Crystalline ice plant [Cryophytum crystallinum (L.) N.E. Br.] is a succulent plant indigenous to South Africa and is a highly invasive weed in North America. There are currently three weevil species from the native range that show promise as potential biological control agents for these invasive populations. The present study used a ddRADseq population genetic technique to match the invasive populations in North America to their source of origin to prioritize survey areas where the best-matched agent genotypes are likely to occur. We found that populations in the Canary Islands and Morocco closely matched those in the invaded North American range, and that this genetic cluster was most similar to the South African native range sites surrounding the Cape Town area and those from Aniston Village further east along the coastline. There was evidence of an invasion route from South Africa to the Mediterranean Basin, and that a secondary bridgehead invasion likely took place from there to North America. Genetic structuring within the native range revealed a total of four distinct populations, where sites north and south of Cape Town were unique and did not match the invasive populations. We found a unique outlier population in the Northern Cape which displayed intermediate morphological traits between C. crystallinum and its close relative, ice plant (Mesembryanthemum guerichianum Pax; syn. Cryophytum guerichianum Pax). Surveys for biological control agents should focus on the areas between Kalk Bay and Yzerfontein in the Western Cape, and sites surrounding Arniston Village.

Burning nettle (Urtica urens L.) and common groundsel (Senecio vulgaris L.) are widespread, economically important weeds in horticultural systems. This laboratory and glasshouse study evaluated the effect of temperature, photoperiod, salinity, osmotic stress, and pH on seed germination, and the effect of burial depth on seedling emergence of these species. A significant interaction between temperature and photoperiod showed that germination depended on combined thermal and light cues rather than either factor alone. Urtica urens germinated higher in complete darkness (53%) than in light/dark (3%) across three temperature regimes studied. Germination peaked at 90% at 25/15C in complete darkness, while no germination occurred for this species at 15/5C and 35/25C day/night temperatures. In contrast, S. vulgaris preferred light/dark conditions (52% germination vs 29% in darkness), reaching 96% at 25/15C under day/night conditions. Salinity and osmotic stress inhibited germination of both species in a non-linear, sigmoidal pattern. Urtica urens germination was completely inhibited at ≥200 mM of sodium chloride (NaCl) and at ≤−0.6 MPa osmotic potential. Senecio vulgaris showed greater tolerance, with complete inhibition at ≥250 mM NaCl concentration and at ≤−1.0 MPa osmotic stress. Urtica urens germination peaked at pH 6 (92%) and declined under more acidic and alkaline conditions, while S. vulgaris germinated >97% across all pH levels (4 – 10). Urtica urens showed overall low emergence with 11% from soil surface and <1% when buried at different depths. In contrast, S. vulgaris showed up to 90% and 38% emergence from surface in sand and soil, respectively, but its seeds could not emerge beyond 0.5 cm burial depth. These findings can help refine integrated weed management in baby leaf crops by identifying periods when emergence is most likely, supporting timely stale seedbed or pre-emergence interventions, avoiding unnecessary soil disturbance when conditions favor germination, and prioritizing surface-focused control tactics for S. vulgaris.

Weed management is a primary barrier to sustainable organic vegetable production, and reducing the germinable soil weed seedbank is a critical long-term strategy for alleviating weed pressure. This study evaluated the effect of cover crops established in alleyways or traffic pathways on germinable warm-season weed seedbank density, species composition, functional group structure, and temporal emergence dynamics during transition to certified organic vegetable production. Treatments included three grass/legume cover crop bicultures of perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.), orchardgrass (Dactylis glomerata L.)/red clover (Trifolium pratense L.), sorghum-sudangrass [Sorghum × drummondii (Steud.) Millsp. & Chas] /white sweet clover [Melilotus officinalis (L.) Lam.], and a tilled fallow control. In the third year of the study, soil samples from cover-cropped and tilled fallow control pathways were subjected to a 60-day greenhouse emergence bioassay with observations recorded at 15, 30, 45, and 60 days after greenhouse setup. All three cover crop treatments reduced total germinable weed seedbank density by 73% to 82% relative to the tilled fallow, with no significant differences among cover crop treatments. Suppression was driven primarily by reductions in the annual broadleaf and annual grass functional groups, with carpetweed and foxtail identified as the principal species suppressed. Weed species richness did not differ among cover crop treatments or between cover crop treatments and the tilled fallow control. The tilled fallow produced a highly concentrated early emergence flush, with approximately 88% of total seedlings emerging within the first 15 days, whereas cover crop treatments substantially reduced and redistributed emergence across the monitoring period. Perennial ryegrass/white clover exhibited the most delayed peak emergence timing among all treatments. These findings demonstrate that traffic pathway cover cropping effectively suppresses the readily germinable warm-season weed seedbank during organic vegetable transition, with both annual and perennial cover crop bicultures providing equivalent suppressive benefits.

