Aminocyclopyrachlor (AMCP) will control many invasive broadleaf weeds, but the susceptibility of desirable forbs is not widely known. Native prairie response to AMCP was evaluated near Fargo, ND, and Felton, MN, in the Northern Great Plains. Both sites had high floristic quality prior to treatment, with 33 and 80 different species at Fargo and Felton, respectively. AMCP was applied at 140 g ha−1 in July 2014 to coincide with leafy spurge and Canada thistle treatment timing. AMCP altered the plant communities and reduced foliar cover of undesirable species, high seral forbs (undisturbed stable communities), and low seral forbs (early succession in disturbed communities) at both locations at 10 and 14 mo after treatment (MAT). AMCP reduced Canada thistle and leafy spurge in Fargo and eliminated hedge bindweed, prickly lettuce, and black medic in Felton. High seral forb foliar cover was reduced at 10 and 14 MAT from 20% to 2% and 3% in Fargo and from 19% to 1.6% and 2% in Felton, respectively. The high seral forb species birdfoot violet, white panicled aster, northern bedstraw, Canada goldenrod, purple meadowrue, and American vetch were reduced at both locations. Low seral forb cover also decreased at 10 MAT from 22% to 10% in Fargo and from 12% to 1% in Felton, respectively. By 14 MAT, low seral species in Fargo recovered to 16%, but recovery was much slower in Felton and slightly increased to 1.5%. After treatment high and low seral monocot species increased at both sites, likely due to reduced competition from susceptible species. AMCP reduced richness, evenness, and diversity at both locations at 10 and 14 MAT; therefore, floristic quality declined. A decline in diversity is generally undesirable but could have beneficial effects if invasive weeds and other undesirable species are reduced or eliminated.

Japanese knotweed (Reynoutria japonica Houtt.) is an invasive Asian plant abundant along rivers in its introduced range. In riparian areas, floods and ice flows uproot the rhizomes, facilitating their dissemination downstream. Control of large, well-established R. japonica clones in riparian areas is difficult if the use of herbicides is prohibited. An alternative to controlling entrenched clones is the rapid detection and manual unearthing of rhizome fragments that have recently rooted after being deposited by floodwaters. We applied this strategy along a Canadian river where spring floods with abundant ice are recurrent. Two river stretches, with approximately 10 km of shoreline each, were selected for the fragment removal campaign. One of the stretches was heavily invaded by R. japonica, while the other was only sparsely invaded. In the heavily invaded stretch, 1,550 and 737 R. japonica rhizome fragments were unearthed in 2019 and 2020, respectively. Unearthed fragments had an average length of 27 to 32 cm. Only 21 fragments were found in the sparsely invaded stretch in 2020. Despite similar distances being surveyed, the detection and unearthing took 62% less time (overall) in the sparsely invaded than in the heavily invaded stretch. Along sparsely invaded riverbanks, a rapid response removal campaign for R. japonica cost, including transportation and labor, an estimated Can$142 (US$105) per aborted clone (i.e., fragment removed). A rapid response removal campaign is economically advantageous compared with the hypothetical eradication of large, well-established clones, but for it to be cost-effective, the time spent locating rhizome fragments must exceed the time spent unearthing them. The question is not whether rapid response unearthing is economically feasible—it is—but rather what invasion level renders the intervention practicable. In highly invaded river stretches generating thousands of fragments annually, finding and removing these fragments year after year would require a massive, unsustainable effort.

Garlic mustard is an invasive, exotic herb that is now widespread in North America. Recent research has shown that garlic mustard exudes biochemical compounds that inhibit the growth of entomopathogenic fungi. We investigated how the removal of garlic mustard would affect the abundance of entomopathogenic fungi in forest soils in eastern New York. Using a standard bioassay, we compared the abundance of entomopathogenic fungi in soil with and without garlic mustard both before and 45 d after garlic mustard had been experimentally removed. In soil from which garlic mustard had been experimentally removed 45 d earlier, the abundance of entomopathogenic fungi was restored to levels found in soil with no history of garlic mustard. These results suggest it is possible to increase the abundance of entomopathogenic fungi in the soil in a short time by eradicating garlic mustard plants from an invaded area. Recolonization by entomopathogenic fungi could be beneficial to humans if it increases the mortality of arthropods that are vectors of infectious disease, such as blacklegged ticks, but harmful if it increases the mortality of arthropods that provide valuable ecosystem services, such as bees and ants.

