Callery pear (Pyrus calleryana Decne.) is a problematic woody invasive plant in eastern North America that invades old fields, forests, and disturbed sites. While management guidance typically suggests foliar, basal bark, cut stump, and hack-and-squirt applications of herbicides for P. calleryana, there is a dearth of studies focusing on the efficacy of specific treatments. We evaluated seven herbicide treatments for control of midstory P. calleryana. Cut stump and hack-and-squirt applications of glyphosate, imazapyr, and triclopyr and a soil application of hexazinone were repeated at six sites within Georgia, Kansas, and South Carolina, and all study trees were monitored for approximately 1 yr after herbicide application. Cut stump applications of glyphosate (478.73 g L-1), imazapyr (22.47 g L-1), and triclopyr (343.90 g L-1) provided the most consistent control with no resprouting and 100% mortality. Hack-and-squirt applications of glyphosate and triclopyr resulted in approximately 80% probability of mortality 1 yr after treatment, while hack-and-squirt application of imazapyr and soil application of hexazinone (287.58 g ai L-1) averaged only 20% and 25% probability of mortality, respectively. Our results demonstrate the efficacy of seven treatment options for P. calleryana control in three geographic locations with varied habitat types, and our data suggest that cut stump applications of glyphosate, imazapyr, or triclopyr or hack-and-squirt application of glyphosate or triclopyr may be useful for reducing populations of P. calleryana. that have grown past the sapling stage.

Invasive plants negatively impact natural areas and impose huge costs associated with control and management. A new approach to significantly reduce these effects is to identify species in the earliest stages of spread, using data collected by public gardens across North America. Known as Public Gardens as Sentinels against Invasive Plants (PGSIP), this network includes multiple gardens, each contributing reports of these problematic species to a shared database using standardized guidelines. We examined this dataset to identify newly spreading species being noticed within gardens within different regions and determined whether they have been reported as state-listed/regulated/noxious outside gardens. As of November 2024, 53 PGSIP gardens in 28 U.S. states and Canadian provinces had submitted 996 reports, consisting of 597 unique species. The most commonly listed species were Amur corktree (Phellodendron amurense Rupr.), burning bush [Euonymus alatus (Thunb.) Siebold], and wintercreeper [Euonymus fortunei (Turcz.) Hand.-Maz.]. Other less frequently listed species included golden rain tree (Koelreuteria paniculata Laxm.), Norway maple (Acer platanoides L.), and castor aralia [Kalopanax septemlobus (Thunb.) Koidz.]. Of the 597 species, 36% were not listed by any state or province; gardens also had several species on watchlists, including Japanese tree lilac [Syringa reticulata (Blume) H. Hara] and Siberian squill (Scilla siberica Andrews). Our results demonstrate the utility of the approach and value of the database. This information can now inform the efforts of land managers, invasion biologists, the horticultural industry, and agencies tasked with invasive plant monitoring and assessment.

Tree of heaven [Ailanthus altissima (Mill.) Swingle] is an invasive tree that inhibits regeneration of forests. Management of forests invaded by A. altissima often includes chemically treating it and leaving dead boles behind. Verticillium wilt (Verticillium nonalfalfae) infects some populations of A. altissima, leading to localized mortality. Areas with population-wide A. altissima mortality may increase as this disease spreads or is used as a biocontrol agent. Ailanthus altissima has documented allelopathic compounds; stems left to decompose may result in soil legacy effects that negatively impact native plant restoration. The goal of this study was to determine whether soil under decomposing A. altissima wood has negative impacts on native perennial plant germination and growth. Ailanthus altissima was grown in a garden for 4 yr, basally cut, and treated with herbicide. The stems were sectioned and stacked into piles to decompose for 18 mo on grass and garden fabric, after which the wood was mulched. Soil from cores taken under each woodpile was added over potting media in pots in which seeds of three native perennials (purple coneflower [Echinacea purpurea (L.) Moench], dogbane (Apocynum cannabinum L.), and false nettle [Boehmeria cylindrica (L.) Sw.]) were planted. Seeds for half the pots were covered with potting media or mulch, respectively. The plants were grown under high- and low-light conditions in a greenhouse for 3 mo. Germinations were tallied, and dry shoot biomass was determined. Pots with woodpile soil had lower germination and biomass production for two of the native species, but mulch reduced the impact. Biomass was greater for all soil treatments with mulch added compared with treatments with no mulch. Plants growing in soil under garden fabric had germination values similar to plants in woodpile soil. This study reveals that soil under decomposing A. altissima wood is likely to negatively impact germination and growth of some newly seeded species for at least 18 mo.