Encapsulated saflufenacil uses a solid phase encapsulation, which is different than traditional herbicide encapsulations. Saflufenacil is released following dry conditions that allow the microcapsule to fracture. Thus, encapsulated saflufenacil is not available for foliar uptake using standard application methods. A trace amount of non-encapsulated saflufenacil remains in the formulation from an incomplete purification process and may cause foliar phytotoxicity from postemergence applications. Experiments were conducted using relative photosystem II (PS II) efficiency of corn leaf tissue to determine encapsulated saflufenacil bioavailability and to characterize saflufenacil microcapsule release under extended solution storage time. To evaluate injury potential, non-encapsulated, free saflufenacil was separated from the encapsulated formulation using microfiltration. An open-capsule treatment was created by allowing the encapsulated formulation to dry and then resolubilizing the herbicide. Relative PS II efficiency of the free, open-capsule, and encapsulated saflufenacil formulations were compared over 48 hours after treatment (HAT). By 48 HAT, dry and non-encapsulated saflufenacil reduced relative PS II efficiency greater than the encapsulated saflufenacil, indicating that saflufenacil was not released from the encapsulation unless it underwent a period of drying. Furthermore, the reduced relative PS II efficiency was similar for the encapsulated and free saflufenacil, corroborating that the level of phytotoxicity from foliar encapsulated saflufenacil applications originates from the trace levels of free saflufenacil in the product. Saflufenacil microcapsule stability was evaluated following mixing with water and storage for 0, 1, 3, 5, or 7 days. Phytotoxicity did not increase with extended storage times, as the reduction in relative PS II efficiency from 0 to 48 HAT remained mostly constant across solution storage times. Overall, this research substantiates that saflufenacil encapsulation works to reduce foliar injury and documents the encapsulation durability under extended storage in water solution.

Biodiversity plantings are effective methods of enhancing on-farm biodiversity. However, farmers are often hesitant to place them adjacent to crop fields due to concerns that they may harbor problematic weeds and pest arthropods, or that the intentionally planted species may escape into the crop and act as weeds. The objective of this research was to compare weed and arthropod communities in planted versus conventionally managed field margins at two sites in New York State. Planted treatments were seeded with either native wildflowers or grasses and then either mowed infrequently or unmanaged after planting. Conventional field margin management treatments included infrequent and frequent mowing, glyphosate application, and an unmanaged control. Measurements included both seedbank and aboveground plant density and diversity, plant biomass, and the abundance of both beneficial and pest arthropods. Pest arthropod abundance both in the margin and in the crop was not affected by the field margin management strategy. Arthropod abundance and plant richness and diversity, both within fields and field margins, were not strongly affected by the field margin management method. Once the plantings were established, weed density was lower within planted margins than conventionally managed margins (P = 0.0002), with a difference of 92.8% per 0.5 m2 in 2025. Treatment affected weed biomass (P = 0.002), but treatment means differed significantly at only one site in 2024 according to Tukey’s HSD. Overall, our results indicate that the establishment of field margin plantings is unlikely to exacerbate weed pressure from field margins.

Sticky nightshade (Solanum sisymbriifolium Lam.) has emerged as a significant invasive weed across agricultural and natural ecosystems globally. The species contains toxic steroidal glycoalkaloids that pose a risk to livestock. Furthermore, its ability to form dense infestations can reduce the abundance of desirable plant species and hinder management of both natural and agricultural systems. Despite its increasing impact, information on its germination ecology and seedling emergence behaviour remains limited. A series of laboratory and glasshouse experiments were conducted to investigate the effects of temperature, light, pH, salinity, moisture stress, and burial depth on the seed germination and seedling emergence of S. sisymbriifolium. Results showed that germination was highest (85.5%) under diurnally alternating temperatures of 35/15 C, while light had no significant effect. Seed germination was 74.1-84.7% across a wide pH range (4 - 10), indicating minimal sensitivity to pH variation. Germination declined sharply with increasing salinity and was completely inhibited at 125 mM NaCl. Similarly, germination decreased from 85.1% to zero as osmotic potential declined from 0 to −0.80 MPa, indicating that S. sisymbriifolium requires sufficient moisture for successful germination. Seedling emergence was greatest (72.4%) at a burial depth of 2.5 cm and declined significantly at greater depth. Overall, this study demonstrates that S. sisymbriifolium can grow in a broad range of environmental conditions but is sensitive to moisture stress, salinity, and deeper burial. This ecological flexibility may facilitate its spread across diverse habitats. These findings provide useful guidance for designing more efficient and sustainable integrated weed management strategies to reduce germination and seedling emergence of this invasive species.

Palmer amaranth (Amaranthus palmeri S. Watson) is among the most problematic weeds in U.S. rowcrop systems. In furrow-irrigated rice (Oryza sativa L.) (FIR), which is typically produced within soybean [Glycine max (L.) Merr.]- and corn (Zea mays L.)-dominated landscapes in the midsouthern U.S. that contain preexisting resistant seedbanks, the absence of continuous flooding allows season-long weed emergence, while effective postemergence control options remain limited. Iptriazopyrid, a novel azole carboxamide 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitor under development for use in rice, possesses a chemical structure distinct from triketones such as mesotrione. Whether this structurally different HPPD-inhibitor endows altered susceptibility to metabolic resistance mechanisms in A. palmeri remains unknown. Therefore, the objectives were to evaluate the postemergence efficacy of iptriazopyrid and to compare its parent compound depletion with mesotrione in a known mesotrione-resistant (MSR2) and -susceptible A. palmeri accessions (1986 and/or 21-115). Dose–response experiments showed that iptriazopyrid maintained consistent efficacy across accessions, with no significant differences among estimated response parameters. In contrast, mesotrione required 2.83 to 9.21-fold higher rates in MSR2 to achieve responses comparable to those observed in susceptible 1986 accession. Quantification of parent compound over time revealed limited depletion of iptriazopyrid across accessions, with >95% of the parent compound remaining up to 12 h after treatment in all three accessions and approximately 75% remaining at 24 h in MSR2. Conversely, mesotrione underwent rapid metabolism in MSR2, declining to 18% of the parent compound by 8 h and to <6% by 24 h, indicating that resistance mechanisms conferring reduced sensitivity to Mesotrione in MSR2 do not similarly compromise iptriazopyrid. Therefore, iptriazopyrid may provide an effective postemergence option for managing A. palmeri in FIR, including mesotrione-resistant populations, and may help diversify herbicide programs and reduce selection for metabolic resistance in midsouthern U.S. cropping systems.