Paragrass is a nonnative category I invasive species in central and south Florida. This perennial grass species outcompetes native vegetation and is capable of rapid spread by vegetative reproduction. Although glyphosate and imazapyr are effective herbicides for paragrass control, the use of herbicides in certain areas may be restricted because of application timing or environmental concerns. Therefore, our objectives were to examine the effect of water depth (saturated vs. flooded) after burning or cutting, and the effect of water depth and duration after simulated roller-chopping, on paragrass regrowth under controlled conditions. In the first study, paragrass plants were cut or burned with a propane burner to 1 cm (0.39 in) above the soil surface. Plants were either watered daily (control), or were subjected to one of two water treatments: water level at the soil surface (saturated) or flooded to a depth of 44 cm. Burned-saturated or burned-flooded plants had 92% less biomass 5 wk after treatment (WAT) than cut-saturated plants. Flooding resulted in plant death regardless of the plant treatment. In the second study, simulated roller-chopping was performed by cutting paragrass stolons into one-, two-, or three-node segments; planting them into flats; and subjecting them to water treatments for 3, 7, 14, 28, and 42 d. Burning, cutting, and roller-chopping could be useful to control paragrass if subsequent flooding is applied. Future research should focus on evaluating the response of these control techniques in natural areas where water depth can be managed.

Greenhouse studies were conducted on two southern Illinois star-of-Bethlehem populations to determine the influence of chilling and bulb chipping on plant growth and reproduction. Chilling was not required for leaf emergence of dormant bulbs, but an increase to 10 wk of chilling proportionally delayed leaf emergence by 41 and 42 d for the Murphysboro and the Marion populations, respectively. Bulb chipping did reduce plant height when compared to plants from nonchipped bulbs. Also, chipped bulbs produced a greater number of small daughter bulbs compared to nonchipped bulbs; however, total bulblet production was variable and dependent on population, mother bulb size, and chipping treatment. Overall, bulb chipping did not have any negative influence on star-of-Bethlehem and might promote increased daughter bulblet production. Therefore, field operations, such as tillage, that cut and chip bulbs might actually accentuate both the spread and density of star-of-Bethlehem infestations.

English ivy (Hedera helix) is an evergreen, perennial vine that was introduced from Europe and Asia and is not endemic in much of the United States. English ivy can be invasive and difficult to control once established. Four similar, but not identical, experiments were conducted in sequence to evaluate selected, POST-applied herbicides for English ivy control. English ivy plants were propagated from cuttings and container-grown to obtain a large population of uniform plants. Aminopyralid and fluroxypyr applied at 1.34 and 0.71 kg ae ha−1, which is more twice the maximum registered rate for either herbicide, were ineffective. Glyphosate and 2,4-D amine were generally more effective, but neither herbicide provided a level of control that could be deemed consistently acceptable. Glyphosate applied at 8.51 kg ae ha−1 (the highest rate evaluated) provided 69, 98, and 89% control in the second, third, and fourth experiments as determined by foliage fresh-weight reduction relative to a nontreated control. Treatment with 2,4-D at 5.60 kg ae ha−1 (the highest rate evaluated) controlled English ivy 28, 98, and 89% in the second, third, and fourth experiments, respectively. Mixtures of 2,4-D and glyphosate were generally no more effective than were the components applied alone. Metsulfuron was the most effective herbicide. Metsulfuron applied at 0.168 kg ai ha−1 controlled English ivy ≥ 97% across the three experiments in which this treatment was included. This treatment also prevented regrowth.

