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Establishment of alfalfa by interseeding it with corn planted for silage can enhance crop productivity but weed management is a challenge to adoption of the practice. Although a simple and effective approach to weed management would be to apply a glyphosate-based herbicide, concerns about herbicide resistance and limitations in available alfalfa varieties exist. Field experiments were conducted to compare the efficacy and selectivity of PRE, POST, and PRE followed by POST herbicide programs to a glyphosate-only strategy when interseeding alfalfa with corn. Experiment 1 compared PRE applications of acetochlor, mesotrione, S-metalochlor, metribuzin, and flumetsulam. Results indicate that acetochlor and metribuzin, and S-metalochlor used at a rate of 1.1 kg ai ha−1 were the most effective and selective PRE herbicides 4 wk after treatment (WAT), but each resulted in greater overall weed cover than glyphosate by 8 WAT. Experiment 2 evaluated applications of bentazon, bromoxynil, 2,4-DB, and mesotrione at early and late POST times. Several herbicides used POST exhibited similar effectiveness and selectivity as glyphosate, including early applications of bromoxynil (0.14 kg ai ha−1) and 2,4-DB (0.84 or 1.68 kg ai ha−1), as well as late applications of bromoxynil (0.42 kg ai ha−1), 2,4-DB (0.84 kg ai ha−1), and mesotrione (0.05 or 0.11 kg ai ha−1). A third experiment compared applications of acetochlor PRE, bromoxynil POST, and a combination of acetochlor PRE with bromoxynil POST. All treatments were effective and safe for use in this interseeded system, although interseeded alfalfa provided 65% to 70% weed suppression in corn planted for silage without any herbicide. Herbicide treatments had no observable impacts on corn and alfalfa yields, so weed management was likely of limited economic importance. However, weed competitiveness can vary based on several different factors including weed species, density, and site-specific factors, and so further investigations under different environments and conditions are needed.

Two experiments were conducted in 2013 and 2014 in Florida to evaluate the effects of protoporphyrinogen oxidase (PPO)-inhibiting herbicides and single versus sequential applications on Palmer amaranth control and peanut injury. Protoporphyrinogen oxidase-inhibiting herbicides are among the last available herbicides for the POST control of acetolactate synthase (ALS)-resistant Palmer amaranth in peanut. Lactofen (219 g ai ha–1) applied 5 d after the initial application provided the highest level of Palmer amaranth control 7 and 14 d after initial application (DAIT). Delaying sequential applications of lactofen to 15 d resulted in the highest level of Palmer amaranth control 21 and 28 DAIT. Similar to Palmer amaranth control, foliar injury to peanut was often highest from lactofen applications, and by 28 DAIT lactofen treatments were the only treatments that caused foliar injury. Although no statistical difference was observed between yields of plots treated with acifluorfen (280 g ai ha–1), bentazon (560 g ai ha–1), 2,4-DB (280 g ae ha–1) alone or in combination with each other, plots treated with sequential applications of lactofen 5 or 15 DAIT produced the lowest yields. Sequential applications of lactofen applied 15 DAIT controlled Palmer amaranth more effectively than any other treatment but also caused the highest level of peanut injury. The use of sequential applications of lactofen was the most effective method for control of Palmer amaranth in this study, but did reduce peanut yield.

Clover inclusion may increase the sustainability of certain low-maintenance turfgrasses. However, selective weed control within mixed turfgrass–clover swards proves problematic because of clover susceptibility to herbicides. Research was conducted to identify common turf herbicides that are tolerated by threeTrifoliumspecies, including white clover, ball clover, and small hop clover, within low-maintenance turfgrass. Leaf and flower density, as well as plant height, were measured 4 wk after treatment as indicators of clover response to 14 herbicides. The threeTrifoliumspp. were moderately tolerant of bentazon (< 35% decrease in leaf density, height, or flowering). Simazine was well tolerated by white clover (< 5% decrease in all response variables), yet moderate injury to ball clover and small hop clover was observed (> 32% decrease in leaf density and > 27% decrease in flower density). Pronamide was well tolerated by white and ball clovers, with no effect on measured response variables; however, pronamide decreased small hop clover height and flower density (38 and 42%, respectively). Imazethapyr and imazamox were moderately well tolerated by white clover and small hop clover (< 39% decrease by all response variables), yet ball clover may be more susceptible to these herbicides than was anticipated based on previously reported tolerance. The herbicides 2,4-DB, halosulfuron, and metribuzin were well tolerated by white clover, with no effect on measured response variables; however, results suggest ball and small hop clovers were less tolerant. Clopyralid, 2,4-D, glyphosate, imazaquin, metsulfuron-methyl, and nicosulfuron resulted in varying degrees of injury across clover species and response variables, but, in general, these herbicides may not be viable options when attempting to maintain any of the three clover species tested. Further research is needed to quantify long-term effects of herbicide application on sward composition and clover succession.

