Hydrilla [Hydrilla verticillata (L. f.) Royle], an invasive aquatic weed, has had a rich introduction history into the United States, with multiple subspecies being introduced since the 1960s. The most recent occurred before 2016, when northern hydrilla (Hydrilla verticillata ssp. lithuanica) was discovered in the Connecticut River. By 2021, following a 3-yr survey from Agawam, MA, to the Long Island Sound by the Connecticut Agricultural Experiment Station Office of Aquatic Invasive Species, H. verticillata ssp. lithuanica was found in more than 113 km of the river, occupying 344 ha. Since this survey, there has been concern that H. verticillata ssp. lithuanica would spread to nearby waterbodies and have a significant negative impact. Here, we report the first documented spread and establishment of H. verticillata ssp. lithuanica from the Connecticut River to five waterbodies in Connecticut and one in Massachusetts. Of the eight sites where H. verticillata observations were made, 75% (n = 6) were confirmed to be H. verticillata ssp. lithuanica and 25% (n = 2) to be Hydrilla verticillata ssp. peregrina (wandering hydrilla). Except for one site, all six locations infested with H. verticillata ssp. lithuanica provide watercraft access through public or private boat ramps. The authors also postulate on the mechanisms facilitating the spread and establishment of this subspecies.

Waterhemp is a dioecious species with wide genetic diversity which has enabled it to evolve resistance to several commonly used herbicide groups in North America. Five field trials were established in Ontario to ascertain the biologically effective doses of diflufenican, a new Group 12 herbicide applied preemergence for control of multiple herbicide–resistant (MHR) waterhemp in corn. Based on regression analysis, the predicted diflufenican doses to elicit 50%, 80%, and 95% MHR waterhemp control were 99, 225, and 417 g ai ha−1, respectively, at 2 wk after application (WAA); 73, 169, and 314 g ai ha−1, respectively, at 4 WAA; and 76, 215, and — (meaning the effective dose was beyond the set of doses in this study) g ai ha−1, respectively, at 8 WAA. The predicted diflufenican doses that would cause a 50%, 80%, and 95% decreases in MHR waterhemp density were 42, 123, and — g ai ha−1; and MHR waterhemp biomass were 72, 167, and 310 g ai ha−1, respectively, at 8 WAA. Diflufenican applied preemergence at 150 g ai ha−1 controlled MHR waterhemp by 64%, 79%, and 73% at 2, 4, and 8 WAA, respectively. Isoxaflutole + atrazine applied preemergence at 105 + 1,060 g ai ha−1 controlled MHR waterhemp by 98%, 98%, and 97% at 2, 4, and 8 WAA, respectively; and S-metolachlor/mesotrione/bicyclopyrone/atrazine applied preemergence at 1,259/140/35/588 g ai ha−1 controlled MHR waterhemp by 100%, 100%, and 99% at 2, 4, and 8 WAA, respectively. Diflufenican applied preemergence reduced MHR waterhemp density and biomass by 83%; in contrast, isoxaflutole + atrazine and S-metolachlor/mesotrione/bicyclopyrone/atrazine reduced MHR waterhemp density and biomass by 99%. All treatments evaluated caused either no, or minimal, corn injury and resulted in corn yield that was similar with the weed-free control. Results indicate that diflufenican applied alone preemergence does not provide superior MHR waterhemp control over the commonly used herbicides isoxaflutole + atrazine or S-metolachlor/mesotrione/bicyclopyrone/atrazine; however, there is potential for using diflufenican as part of an integrated weed management strategy for the control of MHR waterhemp control in corn.

