Boneseed (Chrysanthemoides monilifera subsp. monilifera; syn Osteospermum moniliferum subsp. moniliferum), is a perennial shrub native to the south-western and southern coasts of South Africa. It was introduced to Australia in about 1852 and now represents a significant threat to natural ecosystems. Despite being listed as a Weed of National Significance, momentum on improving boneseed management has dissipated at a national level, beginning in 2008 (when a national research initiative finished) and increasingly after 2013 (when funding for national coordination ceased). A recent synthesis of past management for boneseed and recommendations for guiding future priorities has rekindled interest in Western Australia. To complement this synthesis and to identify improvements for program efficiency or effectiveness, we reviewed research and management findings on this weed with a focus on the past two decades. We collated information across the ecology and biology of boneseed, and the near relative, bitou bush, as well as useful insight from boneseed management programs applied elsewhere. As part of this review we assessed the classical biological control work that has been done on boneseed, focusing on likely explanations for why, despite nine agents and a naturalised fungus, biological control is not an effective management tool. Our synthesis suggests that for the limited populations with low abundance plants in Western Australia, eradication from the state remains a realistic target. This objective, however, needs to build on the collated baseline of past management efforts and deploy a carefully planned management program over the coming two decades. Systematic surveillance using the latest techniques, combined with manual or herbicide removal and controlled burns where possible, remain the most suitable methods to deploy. The long-lived soil seedbank requires detailed monitoring following initial plant removals and long-term funding to ensure the sustained effort required to deliver the goal of eradication for boneseed in Western Australia.

Whilst invasive plants can modify community and ecosystem attributes, there is little information on their impact across different trophic levels. Here, we examined the effects of Gunnera tinctoria Molina (Mirb.; Gunneraceae; “Chilean-rhubarb”) on the soil detrital food chain, the major pathway for energy flow in terrestrial ecosystems and the recycling of nutrients. Measurements of soil physio-chemistry properties and the natural abundances of C and N isotopes, along with assessments of microbial and earthworm populations were used to verify if G. tinctoria drives the soil food web and how C is transferred from decomposing litter to worm populations. Based on the C isotope compositions of plant material and detritivorous worms (i.e., earthworms and enchytraeid worms), all worms contribute to G. tinctoria litter decomposition, irrespective of their feeding preference. The increased role of larger earthworm populations in litter decomposition was also associated with changes in the soil microbial community, with some bacterial genera being absent from invaded areas. Of particular interest was a three-fold increase in Nitrospira spp. in invaded areas, likely due to an increase in earthworm-related ammonia production, with this being rapidly converted to nitrate. Given the poor representation of other ammonia and nitrite oxidizing soil bacteria, many of the Nitrospira spp. present in invaded soils may perform complete ammonia oxidation (i.e., COMAMMOX). Our results indicate a greater role for native earthworms in decomposition processes in areas invaded by G. tinctoria, resulting in modifications in the other soil biota and an increase in soil nitrate.

We report a pair of simple PCR-RFLP assays based on two independently segregating nuclear genes which can differentiate North American native Phragmites australis subsp. americanus Saltonst., P.M. Peterson & Soreng from other lineages. Because nuclear markers are inherited biparentally, researchers can also use them to screen for F1 hybrids between americanus and the other lineages. We show that a previously described assay based on an indel in the nuclear gene NRT2 consistently identifies a wide range of americanus haplotypes and distinguishes them from the Gulf Coast type Phragmites australis (Cav.) Trin. ex Steud. ssp. berlandieri (E. Fourn.) Saltonst. & Hauber. We also demonstrate a new PCR-RFLP assay for a previously described diagnostic single nucleotide polymorphism adjacent to the PaGT4 microsatellite marker which also distinguishes americanus from the other lineages. In addition, we report the first case of Asian haplotype AS identified in North America and make recommendations for its detection. Our findings expand the tools available to those monitoring for invasion by introduced Phragmites in North America.