This study was conducted to determine whether herbicides and adjuvants registered for poste-mergence use in alfalfa have an effect on Sclerotinia crown and stem rot (SCSR). In a controlled environment, disease severity index (DSI) of alfalfa seedlings was reduced by pronamide and 2,4-DB compared with the untreated control, whereas bromoxynil and 13% sethoxydim + petroleum-based adjuvant (PBA) increased DSI. In the field, disease severity in all herbicide treatments was similar to that in untreated alfalfa. In a second controlled-environment study, pronamide and 2,4-DB reduced DSI compared with the no herbicide control when seedlings were inoculated 1 day after herbicide application, but this protective effect was not observed when seedlings were inoculated 8 days or longer after herbicide application. The results demonstrate that several herbicides are capable of suppressing or enhancing SCSR severity in a controlled environment if seedling inoculation occurs soon after herbicide application; however, the residual effect of these herbicides on SCSR appeared to be much shorter than the 4- to 6-week infection period occurring in the field.

Field experiments were conducted in Macon County, Georgia, during 2010 and 2011 to determine the impact of new herbicide-resistant cotton and respective herbicide systems on the control of glyphosate-resistant Palmer amaranth. Sequential POST applications of 2,4-D or glufosinate followed by diuron plus MSMA directed at layby (late POST-directed) controlled Palmer amaranth 62 to 79% and 46 to 49% at harvest when the initial application was made to 8- or 18–cm-tall Palmer amaranth, in separate trials, respectively. Mixtures of glufosinate plus 2,4-D applied sequentially followed by the layby controlled Palmer amaranth 95 to 97% regardless of Palmer amaranth height. Mixing glyphosate with 2,4-D improved control beyond that observed with 2,4-D alone, but control was still only 79 to 86% at harvest depending on 2,4-D rate. Sequential applications of glyphosate plus 2,4-D controlled Palmer amaranth 95 to 96% following the use of either pendimethalin or fomesafen. Seed cotton yield was at least 30% higher with 2,4-D plus glufosinate systems compared to systems with either herbicide alone. The addition of pendimethalin and/or fomesafen PRE did not improve Palmer amaranth control or yields when glufosinate plus 2,4-D were applied sequentially followed by the layby. The addition of these residual herbicides improved at harvest control (87 to 96%) when followed by sequential applications of 2,4-D or 2,4-D plus glyphosate; yields from these systems were similar to those with glufosinate plus 2,4-D. Comparison of 2,4-D and 2,4-DB treatments confirmed that 2,4-D is a more effective option for the control of Palmer amaranth. Results from these experiments suggest cotton with resistance to glufosinate, glyphosate, and 2,4-D will improve Palmer amaranth management. At-plant residual herbicides should be recommended for consistent performance of all 2,4-D systems across environments, although cotton with resistance to glyphosate, glufosinate, and 2,4-D will allow greater flexibility in selecting PRE herbicide(s), which should reduce input costs, carryover concerns, and crop injury when compared to current systems.

Small burnet is a hardy, relatively long-lived evergreen forb with the potential to improve grazing lands, particularly to extend grazing into late fall and winter. Small burnet was evaluated for tolerance to spring and fall POST applications of aminopyralid, bromoxynil, clethodim, clopyralid, dicamba, dimethenamid-P, imazamox, metribuzin, pendimethalin, quinclorac, and 2,4-DB. Injury, seed yield, seed viability, and dry matter yield (DMY) were measured in the spring following application. Injury was observed in response to all spring and fall herbicide applications. Injury from aminopyralid was the highest for both spring and fall applications at 24 and 79%, respectively. Fall application of imazamox and dicamba resulted in 57 and 31% injury, respectively. Spring-applied aminopyralid and 2,4-DB both reduced DMY by 16%, whereas fall applications of imazamox, dicamba, and aminopyralid reduced DMY by 36, 12, and 67%, respectively. Fall applications of imazamox and aminopyralid reduced seed yield by 33 and 65%, respectively. Fall-applied aminopyralid reduced seed germination by 43%. None of the spring-applied herbicides affected seed yield or seed germination. Small burnet is severely injured by aminopyralid and to a lesser degree by imazamox and dicamba. Bromoxynil, clethodim, clopyralid, dimethenamid-P, metribuzin, pendimethalin, and quinclorac did not affect small burnet DMY, seed yield, or germination the year after application.