New machine-vision technologies like the John Deere See & Spray™ could provide the opportunity to reduce herbicide use by detecting weeds and target-spraying herbicides simultaneously. Experiments were conducted for 2 yr in Keiser, AR, and Greenville, MS, to compare residual herbicide timings and targeted spray applications versus traditional broadcast herbicide programs in glyphosate/glufosinate/dicamba-resistant soybean. Treatments utilized consistent herbicides and rates with a preemergence (PRE) application followed by an early postemergence (EPOST) dicamba application followed by a mid-postemergence (MPOST) glufosinate application. All treatments included a residual at PRE and excluded or included a residual EPOST and MPOST. Additionally, the herbicide application method was considered, with traditional broadcast applications, broadcasted residual + targeted applications of postemergence herbicides (dual tank), or targeted applications of all herbicides (single tank). Targeted applications provided comparable control to broadcast applications with a ≤1% decrease in efficacy and overall control ≥93% for Palmer amaranth, broadleaf signalgrass, morningglory species, and purslane species. Additionally, targeted sprays slightly reduced soybean injury by at most 5 percentage points across all evaluations, and these effects did not translate to a yield increase at harvest. The relationship between weed area and targeted sprayed area also indicates that nozzle angle can influence potential herbicide savings, with narrower nozzle angles spraying less area. On average, targeted sprays saved a range of 28.4% to 62.4% on postemergence herbicides. On the basis of these results, with specific machine settings, targeted application programs could reduce the amount of herbicide applied while providing weed control comparable to that of traditional broadcast applications.

Removal and disposal of nonnative trees is expensive and time-consuming. Using these nonnative trees as a substrate to produce edible mushrooms could diversify farming operations and provide additional income to small-scale farmers. This research compared the production of shiitake mushrooms (Lentinula edodes) on nonnative tree logs to shiitake mushroom production on native oak (Quercus L.) logs, which are the traditional substrate. In a 2-yr study, we evaluated nonnative tree species as alternate substrates for growing shiitake mushrooms at farms in northern Florida and southern Georgia. A mix of native Quercus spp. and nonnative trees was targeted for removal on participating farms. Five nonnative tree species were initially tested for their ability to produce edible mushrooms, either shiitake or oyster (Pleurotus ostreatus var. florida). Of the nonnative trees we tested: Chinaberry (Melia azedarach L.), Chinese tallowtree [Triadica sebifera (L.) Small], silktree (Albizia julibrissin Durazz.), earleaf acacia (Acacia auriculiformis A. Cunn. ex Benth.), and paperbark tree [Melaleuca quinquenervia (Cav.) S.F. Blake], only T. sebifera produced shiitake mushrooms, and none produced native Florida oyster mushrooms. In on-farm trials, Quercus spp. logs produced more total mushrooms and more mushrooms per log and had a higher total mushroom yield per log. However, mushrooms produced on T. sebifera logs had higher mean weight per mushroom. Edible fungi can be used to recycle invasive, nonnative T. sebifera and transform their biomass from waste into an income-producing resource.

Drill-interseeding cover crops into corn (Zea mays L.) is an emerging establishment method in northern U.S. production regions. However, cover crop performance in interseeded systems remains variable, and creating environments that are conducive to cover crop but not weed growth is challenging. Cultural practices that partition resources between corn and interseeded cover crops have potential to improve performance if weeds are adequately managed. This study evaluated interactions among corn hybrids differing in leaf architecture (upright, pendulum), corn row spacing (76 cm, 152 cm), and interseeding timing (V3, V6) on light transmittance, relative fitness of cover crop species (cereal rye [Secale cereale L.], annual ryegrass (Lolium multiflorum Lam), red clover [Trifolium pratense L.]) and weeds, and corn grain yield at three U.S. Northeast locations. Results showed that light transmittance through the corn canopy was greater in 152-cm row spacing compared with 76-cm row spacing at the V6 growth stage, with the magnitude of difference increasing at the V10 corn growth stage. Corn hybrids had a marginal effect on light transmittance. The effect of row spacing and interseeding timing on fall cover crop biomass varied across cover crop species and locations. In 76-cm rows, interseeding earlier (V3) increased cover crop biomass production. The relative fitness of cover crops was greater than that of weeds in each combination of cultural practices that included narrow spacing (76 cm), whereas the relative fitness of weeds was greater than that of cover crops when interseeding in wide rows (152 cm). The effect of row spacing on corn yield varied among locations, with higher yields observed in 76-cm row spacing compared with 152-cm at two of three locations. Our results show that interseeding early (V3) on 76-cm row spacing can balance cover crop and corn production management goals, while placing cover crops at a relative fitness advantage over weeds.