Invasive species management is often more successful if desirable species are seeded after the target weed is controlled. However, control of invasive plants must be maintained following reseeding or the seeded species may fail to establish. A regional study conducted in Minnesota, North Dakota, and South Dakota evaluated the effect of aminopyralid, clopyralid, or picloram applied in the fall prior to fall-dormant seeding or seeding the following spring on cool- and warm-season native grass species establishment. Herbicides were applied at standard rates used to control invasive broadleaf weeds in the upper midwestern tallgrass prairie region of the United States. Cool-season species included Canada wildrye, green needlegrass, and intermediate wheatgrass. Warm-season species included big bluestem, little bluestem, sideoats grama, switchgrass, and Indiangrass. Aminopyralid did not reduce seedling establishment in either fall or spring seeding. Grasses generally were not affected by a pretreatment of the pyridine standards clopyralid or picloram either, with the exception of a slight reduction in fall-seeded establishment of intermediate wheatgrass. Picloram also slightly reduced fall-seeded establishment of Canada wildrye. Application of aminopyralid can safely be used to control susceptible invasive species preceding grass species establishment, with a safety margin similar to or slightly better than that with the pyridine standards clopyralid or picloram.

There is limited documentation of cross-tenure collaborative weed management programs, and no consistent set of metrics for evaluating their performance. In this study, 12 weed management practitioners in southeast Australia participated in a qualitative social research project to discuss and document examples of cross-tenure collaborative weed management and critically reflect on whether existing metrics are suitable for evaluating the performance of their programs. Analysis of focus group discussions, project documentation, subsequent reflections, and review of the literature reveal that weed management practitioners, in Australia and elsewhere, mostly rely on metrics that measure weed management inputs, such as herbicides, labor, and costs. Metrics used to evaluate social outcomes focus on benefits for individuals rather than social relationships or achievement of equitable outcomes. Social research on collaborative governance and social science methods more broadly, such as social network analysis and collective narratives, could be used by weed management practitioners to better evaluate and explain social–ecological outcomes over time.

Invasive species pose a threat to the livelihoods of many people living on rangelands of the western United States. Invasive species impact many ecosystem goods and services of the areas they invade and represent one of the largest causes of habitat degradation. On private ranches, economic analyses often find that conservation practices, such as invasive species control, are not economically viable, in contrast to what is found at the landscape scale. In northeast Wyoming, ventenata [Ventenata dubia (Leers) Coss.] is a relatively new invader in the Great Plains ecoregion that threatens forage production on ranches. Our objective was to explore the economic costs of V. dubia for two options available to a ranch operation: purchasing extra hay to offset losses in forage and controlling V. dubia with herbicide. Using a partial budget analysis, we compare these two options in three invasion scenarios using a range of forage utilization rates and discount rates. Controlling V. dubia with herbicide was a cheaper option compared with purchasing additional hay in many cases. In fact, at 50% utilization, it is cheaper to control V. dubia in all of our scenarios at all discount rates given our assumptions. For lower grazing utilization rates, it becomes cheaper to purchase hay in some cases other than in our worst-case invasion scenario. In these cases, coordination among ranchers is needed to effectively control V. dubia. There are many ranch-specific differences that may make a different option more feasible, and we did not explore options of reducing herd sizes. However, our results suggest that controlling V. dubia can be an economically viable option under certain circumstances. Additional assistance in the form of a cost-share program, and facilitation of coordination is needed to overcome the difficulties of private management of invasive species.

Control options for the nonnative common mullein are of increasing interest to land managers in the west. Common mullein is a prolific seed producer, with a single plant able to produce well over 100,000 seeds. We found that mechanical control of common mullein before mature seed capsules developed along the raceme significantly reduced viable seed production. Seeds from immature capsules had very low viability (early reproductive stage = 0.08%, 95% CI = 0.06%, 0.67%; mid reproductive stage = 1.52%, 95% CI = 0.49%, 3.11%). This information allows managers to time their management efforts so that they can reduce the amount of plant material that must be disposed of in order to control the spread of common mullein seeds.

