Research was conducted in North Carolina to compare weed control by various rates of imazapic POST alone or following diclosulam PRE. In a second experiment, weed control by imazapic applied POST alone or with acifluoren, diclosulam, or 2,4-DB was compared. In a final experiment, yellow nutsedge control by imazapic alone and with the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, and tebuconazole was compared. Large crabgrass was controlled more effectively by imazapic POST than diclosulam PRE. Common lambsquarters, common ragweed, and eclipta were controlled more effectively by diclosulam PRE than imazapic POST. Nodding spurge was controlled similarly by both herbicides. Few differences in control were noted when comparing imazapic rates after diclosulam PRE. Applying either diclosulam PRE or imazapic POST alone or in combination increased peanut yield over nontreated peanut in five of six experiments. Few differences in pod yield were noted when comparing imazapic rates. Acifluorfen, diclosulam, and 2,4-DB did not affect entireleaf morningglory, large crabgrass, nodding spurge, pitted morningglory, and yellow nutsedge control by imazapic. Eclipta control by coapplication of imazapic and diclosulam exceeded control by imazapic alone. The fungicides azoxystrobin, chlorothalonil, pyraclostrobin, and tebuconazole did not affect yellow nutsedge control by imazapic.

Field experiments were carried out during two growing seasons at Adnan Menderes University, Faculty of Agriculture, in Aydın-Turkey to evaluate the weed control efficacy of olive processing waste (OPW) in okra, faba bean, and onion. OPW was incorporated into the soil prior to seeding at 10, 20, 30, and 40 tons (t)/ha. Non-treated plots and plots treated with trifluralin in okra and pendimethalin in faba bean and onion were used for comparison. OPW suppressed common purslane, redroot pigweed, and junglerice in okra; littleseed canarygrass, annual bluegrass, wild chamomile, and shepherd's-purse in faba bean and onion. OPW was in most cases equally as effective as soil herbicides; however, 10 t/ha provided sometimes lower efficacy than herbicides. OPW had no negative effects on okra and faba bean, while onion was negatively affected by doses over 30 t/ha. Overall, OPW can be applied at 10 to 20 t/ha doses for weed control with adequate crop safety.

Field experiments were initiated to determine the efficacy of fluazifop as influenced by growth stage for green, yellow, and giant foxtail, large crabgrass, and Japanese millet. Additionally, the influence of air temperature and simulated rainfall on fluazifop efficacy for green foxtail and Japanese millet was determined by greenhouse and growth-room experiments. In both 1983 and 1984, fluazifop activity was reduced as the growth stage increased from 3- to 5- to 7-leaf for all species. Significant differences among species in susceptibility to fluazifop were evident with the descending order of tolerance: green foxtail > large crabgrass > yellow foxtail > giant foxtail > Japanese millet. Increasing the air temperature from 18 to 30 C reduced fluazifop control of green foxtail at herbicide rates less than 0.14 kg ai/ha but did not affect Japanese millet. A 1- to 2-h rain-free interval was required for optimum control of green foxtail and Japanese millet at 0.07 kg/ha fluazifop; the interval was reduced to 45 and 15 min, respectively, when fluazifop rates were 0.14 kg/ha. The longer rain-free interval required for optimum control of green foxtail compared to Japanese millet may reflect a slower rate of herbicide absorption in green foxtail.

Swallowwort, a twining perennial of the Asclepiadaceae family, has become increasingly invasive in cultivated fields, orchards, fence rows, natural areas, and roadsides of some provinces in Iran. The ability of this weed to establish and develop from seed was studied in laboratory and greenhouse experiments. Optimum germination temperature was 25 C. Germination did not occur at ≤ 15 C either in dark or light. In temperature fluctuation experiments, maximum germination occurred at 30/22 C, but light fluctuations had no effect on swallowwort seed germination. At pH 4 to 9 seed germination was 44 to 66%. Osmotic potential up to −0.2 MPa had little effect on germination. Seed germination was less than 5% at −0.8 Mpa. Swallowwort seeds were not able to germinate at 300 mM NaCl; however, there was 12% germination at the 200 mM concentration. Maximum emergence occurred when the seeds were planted at 1.5 cm depth. Seedlings did not emerge when planted at 6.5 cm depth. Germination percentage of the seeds kept under immersed (water) conditions was similar to those of nonimmersing periods; however, seedling growth was greater in treatments without immersing periods.