Clovers are commonly included as utility plants within mixed grass swards, such as pastures and roadside right-of-ways. As such, they provide supplemental nitrogen, quality forage, and insect habitat. Yet weed control within mixed swards is often hampered by the lack of selective herbicides that are tolerated by clovers. Differential tolerance of legumes to common row-crop and pasture herbicides has previously been reported, yet little information is available that is specific to clover species. Herbicide injury of clover is often inconsistent, hypothetically due to differential species tolerance. Field and greenhouse experiments were conducted with the objective of testing differential tolerance amongst four clover species. Our experiments suggest varying tolerances amongst clover species and common broadleaf herbicides. Only imazaquin control differed due to species; however, treatment by clover interactions were further demonstrated due to variable reductions in clover height. Imazaquin, 2,4-D, 2,4-DB, and triclopyr height reductions differed due to clover species. Differential clover response to herbicide treatment should be an important consideration when managing mixed grass–clover swards and should be accounted for in future research. On a more practical level, our experiments demonstrate a range of herbicides that effectively control clover species, including atrazine, dicamba, clopyralid, 2,4-D, triclopyr, metsulfuron, and trifloxysulfuron. However, results suggest that 2,4-DB, imazethapyr, and bentazon are candidate herbicides for weed control in scenarios in which clover is a desirable crop.

Lactofen plus crop oil adjuvants are increasingly being used to combat acetolactate synthase-resistant weeds in peanut production. To control a broader spectrum of weeds, it is desirable to mix 2,4-DB with lactofen. However, lactofen can be highly injurious to peanuts. It is unknown if the addition of 2,4-DB will exacerbate or prolong the injury observed by lactofen. Experiments were conducted in Citra and Jay, FL in 2011 and 2012 to examine the impact of lactofen, 2,4-DB and lactofen + 2,4-DB applied at 15, 30, and 45 days after planting (DAP) on peanut injury and yield. It was observed that 2,4-DB did not increase foliar injury or stunting (as measured by canopy width) compared to lactofen alone. Additionally, yield was not impacted by any herbicide combination or application timing. From these data, lactofen plus 2,4-DB combinations, applied with crop oil adjuvants, can be used with little concern for exacerbating effects on peanut growth or yield relative to lactofen applied alone.

A wide range of agrochemicals can be applied in a peanut production system to control various stresses and manage crop growth and development. Field and laboratory experiments were conducted in North Carolina to define biological and physicochemical interactions when insecticides (fenpropathrin and lambda-cyhalothrin) or plant growth regulator (prohexadione calcium) were applied in combination with other agrochemicals including fungicides, herbicides, and micronutrients. Fenpropathrin or lambda-cyhalothrin combinations did not injure peanut in 2008 and 2009. Two sprays of prohexadione calcium improved row visibility and reduced main stem height compared with one prohexadione calcium spray irrespective of agrochemical combinations. In many instances, applying prohexadione calcium with other agrochemicals resulted in lower main stem height compared to prohexadione calcium alone. In one of the experiments, prohexadione calcium with prothioconazole plus tebuconazole lowered fall army worm population compared with prohexadione calcium alone. Addition of boron, manganese, and 2,4-DB to fenpropathrin, lambda-cyhalothrin, and prohexadione calcium combinations changed solution pH dramatically. Prohexadione calcium had the least effect on pH of the carrier.

A range of fungicides and herbicides can be applied to control pests and optimize peanut yield. Experiments were conducted in North Carolina to define biological and physicochemical interactions when clethodim and 2,4-DB were applied alone or with selected fungicides. Pyraclostrobin consistently reduced large crabgrass [Digitaria sanguinalis (L.) Scop.] control by clethodim. Chlorothalonil and tebuconazole plus trifloxystrobin reduced large crabgrass control by clethodim in two of four experiments while prothioconazole plus tebuconazole and flutriafol did not affect control. Palmer amaranth [Amaranthus palmeri S. Wats] control by 2,4-DB was not affected by these fungicides. Although differences in spray solution pH were noted among mixtures of clethodim plus crop oil concentrate or 2,4-DB and fungicides, the range of pH was 4.40 to 4.92 and 6.72 to 7.20, respectively, across sampling times of 0, 6, 24, and 72 h after solution preparation. Permanent precipitates were formed when clethodim, crop oil concentrate, and chlorothalonil were co-applied at each sampling interval. Permanent precipitates were not observed when clethodim and crop oil concentrate were included with other fungicides or when 2,4-DB was mixed with fungicides. Significant positive correlations were noted for Palmer amaranth control by 2,4-DB and solution pH but not for clethodim and solution pH.

