We analyzed the recent (< 25 yr) spread in New Hampshire, USA, of the exotic tree Kalopanax septemlobus, native to Asia. The invasion was likely initiated by a single tree planted ca. 1972. Our objective was to assess the viability of the invasion, especially in light of the small propagule size. We tallied, mapped, aged, and measured the height and growth of K. septemlobus individuals at two sites, the University of New Hampshire campus (UC) and Thompson Farm (TF), both in Durham. We found over 3,800 plants at UC and 270 at TF in < 120 ha (296 ac) total area. Plant age ranged from 0 to 22 yr, and UC plants were as far as 775 m (2,543 ft) from the purported parent tree. Annual height growth was comparable to midtolerant native trees. Plants occurred in both open and forested habitats, and the mean level of photosynthetically active radiation incident on understory plants was 4 to 6% of full sun. The large population size, shade tolerance, rapid height growth, and ability to sprout from damaged stems suggest potential for K. septemlobus to invade and persist in forests, the most common natural ecosystem in the northeastern United States. We further suggest that small propagule size, likely a single tree, has not prevented K. septemlobus from initiating a spatially extensive and vigorous population. Kalopanax septemlobus has been planted as an ornamental in the northeastern United States, and prevention of region-wide invasion might depend on removal of these trees, even when they occur as single individuals.

Nomenclature: Castor-aralia, Kalopanax septemlobus (Thunb.) Koidz.

Management Implications: Castor-aralia (Kalopanax septemlobus) is capable of spreading via seed from planted individuals to urban and natural forest landscapes in southeastern New Hampshire. The invaded forest types, eastern white pine and sugar maple–beech–red oak, are common in the northeastern United States. Although the impact of castor-aralia on North American communities and ecosystem processes is not yet known, colonization of forest understories and rapid height growth there suggest it is capable of competing with economically important native plants. At present, early detection coupled with rapid removal is a sensible strategy.

Because a single castor-aralia individual is capable of seed production, even small populations and isolated individuals should be eradicated. The large potential dispersal distance and success of seedlings in human-influenced habitats means that even isolated plants in urban environments, including those at urban arboretums, should be removed. Data on age and size of first reproduction are limited, but generally trees must be > 20 cm in diameter at breast height or in their second decade of life before they produce seed. Consequently, in populations of diverse age and size, trees exceeding these values should have first priority for removal. The long juvenile period also means that once all trees have been removed from a site, a second round of control need not occur for ca. 10 yr.

No data on herbicide effects are available for castor-aralia, but plants can be killed by uprooting. The ability of cut plants to produce root and butt sprouts, however, means that removal of entire plants including major roots is essential.

Brachypodium sylvaticum, a shade-tolerant, forest dwelling, and aggressive invasive grass native to Eurasia, is a noxious weed in California, Oregon, and Washington. This species could cause ecosystem collapse by altering forest fire regimes. To examine interactions with fire, we divided two Willamette National Forest sites into eight units and randomly selected half for treatment with prescribed fire in spring 2011. We assessed the effect of B. sylvaticum on fire (severity and intensity) as well as the effect of fire on B. sylvaticum (cover, seedling emergence, and dispersal). We found that B. sylvaticum cover decreased fire severity but had no effect on intensity. Furthermore, fire severity influenced B. sylvaticum cover; in areas receiving low-severity fire, the grass increased from 21 ± 15.05 to 34 ± 15.81%, but in areas of high-severity fire, cover remained consistently around 0% (0 ± 0% cover in yr 1 to 0.2 5± 0.25% in yr 3). In the field, prescribed fire decreased seedling emergence by 32% compared to controls, but not in an associated greenhouse experiment. However, in the greenhouse, severely burned plots had zero emergence, compared to 0.29 ± 0.14 seedlings low-severity m⁻² plot. Fire severity also influenced dispersal in the field; we monitored plots with < 0.5% cover B. sylvaticum initially; when these plots experienced low severity fire, they had greater B. sylvaticum cover (increasing 1,200%), suggesting increased dispersal with less severe fires. High-severity dispersal plots did not experience increased cover. High severity fires have the potential to control the grass, but low-severity fires will likely increase its cover.

Nomenclature: False brome, Brachypodium sylvaticum (Huds.) Beauv.

Management Implications: In the conifer forests of the Pacific Northwest, the nonnative grass Brachypodium sylvaticum (false brome) is forming "lawns" in forests that have never had continuous grass cover. Can prescribed fire be used to control this invasive grass that decreases tree germination and growth? Our results suggest that if a uniform, high-severity fire can be achieved and sustained, this method of treatment can be used to control B. sylvaticum. Unfortunately, fires do not often burn uniformly, but instead usually create mosaics of varying severity across a landscape, thus rendering this objective challenging. The stakes are high given that we showed that low-severity burns actually increase the seedling emergence, apparent dispersal, and cover of B. sylvaticum. Therefore, it is difficult to prescribe fire to control the grass. However, if prescribed burns are being used anyway for other reasons, or if natural fires occur, then there is opportunity for controlling B. sylvaticum by adding in on-the-ground control methods (such as herbicide or mechanical removal) in the less-severely burned zones.

