Crop safety is an important consideration in determining PRE herbicide application, especially when multiple herbicide sites-of-action are used. This research examined relative corn injury as the result of PRE applications containing ALS- and/or HPPD-inhibiting herbicides to a sandy loam soil. Herbicide premixes containing clopyralid, flumetsulam, isoxaflutole, mesotrione, rimsulfuron, tembotrione, thifensulfuron, and thiencarbazone were applied at twice the labeled rate. In general, isoxaflutole alone was the safest herbicide evaluated, while PRE applications of rimsulfuron-containing herbicides caused the most corn stunting, had a lower recovery rate, and lower yields. However, POST applications of mesotrione plus rimsulfuron stunted corn less than 2%. Although there was little correlation between corn injury and yield, growers should be aware of the other factors, such as soil texture and environment that may impact crop production.

Potatoes are an important global food crop typically produced in high-input systems in temperate zones. Growers that have access to compost may use it to improve soil health and increase tuber yields, but compost may also increase weed competition by increasing early-season water availability and weed growth. A field study at the Michigan State University Montcalm Research farm in 2010 and 2011 investigated the impact of compost on weed competition in potato. Potatoes were grown in field plots with 0, 4,000, or 8,000 kg carbon (C) ha−1 of compost under weed-free conditions, and in competition with common lambsquarters, giant foxtail, and hairy nightshade. Compost did not increase biomass or seed production of any weed species. Giant foxtail and hairy nightshade at 5.3 plants per meter of row reduced potato yield by 20%; common lambsquarters reduced yield by 45%. The yield reduction by giant foxtail and hairy nightshade was due to a decrease in tuber bulking, whereas yield reductions from common lambsquarters were a result of lower tuber set and bulking. Potato yield increased 5 to 15% in compost compared to non-compost treatments; tuber specific gravity decreased by 0.3% in composted treatments. Across weed densities, elevated soil potassium levels in the 8,000 kg C ha−1 composted treatment may have increased potato yield and decreased tuber specific gravity.

During the 2015, 2016, and 2017 growing seasons, weed and weed-free mixed tall fescue and legume forage samples were harvested from 29 pastures throughout Missouri for investigation of the nutritive value of 20 common pasture weed species throughout the season. At certain times during the growing season, many broadleaf weed species had greater nutritive values for a given quality parameter as compared with the available weed-free, mixed tall fescue and legume forage harvested from the same location. There were no significant differences in crude protein concentration between the weed-free forage and many weeds throughout the growing season. However, crude protein content of common burdock, common cocklebur, common ragweed, dandelion, horsenettle, and lanceleaf ragweed was greater than that of the corresponding forage sample at multiple collection periods. The digestible neutral detergent fiber (dNDF) content of all broadleaf weeds except lanceleaf ragweed was significantly lower than that of the weed-free forage at all collection periods. Conversely, large crabgrass had significantly greater digestible neutral detergent fiber levels than did the mixed tall fescue forage at all sampling dates. Dandelion and spiny amaranth had greater in vitro true digestibility (IVTD) content than did the forage for the entire growing season. Three perennial weeds—horsenettle, vervains, and late boneset—did not differ in IVTD levels as compared with the mixed tall fescue and legume forage at any collection date. For most summer annual weeds, the trend was toward greater digestibility earlier in the season, with a gradual decline and often lower IVTD by the late summer or early fall. The results of this study will enable producers to make more informed management decisions about the potential benefit or detriment a weed may provide to the overall nutritive value of the pasture system.