One way that climate change is projected to affect invasive plant management is by shifting the ranges of invasive plants. In some regions, hundreds of new, potentially invasive species could establish in coming decades. These species are prime candidates for early detection and rapid response. However, with limited resources, it is unlikely that invasive plant managers will be able to monitor and treat this large number of novel species. Determining which species are likely to have the greatest impacts could inform further risk assessment and mitigate the greatest amount of potential damage. Here, we used the Environmental Impact Classification for Alien Taxa (EICAT) protocol to evaluate the potential impacts of 104 invasive plant species that are projected to establish in Delaware, Kentucky, Maryland, New Jersey, Ohio, Pennsylvania, Virginia, and/or West Virginia by midcentury with climate change. These species were identified using the Invasive Range Expanders Listing Tool to predict which invasive species are likely to shift their ranges into the target states by midcentury. We used Web of Science to search for studies on each species involving impacts to ecological or socioeconomic sectors. We scored ecological impacts on a scale of 1 (“minimal concern”) to 4 (“major concern”) and socioeconomic impacts as present or not present. We evaluated 674 papers and categorized the species into these categories: 32 high-impact species, 20 moderate-impact species, and 13 minor- or minimal-impact species. Two of the 32 high-impact species (panic veldtgrass [Ehrharta erecta Lam.] and Athel tamarisk [Tamarix aphylla (L.) Karst.]) pose a risk to all eight mid-Atlantic states. There were also 46 species that pose a risk to socioeconomic sectors, including agriculture, the economy, and human health. Twenty-four species were listed as data deficient (no data could be found on them). This study provides a comprehensive review of reported impacts of range-shifting invasive plants in the mid-Atlantic.

Waterhemp [Amaranthus tuberculatus (Moq.) Sauer] is a dioecious weed that has evolved resistance to very-long-chain fatty-acid elongase (VLCFAE)–inhibiting herbicides via rapid metabolism. Although detoxification enzyme activities are associated with S-metolachlor resistance in two multiple herbicide–resistant (MHR) A. tuberculatus populations from Illinois, the genetic basis of resistance is unknown. Therefore, our goal was to investigate inheritance of S-metolachlor resistance in the Stanford, Illinois–resistant (SIR) population. Specifically, our research objectives were to: (1) generate a uniformly resistant, full-sib near-inbred line (DK3-2) via three generations of recurrent selection for resistance using preemergence S-metolachlor; (2) develop A. tuberculatus populations segregating for S-metolachlor resistance via reciprocal single-plant (one male × one female) full-sib mating of DK3-2 and a VLCFAE-inhibiting herbicide-sensitive population, SEN; (3) quantify S-metolachlor resistance levels in parental lines and their F1 progenies via greenhouse dose–response analysis; and (4) evaluate inheritance of S-metolachlor resistance in F2 progenies. Dose–response analysis using six to eight S-metolachlor concentrations (0.015 to 15.0 μM, varying per population) generated lethal dose (LD) estimates of 50% (LD50) and 90% (LD90) for SIR, SEN, DK3-2, and F1 progenies. LD estimates indicated DK3-2 has a higher magnitude of S-metolachlor resistance than the SIR population, demonstrating single crosses significantly increased S-metolachlor resistance in DK3-2. Levels of S-metolachlor resistance in F1 populations were intermediate compared with DK3-2 and SEN. Segregation of S-metolachlor resistance in F2 families from the paternal-derived lines fit a single-gene model (R:S = 3:1), indicating a single, dominant gene confers S-metolachlor resistance in SIR. However, F2 segregation results from the maternal-derived lines fit a duplicate recessive epistasis model (R:S = 9:7), indicating a second recessive gene may also modify S-metolachlor resistance in SIR. Results and germplasm derived from this research can assist in identifying the gene(s) conferring resistance to S-metolachlor in A. tuberculatus.