Nicholas Tuschak Basinger

Flumioxazin is a preemergence herbicide that is widely used pretransplant on conventional sweetpotato hectarage as part of weed management programs in North Carolina; despite this, some growers have concerns that flumioxazin may be injurious to sweetpotato, even at recommended rates if rain falls near application. Thus, field studies were conducted in 2021 and 2022 in Clinton, North Carolina, to evaluate the performance of flumioxazin under several simulated rain conditions. Studies evaluated a complete factorial arrangement of treatments with three flumioxazin rates and three simulated rain treatments. Herbicide treatments included no herbicide, and two rates of flumioxazin (107 g ai ha ⁻¹ and 214 g ai ha ⁻¹ ). Irrigation treatments included 1.9 cm of simulated rain applied before flumioxazin, 1.9 cm applied after flumioxazin, and no simulated rain. No visual injury from herbicide or rain treatments was observed. Yields of No. 1 and marketable sweetpotatoes were reduced by 25% and 14%, and total yield was reduced by 11% when the higher rate flumioxazin (214 g ha ⁻¹ ) was applied compared to the no-herbicide treatment. However, the lower (registered) rate of flumioxazin (107 g ha ⁻¹ ) did not lead to a reduction in yield compared with yield from the no-herbicide treatment. No interactions between irrigation timing and herbicide were observed, and irrigation timing alone did not affect sweetpotato yield. Average length-width ratio (LWR) was calculated for No. 1 sweetpotato storage roots as a metric of root shape. In 2021, herbicide did not affect LWR. In 2022, compared with the no-herbicide treatment, the LWR of No. 1 sweetpotato was smaller after the higher rate of flumioxazin (214 g ha ⁻¹ ) was applied compared with LHR of the no-herbicide treatment, resulting in rounder sweetpotato roots. Flumioxazin applied at 107 g ha ⁻¹ did not reduce LWR compared with the no-herbicide treatment. The results of this study highlight both the safety of flumioxazin when applied at registered rates and the importance of appropriate application procedures to prevent overapplication.

Much of humanity’s food, fuel, and fiber is produced by farming systems requiring high external inputs, leading to the depletion and pollution of natural resources. Faced with climate change and th...

Indaziflam is a long-term residual weed control option for Georgia pecan [ Carya illinoinensis (Wangenh.) K. Koch] growers. As a nonselective cellulose biosynthesis inhibitor, indaziflam has a niche for broad-spectrum weed control with long residual activity in various perennial cropping systems. Indaziflam’s soil persistence and chemical behavior at various temperatures have not been fully evaluated; therefore, the objectives of these experiments were to: (1) quantify indaziflam soil dissipation under field conditions in two common Georgia soils and (2) evaluate indaziflam molecular stability as affected by temperature and time using laboratory techniques. Indaziflam soil dissipation followed first-order kinetics and was adequately described by the exponential decay equation. Indaziflam half-life in Greenville sandy clay loam and Faceville loamy sand was 96 and 78 d, respectively. Indaziflam half-life and soil clay content had a direct relationship, while indaziflam half-life and microbial biomass had an inverse relationship. Aqueous solutions of indaziflam were exposed to temperatures that ranged from 20 to 70 C for up to 672 h, with results indicating that temperature had no influence on indaziflam’s molecular stability.

Cover crop utilization is an important strategy for improving row crop sustainability and plays a critical role in managing plant–soil nutrient relations needed to maintain cotton (Gossypium hirsutum L.) yields in the southeastern United States. Most cover crops are annual species, but perennial cover crops, sometimes called “living mulches” (LMs), can provide year‐round benefits. The effects of LM on nitrogen and carbon dynamics have been explored in corn systems. However, information on these dynamics and effects on other nutrients are limited in cotton systems. This project quantified the effect of a white clover LM on nutrient cycling of macro‐ and micronutrients (excluding N) in a cotton production system in the Georgia Piedmont. This included soil, plant, and pore water samples collected at important cotton reproductive states for 2 site‐years with different soil fertility. Additional samples were taken between cotton growing seasons to evaluate soil–clover interactions. Nutrient responses in the system (specifically K) were connected to soil test levels for nutrients at the start of reproduction. Only when the soil had above optimum K levels (2021), the LM luxury consumed excess K from the soil. Cotton leaves had the greatest fluctuations in K concentrations when LM was present from pinhead to cutout when soil K was below optimum. In winter, the soil had the greatest K concentration in treatments with the most clover relative to bare ground. Using optimal LM coverage can prevent excess K from potentially being lost from the system while not affecting cotton leaf K nutrition during reproductive growth.