Bodies of water that are treated with herbicides for aquatic weed control are often used as a source of irrigation water by landowners near the water body, but there is little information regarding the effects of experimental aquatic herbicides on common garden plants. Therefore, the goal of these experiments was to identify phytotoxicity of four herbicides on vegetables frequently cultivated by home gardeners. Sweet pepper, zucchini, tomato, and bush bean were irrigated with water containing bispyribac-sodium, quinclorac, topramezone, and trifloxysulfuron-sodium to identify the herbicide concentrations that damage these garden vegetables. Experiments were conducted during 2009 and repeated in 2010. Plants were irrigated four times during an 11-d period with the equivalent of 1.27 cm of treated water during each irrigation, then irrigated with well water until they were harvested 41 d after the first herbicide treatment. Values of the concentration of herbicide expected to reduce treated plants by 10% compared with control plants (EC10) were calculated from components of nonlinear regression. Analysis of visual quality and dry weight data revealed that bush bean was the most sensitive of the vegetable plants to bispyribac-sodium, trifloxysulfuron-sodium, and topramezone, whereas the species most sensitive to quinclorac was zucchini. Exposure of bush bean to 7.1, 0.9, and 1.2 parts per billion (ppb) of bispyribac-sodium, trifloxysulfuron-sodium, and topramezone, respectively, would be expected to cause 10% reductions compared with control plants, whereas exposure of zucchini to as little as 11.0 ppb of quinclorac would be expected to cause a 10% reduction in dry weight.

Sulfometuron was applied over the top of recently planted oak seedlings in three separate studies. Both preemergent (PRE) and postemergent (POST) timings were utilized in all studies. In 1997, six species of oaks were planted and evaluated, and two species were planted in the 1998 and 1999 studies. Sulfometuron was applied at rates of 0.1 and 0.2 kg ai/ha in 1997 PRE and at 0.1 kg ai/ha POST. In 1998 and 1999, treatment rates were 0.1 and 0.15 kg ai/ha for PRE and 0.1 kg ai/ha POST. Results indicate that sulfometuron is effective for competition control and can be applied PRE with total safety with the tested oaks. However, sulfometuron should not be applied POST over white oak seedlings, as mortality will result.

This article presents an approach to managing and evaluating soil survey data that can aid in soil-applied herbicide decision making. Field experiments were used to quantify the dose responses of corn, shattercane, and velvetleaf to isoxaflutole over a range of soil conditions within an agricultural field. Isoxaflutole doses eliciting crop injury (20% greenness reduction) and weed control (80% biomasss reduction) were projected for a county located in Nebraska based on associations between the plant response and the soil properties. The biologically effective dose of isoxaflutole increased with increasing organic matter and mineral surface area. Mean biologically effective doses for velvetleaf (1 to 27 g/ha) were considerably lower than that for shattercane (42 to 206 g/ha). Over 60% of the surface texture is silty clay loam for Saunders County, suggesting that 17 and 158 g/ha are the minimal doses required to suppress velvetleaf and shattercane, respectively, for a majority of the county. Conceivably, this approach could be used as an initial step to assess the relative value of field-specific applications and variable dose application technologies.

Common dandelion has developed into a troublesome agronomic weed for no-tillage corn and soybean producers in Michigan and throughout the north central region of the United States. Field experiments were conducted on established populations of common dandelion in 2001 to 2002 and 2002 to 2003 to evaluate the effect of preplant and sequential herbicide applications on established populations of common dandelion. Preplant treatments of glyphosate or 2,4-D ester were applied early fall, late fall, early spring, and late spring. For both glyphosate and 2,4-D ester, the fall applications were more effective than the spring applications. Glyphosate at 840 gae/ha was more effective than 2,4-D ester at 1,120 gae/ha at each application timing. A single application of glyphosate or 2,4-D ester applied either in the fall or spring did not provide season-long control of common dandelion. Sequential treatments of glyphosate following preplant applications of either glyphosate or 2,4-D ester provided season-long control of common dandelion.

Field studies were conducted to evaluate corn vigor reduction, weed control, corn yield, and economic returns in a no-till system with various herbicide strategies using full and reduced rates of acetochlor and atrazine with glyphosate, glufosinate, or imazethapyr + imazapyr in their respective type of herbicide-resistant, no-tillage corn. Crop vigor reduction due to herbicide injury was 10% or less with all treatments. A burndown plus a full label rate of a residual herbicide applied early preplant (EPP) generally provided less than 80% control of giant foxtail, common waterhemp, and common cocklebur but usually greater than 85% control of common ragweed and common lambsquarters. Two-pass strategies generally provided greater than 85% control of all species evaluated. Early postemergence, mid-postemergence (MPOST), and late postemergence strategies generally provided inconsistent and poor overall weed control. EPP–MPOST strategies generally provided lower weed control than strategies using acetochlor or atrazine EPP followed by a postemergence application. Corn yield and net economic returns followed a similar trend as weed control, with strategies that provided greater than 80% weed control showing minimal crop vigor reduction and high grain yields. Two-pass strategies with residual herbicides generally provided the highest yields, economic returns, and low coefficients of variation (CV) of net income. Although EPP strategies provided similar economic returns as some of the two-pass strategies, they had higher CVs, implying greater risk to economic return.