In full-season soybean experiments, adding glyphosate, paraquat, or HOE-0661 to chlorimuron, chlorimuron plus linuron, chlorimuron plus metribuzin, or imazaquin was required for effective weed control, especially eastern black nightshade. In double-crop soybean experiments, chlorimuron plus linuron provided similar weed control and yields with or without either glyphosate, paraquat, or HOE-0661. In both full-season and double-crop soybeans, metolachlor combined with chlorimuron mixtures did not enhance weed control or increase yield. These studies indicate a potential for reducing the use of nonselective herbicides or metolachlor when chlorimuron or imazaquin are components of tank mixes, particularly in double-crop no-till soybeans.

Certain linear alcohol ethoxylate surfactants with large hydrophobes enhanced nicosulfuron activity on giant foxtail (Setaria faberi) more effectively at low doses than surfactants with small hydrophobes and commercial standards. The most effective surfactants had a C16–18 hydrophobe and 12 to 30 moles of ethoxylation or a C24 hydrophobe with 13 moles of ethoxylation. Response curve analysis showed these linear alcohol ethoxylate surfactants were five- to 20-fold more active on a dose basis than currently used commercial surfactants.

Field experiments were conducted at Kalispell, MT, and Corvallis, OR, to determine the optimum rate and application timing of imazamox for downy brome control in winter wheat. Crop injury occurred as a reduction in plant height and was minimal at Kalispell, never exceeding 10%. Crop injury at Corvallis was more severe and was dependant on application timing. No injury was observed with spring applications, but fall applications resulted in as much as 33% injury at the highest rate of imazamox. Fall applications generally provided more consistent control of downy brome, as evidenced by the lower dosage required to reduce downy brome dry weight by 50% (lower I50 values). Nonetheless, spring applications generally provided control comparable with that of fall applications when imazamox was applied at the highest rate. The one exception was at Corvallis during 1997 to 1998, where spring applications failed to provide adequate control of downy brome even at the highest rate applied. Although imazamox generally provided excellent control of downy brome, wheat yield response to downy brome interference was negligible, declining by less than 10% in the absence of imazamox. The absence of a yield response to downy brome interference was attributed to the lack of competition for soil moisture from downy brome under the high-rainfall conditions of the experiment.

Changing the number of ethylene oxide (EO) units on a nonylphenol surfactant changes its physicochemical and biological properties. Increasing the number of EO units makes the surfactant more hydrophilic and increases its hydrophilic-lipophilic balance (HLB). Surfactants with high HLB values, more than 16, were the most active with the hydrophilic herbicide glyphosate. More lipophilic surfactants with HLB values from 11 to 13 were more active with the lipophilic herbicide, the ethyl ester of quizalofop-P. Surfactants with intermediate HLB values were the most active with the herbicide that had intermediate water solubility, nicosulfuron. Matching the physicochemical properties of the herbicide and surfactant improved biological efficacy on giant foxtail.

Field studies were conducted for two years at two locations near Pendleton and Moro, OR to evaluate the influence of single sub-surface nitrogen (N) fertilizer application timings and multiple N applications on downy brome and winter wheat growth and yield. N applications in fallow, at planting, during the crop season, and several split N application timings were compared to evaluate downy brome interference in winter wheat. N application rates varied between locations as a function of average annual precipitation and accepted agricultural practice. Pendleton and Moro were considered high and low precipitation sites, respectively. At Pendleton in a year of above average precipitation, N applied at planting, in-crop, or split applications of N with part of N applied at planting and part in-crop, increased downy brome dry matter production compared to N applied in fallow. Downy brome infestation eliminated otherwise positive wheat yield benefits of split N application compared to the conventional commercial practice of N application in fallow. In a year of moderate precipitation, N applications at planting, in-crop, or split N applications did not benefit wheat yield compared to N application in fallow, but downy brome dry matter was increased. In a dry season, N rates and timings did not increase downy brome dry weight or wheat grain yield. In the absence of downy brome, alternative N application techniques increased wheat yield only under high growing season precipitation.