Mangroves are a critical component of many coastal ecosystems in Florida. Woody species, including Brazilian peppertree (Schinus terebinthifolia Raddi), have invaded thousands of hectares of mangrove habitat. The difficulty associated with ground-based management of invasive plants in mangrove communities has warranted a need to identify selective herbicides that can be applied aerially. Recent work suggests that Florida mangrove species are extremely sensitive to synthetic auxin herbicides; however, other herbicides have yet to be tested for selectivity. Greenhouse studies in 2018 and 2019 evaluated broadcast foliar applications of the acetolactate synthase inhibitor imazamox and protoporphyrinogen oxidase inhibitor carfentrazone-ethyl, both as individual treatments and in combinations, for control of S. terebinthifolia and injury to four non-target mangrove species. Across all posttreatment sample dates and species tested, there were no significant interactions between imazamox applied at 0.28 or 0.56 kg ai ha−1 in combination with carfentrazone-ethyl applied at 0 or 0.1 kg ha−1. Main effects of imazamox applied at 0.56 kg ai ha−1 and carfentrazone-ethyl applied at 0.1 kg ha−1 resulted in 99% and 97% defoliation, respectively, of Schinus terebinthifolia at 180 DAT. However, S. terebinthifolia percent survival was 56% and 44% for the same treatments. Both herbicides severely injured all four mangroves by 90 DAT and resulted in 58% to 100% defoliation across species. At 180 DAT, significant increases in percent cambium kill were also observed for all four species. Across species, mangrove survival varied, but red mangrove (Rhizophora mangle L.) survival was reduced to 6% when imazamox was applied at 0.56 kg ha−1. These results indicate both imazamox and carfentrazone-ethyl exhibit activity on S. terebinthifolia but also injure all four mangroves enough to preclude their use as selective treatments.

We assessed pre- and posteradication nitrogen and phosphorus dynamics in longleaf pine sandhill stands severely affected by cogongrass. Across a 7-yr posteradication (glyphosate + imazapyr) “recovery chronosequence,” which included untreated cogongrass, uninvaded reference, and treated plots, we analyzed soils for total N, potentially available P (Mehlich-1 [M1]), pH, and organic matter content. We also used resin bags to assess fluxes of plant available N and P in the soil solution. Additionally, we used litterbags to monitor the decomposition and nutrient mineralization patterns of dead rhizome and foliage tissue. Our results indicate similar total N and M1-P contents in both cogongrass-invaded and uninvaded reference plots, with levels of M1-P being lower than in cogongrass plots for 5 yr after eradication. Soil organic matter did not differ between treatments. Resin bag analyses suggest that cogongrass invasion did not affect soil nitrate availability, although a pulse of NO2 + NO3 occurred in the first 3 yr after eradication. No such trends were observed for ammonium. Resin-adsorbed PO4 was lowest 3 yr after eradication, and pH was highest 5 yr after eradication. Our litterbag study showed that approximately 55% of foliar biomass and 23% of rhizome tissue biomass remained 18 mo after herbicide treatment. Substantial N immobilization was observed in rhizomes for the first 12 mo, with slow mineralization occurring thereafter. Rapid P mineralization occurred, with 15.4 and 20.5% of initial P remaining after 18 mo in rhizomes and foliage, respectively. Overall, our findings indicate that cogongrass invasion has little to no effect on soil nutrient cycling processes, although some significant—but ephemeral—alterations develop after eradication.

The name of the genus Lycium originates from the Greek name lykion for a thorny shrub, derived from Lycia, the name of an ancient country in Asia Minor where a similar spiny shrub was found. The specific epithet ferocissimum comes from the Latin ferox, meaning “bold” or “fearless,” referring to the very spiny nature of the shrub (Green 1994; Parsons and Cuthbertson 2001).

Most turfgrass species have been listed as either invasive or potentially invasive species in the U.S., but few data exist to verify their invasiveness. Our objective was to determine cool-season turfgrass survival on two abandoned golf courses to assess their invasive potential in unmanaged sites. Maintenance operations ceased at Matheson Greens Golf Course in 2000 and at Four Winds Golf Course in 2003. The frequency and abundance of creeping bentgrass, Kentucky bluegrass, and fine fescues in quadrats placed along transects were recorded and compared to other cover such as herbaceous dicots and bare soil in 2005 and 2007. Turfgrasses at both courses were unable to maintain monocultures. All turfgrasses were nearly absent from Matheson Greens Golf Course 5 yr after maintenance operations ceased. At the Four Winds Golf Course site, creeping bentgrass comprised less than 25% cover on former putting greens by 2007, and was rarely found outside of the former putting green areas. Kentucky bluegrass cover ranged from 5 to 75% on the former fairways. Herbaceous dicots usually dominated the former turf areas at both sites, and included noxious weeds such as Canada thistle and invasive weeds such as spotted knapweed.