The macrophyte swamp stonecrop has invaded a wide range of wetland habitats across Europe. An experiment was conducted within an invaded fen habitat, which tested whether the presence of grazing disturbance affected the relative abundance of swamp stonecrop, and whether any detected effect was suppressive or facilitative. The abundance of swamp stonecrop and co-occurring resident plants was monitored within fenced grazing exclosures and in adjacent unfenced plots. Swamp stonecrop abundance was higher in the unfenced plots compared to the fenced exclosures (t₍₈₇₎  =  28.974, P < 0.001), whereas the abundance of co-occurring plants was higher in the fenced exclosures compared to the unfenced plots (t₍₈₇₎  =  6.264, P < 0.001). These results indicate that the presence of large vertebrates could facilitate a higher abundance of swamp stonecrop in situations where competitive resident plant species were selectively removed by these grazing animals.

Nomenclature: Swamp stonecrop, rassula helmsii (Kirk) Cockayne.

Management Implications: It is important to understand the efficacy of management practices designed to increase native plant diversity in communities that have been invaded by a nonnative invasive plant. The results from this study suggest that in fen habitats, disturbance from vertebrate grazing animals along drawdown zones facilitates the development of high Australian swamp stonecrop (Crassula helmsii (Kirk) Cockayne) abundance. If replications of this experimental design produce concurrent results, it could be concluded that wetland habitat grazed by livestock is particularly vulnerable to C. helmsii colonization and the extensive spread of this species. It would therefore follow that land managers of such habitat should enforce biosecurity measures to reduce the likelihood of C. helmsii propagules being introduced, and should invest time into frequently checking grazed drawdown zones for colonizing C. helmsii and act quickly to eliminate any that is found. It is advisable to prevent grazing livestock access to drawdown zones where C. helmsii already occurs, or in areas near to where C. helmsii occurs, in order to limit C. helmsii plant community dominance. Such actions would, however, present a dilemma for land managers, who would otherwise use livestock to create patches of vegetation with an open structure in order to encourage native plant species that require this type of microhabitat.

Southern California grasslands have largely been type-converted to dominance by exotic annual grasses, leading to displacement of many native grass and forb species. Crimson fountaingrass, Pennisetum setaceum, an exotic perennial C₄ species and a relatively new invader to California, is expanding to areas currently occupied by purple needlegrass, Stipa pulchra, a C₃ native. We predicted that fountaingrass seedlings might withstand cool season competition in California’s Mediterranean-type climate and establish in Stipa pulchra grasslands due to less competition during the warm, dry summer season, and that interactions might be influenced by density. A field experiment was conducted to examine competitive interactions of the two species from the cool winter season to the warm summer season. As predicted, Stipa produced greater aboveground biomass in the cool season and showed strong intraspecific competition, as well as interspecific suppression of Pennisetum growth, whereas Pennisetum showed no suppression of Stipa. In the warm season, Stipa showed relatively less suppression of Pennisetum, erasing significant differences, and Pennisetum showed increased growth. Results of this study show that C₃ Stipa can suppress initial growth of C₄ Pennisetum in the cool season, but in warmer months, Pennisetum can overcome this initial suppression at both low and high densities, even within a Mediterranean-type climate with little to no summer rainfall. Thus, in southern California, temporal niche partitioning due to photosynthetic pathway in these two species can allow Pennisetum invasion. Given the similarity in life history and growth form of Stipa and Pennisetum, few options exist for controlling Pennisetum in habitats where Stipa occurs. In these cases, restoration plantings of desirable species are essential in order to reestablish competitive vegetation that will be more resistant to invasion.

Nomenclature: Crimson fountaingrass, Pennisetum setaceum (Forsk.) Chiov.; purple needlegrass Stipa pulchra Hitchc. (synonym, Nassella pulchra (Hitchc.) Barkworth).