Vegetable production on plastic mulch in Georgia often combines fumigation, drip tape, raised beds, and plastic mulch, where three to five high-value crops are produced over 2 yr. With the elimination of methyl bromide as a soil fumigant, herbicides applied over plastic mulch before crop transplanting have become essential to maintain weed control. However, proper care must be taken to avoid crop damage from any herbicide residue. Experiments using simulated vegetable beds covered with totally impermeable film (TIF) were conducted to quantify the concentration of halosulfuron-methyl, glufosinate, glyphosate, S-metolachlor, and acetochlor remaining on the mulch and the amount of each herbicide that moved into the crop transplant hole when irrigation water was applied. With 0.63 cm of water irrigation, glufosinate > halosulfuron-methyl > S-metolachlor > acetochlor. All herbicide concentrations were below 1.0 mg ai/ae in the transplant hole regardless of irrigation volume. For halosulfuron, glyphosate, and glufosinate, these concentrations were equal to a 1.3 to 8.9 times the field use rate washing into the transplant hole. Acetochlor and S-metolachlor concentrations in the transplant hole were equivalent to 0.1× to 0.7× of field use rates, respectively. With further evaluations, the quantified herbicide concentrations in the transplant hole can be used to make changes to recommended rates and potentially create new options for growers to utilize.

Hairy vetch is a promising legume cover crop ( Vicia villosa Roth) for the northern United States. Based on evidence from molecular markers, multi‐site evaluations, and morphological observations, a distinct second species exists within US hairy vetch germplasm, referred to hereafter as smooth vetch ( Vicia varia Host). Morphologically, hairy vetch is highly variable, but this study found statistically significant differences between smooth and hairy vetch in visual pubescence scores, plant maturity, and calyx lobe lengths. We used a panel of single sequence repeat (SSR) markers to assign cultivars and breeding materials to the two species and found that many commercial cultivars are smooth vetch. Interestingly, the SSR panel indicated that woollypod vetch ( Vicia dasycarpa Ten.) is a subpopulation of hairy vetch. Based on an elastic net model trained with multi‐site trial results from >35 site‐years, smooth vetch is not winter hardy in the northern United States but has superior performance relative to hairy vetch in the south‐central and Pacific Northwest United States. Specifically, smooth vetch has greater performance in environments with mild winters, cool spring temperatures, or low clay soils. Because of these differences in adaptation, differentiating these species will greatly improve agronomic outcomes and accelerate ongoing cover crop breeding progress.

Novel management strategies for controlling smutgrass have potential to influence sward dynamics in bahiagrass forage systems. This experiment evaluated population shifts in bahiagrass forage following implementation of integrated herbicide and fertilizer management plans for controlling smutgrass. Herbicide treatments included indaziflam applied PRE, hexazinone applied POST, a combination of PRE + POST herbicides, and a nonsprayed control. Fertilizer treatments included nitrogen, nitrogen + potassium, and an unfertilized control. The POST treatment reduced smutgrass coverage regardless of PRE or fertilizer application by the end of the first season and remained low for the 3-yr duration of the experiment (P < 0.01). All treatments, including nontreated controls, reduced smutgrass coverage during year 3 (P < 0.05), indicating that routine harvesting to remove the biomass reduced smutgrass coverage. Bahiagrass cover increased at the end of year 1 with POST treatment (P < 0.01), but only the POST + fertilizer treatment maintained greater bahiagrass coverage than the nontreated control by the end of year 3 (P < 0.05). Expenses associated with the POST + fertilizer treatment totaled US$348 ha⁻¹ across the 3-yr experiment. Other smutgrass control options could include complete removal of biomass (hay production) and pasture renovation, which can cost 3-fold or greater more than POST + fertilizer treatment. Complete removal of biomass may reduce smutgrass coverage by removing mature seedheads, but at a much greater expense of US$2,835 to US$5,825 ha⁻¹, depending on herbicide and fertilizer inputs. Bahiagrass renovation is US$826 ha⁻¹ in establishment costs alone. When pasture production expenses are included for two seasons postrenovation, the total increases to US$1,120 ha⁻¹ across three seasons. The importance of hexazinone and fertilizer as components of smutgrass control in bahiagrass forage was confirmed in this study. Future research should focus on the biology of smutgrass and the role of a PRE treatment in a long-term, larger-scale forage system.