Desert grasslands of the southwestern United States have experienced an increase in the abundance and distribution of woody plant species over the past century. Shrub encroachment has caused a substantial loss of grasslands in the northern Chihuahuan Desert. The Chihuahuan Desert has also been invaded by Lehmann lovegrass, a fire-adapted species from southern Africa. In 1999, the U.S. Department of Agriculture–Agricultural Research Service burned a remnant desert grassland to determine the effects of prescribed fire on shrub–perennial grass dynamics. The grassland also contained the nonnative perennial grass Lehmann lovegrass. I am reporting on a study that was initiated to determine whether prescribed burning would alter the vegetative community within and proximal to a Lehmann lovegrass–dominated patch. Cover of Lehmann lovegrass showed no significant response to the burn treatment. Of the dominant native species, only black grama and broom snakeweed had a significant year by treatment interaction. No species or growth form had a significant vegetation type by year by treatment interaction. After 6 yr, differences between burned and unburned transects were not significant for any species or growth form.

Yellow toadflax (Linaria vulgaris Mill.; Scrophulariaceae) is an invasive herbaceous perennial weed of agricultural and natural habitats throughout North America. In pastures or native rangelands, use of biological control is an attractive option, particularly if the agent can be established quickly. Rhinusa pilosa (Gyllenhal) (Coleoptera: Curculionidae), a stem-galling weevil, was first released in Canada in 2014 to evaluate its potential to control L. vulgaris. Rhinusa pilosa requires young, vigorously growing shoots to establish. Ability to estimate when adequate shoots will be available could inform release timing, thus improving establishment success. There is currently no growing degree-day (GDD) model for L. vulgaris. Our main objective was to develop a GDD model for the emergence of L. vulgaris shoots and discuss the utility of such a model in relation to the establishment of R. pilosa in Nova Scotia. Four sites containing five randomly placed 1-m2 quadrats were monitored for the emergence of L. vulgaris shoots twice weekly in spring to summer 2017 and 2018 by recording number of shoots and shoots with flower buds. A GDD (Tbase 2 C) model for shoot emergence of L. vulgaris was developed and validated using independent shoot emergence data. Shoots emerged in the spring between 124 and 244 GDD with 90% of all shoots emerged between 681 and 1,117 GDD. Model estimation for the initiation of shoot emergence was 74 GDD, with 10%, 50%, and 90% shoot emergence estimated to occur at 179, 409, and 811 GDD, respectively. Rhinusa pilosa adults were released in 2016 (three sites) and 2017 (one site), and number of shoots with galls was recorded. Galls were observed in all three sites in 2016 and in three of the four sites in 2017, with none found in 2018. Timing of release and soil moisture are discussed as factors affecting establishment of R. pilosa in Nova Scotia.