Management Implications: Fountaingrass is a warm-season exotic invasive grass that is adapted to extensive areas of southern California where it is able to respond to moisture with opportunistic growth year-round. Remnant native Stipa pulchra communities occur in proximity to populations of invasive Pennisetum setaceum in several coastal and inland areas in southern California. The goal of this study was to investigate establishment-stage competition of Pennisetum and Stipa. In this experiment, Pennisetum was competitively suppressed by Stipa in the early spring portion of the experiment, but ultimately thrived and set seed during the latter summer portion of the study. Results of this study are relevant to first-year grassland invasions, especially in disturbed or patchy areas where recruitment can occur largely by seed. For disturbed grassland areas with a seedbank of Stipa, newly-arrived seedlings of Pennisetum can experience suppression by Stipa in the cool season but have an opportunity to thrive later in the season, once competition from Stipa is reduced. The similar respective life histories and growth forms, as well as the overlap in phenology of these two grasses as seen here does not appear to provide a sufficient window of time to control of Pennisetum using chemical methods without injury to Stipa. Planting competitive summer annual species in these areas might provide additional competitive suppression of Pennisetum as a component of proactive management programs. With relevance to natural systems in southern Ca

Grazing represents a sustainable alternative for the control of medusahead infestations but intake of medusahead by ruminants is typically low. We determined in sheep whether (1) high-energy supplements enhance medusahead intake and preference relative to a treatment without supplementation and (2) individual differences in medusahead intake transfer to individual differences in the ingestion of a silica-containing ration. Groups of lambs (n  =  10) were individually penned and randomly assigned to three supplementation treatments: (1) Control (no supplement); (2) Calcium (Ca) Propionate (beet pulp : barley : Ca propionate, 67 : 30 : 3); or (3) Yeast (beet pulp : barley : yeast culture, 65 : 30 : 5). After supplementation, all animals had ad libitum access to medusahead in late vegetative to mid-reproductive (Trial 1), and late-reproductive phenological stages (Trial 2). Medusahead preferences were assessed by offering sheep a choice between medusahead and tall fescue hay. Plant part preferences were assessed by offering a choice between medusahead tops (mostly seedheads and awns) and mid-plant parts (mostly stems leaves). Intake of medusahead was low and cyclic, declining towards the end of each trial (P < 0.0001) and there were no treatment differences (P > 0.10). Lambs preferred tall fescue hay to medusahead and medusahead tops to mid-plant parts (P < 0.0001). Supplemented lambs gained more weight than control lambs (P < 0.10). Thus, supplemented lambs performed better than nonsupplemented controls without reducing their intake of medusahead. In Trial 3, two new groups of lambs were formed based on their intake of medusahead during Trials 1 and 2 (n  =  10). One group consistently ate more medusahead and more of a ration containing silica (alfalfa : silica, 97 : 3) than the other (P < 0.10). A significant and consistent degree of individual variation was measured among lambs—irrespective of treatment—regarding their ability to ingest medusahead and silica. This variation represents a promising option for maximizing use of medusahead by livestock in rangelands.

Nomenclature: Medusahead, Taeniatherum caput-medusae (L.) Nevski.

Management Implications: High-energy supplements containing glucogenic agents (Ca propionate) or yeast cultures (S. cerevisiae fermentation products) did not increase medusahead use by lambs relative to unsupplemented animals. However, our results suggest that supplementation programs can improve the production of grazing animals in targeted grazing treatments without depressing the ingestion of medusahead relative to unsupplemented (i.e., forced to ingest medusahead) animals. Intake of medusahead was low and cyclic suggesting a metabolic constraint which restricts the amount of forage consumed by an animal on a daily basis. However, a significant degree of individual variation was measured in the animals under study—irrespective of treatment—suggesting that these differences were more relevant than the treatments used to enhance intake of the weed. Individual differences in medusahead intake by livestock represents a promising option for maximizing use of medusahead by livestock on rangelands.

Chinese tallowtree is an invasive tree found throughout the southeastern United States and in California. Its negative effects can be seen in numerous natural and managed ecosystems, including bottomland hardwood forests, pastures, pine plantations, and along lakes, ponds, streams, and rivers. Despite its troublesome presence for many decades, relatively few effective control strategies are available. Root sprouting following management efforts is a major impediment to successful control. Studies were conducted in Alabama and Louisiana at three locations to test several herbicides for cut stump, basal bark, and foliar individual plant treatment (IPT) methods. Herbicide treatments included triclopyr amine and ester formulations, imazamox, aminopyralid, aminocyclopyrachlor, and fluroxypyr. Data were collected just before leaf senescence at one and two growing seasons after treatment and included Chinese tallowtree foliar cover, number of stump or root collar sprouts, and number of sprouts originating from lateral roots within a 1-m radius of each tree. For the cut stump and basal bark studies, most herbicide treatments prevented sprouting from the stump or root collar region better than they did from the lateral roots. Aminopyralid reduced total sprouting better than all other treatments in the cut stump study. The high rates of aminocyclopyrachlor and fluroxypyr resulted in the highest mortality in the basal bark study. Aminocyclopyrachlor reduced total sprouting better than all other herbicides in the foliar treatment study. Triclopyr amine and ester formulations, which are commercial standards, did not consistently control Chinese tallowtree across these IPT studies. These studies provide some promising treatments to increase the number of effective tools that can be used to manage Chinese tallowtree. Additional research is needed to address the prolific nature of lateral root sprouting following any of these treatment methods.