Much research has evaluated herbicide safety on established bermudagrass turf, but information is lacking on seedling response to herbicides. Three field experiments were conducted in Blacksburg, VA, to assess turfgrass and smooth crabgrass response to selected sulfonylurea herbicides during seedling bermudagrass establishment. Herbicides injured bermudagrass 9 wk after treatment in the following order from most to least injurious: flazasulfuron = trifloxysulfuron > rimsulfuron > metsulfuron = sulfosulfuron > foramsulfuron. Herbicides applied 3 wk after seeding (WAS) were generally more injurious than when applied 1 WAS. Flazasulfuron and trifloxysulfuron-sodium controlled smooth crabgrass greater than 90% at 6 WAS, and metsulfuron and rimsulfuron suppressed smooth crabgrass 76 and 84%, respectively. Foramsulfuron, metsulfuron, and sulfosulfuron appear safe to apply 1 and 3 WAS, causing very little chlorosis and no reduction in turf cover. Rimsulfuron is injurious when applied at those timings; however, long-term cover is not reduced. Flazasulfuron and trifloxysulfuron-sodium are not safe to use 1 and 3 WAS unless weed pressure is extreme, and a delay in bermudagrass cover is acceptable.

Field trials were conducted in East Lansing, MI in 2004 and 2005 and in St. Charles, MI in 2004, 2005, and 2006 to compare weed control and sugarbeet tolerance from microrate herbicide treatments that included s-metolachlor and dimethenamid-P. Treatments included the base microrate treatment alone and with full- and split-application rates of s-metolachlor at 1.4 kg/ha or dimethenamid-P at 0.84 kg/ha at the various microrate application timings. All treatments injured sugarbeet. In 2004 and 2006, full rates of both s-metolachlor and dimethenamid-P applied PRE or in the first microrate application injured sugarbeet more than the base microrate treatment. When s-metolachlor or dimethenamid-P were split-applied between PRE and the third microrate application or between the first and the third microrate applications, injury was still greater than from the base microrate treatment. Furthermore, applying dimethenamid-P at one-fourth the full rate in all four microrate applications injured sugarbeet more than the base microrate treatment. A full rate of s-metolachlor or dimethenamid-P applied in either the third or fourth microrate applications or splitting the applications between the second and fourth microrate treatments did not increase sugarbeet injury compared with the base microrate treatment. Control of common lambsquarters and giant foxtail from all treatments containing s-metolachlor or dimethenamid-P, regardless of the time of application, was greater than from the base microrate treatment at all locations. Pigweed spp. control was 94% or greater from all treatments. In 2004, late-season control of giant foxtail was greater from all treatments that included s-metolachlor or dimethenamid-P compared with the base microrate treatment. In 2005, the only treatments that did not improve late-season giant foxtail control compared with the base microrate treatment were the treatments that included a full rate of s-metolachlor or dimethenamid-P applied in the fourth microrate application. Even though some herbicide treatments that included s-metolachlor or dimethenamid-P injured sugarbeet more than the base microrate treatment, recoverable sucrose per hectare was similar among treatments.

Experiments were conducted to study the effect of application rate, growth stage, and tank-mixing azimsulfuron or bentazon on the activity of cyhalofop, clefoxydim, and penoxsulam against two morphologically distinct Echinochloa species from rice fields in Greece. Mixtures of penoxsulam with MCPA were also evaluated. Cyhalofop (300 to 600 g ai/ha) applied at the three- to four-leaf growth stage provided 62 to 85% control of early watergrass but 41 to 83% control of late watergrass averaged over mixture treatments. Control ranged from 37 to 80% for early watergrass and from 35 to 78% for late watergrass when cyhalofop was applied at the five- to six-leaf growth stage averaged over mixture treatments. Mixtures of cyhalofop with azimsulfuron or bentazon reduced efficacy on both species irrespective of growth stage or cyhalofop application rate compared with cyhalofop alone. Clefoxydim (100 to 250 g ai/ha) applied alone at the three- to four-leaf growth stage provided 98 to 100% control of early watergrass and 91 to 100% control of late watergrass; when clefoxydim was applied alone at the five- to six-leaf growth stage the control obtained was 91 to 100% for early watergrass and 79 to 100% for late watergrass. Mixtures of clefoxydim with azimsulfuron or bentazon reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Penoxsulam (20 to 40 g ai/ha) applied alone provided 94 to 100% control of both species at both growth stages. Mixtures of MCPA with penoxsulam reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Mixtures of penoxsulam with azimsulfuron or bentazon reduced efficacy only on late watergrass at the late growth stage.