Field studies were conducted from 1982 to 1984 to evaluate the effectiveness of SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] for quackgrass [Agropyron repens (L.) Beauv. # AGRRE] control. The herbicides were compared 1) in different rates and carrier volumes, 2) on several spring and fall application dates, and 3) with varying time intervals between application and moldboard plowing. Glyphosate and SC-0224 controlled quackgrass equally well at carrier volumes of 25 to 400 L/ha. Both herbicides generally provided similar control as fall and spring applications and with time intervals of 12 to 96 h between application and plowing. Occasionally the low rate of SC-0024 gave less quackgrass control the next season than the same rate of glyphosate. Adding nonionic surfactant at 0.5% (v/v) did not influence the phytotoxicity of these herbicides at the rates and carrier volumes tested. These herbicides controlled quackgrass comparably and greater than 85% when applied under appropriate environmental conditions.

Experiments were conducted to evaluate imazaquin and selected herbicides for POST control of wild garlic. At the same dosages, imazaquin applied in late November/early December (late fall) controlled wild garlic better than when applied in early March (late winter) when assessed in May. Imazaquin provided control equivalent to 1120 g ae ha–1 2,4-D plus imazaquin. Imazapyr, imazamethabenz, or imazethapyr at 280, 1120, or 560 g ai ha–1, respectively, provided control equivalent to 560 g ai ha–1 imazaquin. Thifensulfuron at 70 g ai ha–1 provided better control applied in late winter (85%) than late fall (45%). All herbicides consistently provided better control than 2,4-D plus mecoprop plus dicamba, except thifensulfuron applied in late fall, at the final evaluation. Common bermudagrass growth in early spring was delayed 2 mo by ≥ 560 g ha–1 imazaquin, 70 g ha–1 thifensulfuron, imazethapyr, and imazapyr or 2,4-D plus mecoprop plus dicamba applied in late winter. Imazamethabenz did not delay common bermudagrass growth. Late fall applications of 1120 g ha–1 imazaquin did not delay growth while ≥ 560 g ha–1 imazethapyr delayed common bermudagrass growth through April.

Experiments were conducted to evaluate the effect of tillage, rye residue levels, and control strategies on weed suppression and potato yield. Reduced tillage (RT) yields in 1989 were lower than in conventional tillage (CT) due to high hairy galinsoga populations. However, in 1990, potato yields were greater in RT when early emerging weeds were suppressed. Increasing residue levels up to 2300 kg ha-1 had no effect on weeds or yields in either year. In a separate study, preemergence herbicides (linuron plus metolachlor, 1.7 kg ai ha-1 each) applied 10 d after planting (DAP) in reduced tillage controlled weeds for 6 wk, but efficacy decreased after hilling. Metribuzin applied postemergence (0.19 kg ai ha-1) 7 d after hilling controlled late germinating weeds. Potato yields were greatest when the preemergence herbicides were applied.

Field studies were conducted in 1989 and 1990 to determine if corn seed treated with naphthalic anhydride (NA) at 0.5% (w/w) would result in a reduction in corn injury caused by clomazone applied preplant incorporated (PPI) or preemergence (PRE) at 0.56 and 0.70 kg a.i. ha–1. NA significantly reduced corn injury, especially where clomazone was incorporated. Plant population, height, ear number, and grain yield also were higher in plots where NA was used. In most instances, corn injury was less and plant population, height, ear number, and grain yield were higher in plots where clomazone was applied PRE compared with PPI.