An online survey was distributed to South Dakota stakeholders to understand how noxious weeds are currently being managed. The response rate was 26%; 129 stakeholders completed the survey of the 491 stakeholders who opened the survey. Eighty percent of respondents stated noxious weeds were a problem. Canada thistle (Cirsium arvense), leafy spurge (Euphorbia esula) and absinth wormwood (Artemisia absinthium) were the most common and troublesome but all statewide noxious weeds were reported. Herbicides alone (25%) was the most common singular response to manage noxious weeds, but respondents utilized two (27%) to three (24%) other tactics as well. Most respondents (47%) were somewhat satisfied with management tactics while others were completely satisfied (9%), neither satisfied nor dissatisfied (20%), somewhat unsatisfied (11%), or very unsatisfied (15%). A covariate analysis showed that the more management tactics a stakeholder utilized, the less satisfied they were with control (P < 0.0001). The most common barrier of adopting new tactics was effectiveness (26%) followed by a combination of effectiveness + current production practices + cost + labor (13%). An additional covariate analysis showed that the increase of management tactics increased the barriers of adoption (P = 0.04) and increasing the number of barriers of adoption resulted in stakeholders being dissatisfied with control (P = 0.0003). Overall, the results of the survey suggest that statewide noxious weeds remain a problem, and multiple tactics are used to manage these weeds. However, Extension efforts need to address how to use current and implement new management to increase effectiveness.

Invasive common reed, Phragmites australis ssp. australis ((Cav.) Trin. ex Steud.) has established and dominated Ontario wetlands for decades. The detrimental effects of P. australis invasions on wetland habitats have demanded intervention through aggressive suppression efforts. However, constraints in available control methods to suppress P. australis have led to persistent invasions. To improve P. australis management in wetlands, we investigated remotely-piloted aircraft systems (RPASs) as a precision tool for herbicide application. We applied an imazapyr-based herbicide (240 g active ingredient L-1) with a spray-equipped RPAS at selected test sites, marking the first-ever application of its kind in Canada. We evaluated 1) the efficacy of RPAS-based herbicide application to P. australis and 2) examined the plant community changes one year after the initial herbicide application. We found a > 99% reduction in live P. australis stems, along with reductions in species richness (33%), Shannon-Weiner diversity (73%), Simpson’s reciprocal diversity (50%), and Pielou’s evenness (73%) in the year following herbicide application. Plant community changes varied by field site; one wetland underwent a secondary invasion by European Frog-bit (Hydrocharis morsus-ranae (L.)) while the other was dominated by the native Spotted Jewelweed (Impatiens capensis (Meerb.)), highlighting the complexities of plant community succession following herbicide application in biodiverse wetlands.

Biological invasions pose a major threat to biodiversity conservation in protected areas, with roads, tracks, and trails being the main pathways for the spread of non-native species. This study aimed to assess the distribution patterns of non-native and native plant species in relation to elevational gradient, public use intensity, and disturbance by roads and trails in a protected tropical mountain forest in southeastern Brazil. Specifically, we recorded plant species along this gradient and tested whether the richness of native and non-native species differed with elevation. Additionally, we investigated whether the high-altitude non-native species community was a subset of lower-elevation communities and whether non-native species richness was linked to anthropogenic disturbances and public use intensity. Our findings revealed that native and non-native species richness varied along the elevational gradient. Native species exhibited a hump-shaped pattern, with richness peaking at mid-elevations. In contrast, non-native species did not show a clear trend along the altitudinal gradient. Notably, higher non-native species richness was observed in roadside and trailside plots. The non-native species communities at higher altitudes were not simply subsets of those found at lower elevations. Thus, while the richness and composition of native species appeared to be driven by environmental factors along the elevational gradient, the presence of non-native species was more closely associated with anthropogenic disturbances. In summary, our results indicate that non-native plants, although widespread along trails and roads, establish primarily in the most disturbed areas. Therefore, roads, trails, and human and vehicular traffic are key determinants of biological invasions in this mountainous protected area.

