass, a nonnative species, has invaded rangelands in the United States and is currently present in most rangelands across the Northern Great Plains. Despite its accelerated expansion, the consequences of Kentucky bluegrass on the diversity of native plant species and on ecosystem services remain largely unknown. We synthesized the available data related to Kentucky bluegrass and how it affects native plant diversity and ecosystem services. We found that invasion may bring negative consequences to ecosystem services, such as pollination, habitat for wildlife species, and alteration of nutrient and hydrologic cycles, among others. To maintain the flow of ecosystem goods and services from these rangeland ecosystems, range science must adapt to the challenge of introduced, cool-season grass dominance in mixed-grass prairie. Based on our findings, we identify research needs that address ecosystem changes brought on by Kentucky bluegrass invasion and the corresponding effects these changes have on ecosystem services. We are dealing with novel ecosystems, and until we have better answers, adaptive management strategies that use the best available information need to be developed to adapt to the invasion of this pervasive invasive species.

Nomenclature: Kentucky bluegrass, Poa pratensis L.

Management Implications: Maintaining the flow of ecological goods and services instead of unrealistically managing for the past under changing cultural and climatic conditions (i.e., urbanization, climate change, and increased atmospheric nitrogen deposition) has become a reality. This has increased the need to implement adaptive management and new research approaches. Managing these novel ecosystems requires adjustment to timing and application of traditional management tools, such as grazing, fire, deferment, and rest, as well as bringing the collective knowledge and resources of government and educational and private sectors to bear. We need to be open to changing our traditional management practices and working on improving the flow of goods and services provided by natural areas.

Japanese hedgeparsley is an annual (or sometimes biennial) forb introduced from Eurasia and found throughout much of the eastern United States and parts of extreme southern Canada. In North America, Japanese hedgeparsley is commonly found in ruderal habitats, such as roadsides, railroad rights-of-way, forest edges, and urban waste spaces. This species has not yet been listed as a noxious invasive, but its expanding populations have caused concern in several Midwestern states. The primary threat from Japanese hedgeparsley is its vigorous growth habit, which creates dense patches, and its dispersal ability, facilitated by its clinging, burr-like fruits. Some confusion on identification exists within the Torilis genus, with similar species (particularly T. arvensis) frequently misidentified in herbaria and the literature. Here, we review aspects of the etymology, taxonomy, biology, distribution, and management of Japanese hedgeparsley with the objective of increasing awareness of the potential threat posed by this species and its closely related congeners.

Nomenclature: Japanese hedgeparsley, Torilis japonica (Houtt.) DC., hedgeparsley, Torilis arvensis (Huds.) Link.

Previous research has shown that pyridine growth regulator herbicides can affect seed production in annual grasses including downy brome, Japanese brome, wheat, and other cereal grain crops. Aminocyclopyrachlor is a pyridine carboxylic acid growth regulator herbicide that has recently been registered for broadleaf weed and brush control in nonagricultural areas, which may help facilitate release of native perennial grasses in native plant restoration sites. The influence of aminocyclopyrachlor on downy brome seed production was evaluated at multiple application rates and timings under controlled field conditions. The effect of aminocyclopyrachlor on seed production was compared with aminopyralid, another pyridine growth regulator herbicide. When applied to downy brome plants in the early vegetative stage (EPOST) at approximately 580 growing degree days (GDD), aminocyclopyrachlor at 320 g ae ha⁻¹ reduced seed germination by 50 to 88% in the first and second study years, respectively. Aminopyralid reduced seed germination by 94% in the first study year, but only 20% in the second year. When applied to downy brome plants in the early heading stage at approximately 1,235 GDD (LPOST), aminocyclopyrachlor at 320 g ae ha⁻¹ reduced seed germination by 100% both years. Aminopyralid reduced seed germination by 95% in the first year, and 81% in the second year. Other than the observed reduction in seed germination, herbicides did not produce any visible changes in downy brome aboveground plant growth or development. Because downy brome seeds are relatively short-lived in soil, aminocyclopyrachlor and aminopyralid applications to downy brome–infested rangelands and other natural areas could result in reductions in downy brome population densities over time. No published data exist on the effect of aminocyclopyrachlor on seed production of desirable perennial grasses in natural ecosystems, thereby suggesting the need for further research.