Water hyacinth (Pontederia crassipes Mart.) is a free-floating aquatic plant native to South America that has spread to nearly 50 countries, becoming one of the world’s most invasive aquatic weeds. In Florida, the biocontrol agents Neochetina eichhorniae and Neochetina bruchi were released in 1970s, while Megamelus scutellaris was released in 2010. Assessing the impact of these biocontrol agents is crucial in evaluating efficacy, distribution, and overall progress in management efforts. The traditional survey and monitoring methods used to evaluate the impact of biocontrol present numerous challenges in data acquisition, especially in remote areas and aquatic habitats. This study aimed to detect damage caused by Neochetina spp. and M. scutellaris on P. crassipes using hyperspectral remote sensing. Plants were exposed to varying levels of Neochetina spp. and M. scutellaris herbivory for 2 and 4 wk under laboratory conditions. After the exposure period, the plants were scanned using a visible and near-infrared hyperspectral imaging system. Two classification algorithms, partial least-squares discriminant analysis (PLS-DA) and support vector machine (SVM) were employed for classification. SVM achieved high classification accuracy at both low and high damage levels, with overall training and validation accuracies of 84.9% and 78.79%, respectively, while PLS-DA only achieved high classification accuracy at high damage levels, with overall training and validation accuracies of 56.3% and 60.38%. Based on the observed performance metrics, both algorithms demonstrated improved classification accuracy as damage increased over time. The results indicated that hyperspectral remote sensing can be used to monitor and assess biocontrol agents damage on P. crassipes.

The invasive plant species Japanese hop (Humulus japonicus Siebold & Zucc.) and reed canarygrass (Phalaris arundinacea L.) are increasing in cover in Upper Mississippi River (UMR) floodplains, where they negatively impact native vegetation. This study evaluated novel reforestation methods to rapidly close canopy openings colonized by invasives and reduce their cover at four study sites ranging from southern Wisconsin to southwestern Illinois. Each site contained three replicates of four 20 by 20 m plots comprising four tree-planting treatments. These included two using large-diameter willow (Salix) cuttings planted at different densities, one using container stock of American sycamore (Platanus occidentalis L.) and eastern cottonwood (Populus deltoides W. Bartram ex Marshall), and a control plot with no planted trees. Half of each planting treatment also received maintenance treatments for invasives control. Results indicated that planting and maintenance had significant effects on tree survival, invasives cover, and plant community diversity. Specifically, trees that received maintenance had higher survival than those that did not, and Salix cuttings had higher survival than container stock. Annual tree height growth was greatest in Salix cuttings planted at the highest density. Invasive species cover declined significantly in maintenance treatments and Salix plantings. Change in plant community diversity was greater in maintenance treatments and in Salix plantings, but was still extremely low at the northernmost site. Vegetation patterns were strongly influenced by invasives and reinforced the general inverse relationship between plant community diversity and invasives cover. Overall, results indicated that tree plantings using large Salix cuttings can be an effective method to quickly reforest areas along the UMR that have been colonized by invasive plant species and that incorporating tree-planting maintenance activities in early years can lead to better survival.

Cogongrass [Imperata cylindrica (L.) P. Beauv.] is a recalcitrant invasive grass widespread in the southeastern United States. In non-crop systems, management relies on foliar applications of glyphosate and imazapyr; multiple applications over several years are often required, increasing labor, logistical, and chemical costs. Although numerous herbicide alternatives have been evaluated, few match the efficacy of glyphosate or imazapyr. Glufosinate is a broad-spectrum herbicide, and demand for glyphosate alternatives has generated interest in its potential for invasive grass management, but long-term evaluations of glufosinate and tank mixes for I. cylindrica are limited. This study evaluated single foliar spot applications of glufosinate (2.0 kg ae ha−1) alone and in tank mixtures with glyphosate (3.4 kg ae ha−1) or imazapyr (1.1 kg ae ha−1) at three Florida field sites heavily invaded (88% to 92% cover) by I. cylindrica using percent cover and belowground biomass. All treatments containing glufosinate produced rapid foliar necrosis, reducing cover to 15% to 21% within 14 days after treatment (DAT). By 270 DAT, cover increased in the glufosinate-alone (43%) and glufosinate + glyphosate (42%) treatments but remained approximately 25 to 30 percentage points lower than the control. At 540 DAT, cover in these treatments did not differ from that in the control. Across all sites, I. cylindrica cover at 540 DAT was reduced relative to the control by glyphosate (37%), imazapyr (9%), imazapyr + glufosinate (7%), and imazapyr + glyphosate (11%). Notably, the imazapyr + glufosinate mixture produced both rapid and sustained reductions in I. cylindrica cover. These results suggest glufosinate alone provides short-term suppression of aboveground tissue but can be enhanced through tank mixing with soil-active herbicides such as imazapyr to improve long-term suppression of belowground meristems.