The southern African shrub boneseed [Chrysanthemoides monilifera subsp. monilifera (L.) Norl.] is a perennial shrub that is a significant threat to natural ecosystems and is listed as a Weed of National Significance in Australia. In Western Australia (WA) it has spread across peri-urban and natural environments. We assembled a single standardized database containing more than 2,050 presence records for individual plants and 135 absence records at a local population level. We further refined the populations into 89 sites that require different management trajectories due to topography and capacity of land managers to implement control. Forty-nine of these sites were in urban regions and 40 sites were in regional WA. We split these 89 sites into three near-term management goals: watch (12), extirpate (68), and contain (9). The 12 watch sites are those where all available evidence suggests that there have been no new inputs into the seedbank for 15 yr. The 68 sites marked for extirpation are those where delimitation is already achieved or easily achievable, where there have been minimal seed inputs into the soil seedbank in recent years due to consistent surveillance and control, and where surveys for new plants are likely to be efficient to conduct. Finally, for nine sites in urban regions around Perth, we recommend containment in the near term with a longer-term goal to achieve delimitation and extirpation. To achieve the objective of state-level eradication, a coordinated and sustained campaign involving three components—delimitation of all sites, prevention of further inputs into the soil seedbank, and systematic field surveys to remove plants—must commence without delay. While resourcing requirements for delimitation and overall program management are not possible to estimate, our prior experience suggests that it will take at least 1,900 h of on-ground surveying by experienced personnel to achieve extirpation of C. monilifera subsp. monilifera in WA.

Vallisneria × pseudorosulata S. Fujii & M. Maki is an invasive aquatic weed that has recently become a major issue within the U.S. Southeast. Vallisneria × pseudorosulata is a hybrid between two nonnative eelgrass species (Vallisneria spiralis L. and Vallisneria denseserrulata Makino) and has rapidly overtaken water bodies in Tennessee, Alabama, and Florida. This hybrid can reproduce rapidly through offshoot formation and floating propagules capable of drifting large distances before establishing. Vallisneria × pseudorosulata has been previously found in Japan and is thought to have been introduced in the United States by the aquarium trade or through dumping.

We evaluated herbicides for controlling the annual grass ventenata [Ventenata dubia (Leers) Coss.], with particular interest in indaziflam, a preemergence cellulose biosynthesis inhibitor. In 2016, indaziflam was applied postemergence alone and in mixture with glyphosate, imazapic, propoxycarbazone-sodium, or rimsulfuron to an improved pasture in southwestern Montana. A non-sprayed control was included for comparison purposes. Canopy cover of each species was assessed annually for 7 yr; cover was grouped by life-form and longevity, and species richness was calculated. Five years (2021) after treatment, the seedbank was assessed. Our results indicated that treatments including indaziflam reduced V. dubia cover 1 to 3 yr and even up to 6 yr after application, with V. dubia cover being zero or close to zero. However, at 7 yr (2023) after treatment, V. dubia was low across all treatments, including the non-sprayed control. Perennial grasses and forbs and annual forbs were generally unaffected by any treatment and did not increase in cover over the 7 yr, even though V. dubia decreased. Two years after treatment, species richness was lowest in treatments that included indaziflam, but at 7 yr, species richness was similar across all treatments. Indaziflam depleted the monocot and dicot seedbank, with fewer than 5 seedlings of any species emerging from treatments that included indaziflam, while other treatments resulted in 60 to 165 seedlings per sample (40 cm3 of soil). In summary, at our study site, a single application of indaziflam controlled V. dubia for 6 yr, appeared to deplete the seedbank at 5 yr, and cover of perennial and annual vegetation and species richness was unaffected. By the end of the study, though, V. dubia cover appeared to be influenced by factors other than herbicide treatments, possibly variable precipitation over time, an exclusion of grazing, and competitive perennial grasses dominating the site.

Citizen science is becoming very useful in surveying and monitoring biodiversity. Within the European Union LIFE medCLIFFS project, a network of volunteers has been established for the detection and long-term monitoring of invasive plant species that threaten the endemic flora of Mediterranean cliffs in northeastern Spain. Through iNaturalist, volunteers record various data along a series of 1-km transects. Based on the ca. 700 observations collected by volunteers in 2023 (the first year of the project), a simple and visually attractive methodology for assessing the recorded populations has been developed. This method classifies populations into one of three population dynamics categories: (1) propagative behavior (i.e., populations with seedlings or young plants but lacking senescent or dead individuals); (2) senescent behavior (i.e., showing senescent/dead plants but lacking seedlings/juveniles); and (3) a mixed behavior (i.e., containing both). This methodology, whose outputs are easily interpretable as heat maps, allows the collection of large datasets on invasive plants by citizen scientists, with two main purposes: (1) knowing which species are most concerning based on simple, straightforward observations of their population dynamics; and (2) identifying which regions of the study area are more problematic and where management efforts should therefore be directed.