Nomenclature: Aminocyclopyrachlor, formerly DPX MAT28, 6-amino-5-chloro-2-cyclopropylpyrimidine-4-carboxylic acid, aminopyralid, 4-amino-3,6-dichloropyridine-2-carboxylic acid, downy brome, Bromus tectorum L. BROTE, Japanese brome, Bromus japonicus Thunb. ex Murr. BROJA, wheat, Triticum aestivum L.

Management Implications: Aminocyclopyrachlor (formerly DPX MAT28) is a growth regulator herbicide that has been registered for broadleaf weed and brush control in nonagricultural areas, which can facilitate the release of native perennial grasses in native or improved plant community sites. In addition to controlling many invasive broadleaf weeds in rangeland and other natural areas, this herbicide may significantly reduce seed production in downy brome. In this controlled study, application of aminocyclopyrachlor to downy brome plants in the vegetative stage reduced seed germination by 50 to 88%. When applied to downy brome plants in the early heading stage, aminocyclopyrachlor reduced seed germination by 100%, even though aboveground biomass of downy brome was not significantly reduced. Because aminocyclopyrachlor has soil residual properties and because of the relatively short viability of downy brome seeds in the seed bank, it may be possible to use this herbicide to reduce downy brome in infested rangeland areas. A reduction in the downy brome seed bank caused by aminocyclopyrachlor may facilitate the restoration of native or improved plant communities. How aminocyclopyrachlor will affect plant community composition may be difficult to predict, because this herbicide also affects native forbs and shrubs, and may reduce seed production of desired, perennial grasses. Further field testing is needed to assess the effects of aminocyclopyrachlor on long-term changes in plant community composition.

In this paper, we describe five successful classical biological weed control agents released in the United States. For each of the five arthropod species, we compared data from prerelease studies that experimentally predicted the agent's host range with data collected postrelease. In general, experimental host range data accurately predicted or overestimated risks to nontarget plants. We compare the five cases with insects recently denied for introduction in the United States and conclude that none of the discussed agents would likely be approved if they were petitioned today. Three agents would be rejected because they potentially could attack economic plants, and two because of potential attack on threatened or endangered plants. All five biocontrol agents have contributed significantly to the successful management of major weeds with no or minimal environmental risk. We believe that the United States may miss opportunities for sustainable and environmentally benign management of weeds using biological control if the regulatory framework only considers the risks of agents as potential plant pests and treats any host-range data regarding economic or threatened and endangered species as a binary decision (i.e., mandates rejection if there is any chance of feeding or development). As a way forward we propose the following: (1) the addition of risk and benefit analyses at the habitat level with a clear ranking of decision-making criteria as part of the U.S. Department of Agriculture Animal and Plant Health Inspection Service Technical Advisory Group's evaluation process of biocontrol agents; (2) recognition of the primacy of realized host range data for potential agents that considers the insect's host selection behavior instead of emphasizing fundamental host range data during release evaluations, and (3) development of formalized postrelease monitoring of target and nontarget species as part of the release permit. These recommendations may initially be advanced through reassessment of current policies but may in the longer term require the implementation of dedicated biocontrol legislation.

Neotropical bracken fern invades disturbed forests and burned and abandoned pastures in Latin America, inhibiting the growth of associated vegetation and altering community structure. Cutting of all aboveground vegetation every 6 to 12 mo has proven to be inefficient as a control method. We studied the impact of selective cutting of bracken every 2 mo, shading, and a combination of cutting shading during 14 mo in a bracken-dominated, abandoned pasture in Veracruz, Mexico. At the end of the experiment, cutting with or without shading drastically reduced bracken cover from >90% to less than 1%, decreased leaf number from 18 to fewer than two leaves per m², and depleted bracken leaf biomass. The significant reduction of bracken was correlated with a significant 3.9- to 5.7-fold increase in richness of other plant species. Cutting without shading was the only treatment that significantly reduced rhizome biomass to less than 62% of control plots, whereas cutting shading was the only treatment to promote a significant increase in both cover and shoot biomass of successional plant species. Selective cutting of P. arachnoideum repeated every 2 mo was more successful than nonselective cuttings repeated at longer intervals, because it removed newly emerging leaves before their complete expansion and supported the recovery and reestablishment of other plant species, which may help to control bracken. Although costs for the first year of selective cutting were twice as much as for nonselective cutting, it may prove less expensive and more efficient than nonselective cutting in the long term.