Nomenclature: Aminocyclopyrachlor; aminopyralid; fluroxypyr; imazamox; triclopyr; Chinese tallowtree, Triadica sebifera (L.) Small.

Management Implications: Chinese tallowtree is an increasing problem across the southeastern United States. However, there is little published research examining effective control methods. We compared several newer herbicides with the commercial standards triclopyr ester and triclopyr amine for foliar, cut stump, and basal bark individual plant treatment (IPT) methods in natural areas. We examined both root collar and lateral root sprouting response to herbicide treatment, which is rarely done in invasive plant studies. We found that aminocyclopyrachlor, aminopyralid, fluroxypyr, and imazamox all controlled Chinese tallowtree similar to, or better than, triclopyr in specific IPT studies. Aminocyclopyrachlor resulted in greater mortality of Chinese tallowtree than triclopyr did in foliar and basal bark studies, whereas aminopyralid was more effective than triclopyr in cut stump studies. Fluroxypyr resulted in greater mortality than triclopyr in cut stump and basal bark studies but not in foliar studies. This research highlights the strong need to continue to evaluate new tools for invasive plant control and the need to continuously collect better data on invasive plant responses to treatment.

An ecosystem’s invasibility is influenced by changes in biotic and abiotic resistances, which often occur due to shifts in the prevailing disturbance regime. The susceptibility of a community to intrusion by nonnative species may interact with propagule pressure to determine the extent of a biological invasion. We examined how propagule pressure, forest community structure, and disturbance interact to influence the invasibility of temperate Pacific Northwest forests by the newly invasive grass, perennial false-brome (Brachypodium sylvaticum). Our goal was to identify factors enabling shifts from establishment to population growth in B. sylvaticum populations at the edge of its expanding range. Ecological sampling methods were used to identify patterns in B. sylvaticum habitat. An inverse relationship between the amount of B. sylvaticum and all perennial vegetation types and soil litter depth was found, suggesting that disturbance might play a role in B. sylvaticum population establishment or growth. An experimental study was then performed to test the effects of disturbance, propagule pressure, and habitat on B. sylvaticum seedling establishment in sites where B. sylvaticum was already naturalized. We found evidence that disturbance of the soil and vegetation led to increased B. sylvaticum seedling recruitment within naturalized sites, especially where conditions of high propagule pressure and deciduous forest canopy existed. In contrast, B. sylvaticum populations dominated by coniferous forest canopy were much more invasible than deciduous forests and did not show increased seedling recruitment in response to our disturbance treatments. Our study shows how propagule pressure and plant community dynamics interact to alter the invasibility of Pacific Northwest forests allowing B. sylvaticum to transition from establishment to population growth thus allowing this weed to cause greater negative impacts on the ecosystem.

Nomenclature: Perennial false-brome, Brachypodium sylvaticum (Huds.) P. Beauv. BRSY.

Management Implications: The results of this study reinforce the growing consensus that avoiding or minimizing disturbance of native vegetation is one of the best ways to prevent exotic plant invasion. Native vegetation growing near Brachypodium sylvaticum populations or in areas at risk of B. sylvaticum introduction should be harmed as little as possible during human activities, whereas disturbed areas should be replanted with appropriate native plants as soon as possible after the disturbance. Our research also shows that propagule pressure (the amount and frequency of reproducible units entering a site), in this case seed rain and soil seed bank, is primarily responsible for the severity of B. sylvaticum invasion. Thus B. sylvaticum population growth and spread could be minimized by discouraging B. sylvaticum seed-set by mowing, weed-whacking, or hand-pulling the flowering culms before seeds have matured (typically before mid-August). Care should be taken to limit disturbance of intermixed native vegetation while doing this. Consistently cleaning shoes, clothing, and equipment that have come in contact with B. sylvaticum populations should also greatly help discourage its spread into new sites. Informational signage and cleaning stations positioned at trailheads frequented by the public where B. sylvaticum is prevalent may also help educate citizens of the role they can play to help conserve natural area biodiversity and facilitate their participation. Finally, while our study did not show hemlock mulch to suppress B. sylvaticum establishment, deciduous leaf cover (big-leaf maple, red alder, and black cottonwood)was associated with lower germination and establishment, and therefore may be a fruitful material for experimental