Urban areas are increasingly recognized as important centers of biodiversity. Nonetheless, invasive species can reduce this biodiversity, and cities can be hubs for alien plant invasions, highlighting the need to monitor urban biodiversity and problematic alien species. The goal of our study was to assess the distribution of wild chervil [Anthriscus sylvestris (L.) Hoffm.] and anise [Myrrhis odorata (L.) Scop.] in green spaces of Reykjavík, Iceland. This information is necessary to implement the city’s biodiversity strategy regarding invasive species. Both of these alien plants are spreading throughout Iceland, and Reykjavík’s high-latitude location (≥63°N) and remoteness make it an ideal case study to assess alien plant introductions and invasions in subarctic urban areas. We surveyed four green spaces (Laugarnes, Vatnsmýri, Elliðaárdalur, and Ægisiða) from May to October 2017 using AllTrailsPro and ArcGIS mobile applications. ANOVA and Bonferroni correction (post hoc test) were used to compare the distribution and patch sizes of A. sylvestris and M. odorata among the study sites. We found that A. sylvestris covered at least 10% (15.5 ha) of the total area surveyed (158 ha), while M. odorata only covered ≤1 ha. Both plants were abundant near buildings, pathways, riversides, and streams, and they are expanding their distribution in Reykjavík’s green spaces. While A. sylvestris is clearly more established and widespread with larger patches (>100 m2), the distribution of M. odorata is more localized, occurring mainly in smaller patches (<100 m2). We recommend long-term monitoring to further assess M. odorata’s invasive potential, as well as testing and adopting integrated weed management strategies via adaptive management to control the distribution of A. sylvestris and that of other problematic alien plants. These actions, which are applicable to other subarctic cities, will help foster more proactive management encouraging urban biodiversity.

In places where multiple related taxa are invasive and known to hybridize, it is important to have correct identifications to enable an appropriate legal, ecological, and management understanding of each kind of invader. Invasive knotweeds in the genus Reynoutria Houtt. are noxious weeds in Europe, North America, Africa, and Oceania, where they disrupt native plant communities and negatively impact human activities. Two species (Japanese knotweed [Reynoutria japonica Houtt.; syn.: Polygonum cuspidatum Siebold & Zucc.] and giant knotweed [Reynoutria sachalinensis (F. Schmidt ex Maxim.) Nakai; syn.: Polygonum sachalinense F. Schmidt ex Maxim.]) and their hybrid (known as Bohemian knotweed [Reynoutria ×bohemica Chrtek & Chrtková; syn.: Polygonum ×bohemicum (J. Chrtek & Chrtková) Zika & Jacobson [cuspidatum × sachalinense]]) have similar invasive tendencies, although there are some noted differences among them in their reproduction potential, ecological tolerance, and effect on native communities. Prior studies demonstrated that not only one kind of interspecific hybrid exists, but in fact there are at least four kinds that differ in the sequence variants they possess from each parent. Thus, in addition to identifying plants as hybrids, it may become important to distinguish each kind of hybrid when considering control or treatment strategies. In the current study, we expand the available genetic information for invasive Reynoutria by providing expanded DNA sequence data for the low-copy nuclear gene LEAFY, which has become important for characterizing hybrids. Our methods recover the same LEAFY genotypes that were identified previously for the commonly sequenced second intron, and we also provide sequence data for the first intron and second exon of the gene.

Adaptive management studies of invasive plants on non-agricultural lands typically employ an empirical approach based on designed field experiments that permit rigorous statistical analysis of results to quantify outcomes and assess the efficacy of management practices. When habitat restoration is the primary goal of a project, traditional plot-based study designs (e.g., the randomized complete-block design) are sometimes infeasible (this is often true in aquatic habitats) or inappropriate (e.g., when the goal is to assess effects of management practices on survival or resprouting of individual plants, such as trees or shrubs). Moreover, the assumptions of distribution-specific parametric statistical methods such as ANOVA often cannot be convincingly verified or are clearly untenable when properly assessed. For these reasons, it is worthwhile to be aware of alternative study designs that do not employ plots as experimental units and nonparametric statistical methods that require only weak distributional assumptions. The purpose of this paper is to review several of these alternative study designs and nonparametric statistical methods that we have found useful in our own studies of invasive aquatic and terrestrial plants. We motivate each statistical method by a research question it is well suited to answer, provide corresponding references to the statistical literature, and identify at least one R function that implements the method. In the Supplementary Material, we present additional technical information about the statistical methods, numerical examples with data, and a set of complete R programs to illustrate application of the statistical methods.