Nomenclature: Bracken, Pteridium spp., Neotropical bracken fern, Pteridium arachnoideum (Kaulf.) Maxon.

Management Implications: The selective cutting of bracken leaves and the removal of all leaf litter is a viable strategy to restore abandoned, bracken-infested pastures. Selective cutting of bracken promotes the establishment and recovery of pasture species, which help to control bracken. Repeated cutting should be performed according to the rate of bracken regrowth at each site and should always be applied before newly emerging leaves have completely expanded and begun to return photosynthetic products back into the rhizome. After six subsequent cuttings, bracken cover should be less than 1%. In tropical humid climates, cutting should be performed up to six times per year because of continuous plant growth throughout the year. Monitoring the reduction of the rhizome biomass within 1 m soil depth may serve as an indicator of the success of treatments. Trenches of 1 m in depth dug along the peripheral zone may halt further vegetative expansion of bracken rhizomes.

Restoration in Mediterranean-climate grasslands is strongly impeded by lack of native propagules and competition with exotic grasses and forbs. We report on a study testing several methods for exotic plant control combined with planting native grasses to restore prairies in former agricultural land in coastal California. Specifically we compared tarping (shading out recently germinated seedlings with black plastic) once, tarping twice, topsoil removal, herbicide (glyphosate), and a control treatment in factorial combinations with or without wood mulch. Into each treatment we planted three native grass species (Elymus glaucus, Hordeum brachyantherum, and Stipa pulchra) and monitored plant survival and cover for three growing seasons. Survival of native grass species was high in all treatments, but was slightly lower in unmulched soil removal and control treatments in the first 2 yr. Mulching, tarping, and herbicide were all effective in reducing exotic grass cover and enhancing native grass cover for the first 2 yr, but by the third growing season cover of the plant guilds and bare ground had mostly converged, primarily because of the declining effects of the initial treatments. Mulching and tarping were both considerably more expensive than herbicide treatment. Topsoil removal was less effective in increasing native grass cover likely because soil removal altered the surface hydrology in this system. Our results show that several treatments were effective in enhancing native grass establishment, but that longer term monitoring is needed to evaluate the efficacy of restoration efforts. The most appropriate approach to controlling exotics to restore specific grassland sites will depend not only on the effectiveness, but also on relative costs and site constraints.

Nomenclature: Glyphosate, blue wild rye, Elymus glaucus Buckley, meadow barley, Hordeum brachyantherum Nevski, purple needlegrass, Stipa pulchra Hitchc.

Management Implications: Restoring California grasslands requires extensive efforts to reduce competition with exotic grasses and forbs and reintroduction of native species. Herbicides are frequently used to control exotic species, but given various concerns about their negative effects, cost-effective non-chemical strategies are needed. We compared five strategies for controlling exotic species in former agricultural lands to restore California coastal prairie species: tarping (shading out recently germinated seedlings with black plastic) once, tarping twice, topsoil removal, glyphosate herbicide, and wood mulch. Into each treatment we planted three native perennial grass species (blue wild rye, meadow barley, and purple needlegrass) and monitored plant survival and cover for three growing seasons. Our results show that using black plastic tarps to shade out recently germinated seedlings and applying wood mulch are both effective non-herbicide methods for reducing exotic grass cover and enhancing native grass cover in the initial stage of grassland restoration. Both approaches, however, are considerably more expensive than using herbicides unless they can be done with volunteer labor. Overall, tarping twice was no more effective than tarping once, so we do not recommend a second tarping. Removing topsoil resulted in a sufficient change in hydrology that the sites experienced extended flooding in the first year which reducing native grass survival, but this approach may be more effective in sites with different topography. The effectiveness of our restoration treatments declined substantially by the third year, highlighting the importance of ongoing monitoring to compare the efficacy of restoration strategies, combined with continued exotic control. Herbicide, tarping, and mulch were all effective in reducing exotic grasses for the first 2 yr of restoration. The most cost-effective strategy for reducing ex