Energy-extraction disturbances entail soil handling and often have large edge-to-area ratios. These characteristics should be considered when designing weed-control strategies. In western North America, many energy developments coincide with infestations of downy brome, an annual grass that severely curtails productivity, diversity, and habitat value of invaded areas. Downy brome is sensitive to soil compaction and seed burial, both of which may occur when soil is handled. In this study, I examined the effect of soil-density manipulations and herbicide application (105 g ai ha⁻¹ imazapic with 280 g ai ha⁻¹ glyphosate) on six simulated pipeline disturbances in a Wyoming big sagebrush ecosystem invaded by downy brome. Disturbances occurred at the end of the growing season, after ambient downy brome seed rain in the study areas had abated. Treatments and seeding occurred shortly after disturbances. The following spring, downy brome seedling density was 10-fold lower within disturbances than in control areas, but seedling density quickly rebounded in disturbed areas where no herbicide had been applied. In herbicide plots, downy brome seedling density remained low during the first growing season, and shrub cover after 3 yr was eight times higher than in no-herbicide plots. Soil density manipulations via disking and rolling treatments had little effect on downy brome. Prior research has shown that imazapic is more effective when combined with disturbances, such as fire. This study demonstrates that imazapic may also be effective in combination with a disturbance that is timed to bury downy brome seeds.

Nomenclature: Glyphosate; imazapic ammonium salt; downy brome, Bromus tectorum L. BROTE; Wyoming big sagebrush, Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young ARTRW8.

Management Implications: Downy brome (Bromus tectorum L.) often increases after disturbances, but disturbances that turn the soil over can also be used to help control downy brome because downy brome seeds are sensitive to burial and soil compaction. Success may depend on the timing of the disturbance, and on coupling the disturbance with other measures to help control downy brome. In this experiment, we assessed the effectiveness of 105 g ai ha⁻¹ imazapic plus 280 g ai ha⁻¹ glyphosate coupled with simulated pipeline disturbances. Pipeline disturbances were simulated by scraping vegetation, removing topsoil, and digging trenches, followed by refilling trenches and replacing topsoil. Disturbances occurred in September 2008, directly following the period of downy brome seed distribution for the season. Herbicide application was crossed with tillage treatments (control, disked, rolled, rolled plus disked, and rolled by vibratory drum) applied within pipeline disturbances to further examine how soil compaction affects downy brome. As disturbances occurred in areas already compromised by downy brome, the initial effect of the disturbance was a 10-fold reduction in downy brome density. Where imazapic was applied, this reduction persisted through the first growing season after the disturbance. Where imazapic was not applied, downy brome densities quickly rebounded to values similar to undisturbed areas. Three years after treatment, downy brome cover was twofold lower and shrub cover was eightfold higher where herbicide had been applied than where it was not applied. The tillage treatments had little effect on downy brome density or cover, possibly because the disturbances themselves had already achieved the goal of burying downy brome seed under slightly compacted soil. In the study area, downy brome seeds distributed throughout the growing season and prior work has shown that downy brome seeds distribute much more readily over bare soils than they do in intact ecosystems. The success of restoration in this study may be related to t

Rural landscapes are increasingly diverse and heterogeneous, involving a mix of small and large parcels, amenity and agricultural properties, and resident and absentee owners. Managing invasive plants in landscapes with changing ownership requires understanding the views and practices of different landowners. We surveyed landowners in two rural valleys with 26% absentee ownership and a large number of small parcels in Missoula County, Montana. Landowners indicated a high level of awareness and concern about weeds; more than 80% agreed that weeds are a problem in their valley. Seventy-eight percent of landowners managed weeds, but only 63% were effective at weed management. Absentee owners were far less likely to manage weeds on their properties and less likely to utilize herbicides, as compared with resident landowners. Landowners reported that seeds coming from adjacent properties were the most significant barrier to effective weed control. Many landowners manage weeds to be a good neighbor and believe that cooperation between neighbors is critical to weed management.

Management Implications: Most rural areas have a diversity of landowners with a range of parcel sizes and management goals. Many of these landscapes are experiencing an influx of amenity migrants and absentee landowners, increasing the number of landowners responsible for weed management. Weed managers and extension agents can benefit from a better understanding of the views and practices of these landowners so that they can develop programs to meet landowner needs. Based on a survey of rural landowners in western Montana, we recommend that in landscapes with a diversity of landowners, practitioners emphasize a range of weed management approaches (from herbicides to biocontrols) and benefits (from wildlife habitat to scenic beauty). In particular, landowners who are concerned about the safety of herbicides might need information on alternative methods. Because absentee landowners are less likely to manage weeds, managers need to find ways to engage these landowners in weed management. Effectively engaging absentee landowners might require innovative communication strategies that involve neighbors, emails, and real estate agents. Further, because seeds coming in from neighboring properties are often seen as a major barrier to effective weed management, engaging a broad range of landowners, including absentee landowners, is critical. Weed managers, extension agents, and community groups can organize landowners and small groups of neighbors to share information, resources, and labor, and build social norms about appropriate weed management.