Fast and efficient identification is critical for reducing the likelihood of weed establishment and for appropriately managing established weeds. Traditional identification tools require either knowledge of technical morphological terminology or time-consuming image matching by the user. In recent years, deep learning computer vision models have become mature enough to enable automatic identification. The major remaining bottlenecks are the availability of a sufficient number of high-quality, reliably identified training images and the user-friendly, mobile operationalization of the technology. Here, we present the first weed identification and reporting app and website for all of Australia. It includes an image classification model covering more than 400 species of weeds and some Australian native relatives, with a focus on emerging biosecurity threats and spreading weeds that can still be eradicated or contained. It links the user to additional information provided by state and territory governments, flags species that are locally reportable or notifiable, and allows the creation of observation records in a central database. State and local weed officers can create notification profiles to be alerted of relevant weed observations in their area. We discuss the background of the WeedScan project, the approach taken in design and software development, the photo library used for training the WeedScan image classifier, the model itself and its accuracy, and technical challenges and how these were overcome.

Crested floating heart [Nymphoides cristata (Roxb.) Kuntze] is an invasive aquatic plant in the southeastern United States. For clonal plants like N. cristata, clonal diversity may influence response to control tactics and/or evolutionary potential. However, little is known about the diversity of introduced N. cristata. In this study, we used genotyping by sequencing to quantify N. cristata diversity in the southeastern United States and determine how that diversity is distributed across the invaded range. Our results show that at least three distinct genetic lineages of N. cristata are present in the southeastern United States. Geographic distribution of the lineages varied, with one widespread lineage identified across several states and others only found in a single water body. There is also evidence of extensive asexual reproduction, with invaded water bodies often host to a single genetic lineage. The genetic diversity reported in this study likely results from multiple introductions of N. cristata to the southeastern United States and should be considered by managers when assessing control tactics, such as screening for biocontrol agents or herbicide testing. The extent and distribution of genetic diversity should also be considered by researchers studying the potential for invasive spread of N. cristata within the United States or hybridization with native Nymphoides species.

Flowering rush (Butomus umbellatus L.) is an emergent perennial monocot that has invaded aquatic systems along the U.S.–Canadian border. Currently, there are two known cytotypes of flowering rush, diploid and triploid, within the invaded range. Although most studies have focused on the triploid cytotype, little information is known about diploid plants. Therefore, phenology and resource allocation were studied on the diploid cytotype of flowering rush in three study sites (Mentor Marsh, OH; Tonawanda Wildlife Management Area, NY; and Unity Island, NY) to understand seasonal resource allocation and environmental influences on growth, and to optimize management strategies. Samples were harvested once a month from May to November at each site from 2021 to 2023. Plant metrics were regressed to air temperature, water temperature, and water depth. Aboveground biomass peaked from July to September and comprised 50% to 70% of total biomass. Rhizome biomass peaked from September to November and comprised 40% to 50% of total biomass. Rhizome bulbil densities peaked from September to November at 3,000 to 16,000 rhizome bulbils m−2. Regression analysis resulted in strong negative relationships between rhizome starch content and air temperature (r2 = 0.52) and water temperature (r2 = 46). Other significant, though weak, relationships were found, including a positive relationship between aboveground biomass and air temperature (r2 = 0.17), a negative relationship between rhizome bulbil biomass and air temperature (r2 = 0.18) and a positive relationship between leaf density and air temperature (r2 = 0.17). Rhizomes and rhizome bulbils combined stored up to 60% of total starch, and therefore, present a unique challenge to management, as these structures cannot be reached directly with herbicides. Therefore, management should target the aboveground tissue before peak production (July) to reduce internal starch storage and aim to limit regrowth over several years.