Introduced exotic plants can drive ecosystem change. We studied invasion and establishment of Brassica tournefortii (African mustard), a noxious weed, in the Chemehuevi Valley, western Sonoran Desert, California. We used long-term data sets of photographs, transects for biomass of annual plants, and densities of African mustard collected at irregular intervals between 1979 and 2009. We suggest that African mustard may have been present in low numbers along the main route of travel, a highway, in the late 1970s; invaded the valley along a major axial valley ephemeral stream channel and the highway; and by 2009, colonized 22 km into the eastern part of the valley. We developed predictive models for invasibility and establishment of African mustard. Both during the initial invasion and after establishment, significant predictor variables of African mustard densities were surficial geology, proximity to the highway and axial valley ephemeral stream channel, and number of small ephemeral stream channels. The axial valley ephemeral stream channel was the most vulnerable of the variables to invasions. Overall, African mustard rapidly colonized and quickly became established in naturally disturbed areas, such as stream channels, where geological surfaces were young and soils were weakly developed. Older geological surfaces (e.g., desert pavements with soils 140,000 to 300,000 years old) were less vulnerable. Microhabitats also influenced densities of African mustard, with densities higher under shrubs than in the interspaces. As African mustard became established, the proportional biomass of native winter annual plants declined. Early control is important because African mustard can colonize and become well established across a valley in 20 yr.

Nomenclature: Brassica tournefortii Gouan BRSTO.

Management Implications: Our models of African mustard invasion and establishment in the western Sonoran Desert have broad application for designing surveillance and monitoring systems in other arid and semiarid lands in the American West. With this study we now know that topography (major and small ephemeral streams or “washes” in valleys) and ages of geological deposits and soils are important predictors of sites for African mustard invasion. In addition to roads, African mustard is most likely to invade and colonize areas through active major and minor ephemeral stream channels, especially where these features are numerous on the landscape or intersect highways and roads. These features are highly vulnerable because they are naturally disturbed and composed of young geological deposits (1 to 7 yr old). Less vulnerable are older deposits associated with desert pavements (20,000 to 300,000 yr old), and least vulnerable are the oldest geological deposits (140,000 to 300,000 yr) with well-developed desert pavements. Weed control specialists and land managers can use existing regional maps of topography, surficial geology, and landforms, coupled with aerial imagery, to design surveillance systems that emphasize ephemeral stream channels and young geological surfaces. Aerial views of desert ephemeral stream channels suitable for mapping can be obtained from sources such as the National Agricultural Imagery Program. Monitoring for evidence of arrival and early invasion can be achieved by walking transects several kilometers in length, both up and down stream channels, and where such channels cross or parallel roads or other disturbed areas. When the mustard is located, weed control specialists can take action to eradicate or limit spread with herbicides, which can be more effective and less costly than physical methods. Timing of herbicide application, i.e., at an early phenological stage, may determine effectiveness in controlling not only the mustard but also other exotic plant species. Herbicides that do not negatively affect native annuals (based on limi

African rue is a poisonous, perennial forb that readily invades salt-desert shrub and sagebrush-steppe rangelands. Information detailing options for integrated management of African rue is lacking. To date, a few studies have researched the efficacy of different herbicides for controlling African rue, but none have investigated integrated approaches to its management. Broadcast applications of imazapyr at three rates (0.275, 0.55, and 0.85 kg ae ha⁻¹) were made, with and without a prior mowing treatment, to African rue when it was in full bloom. Imazapyr resulted in significant reductions in both the cover and density of African rue, regardless of application rate or mowing treatment (P < 0.05). Mowing had no effect on African rue cover or density (P > 0.05). Higher rates of imazapyr resulted in significant reductions in the cover of native perennial bunchgrasses (P < 0.05), whereas the low rate did not affect perennial grass cover, regardless of mowing treatment (P > 0.05). Integrating a mowing treatment with imazapyr applications was less effective for controlling African rue than applying herbicide alone. Mowing before imazapyr application did not increase survival of perennial grasses. Our results suggest that the recommended rate of imazapyr for controlling African rue (0.85 kg ae ha⁻¹) could be reduced by as much as one-third on dry floodplain ecological sites within the northern Great Basin without comprising its effectiveness for controlling African rue. This lower rate would reduce nontarget damage to native perennial grasses, which are the dominant functional group in the herbaceous understory. Less damage to native perennial grasses would probably accelerate understory recovery and help prevent invasion by other invasive species.