Hydrilla [Hydrilla verticillata (L.F.) Royle] is a known, persistent aquatic weed in many lakes and reservoirs across the United States. Recently, focus has been placed on the management of invasions of H. verticillata into flowing systems due to increased difficulty in achieving effective control. In flowing environments, increased flow and water exchange rates commonly result in shorter herbicide exposure times using traditional application techniques. This research evaluated the concept of intermittent herbicide exposure as a potential management strategy to overcome operational challenges in high water exchange environments. Monoecious H. verticillata response to intermittent exposure to florpyrauxifen-benzyl, endothall, and fluridone at multiple concentrations and nontreatment intervals was evaluated in greenhouse-scale mesocosm experiments. Decreased efficacy was not observed when nontreatment intervals between exposures were introduced in florpyrauxifen-benzyl treatments. Monoecious H. verticillata treated with 30 µg ai L−1 florpyrauxifen-benzyl and a 6-d nontreatment interval resulted in 89% reduction in aboveground biomass. Nontreatment intervals did not influence endothall efficacy and biomass reduction increased with herbicide concentration (66% to 93%). Fluridone treatments at 5 µg L−1 resulted in 82% biomass reduction, while treatments at 10 and 15 µg L−1 resulted in 89% biomass reduction. Biomass reduction was slightly lower in fluridone applications with a 12-d nontreatment interval (83%) compared with other nontreatment intervals (85% to 91%). The high biomass reduction and similar response between treatments observed suggests the need for additional refinement and operational verification of intermittent herbicide exposures for monoecious H. verticillata control to increase cost-effectiveness and efficiency in public H. verticillata control programs.

Invasive, non-native plants frequently restructure ecosystems by homogenizing vegetation and altering trophic interactions, but the ecological consequences of invader removal are less predictable. Removal can redistribute light, nutrients, and detrital resources, initiating community reassembly that extends beyond vegetation recovery and may facilitate secondary invasions. We used a single-site invasive-removal field study to examine how management of European buckthorn (Rhamnus cathartica L.) reshaped vegetation structure, litter accumulation, and faunal communities in a postindustrial forest preserve in western New York State, USA. Across 18 plots representing managed, not-treated, and regrown R. cathartica conditions, we quantified herbaceous vegetation, leaf litter biomass, and the abundance of arthropods, pollinators and small mammals. Rhamnus cathartica removal was associated with a 10-fold increase in herbaceous plant cover and species richness, producing structurally complex understories and higher arthropod and pollinator abundance. However, managed plots also supported 3- to 5-fold higher densities of the invasive European fire ant (Myrmica rubra)—corresponding with increased leaf litter in managed plots. Ant abundance was positively associated with thicker, more persistent litter layers rather than canopy openness, and increasing M. rubra density, in turn, corresponded with reduced pollinator abundance. Detritivore and rodent responses were more closely linked to vegetation structure and litter conditions than to ant abundance.

Many non-native invasive grass species increase wildfire activity and regenerate more quickly than native species. This invasive grass–fire cycle has severe negative consequences for ecosystems, creating a need to understand how different invasive grass species alter fuel characteristics and fire behavior, as well as effective treatments to control their abundance. To address these needs and increase fire and natural resource management preparedness, we performed a review and meta-analysis of recent (1985 to 2023) scientific literature. We focused on the Intermountain West, USA, where six dominant invasive grass species have already transformed ecosystems, including winter annuals—cheatgrass (Bromus tectorum L.), medusahead [Taeniatherum caput-medusae (L.) Nevski], red brome (Bromus rubens L.), and Mediterranean grass [Schismus arabicus Nees and Schismus barbatus (Loefl. ex L.) Thell]; and summer perennials—buffelgrass [Pennisetum ciliare (L.) Link] and Lehmann’s lovegrass (Eragrostis lehmanniana Nees). Within the 204 selected articles, B. tectorum was the most well-studied species, treatment effectiveness was the most common study type, and more studies addressed fuel accumulation than fire characteristics. While initial reductions in B. tectorum following wildfire were followed by large increases, P. ciliare initially increased and then steadily declined, and other invasive grass species had no significant post-fire changes over time. Chemical treatments were more effective than other treatments for B. tectorum, P. ciliare, and Schismus spp., although T. caput-medusae had a greater reduction with chemical treatments compared with the other species. In many cases, treatment effectiveness was enhanced when treatment types were combined or repeat treatments were conducted. Both B. tectorum and T. caput-medusae increased to pretreatment conditions within 3 and 5 yr, respectively, although there were no detectable trends for other species. Our results provide comprehensive comparisons of the effect of invasive grass species on fuel and fire characteristics and much needed insight on effective strategies for reducing invasive grass impacts to ecosystems.

Submerged aquatic vegetation (SAV) is often underdocumented at the species level in routine monitoring and regulatory assessments, where vegetation is commonly recorded without species-level identification. Here, we present a summary of existing records and field collections made in the Pennsylvania portion of Monongahela River system. Our findings suggest that the dominant SAV in this river is hydrilla [Hydrilla verticillata (L. f.) Royle], one of the most aggressive invasive macrophytes in North America. Further, our recent collections indicate the presence of other invasives: Eurasian watermilfoil (Myriophyllum spicatum L.) and curlyleaf pondweed (Potamogeton crispus L.). Native species such as coontail (Ceratophyllum demersum L.) and vallisneria (Vallisneria americana Michx.) were present but not prominent in sampled locations. The documentation of H. verticillata and other non-native invasive SAV species suggests that the Monongahela River is now hosting an invasive epidemic, one that may have widespread ecological implications.