Pimelea poisoning is an ongoing, periodically serious problem for cattle producers in inland Australia. The annual native plants of the Thymelaeaceae family that cause the problem are widespread and animal management is currently the main means of minimizing poisoning. However, there are situations in the higher rainfall parts of the natural distribution area of these plants where farming and quite intensive property development do occur and here the use of selective herbicides may be an option. This research looked for herbicides that could be considered for registration for Pimelea control, bearing in mind the large potential costs involved if used over large areas. Group I hormone herbicides (for example 2,4-D) were quite effective as was metsulfuron-methyl and glyphosate at doses commonly registered for use on broad-leafed weeds. On the basis of minimizing costs and quickly suppressing seed-set, metsulfuron-methyl at 3.5e5 g a.i. ha1 and 2,4-D at 375e500 g a.i. ha1 were the most promising. Where medic (Medicago spp.) persistence is vital, 2,4-DB at 240e300 g a.i. ha1 could be used and glyphosate at 1 kg a.i. ha1 would be effective on fallowed ground if costwas not an overriding concern.

In Chile, Fusarium root rot reduces red clover (Trifolium pretense L.) pasture yield and persistence. Fusarium oxysporum (Schlect.) is the most prevalent pathogen in diseased red clover plant roots. Agronomic management of red clover includes applying herbicides such as MCPA, 2,4-DB, flumetsulam, bentazon, and haloxyfop-methyl. In addition to weed control, herbicides can modify disease development, generally as a result of the interaction between direct effects on the pathogen and indirect effects via plant-mediated responses. The objective of this study was to evaluate the influence of these herbicides on in vitro growth of F. oxysporum at four application rates 0, 50, 100, and 200% at the field-recommended active ingredient rate. Herbicides were amended on Petri dishes containing potato dextrose agar (PDA) and buffer MUB (tris-hydroxymethyl-aminomethane). Fusarium oxysporum was cultivated at 22°C for 25 days and colony area was measured every 5 days. The herbicides MCPA and Flumetsulam had no effect on fungal growth. 2,4-DB showing an inverse dose effect on fungal growth varying between 16 and 35% at the end of the experimental period. The contact herbicide Bentazon exhibited the strongest inhibitory effect on F. oxysporum development by the application of the field recommended rate, with a 54% decrease with regard to the control at the end of the experiment. Haloxyfop-methyl showed the highest colony stimulation since 15 days after of the application, increasing 29% the colony area respect to the control at the end of the experiment. These results suggest that applying some herbicides to red clover could affect soil pathogens such as Fusarium oxysporum, increasing or inhibiting its development.

BACKGROUND: The introduction of transgenic soybean (Glycine max, L.) varieties resistant to glyphosate (GR soybeans) has rapidly expanded in Argentina, increasing pesticide use where only grasslands were previously cultivated. The authors compared an estimate of environmental risk for different crops and active ingredients using the IPEST index, which is based on a fuzzy-logic expert system. For IPEST calculations, four modules are defined, one reflecting the rate of application, the other three reflecting the risk for groundwater, surface water and air. The input variables are pesticide properties, site-specific conditions and characteristics of the pesticide application. The expert system calculates the value of modules according to the degree of membership of the input variables to the fuzzy subsets F (favourable) and U (unfavourable), and they can be aggregated following sets of decision rules. IPEST integrated values of ≥ 7 reflect low environmental risk, and values of < 7 reflect high risk. RESULTS: Alfalfa, soybean and wheat showed IPEST values over 7 (low risk), while maize had the lowest IPEST values (high risk). Comparing active ingredients applied in annual and perennial crops, atrazine and acetochlor gave the highest risks of environmental contamination, and they are mainly used in maize. Groundwater was the most affected compartment. CONCLUSIONS: Fuzzy logic provided an easy tool combining different environmental components with pesticide properties to give a simple and accessible risk assessment. These findings provide information about active ingredients that should be replaced in order to protect water and air from pesticide contamination. Copyright © 2010 Society of Chemical Industry

