Italian ryegrass is a significant weed in Oregon, and resistance to multiple herbicide sites of action is widespread. Nonchemical tools are needed to improve management of Italian ryegrass in orchard systems. Field studies were conducted in Oregon to evaluate electrical weed control (EWC) of Italian ryegrass at two voltage ranges (3.9 kV and >5.0 kV) and multiple energy rates generated by varying travel speed. Energy was the primary factor affecting EWC efficacy. Control increased with increasing operational energy rate and, in two studies conducted when Italian ryegrass was at tillering to stem elongation stages, visible estimates of control reached 70% to 80% at 67.5 to 168.8 kJ m−2, corresponding to travel speeds of 0.8 to 0.32 km h−1. Control was lower in a third study when plants were at a more advanced growth stage. Plant density was not consistently reduced, indicating that a single EWC application suppressed growth but did not consistently kill Italian ryegrass plants. When energy was increased shoot and inflorescence dry weight and inflorescence number were reduced, indicating lower reproductive output among surviving plants. Voltage effects were limited and inconsistent across studies. These results indicate that EWC can suppress herbicide-resistant Italian ryegrass and reduce reproductive output in orchard systems, but a single treatment does not provide complete control. Growers will likely need to repeatedly apply EWC or to integrate it with other weed control tactics to improve suppression and reduce reproductive output.
Abstract Cutleaf evening primrose, a member of the Onagraceae family and native to the southeastern United States, is found in agricultural fields, nursery crops, roadsides, landscaped areas, and no-till production systems. Cutleaf evening primrose management has become increasingly difficult due to its ability to endure control measures beyond the rosette stage. Greenhouse trials were conducted during the 2025 growing season to assess the efficacy of labeled burndown herbicides for cutleaf evening primrose control. Field-collected cutleaf evening primrose seedlings were transplanted into pots and placed in a greenhouse for evaluation at two growth stages. The recommended herbicide rates (at 1×) tested were glyphosate at 1,260 g ae ha −1 , glufosinate at 672 g ai ha −1 , 2,4-D at 1,065 g ae ha −1 , paraquat at 840 g ai ha −1 , and glyphosate + 2,4-D, respectively. Herbicides were sprayed at late rosette and bolting growth stages. Control of cutleaf evening primrose was evaluated at 7, 14, 21, and 28 d after herbicide treatments (DAT). Shoot dry biomass data were collected at 28 DAT. Application of 2,4-D either alone or mixed with glyphosate resulted in 98% to 100% control at both growth stages. Depending on the growth stage at which herbicides were applied, cutleaf evening primrose was controlled 66% to 75% with glyphosate, 60% to 81% with glufosinate, and <25% with paraquat. The highest dry biomass reductions (≥80%) were observed with glyphosate, 2,4-D, and glyphosate + 2,4-D applications at the rosette stage. The study revealed that 2,4-D-alone or with glyphosate provided near-complete control of cutleaf evening primrose.
Farmers in the U.S. Midwest are increasingly planting soybean earlier in the growing season, which is prompting an investigation of which herbicide programs are most effective for achieving season-long weed control. The use of overlapping residual herbicides involves applying a full rate of a soil-residual herbicide preemergence, followed by an early postemergence application of a residual herbicide before the next flush of weeds emerge. Field experiments conducted in 2024 and 2025 at three locations in Indiana evaluated the interaction between soybean planting date and herbicide programs on season-long weed control, soybean stand, and grain yield. Soybean planting date factor included early (March to May) or late (May to June) planting dates, and herbicide programs factor included overlapping residuals followed by non-residual postemergence applications (Overlapping fb NRPOST), preemergence followed by NR POST (PRE fb NR POST), and POST only programs. Early planting resulted in 7% to 25% lower soybean stand, whereas herbicide program had minimal effect on soybean stand. Crop injury from residual herbicides was minimal with both early and late planting dates (≤5%). Compared to late planting, early planting resulted in 44% greater common lambsquarters density at POST herbicide application and 66% and 44% greater biomass at soybean harvest of common lambsquarters and giant ragweed, respectively. In giant ragweed-infested fields under early planting, the POST only herbicide program, which included soil residual and foliar-active herbicides, resulted in at least 34% lower yield than the Overlapping fb NR POST and PRE fb POST programs. In contrast, under late planting, soybean yield did not differ among herbicide programs.
Managing yellow nutsedge and southern root-knot nematode (SRKN) is particularly challenging in organic sweetpotato production. Anaerobic soil disinfestation (ASD) has emerged as a promising nonchemical pest management strategy that entails incorporating labile carbon amendments into the soil, covering the soil with impermeable plastic mulch, and irrigating the amended soil to saturation. Field studies were conducted at Clemson University in Charleston, South Carolina, in the 2023 and 2024 growing seasons, to evaluate the effect of ASD on yellow nutsedge and SRKN. Treatments were structured as a factorial arrangement of three carbon amendments (Brassica residue [BR], chicken manure + molasses [CM+M], and cotton seed meal [CSM]) and an unamended control (UC) by four sweetpotato clones (Bayou Belle, Monaco, Murasaki-29, and USDA-18-040) with four replications using a randomized complete block design. ASD was terminated 3 wk after initiation, and sweetpotato slips were planted 1 wk after ASD termination. Greater cumulative anaerobicity was observed in the CM+M and CSM treatments with increments exceeding 220% relative to UC at ASD termination. Six weeks after planting, yellow nutsedge densities across all sweetpotato clones were significantly lower with CM+M (4 to 10 plants m-2) and CSM (6 to 8 plants m-2) treatments than the UC (21 to 27 plants m-2). Both bunch cultivars (Monaco and USDA-18-040) and spreading cultivars (Bayou Belle and Murasaki-29) sweetpotato clones resulted in similar yellow nutsedge densities. Soil population densities of SRKN at 16 wk after planting were reduced by 23% to 44% in CM+M treatments and by 29% to 46% in CSM treatments, relative to the UC. Marketable sweetpotato yield rose from 47% to 131% with the CMM and CSM treatments compared with UC yield. The findings of this study demonstrate that CM+M and CSM-induced ASD have the potential to suppress yellow nutsedge and SRKN in organic sweetpotato production systems while increasing the marketable sweetpotato yield.
Timely soybean planting is important for maximizing yield, with farmers tending to plant their crops earlier. However, when a soybean crop is planted ultra-early (before April 15th in Ohio), seedlings are exposed to cold and moist conditions that can lead to a smaller plant population, delayed canopy closure, and reduced ability to compete with weeds. The objective of this study was to evaluate herbicide treatments for their effect on weed development and soybean yield when the crop was planted ultra-early (before April 15) and at a normal time (early to mid-May in Ohio). Weed biomass was significantly reduced when the crop was treated at early postemergence. However, preemergence followed by early postemergence herbicide applications were generally less effective at suppressing weeds than treatments that included an early postemergence and late postemergence application, for which weed density was reduced and weed control was improved later in the season. In 2024, when the number of soybean plants was very low due to freeze damage, an early postemergence application of dicamba + glyphosate and a late postemergence application of glyphosate + glufosinate + S-metolachlor resulted in the greatest weed control and yield from the crop that was planted ultra-early. The results from this study indicate that when soybean was planted ultra-early, treatments that included two postemergence applications, particularly those that included a residual herbicide applied at late postemergence, were better suited to maintain weed suppression later in the season and protect soybean yield potential when the soybean plant population was very low and pressure from grass weeds was high.