The level of past industry participation in registering herbicide minor crop uses has been a function of active ingredient discovery output and the combination of incentives and barriers that drive minor use registration decisions. Over the past 10 yr there have been several external factors negatively impacting the rate of new herbicide introductions by industry. These include industry consolidation, a decrease in the global value of the conventional herbicide market, adoption of Herbicide-Resistant Crop (HRC) technology, a substantial increase in required regulatory activity primarily through reregistration programs, and increased costs of discovery research and product development. The increased cost of conducting business in an increasingly competitive market has undoubtedly influenced herbicide registrants to adopt different discovery strategies. Economics dictate registration efforts only towards crops that will create a significant, positive return on investment. In most cases, development of new herbicides for minor crops is not economically viable due to low or negative return on investment and disproportionate liability risk. Therefore, to motivate increased participation, companies need incentives and mechanisms to mitigate risk and registration barriers. Increased data protection and the Interregional Project 4 (IR-4) program, a cooperative government program with the goal of developing data to support regulatory clearances of pest control products for specialty crops, are current government programs in place that provide incentives and defray cost. Other incentives should be explored to make minor crops more attractive targets. However, product registration, liability risk, and dedicating the necessary resources to adequately research crop selectivity are still major economic barriers. Creative solutions that ensure companies are not unreasonably exposed to yield loss claims would remove a primary reason why companies are reluctant to register herbicides for minor crops.

Field studies were conducted in Crowley, LA, and Stoneville, MS, in drill-seeded rice to evaluate economical returns of weed control with imazethapyr. Red rice and barnyardgrass control was evaluated with imazethapyr alone at various rates and application timings. Imazethapyr, averaged across rate, controlled red rice 89% and barnyardgrass 90% when the initial application of imazethapyr was applied at emergence followed by a second application of imazethapyr 2 wk later. No difference in red rice and barnyardgrass control was observed with imazethapyr, averaged across timing. Yield and economical returns were maximized when the initial application of imazethapyr was applied at rice emergence followed by a second application of imazethapyr 2 wk later.

Several commercial and experimental adjuvants were evaluated for efficacy in enhancing activity and selectivity of quinclorac in two cultivars of canola and four turfgrass species. Weed species investigated included cleavers, annual sowthistle, large crabgrass, and goosegrass. Turfgrass species evaluated included Kentucky bluegrass, perennial ryegrass, tall fescue, and creeping bentgrass. A variety of adjuvant types were selected, such as a methylated seed oil (Sunit II), a petroleum-based crop oil concentrate, the silicone-based Sylgard 309, a cationic fatty amine ethoxylate surfactant (Frigate), and modified crop oils (Dash and Merge). Adjuvant efficacy was evaluated by calculating the quinclorac rate required to reduce plant growth 50% (GR50) based on rates applied at 0, 15.6, 31.2, 62.5, and 125 g ai/ha. For goosegrass, quinclorac rates evaluated were increased to 250, 500, 1,000, and 2,000 g ai/ha. All evaluated adjuvants provided similar enhancement of control for cleavers and annual sowthistle. Sylgard 309 was the least effective adjuvant for control of large crabgrass. Goosegrass was tolerant to quinclorac across the evaluated rate range regardless of adjuvant; therefore, GR50 values could not be determined. None of the adjuvants alone caused phytotoxicity to canola or any turfgrass species.

Drip-applied herbicides provide farmers with a more timely and cost-effective approach for applying PRE herbicides; however, herbicide movement is often limited. Field studies were conducted evaluating drip-application methods for applying PRE herbicides under polyethylene-mulched beds on yellow nutsedge punctures and the corresponding responses of a tomato crop (height and yield). The experiment was a factorial treatment arrangement of three drip application methods and three PRE-applied herbicides [halosulfuron (54 g ai ha−1), S-metolachlor (1.4 kg ha−1), and fomesafen (280 g ha−1)]. Herbicides were applied either immediately following saturation of the planting beds (method A), over an extended period while saturating the beds (method B), or prior to bed saturation (method C). Additional treatments included a commercial standard (S-metolachlor sprayed to the bed surface prior to mulch application) and a nontreated control (polyethylene mulch only). Drip-applied fomesafen, halosulfuron, and S-metolachlor provided similar control of yellow nutsedge, produced comparable yields, and failed to elicit any negative growth responses when compared to our commercial standard. With the exception of nutsedge punctures counted 56 DAT, application method did not influenced measurable outcomes. At 56 DAT nutsedge punctures were significantly lower in treatments applied by method B compared to those applied with method A.