Skunk-vine (Paederia foetida L.) is an invasive vine native to eastern and southern Asia and is widely distributed in Florida, Hawaii, and other southeastern U.S. states; however, little research has focused on herbicide control. Greenhouse and field experiments were conducted to determine efficacy of aminocyclopyrachlor, aminopyralid, fluroxypyr, glyphosate, imazapic, triclopyr amine, and triclopyr ester at low and high labeled rates when foliar applied to P. foetida at various growth stages in greenhouse experiments. Longer-term control was evaluated in field experiments in central Florida using the same herbicides. PRE herbicides labeled for use in landscape plantings, including dimethenamid-P, flumioxazin, indaziflam, isoxaben, and prodiamine, were also evaluated in greenhouse trials by seeding containers with P. foetida seed. In greenhouse experiments, POST herbicides, including aminocyclopyrachlor, aminopyralid, glyphosate, both triclopyr formulations, and the high rate of fluroxypyr (0.24 kg ae ha−1), provided >90% control across all growth stages at 4 mo after treatment with no regrowth observed. Imazapic provided 49% to 89% control, with efficacy decreasing with P. foetida size, and generally provided less control than other treatments. Field experiments confirmed results from greenhouse studies. In PRE trials, flumioxazin and prodiamine provided better control than all other PRE herbicides evaluated, reducing shoot weights by 99% and 84%, respectively, compared with nontreated controls. Our data suggest all herbicides evaluated POST could potentially be used to manage P. foetida, although less control was achieved with imazapic compared with other herbicides. Further research is needed to determine herbicide efficacy on more mature plants and to develop application methods that would be less injurious to non-target vegetation. In landscapes, flumioxazin or prodiamine could be used for PRE control, but POST options that are labeled for landscape use should be identified in future research.

Canada thistle can cause greater than 50% yield loss in small grain crops, but little is known about production losses when the weed invades pasture and wildlands. Change in grass, forb, and woody species production from Canada thistle infestations was evaluated in two separate studies in North Dakota. The first measured change in production following aminopyralid applied at 120 g ha−1 to control Canada thistle at two prairie sites. In general, grass, broadleaf, woody, and total plant yields were similar between treated and untreated prairie, regardless of the near-complete control of Canada thistle following aminopyralid application. Grass yield increased by 365 kg ha−1 the year after treatment at one location, with no change in forb or woody species production. Plant production was also estimated at 20 ungrazed wildland preserves located within two Major Land Resource Areas (MLRAs). Similar to the prairie sites, minimal differences in production between Canada thistle–infested and noninfested sites were observed. The only exception was an increase in grass production of 425 kg ha−1 at one of the MLRAs, with no change in broadleaf or woody species production between the Canada thistle–infested and noninfested sites. In contrast to cropland, pasture and wildland production of other species was not consistently reduced by Canada thistle.

Sulfur cinquefoil, a perennial invasive weed of many different habitats in the United States, reproduces and spreads predominately through seed production, making seed bank survival and successful germination essential steps in the invasive process. To evaluate its potential to invade water-stressed environments, field and growth chamber studies were conducted in two areas of sulfur cinquefoil seed ecology: (1) monitoring the seed bank population and (2) determining the effect of salt and water stresses on germination of two sulfur cinquefoil seed populations differing in site characteristics of precipitation, temperature, and soil conditions. Field sampling demonstrated that a 2-yr average seed rain of 73,700 seeds m−2 resulted in an average 26,600 seeds m−2 annual increase in the seed bank. Regression analysis showed seed rain accounted for only 7 and < 1% of the variation in seedling density in 2003 and 2004, respectively. Seeds from the two populations showed a difference in the level of decrease in germination in response to increasing water and salt stresses. Managers should be aware that some populations of sulfur cinquefoil may be able to survive under drier or saltier conditions than previously thought. It appears that several years of control of mature sulfur cinquefoil would dramatically reduce the sulfur cinquefoil seed bank.

Geographic information systems (GIS) analysis considering size and spatial distribution of infestations of invasive species on a landbase can assist with developing appropriate control strategies for that species. We used GIS to evaluate strategies that placed highest priority on: smallest patches of cogongrass, largest patches of cogongrass, and cogongrass patches on land considered high-value under military training and conservation priorities on Camp Shelby Joint Forces Training Center (CSJFTC), MS. Strategies were first evaluated using predicted increase in area of new growth prevented, if prioritized patches were treated with herbicide. Travel and other time needed to implement strategies were then assessed as they affected total area treated. Assuming equivalent areas treated, predicted total reduction in area was consistently highest for the strategy prioritizing smallest patches and lowest for the strategy prioritizing largest patches. However, travel and other time was sufficiently reduced for the strategy prioritizing patches on high-value land compared to the other strategies to suggest that this strategy would result in the greatest reduction in area infested with cogongrass. Analyses of spatial distribution and size of infestations can assist land managers with selecting the appropriate strategy for controlling invasive species.