Greenhouse and field studies were conducted to examine the interaction of sethoxydim or fluazifop-P tank mixed with chlorsulfuron or thiameturon for selective weed control in safflower. Under greenhouse conditions, the addition of chlorsulfuron to sethoxydim or fluazifop-P slightly improved the control of green foxtail above that achieved with either herbicide alone. Control of wild oat and wild mustard was similar with the tank mixes and each herbicide alone. In the field, control of wild oat with sethoxydim or fluazifop-P was not altered by adding chlorsulfuron or thiameturon in tank mixes. Similarly, control of common lambsquarters and wild mustard with chlorsulfuron or thiameturon was not affected by adding either sethoxydim or fluazifop-P in tank mixes. Plant height, date of flowering, seed yield, and quality data indicated that safflower tolerated these herbicides applied alone or in combination. Sethoxydim or fluazifop-P tank mixed with chlorsulfuron or thiameturon provide a postemergent alternative for selective control of grass and broadleaf weeds in safflower.

Field studies were conducted near Marianna, FL during 1999 and 2000 to evaluate weed control and peanut response to PPI treatments of diclosulam alone, PRE treatments of flumioxazin alone, and in systems with POST commercial standard herbicides. Diclosulam and flumioxazin alone did not control sicklepod. Paraquat plus bentazon plus 2,4-DB applied early POST fb chlorimuron plus 2,4-DB or imazapic controlled sicklepod and pitted morningglory at least 83%. These treatments were equal to or greater than diclosulam or flumioxazin with or without paraquat plus bentazon plus 2,4-DB, or the same system fb 2,4-DB mid POST. Peanut yield was similar when treated with diclosulam or flumioxazin fb the standard early POST (EPOST) system, flumioxazin alone, or imazapic alone. Peanut treated with diclosulam alone or paraquat plus bentazon plus 2,4-DB fb 2,4-DB yielded lower than other treatments because of late-emerging Florida beggarweed. Peanut treated with chlorimuron, regardless of which soil-applied herbicide was used, yielded less due to a longer period of interference from Florida beggarweed, sicklepod, and pitted morningglory because of the timing of chlorimuron application (60 d after planting).

Studies on the efficacy and economic analysis of Texas panicum management systems in corn were conducted in Georgia on a loamy sand soil in 1987, 1988, and 1989. Management systems that included butylate, EPTC, atrazine plus tridiphane, atrazine plus pendimethalin, atrazine plus trifluralin, paraquat, or ametryn acceptably control Texas panicum. Corn yields were not affected significantly by the Texas panicum management systems. Overall net returns calculated for corn production indicated that systems which included postemergence applications of atrazine, pendimethalin, trifluralin, paraquat, ametryn, or cultivation alone gave the highest net returns. Systems which included butylate, EPTC, or tridiphane frequently had significantly lower net returns.

Currently, there are no effective herbicides registered for the control of hoary cress (Cardaria draba) in alfalfa (Medicago sativa) or alfalfa/grass mixtures. Due to this lack of control options, field experiments were conducted near St. Ignatius, MT, from 1995 through 1997 to determine the optimum imazethapyr rate and adjuvant combination for hoary cress control in alfalfa/orchardgrass (Dactylis glomerata) pastures. Imazethapyr was applied in the spring to rosette stage hoary cress plants at 33, 67, and 100 g ai/ha with either a nonionic surfactant or methylated seed oil alone or combined with 28% urea ammonium nitrate (UAN) liquid fertilizer. Hoary cress control was poorest when imazethapyr was applied at 33 g/ha, yet provided a minimum of 80% control. Imazethapyr applied at 67 and 100 g/ha provided greater than 90% control during the year of application regardless of surfactant or UAN additions. None of the treatments controlled hoary cress the year following application. Alfalfa yield was unaffected by imazethapyr applications. First-cutting orchardgrass yield decreased as imazethapyr rate increased, but total seasonal forage yield was unaffected.