Two field experiments were conducted during 2012 and 2013 at Roseworthy, South Australia to identify effective herbicide options for the management of clethodim-resistant rigid ryegrass in faba bean. Dose–response experiments confirmed resistance in both field populations (B3, 2012 and E2, 2013) to clethodim and butroxydim. Sequencing of the target site of acetyl coenzyme A carboxylase gene in both populations identified an aspartate-2078-glycine mutation. Although resistance of B3 and E2 populations to clethodim was similar (16.5- and 21.4-fold more resistant than the susceptible control SLR4), the B3 population was much more resistant to butroxydim (7.13-fold) than E2 (2.24-fold). Addition of butroxydim to clethodim reduced rigid ryegrass plant density 60 to 80% and seed production 71 to 88% compared with the standard grower practice of simazine PPI plus clethodim POST. Clethodim + butroxydim combination had the highest grain yield of faba bean (980 to 2,400 kg ha−1). Although propyzamide and pyroxasulfone plus triallate PPI provided the next highest levels of rigid ryegrass control (< 60%), these treatments were more variable and unable to reduce seed production (6,354 to 13,570 seeds m−2) to levels acceptable for continuous cropping systems.

Poor weed control, resulting from limited herbicide availability and undeveloped integrated weed management systems, is a major hurdle to production of vegetable soybean in the United States. Vegetable soybean, the same species as grain-type soybean, has few registered herbicides because of unknown crop tolerance. Tolerance of as many as 128 vegetable soybean entries to a 2X registered rate of bentazon, fomesafen, imazamox, linuron, and sulfentrazone were quantified within 4 wk after treatment in field trials. Several grain-type soybean entries were included for comparison, including entries with known herbicide tolerance or sensitivity. Injury and seedling growth reduction to all vegetable entries was comparable to all grain-type entries for fomesafen, linuron, and sulfentrazone; and less than all grain-type entries for bentazon and imazamox. Responses of ten of the more widely used vegetable soybean entries were comparable to grain-type entries with known herbicide tolerance. Bentazon, fomesafen, imazamox, linuron, and sulfentrazone pose no greater risk of adverse crop response to vegetable soybean germplasm than the grain-type soybean to which they have been applied for years. Since initiation of this research, fomesafen, imazamox, and linuron are now registered for use on the crop in the United States. Development of integrated weed management systems for vegetable soybean would benefit from additional herbicide registrations.

Obtaining spatially explicit, cost-effective, and management-relevant data on invasive plant distributions across large natural areas presents considerable challenges. This is especially true when multiple monitoring objectives exist, because the utility of different monitoring methodologies varies with scale, logistical considerations, and information needs. The Florida Everglades is a vast wetland landscape with widespread invasive plant infestations and multiple management jurisdictions. A multi-agency team Working Group conducted a workshop in 2013 to explore opportunities to enhance the performance of a regional weed control program. Among the most important developments occurring at this meeting was the recognition that relevant management questions are scale-dependent. This led the team to define multiple monitoring objectives. Essential for conveying the success of the weed management program is quantifying large-scale patterns of change, as are quantifying fine-scale patterns informing control activities, defining mechanisms of spread, recognizing accelerating rates of spread, and detecting patterns of occupancy immediately before management intervention. The group’s deliberation resulted in the emergence of a multiscale monitoring program utilizing several distinct monitoring protocols, including systematic landscape-level reconnaissance, a sample-based spatially stratified monitoring system, detailed inventories in planned treatment areas, and a set of methods focused solely on early detection and rapid response. Here we provide an overview of the Everglades multiscale invasive plant monitoring program, highlight benefits and challenges of each program component, and discuss how this program has improved regional invasive plant management.