This study examined the growth parameters of both glyphosate‐susceptible and glyphosate‐resistant biotypes of Amaranthus palmeri, designated as GA2005 and GA2017, respectively. A two‐year microplot field study was conducted to assess their growth characteristics. Scheduled destructive harvests on named harvest days (HD) were conducted to collect measurements for further calculation of net assimilation rate (NAR; g m⁻² day⁻¹), specific leaf area (SLA), leaf weight ratio (LWR), stem‐to‐leaf ratio (SLR), leaf area index (LAI), leaf area ratio (LAR; cm² g⁻¹), leaf area duration (LAD; days), relative growth rate (RGR; g.g⁻¹ day⁻¹) and plant volume (m³). In addition, stem diameter, number of leaves, and Chlorophyll content (μmol m²) were determined. The main objective was to identify growth parameters that differentiate biotypes along the plant life cycle. While certain growth parameters showed no variation among biotypes, differences in leaf area index (LAI) over HD and chlorophyll content and leaf area duration (LAD) were observed as the main effects. Glyphosate‐resistant biotypes exhibited higher LAD and chlorophyll content, potentially conferring a competitive advantage, especially in heavily used glyphosate environments. The study highlights the complexity of intraspecific genetic differentiation, adaptation, and environmental factors affecting A. palmeri. It may offer insights into biotype distinction and resistance spread while advancing our comprehension of species adaptation and growth strategies for enhanced control.

Accounting for 53% of U.S. peanuts (Arachis hypogaea L.), Georgia is the top peanut-producing state, with approximately 1.42 billion kg produced in 2023. Peanut producers often use the acetolactate synthase (ALS) imidazolinone herbicide imazapic, but reduced yellow nutsedge (Cyperus esculentus L.) control was reported in Georgia peanuts after 4 yr of continuous imazapic use. This study aimed to determine the level of resistance (LD_50, I₅₀, and GR₅₀) and potential cross-resistance for the suspected resistant population and to identify the associated genetic mutations conferring resistance. A susceptible biotype was treated with 0, 0.0088, 0.0175, 0.035, 0.07, 0.14, 0.28, and 0.56 kg ai ha⁻¹, and a resistant biotype was sprayed with 0, 0.07, 0.14, 0.28, 0.56, 1.13, 2.26, and 4.5 kg ai ha⁻¹ of imazapic. To determine whether the suspected resistant biotype was cross-resistant to halosulfuron-methyl, an ALS herbicide used to control Cyperus spp., both biotypes were treated with 0, 0.0117, 0.0233, 0.0466, 0.0933, 0.187, 0.373, and 0.746 g ai ha⁻¹ of halosulfuron-methyl. Plants were rated for injury at 7, 14, and 28 d after treatment (DAT), and aboveground biomass was harvested at 28 DAT. For imazapic, LD₅₀ was 0.041 and 1.503 kg ai ha⁻¹ and the GR₅₀ was estimated to be 0.0128 and 1.853 kg ha⁻¹ for Sus and Res biotypes, respectively, indicating 36- and 145-fold increase in resistance of the Res biotype for I₅₀ and GR₅₀, respectively. Both biotypes responded similarly to applications of halosulfuron-methyl, with biomass reduction at rates greater than 0.023 kg ai ha⁻¹. Transcriptome profiles revealed a mutation in the target-site gene of the resistant biotype causing an amino acid substitution from alanine to valine at position 205 (Ala-205-Val). Growers should continue to rotate chemistries and implement integrated weed management approaches for control of C. esculentus, as the use of imazapic over consecutive years has led to resistance in C. esculentus.

Knotroot foxtail [Setaria parviflora (Poir.) Kerguélen], a perennial Setaria species, is becoming more problematic in forage and grazing systems across the southeastern United States. Setaria parviflora reproduces through the production of rhizomes and seeds, further complicating management strategies. Significant knowledge gaps exist regarding the biology and control of this species. This research aimed to understand the influence of burial depth on S. parviflora propagules and the physiological differences between it and other Setaria spp. Experiments were conducted between October 2019 and February 2021 in Clarke County, GA, to investigate the influence of burial depth (1, 2, 4, 8, and 16 cm) on the emergence and growth of S. parviflora rhizomes and seeds. Zero emergence was estimated at 8.7, 10.8, and 11.2 cm for small rhizomes, large rhizomes, and seeds, respectively. Therefore, producers could implement tillage events to a depth of 11.2 cm or greater to control S. parviflora. A separate study compared S. parviflora, yellow foxtail [Setaria pumila (Poir.) Roem. & Schult.], green foxtail [Setaria viridis (L.) P. Beauv.], and giant foxtail (Setaria faberi Herrm.) plant morphology. Despite similar aboveground appearances, S. pumila and S. parviflora had different total and belowground biomass 2 to 5 mo after emergence, which suggests differences in root formation and perennialization of S. parviflora. The present research determined that burying propagules using tillage could be included in management recommendations concerning S. parviflora; however, it should be complemented with herbicide applications during the growing season to assist in controlling S. parviflora plants produced by seeds.