Effective regulation is essential for preventing the establishment of new invasive plants and managing the environmental, social, and economic impacts of those already established. Invasive plants are regulated by jurisdictions at a mix of local, regional, national, and international levels. Enhanced coordination of policy and regulations has been identified as a key strategy for addressing the impacts of invasive species; however, coordination between jurisdictions, and even within jurisdictions, is not always considered. To review regulatory coordination in Australia, we compiled a comprehensive dataset of noxious weeds (defined as invasive plants and potentially invasive plants with controls specified in regulation) in each Australian jurisdiction (i.e., state or territory). We found that jurisdictions on average shared ca. 67% (SD = 15%) of noxious weed listings. Neighboring jurisdictions were not more similar than separated jurisdictions in their noxious weed listings. There were significant differences in the biogeographic native ranges of noxious weeds between jurisdictions, with species native to temperate Asia being most frequently listed overall. The predominant likely entry pathway for noxious weeds in Australia was the ornamental trade. Listings were primarily dedicated to proactive control, prohibiting the cultivation of noxious weeds to avoid their naturalization. There were 415 noxious weeds regulated in a harmonious manner across jurisdictions. However, there were 327 noxious weeds regulated by jurisdictions in a discordant manner, potentially leaving neighboring jurisdictions vulnerable to invasion. We suggest jurisdictions reassess the regulation of these 327 discordant noxious weeds in Australia and utilize a national taxonomic standard to avoid problematic synonyms. Improved cohesion of policies could be achieved through wider adoption of existing regulatory systems and codevelopment of regulations between government and industry.

Among the most widely distributed species globally, common reed [Phragmites australis (Cav.) Trin. ex Steud.] has generated extensive interest in invasive plant science and management because its introduced strains are highly invasive and often form monocultures that alter ecosystem properties. In desert wetlands in Las Vegas, NV, USA, where management goals included reducing hazardous P. australis fuels and increasing native plant diversity, we assessed variation in P. australis cover, the degree of native plant colonization, and soil seedbanks after P. australis management treatments (cutting, glyphosate–imazapyr herbicide) and wildfires across gradients in soil properties. Based on change in P. australis cover during six measurement events over 24 mo, 24 study sites formed three groups: (1) decreasing cover, where initially high P. australis cover (60% to 85%) decreased to <5% following multiple cutting or herbicide treatments; (2) sustaining low cover, where wildfire or clearing was associated with initially low P. australis cover which remained low (<30%) after multiple herbicide applications; and (3) sustaining high cover (45% to 100% initially and remaining at 30% to 100%), including sites unmanaged or treated/burned only once. High soil salinity correlated with low postmanagement P. australis cover. No native plants were detected in the sustaining high P. australis cover group, despite natives occurring in the seedbank. Where management reduced P. australis cover, minimal native plant colonization did occur. Secondary invasion by other non-native plants was nearly absent. Our results suggest that if P. australis can be initially cleared, multiple herbicide applications can persistently keep cover low, especially on drier, saline soils. Slow native plant colonization suggests that a phased approach may be useful to initially reduce P. australis cover, keep it low via repeated treatments, and actively revegetate sites with native species tailored to the moisture–salinity gradient across P. australis–invaded habitats.

Herbicides that persist in the forest litter and soil following their use for managing invasive plant species may negatively affect restoration efforts as well as minimize reinvasion via their residual phytotoxic activity. This study determined the impact of an herbicide mixture comprising triclopyr, dicamba, picloram, and aminopyralid (TDPA) for the control of dense infestations of a woody invader, Pinus contorta Douglas ex Loudon, on the germination of reinvading P. contorta and three New Zealand native species (Chionochloa rubra Zotov, Nothofagus cliffortiodes (Hook. f.) Oerst., and Leptospermum scoparium J.R. Forst. & G. Forst.) used in restoration. Given the essential role of ectomycorrhizal fungi in facilitating conifer reinvasion, the impact of residual herbicides present in mineral soil on the ectomycorrhizal infection of P. contorta seedling roots was also examined. Germination trials were conducted using intact forest litter–soil cores collected at 27, 112 and 480 d (after herbicide spraying) from sprayed and adjacent unsprayed dense P. contorta infestations. At the same time, mineral soil was also collected for the ectomycorrhizal infection study. Post-spray herbicide residue bound in the litter significantly decreased survival, germination rate, root and shoot growth, and also caused malformation of P. contorta seedlings. Similar results were recorded for native species’ germination; however, overall viability of native seed was poor, resulting in low germination rates. There was no difference in levels of ectomycorrhizal infection rates of P. contorta between treatments. Results indicate residual levels of TDPA herbicide in forest floor litter negatively affect P. contorta reinvasion, native recruitment, and active restoration management. Ectomycorrhizal fungi, however, are unaffected by this herbicide mixture and therefore remain a risk to facilitating reinvasion as residual herbicide declines.