Waterhyacinth is a free-floating aquatic weed that is considered a nuisance worldwide. Excessive growth of waterhyacinth limits recreational use of water bodies as well as interferes with many ecological processes. Accurate estimates of biomass are useful to assess the effectiveness of control methods to manage this aquatic weed. While large water bodies require significant labor inputs with respect to ground-truth surveys, available technology like remote sensing could be capable of providing temporal and spatial information from a target area at a much reduced cost. Studies were conducted at Lakes Columbus and Aberdeen (Mississippi) during the growing seasons of 2005 and 2006 over established populations of waterhyacinth. The objective was to estimate biomass based on nondestructive methods using the normalized difference vegetation index (NDVI) derived from Landsat 5 TM simulated data. Biomass was collected monthly using a 0.10m² quadrat at 25 randomly-located locations at each site. Morphometric plant parameters were also collected to enhance the use of NDVI for biomass estimation. Reflectance measurements using a hyperspectral sensor were taken every month at each site during biomass collection. These spectral signatures were then transformed into a Landsat 5 TM simulated data set using MatLab® software. A positive linear relationship (r²  =  0.28) was found between measured biomass of waterhyacinth and NDVI values from the simulated dataset. While this relationship appears weak, the addition of morphological parameters such as leaf area index (LAI) and leaf length enhanced the relationship yielding an r²  =  0.66. Empirically, NDVI saturates at high LAI, which may limit its use to estimate the biomass in very dense vegetation. Further studies using NDVI calculated from narrower spectral bands than those contained in Landsat 5 TM are recommended.

Nomenclature: Waterhyacinth, Eichhornia crassipes (Mart.) Solms EICCR.

Management Implications: Typically, the biomass of waterhyacinth is estimated using quadrats with a specific unit area placed over the plant mat. However, it is labor and time intensive to collect and process samples. Moreover, this method is destructive because it removes plant material from the system which affects long term studies of plant growth. The normalized difference vegetation index (NDVI) is a well-known vegetation index that can be used to monitor aquatic plants. However, limitations due canopy complexity during the growing season often limit its use. Based on the results, NDVI alone is not sufficient to estimate the biomass of waterhyacinth. The poor predictive performance of band 4, as well as canopy complexity related to waterhyacinth phenology during the growing season and vegetation cover/water background ratio likely affected the performance of NDVI. According to this study, measuring morphometric parameters such as leaf area index may enhance the performance of NDVI derived from Landsat 5 TM or other multispectral sensors with same spectral resolution. Therefore, the sole use of NDVI from Landsat 5 TM is not recommended to estimate the biomass of waterhyacinth. It is suggested that large-scale waterhyacinth management would consider NDVI derived from other multispectral sensors (e.g. Landsat 8 OLI). Current results could be useful to test new multispectral or hyperspectral sensors for aquatic vegetation management.

The invasive aquatic plant hydrilla rapidly spread through the 28,500 ha Kissimmee Chain of Lakes (KCOL) system in Florida in the late 1980s and early 1990s. Large-scale herbicide treatments with fluridone were initiated in 1993 and resulted in widespread reduction in hydrilla; however, by 2000, sustained use of fluridone resulted in dominance of fluridone-resistant strains of hydrilla throughout these lakes. The last large-scale fluridone applications on the KCOL were conducted in 2004, and in 2012, a sampling effort was initiated to determine the status of fluridone-resistant strains of hydrilla given an 8-yr period with no further selection pressure from fluridone. A total of 260 sites were sampled on the lakes during March, May, September, and December 2012. Plants were returned to the lab and exposed to fluridone at concentrations of 5, 10, and 20 μg L⁻¹ and a pulse-amplitude-modulated (PAM) fluorometer was utilized to measure fluorescence yield of new shoot tissue growth following a 14-d exposure period. Results indicate that 80 to 90% of the sites sampled on the four lakes of the Kissimmee Chain remain resistant to fluridone. Three distinct patterns of response to fluridone were noted, suggesting that susceptible, moderately tolerant, and highly tolerant strains of hydrilla currently coexist on these lakes. Although fluridone-susceptible plants were present on the KCOL, this study clearly demonstrates that most of the hydrilla remained resistant despite an 8-yr period with no fluridone selection pressure.

Nomenclature: Fluridone; hydrilla, Hydrilla verticillata (L.f). Royle HYLLI.