Meadow foxtail is a rhizomatous grass widely grown for hay and pasture in wet meadows of the western United States and Canada. Two sulfonylurea herbicides, chlorsulfuron and metsulfuron-methyl, were evaluated for their effects on meadow foxtail biomass. Both herbicides were applied at four doses, 0.035, 0.070, 0.105, and 0.140 kg ai/ha, together with a control at each of two sites in October 2003. Treatments were replicated four times at each site and arranged in a randomized complete block design and sampled in July 2004 and 2005. Meadow foxtail biomass depended on site (P = 0.001) or year (P = 0.001), but not herbicide treatment (P = 0.182). No biomass production losses resulted from applying up to 0.14 kg/ha of either chlorsulfuron or metsulfuron-methyl on meadow foxtail, even in relatively high-pH soils.

A postemergence (POST) timing study was conducted on established populations of burcucumber (Sicyos angulatus) in corn (Zea mays), and a second study examined the residual activity of several herbicides for burcucumber control under greenhouse conditions. In the field study, flumiclorac, halosulfuron, primisulfuron, CGA 152005, and CGA 152005 + primisulfuron (45, 71, 40, 40, and 20 + 20 g ai/ha, respectively) were applied at two POST timings. CGA 152005, primisulfuron, and the combination provided greater than 85% control of burcucumber 14 wk after planting (WAP). Flumiclorac and halosulfuron provided 60% control or less by 8 WAP. Timing of the POST applications did not influence burcucumber control by 11 WAP with any herbicide. In the greenhouse, germinated burcucumber seeds were placed in soil treated with atrazine, chlorimuron, primisulfuron, or CGA 152005 at normal field use rates. All treatments provided similar residual control early; however by 4 wk after treatment (WAT), control from atrazine was less than 10% compared to 69% for chlorimuron and about 50% for primisulfuron and CGA 152005. This research suggests that CGA 152005 and primisulfuron can both be effective for managing burcucumber in corn, whereas flumiclorac and halosulfuron proved ineffective.

Canada thistle control in no-tillage corn was studied in Western Maryland from 1990 to 1992. The best treatment at planting for controlling Canada thistle was a tank mixture of 2240 g/ha glyphosate plus 560 g/ha 2,4-D. Clopyralid applied at 210 and 280 g/ha alone and 106 g/ha tank mixed with 560 g/ha 2,4-D effectively controlled Canada thistle in no-tillage corn (85 to 96%). Nicosulfuron applied at 35 g/ha and 20 or 40 g/ha primisulfuron suppressed Canada thistle (59 to 75%). Tank mixtures of nicosulfuron or primisulfuron with 2,4-D or dicamba generally increased Canada thistle control (75 to 87%) compared with control by these herbicides applied alone. Treatments that controlled Canada thistle generally increased corn yields compared with the weedy controls. Yield increases were most dramatic in 1991 when precipitation was low.

Biennial wormwood has become an important weed for soybean producers in the northern Great Plains states of the United States. Research was conducted at Fargo, Leonard, and Wyndmere, ND, in 2000 and 2001 to evaluate postemergence control of biennial wormwood in soybean. Biennial wormwood densities at Fargo, Leonard, and Wyndmere were 290, 290, and 130 plants/m2 in 2000 and 22, 670, and 88 plants/m2 in 2001, respectively. Across years, biennial wormwood control with postemergence herbicides 4 wk after treatment was 81 to 97% at Fargo, 5 to 89% at Leonard, and 2 to 95% at Wyndmere. Biennial wormwood control was greater at Fargo than at the other locations probably because of smaller seedling size at the time of treatment. Bentazon split applied at the rate of 560 g ai/ha followed by 560 g/ha approximately 12 d after the first treatment generally provided the least amount of injury to soybean, the greatest control of biennial wormwood, and the fewest escaped plants. Lactofen at 220 g ai/ha or split applied at 110 g/ha followed by 110 g/ha approximately 12 d after the first treatment provided 84% or greater biennial wormwood control at Fargo but less than 40% control at Leonard and Wyndmere. The 4.5:1 bentazon plus acifluorfen premix full-rate and split treatments provided slightly better control than the 2:1 bentazon plus acifluorfen premix full-rate and split treatments. High levels of biennial wormwood control can be achieved with a better understanding of seedling emergence patterns and by targeting postemergence herbicide applications to seedlings less than 5 cm tall.