Nomenclature: Imazapyr, African rue, Peganum harmala L.

Management Implications: African rue (Peganum harmala L.) is a poisonous, exotic, perennial desert forb that has the potential to cause extensive ecological and economic losses in the western United States. Broadcast applications of imazapyr at three rates (0.275, 0.55, and 0.85 kg ae ha⁻¹) were made, with and without a prior mowing treatment, to African rue during full bloom. The current rate recommended for control of African rue using broadcast applications of imazapyr is 0.85 kg ae ha⁻¹. Results of this study suggest that this rate can be reduced by as much as one-third on sagebrush–steppe rangeland without comprising the short-term effectiveness of imazapyr for controlling African rue; however, follow-up treatments or restorative actions may be required to sustain long-term control of African rue and to prevent invasion by exotic annual species. In addition, our results indicate that perennial bunchgrasses readily recover from imazapyr application rates of 0.55 kg ae ha⁻¹ or less, whereas rates of 0.85 kg ae ha⁻¹ resulted in suppression of desirable perennial grasses for 2 yr or more. Limiting damage to native perennial grasses is important because this functional group dominates the understory in noninvaded plant communities and, therefore, is critically important for preventing invasions by exotic plants in sagebrush–steppe rangelands.

Black henbane can be either annual or biennial. We investigated which life cycle is found in four introduced western North American populations. Plants were grown in a greenhouse common garden until half were vernalized by exposure to natural winter temperatures, while the other half remained in the greenhouse above 20 C, with 16 h of light and 8 h of dark. In total the plants were monitored 313 d after germination. We measured whether plants bolted, the time it took for bolting to commence, and the size at bolting. All vernalized plants bolted after 117 d of active growth (within 26 d of the end of the vernalization treatment), whereas only 26% of the nonvernalized plants bolted after an average of 278 d of active growth. Vernalized plants bolted at a smaller size than the nonvernalized plants that bolted (28 vs. 41 leaves on average). In the nonvernalized plants, the relationship between time to bolting and size was strong, but not so with the vernalized plants. Our results indicate that introduced black henbane plants are biennial, and that vernalization is more critical to bolting and flowering than reaching a certain size. Nonetheless, the fact that nonvernalized plants were capable of bolting if grown long enough suggests that vernalization is not the only cue that can trigger reproduction in introduced populations.

Nomenclature: Black henbane, Hyoscyamus niger L. HSYNI.

Management Implications: Knowledge of the life cycle of an introduced plant is a fundamental component of its successful management. Black henbane (Hyoscyamus niger) is a state-listed noxious weed that is toxic to both livestock and humans. There is surprisingly little information on the introduced populations in North America. We explored whether introduced populations follow an annual life cycle, biennial life cycle, or both. We first collected seeds from several naturalized populations. The seeds were germinated, and the resulting plants were grown in a common environment in Fort Collins, CO. We then subjected half of the plants to a winter cold treatment (vernalization), while the other half remained in the greenhouse. All plants sampled appeared to be biennials, with cold being required for timely flowering. This has important implications for the potential of black henbane to spread: it is likely limited to areas that experience at least 10 wk of cold (3 to 11 C) winter temperatures. Combining this information with this species being a poor competitor, requiring open space to thrive, we can infer that it will perform best in fairly open western North American environments with a cold winter. Additionally, given that it is biennial, where active management is necessary in the western United States, monitoring and managing populations over multiple years will likely be key to effective control. Finally, it is critical to guard against the introduction of annual henbane plants to North America. Currently, USDA-APHIS requires a permit to import any part of the black henbane plant or plant products into the United States. Adhering to the current set of national regulations will help limit the range of naturalized black henbane populations.