Management Implications: In this case study we evaluated the frequency of fluridone-resistant hydrilla on the 28,500 ha Kissimmee Chain of Lakes, FL, 8 yr following the last large-scale fluridone application. Resource managers had become highly reliant on whole-lake use patterns of fluridone, and they particularly favored the cost effectiveness, selectivity, low-use volumes, and the limited water-use restrictions on the label. We hypothesized that a series of hurricanes and large-scale hydrilla management with alternate herbicide modes of action would result in a higher frequency of fluridone-susceptible hydrilla given the 8-yr absence of fluridone pressure. The source of the susceptible hydrilla was an extensive tuber bank that can persist in the sediments for years. Our results suggest that fluridone-resistant hydrilla remains dominant throughout the KCOL. Although we did find areas of the lake with susceptible plants, resistant hydrilla continued to make up 80 to 90% of the overall population. Numerous managers have inquired about the potential for Florida lakes to revert to fluridone-susceptible populations. Our results suggest this is an unlikely scenario in the KCOL because the resistant plants remain both widespread and dominant.

Lake Pend Oreille is the largest (36,000 ha or 91,000 ac) freshwater lake in Idaho. Approximately 27% or 10,000 ha of the lake is littoral zone habitat supporting aquatic macrophyte growth. Eurasian watermilfoil has invaded large areas of this littoral zone habitat, with early estimates suggesting approximately 2,000 ha by the mid 2000s. Idaho State Department of Agriculture developed a state-wide eradication program in response to the threats posed by Eurasian watermilfoil, which attempts to quantify Eurasian watermilfoil infestations and its effects on the native plant community. Littoral zone point intercept surveys were conducted in 2007 and 2008 to monitor the trends in aquatic macrophyte community structure and assess management strategies against Eurasian watermilfoil. Lake Pend Oreille has a species-rich aquatic macrophyte community of more than 50 species. Lake-wide, the presence of Eurasian watermilfoil significantly decreased from 2007 (12.5%) to 2008 (7.9%). The native plant community has remained stable from 2007 to 2008 despite lake-wide management activities. In managed areas, the frequency of Eurasian watermilfoil during the 2008 assessment was 23.6% after herbicide applications. This represents a 63% reduction in Eurasian watermilfoil presence from the 2007 (64.5%) survey. When 2,4-D was combined with endothall, the presence of Eurasian watermilfoil declined from 63% (2007) to 36.5% in 2008. Eurasian watermilfoil treated with triclopyr also declined significantly, 64% to 18.2%. When all treatment methods were pooled and compared with areas that were not treated, the presence of Eurasian watermilfoil was significantly greater (52.5%) in untreated areas as opposed to treated areas (23%). The removal of Eurasian watermilfoil resulted in an increase in native species in most areas. Currently, there is as little as 200 ha of Eurasian watermilfoil remaining, which represents an overall reduction of 90% in approximately 7 yr of management.

Nomenclature: Fluridone; triclopyr; 2,4-D; endothall; Eurasian watermilfoil, Myriophyllum spicatum L. MYSP2.

Management Implications: Lake Pend Oreille is a large fluctuating reservoir with a species-rich aquatic macrophyte community that shifts from early- to late-season species. The management of Eurasian watermilfoil has promoted growth of native plants. Eurasian watermilfoil was reduced by 63% at sites treated before September 2008. Results suggest that fluridone applications should be limited to areas of low water exchange to enhance efficacy. The combination of 2,4-D and endothall applied in areas of higher water exchange rates resulted in significant reductions of Eurasian watermilfoil, although the addition of a contact herbicide may have resulted in a temporary loss of some native species. Triclopyr use also resulted in a reduction of Eurasian watermilfoil frequency in treatment plots, with less effect on native plants. The combination of triclopyr and endothall in areas of high water exchange was effective in a preliminary assessment, although additional studies are needed. On the basis of our analyses, the presence of Eurasian watermilfoil was more detrimental to the native plant community than the herbicide treatments.

Weed prevention is recognized as one of the most cost-effective management strategies for invasive plants. In the field of invasive plant management increasing emphasis is being directed toward proactive management. However, land managers are still somewhat reluctant to aggressively employ prevention programs. Part of this reluctance could be due to lack of understanding of what a comprehensive prevention program entails. The purpose of this paper is to improve strategic decision-making for site-specific prevention programs, such as those on ranches or in watersheds. Our interest is in advancing prevention planning for land managers—the people who are faced with the constant pressure of potential invasive species infestations on a day-to-day basis. To facilitate more widespread use of prevention programs we are proposing definitions for key terminology to standardize and facilitate communication about prevention programs. Additionally, we present a flow model with the steps necessary to successfully implement such programs. The model has three categories from which specific prevention planning occurs: (1) education, (2) early detection and eradication, and (3) interruption of movement. The flow model directs users through a series of interlinked steps. Finally, we provide a case study in which a ranch manager implemented a prevention program using this framework. By using this model, managers are poised to conduct more strategic planning. This model also has applications in outreach and education programs to assist land managers in prevention planning.

Green spaces such as golf courses that intermingle within or exist on fringes of urban landscapes can provide opportunities for increasing the ecological value of urban areas. To that end, more naturalistic and less input-intensive “links”-style golf courses have recently gained favor over input-intensive parkland courses. The Osgood Public Golf Course in Fargo, ND is a links-style golf course set adjacent to suburban housing developments. This course incorporated large areas of prairie plantings, or “constructed grasslands,” which over time became dominated by fescue species and infested with Canada thistle. Our objective was to explore the efficacy of using prescribed fire combined with aminopyralid herbicide to control Canada thistle and promote a more diverse mix of warm-season C₄ and cool-season C₃ grasses. Aminopyralid was applied during fall 2010 and prescribed fire was applied during spring 2011. We found that aminopyralid provided excellent control of Canada thistle 1 and 2 yr post-treatment. Open niches created from Canada thistle control were readily filled by C₃ grasses, primarily fescue species, which were the dominant species on the constructed grasslands prior to treatment. Fire intensity was variable within and across plots and was associated with reductions of litter and C₃ grasses, but was not associated with increases of C₄ grasses within the time frame of this study. Our results demonstrate the effectiveness of aminopyralid for Canada thistle control in constructed grasslands. Prescribed fire maintained C₃ grass dominance while removing litter, but C₄ grass response was variable and appeared dependent on pretreatment C₄ species abundance. Reduction of litter in constructed grasslands dominated by fescue could potentially lead to microsite conditions that would favor C₄ and other C₃ species, especially if short-term management promoted additional facilitation efforts, such as repeat spring fire treatments and seeding.

Nomenclature: Aminopyralid; Canada thistle, Cirsium arvense (L.) Scop. CIRAR.

The objective of this article is to extend the reported period in which flood-distributed knotweed propagules may be successfully managed using only manual labor. During a second round of early detection and rapid response (EDRR) management along the Green River in Guilford, VT, we collected and measured all Japanese knotweed propagules that had been distributed by flooding approximately 21 mo earlier, in August 2011, at a single site. Our data suggest that knotweed s.l. prioritizes the growth of new stems over new rhizomes at the start of a growing season. Because the limiting factor for successful removal of new knotweed s.l. plants by hand is the size of the rhizome system, our findings support extending the time frame for EDRR management of flood-distributed knotweed s.l. into the second spring after its initial dispersal. Additionally, in November 2013, surveys of our work sites found no new knotweed s.l. plants in locations accessible to work crews. In addition to validating our EDRR management techniques, this implies that knotweed s.l. fragment viability does not extend past the second spring following its dispersal.

Nomenclature: Knotweed sensu lato; Japanese knotweed; Polygonum cuspidatum Siebold & Zucc.; Fallopia japonica (Houtt.) Ronse Decr.; Reynoutria japonica Houtt.

Management Implications: Continuing the summer of 2012 early detection and rapid response (EDRR) work detailed in Colleran and Goodall (2014), we manually eliminated knotweed propagules distributed by Tropical Storm Irene in August 2011 in southern Vermont, during the early spring of 2013. We collected data showing that the period of opportunity can be extended for EDRR management of flood distributed knotweed s.l. propagules beyond that which we had previously established.

Additionally, our data showed that knotweed s.l. prioritized its spring growth in aboveground biomass, nearly to the exclusion of rhizome growth. The relatively large size of second-year knotweed s.l. plants compared with other vegetation in the early spring allows for highly effective visual surveys, whereas their small rhizome network, which had yet to expand from the previous year’s growth, allows for effective manual removal of the whole plant.

Although we found no new plants in November 2013 in areas accessible to manual removal, we feel this was only because of the management conducted in May 2013, as a follow-up to our summer 2012 efforts. Knotweed propagules will sprout at any point in the growing season, and significant numbers emerged at managed sites after our 2012 work was completed. The lack of plants in November 2013 suggests that our May 2013 management activities took place after the period for propagules to sprout had closed and, therefore, effectively controlled those that emerged between management efforts.

Based on our experiences, we feel we have developed a viable method to control these plants. We suggest initial removal work be performed during the first growing season to remove the fastest-emerging plants to prevent them from establishing a vigorous rhizome network. Follow-up work must be conducted either after the first growing season or early in the second growing season to ensure eradication of plants that are slower to emerge. Such a strategy is capable of eradicating new knotweed s.l. propagules following flood events. Our findings would be complimented by research that explores the effect of various forms of flooding on knotweed propagule creation and distribution.