Field trials were conducted in 2005 and 2006 in central and southwest Missouri to investigate the effect of seeding rate and herbicide programs on weed control, forage quality, and yield within the year of establishment in spring seeded glyphosate-resistant (GR) alfalfa (Medicago sativa L.). In all experiments, EPTC (4.4 kg ha -1 ), 2,4-DB plus sethoxydim (1.1 plus 0.21 kg ha -1 ), imazamox (0.043 kg ha -1 ) and glyphosate (0.86 kg ae ha -1 ) were applied to GR alfalfa that was seeded at 4.5, 8.9, 13.5, and 18 kg ha -1 . Across all locations, the glyphosate application provided good control of weeds regardless of alfalfa seeding rate. When applied at the same timing, imazamox provided similar levels of annual broadleafweed control as glyphosate, while 2, 4-DB plus sethoxydim provided similar levels of annual grass and broadleafweed control as glyphosate. Neither glyphosate nor the conventional herbicide treatments reduced alfalfa stem density between the first and last annual harvests, but 2, 4-DB plus sethoxydim resulted in the most visual injury to seedling alfalfa stands and lowered initial yields at all locations. In addition, alfalfa annual yields were similar or higher in the glyphosate treatment compared to the other herbicide programs. Harvested forage in the herbicide treatments generally had greater crude protein (CP) content than the untreated control forage. Application of glyphosate resulted in similar or higher forage CP content compared to conventional herbicide treatments. In vitro true digestibility of the harvested GR alfalfa ranged from 750 to 860 g kg -1 DM at all locations with few differences across herbicide treatments.

Recurrent problems with peanut seed germination and stand establishment have raised concerns about the potential effects of herbicides on peanut seed quality. Field trials were conducted in south Georgia in 2005 and 2006 to evaluate the effects of imazapic and 2,4-DB on peanut yield, grade, incidence of tomato spotted wilt virus (TSWV), and seed germination. Imazapic at 71 g ai ha−1, applied at 30 and 40 days after planting (DAP), and 2,4-DB at 270 g ai ha−1, applied at 75 or 90 DAP, had no effect on peanut yield, grade, incidence of TSWV, and seed germination when averaged over two locations (Dawson and Tifton) and three cultivars (Georgia Green, Georgia-01R, and C-99R). Normal cultivar yield variations were observed; however, Georgia-01R had reduced standard (25 C) and cold (15 C) germination when compared to the other cultivars.

Field studies were conducted from 2004 to 2006 to evaluate the tolerance of three annual medic species (bur, black, and barrel medic) to selected POST herbicides. 2,4-DB at 0.56 and 1.12 kg/ha caused the most stunting across all three species. Imazethapyr at 0.1 kg/ha stunted all three annual medics in 1 of 3 yr whereas flumetsulam at 0.04 kg/ha stunted black and barrel medics in 1 of 3 yr. Clethodim at 0.28 kg/ha did not cause any medic stunting. Imazethapyr, imazamox, and 2,4-DB at 0.56 kg/ha reduced henbit dry matter composition compared to the untreated check whereas clethodim, flumetsulam, and 2,4-DB at 1.12 kg/ha did not. In 2004, 2,4-DB at 1.12 kg/ha reduced dry weight yield of bur and barrel medic but not black medic when compared with the untreated check. Black medic treated with imazethapyr at 0.05 and 0.1 kg/ha and clethodim at 0.28 kg/ha produced higher dry weight yield than the untreated check. In 2006, both rates of 2,4-DB and flumetsulam at 0.04 kg/ha reduced dry weight yield of bur medic compared to the untreated check. Barrel medic dry weight yields were reduced by both rates of 2,4-DB and flumetsulam compared to untreated check. No herbicides reduced dry weight yields of black medic.

Experiments were conducted during 2003 and 2004 to determine if peanut yield and market grade characteristics differed when paraquat was applied 24 to 28 days after emergence to peanut seeded in early, mid-, and late May and early June. Peanut pod yield and percentages of extra large kernels, total sound mature kernels, and farmer stock fancy pods were affected by planting date and paraquat independently. Paraquat did not affect yield compared with non-treated peanut regardless of planting date. In other experiments from 2003–2005, peanut was planted with or without aldicarb in the seed furrow and followed either paraquat applied 24 to 28 days after emergence or 2,4-DB applied in mid-August during 2003 and 2004. In 2005, experiments included a no-paraquat control rather than 2,4-DB. Pod yield was reduced at 3 of 9 sites due to damage from tobacco thrips, Franklinella fusca Hinds, feeding when aldicarb was not applied. Paraquat reduced yield in 4 experiments during 2005 but not in 5 experiments during 2003–2004. Aldicarb and paraquat affected peanut independently. Experiments were also conducted during 2005 and 2006 to compare interactions of paraquat formulations alone or with co-applied herbicides. Paraquat formulation (Gramoxone INTEON versus Gramoxone MAX or Firestorm) did not affect peanut response to paraquat, and interactions of paraquat formulation (Gramoxone MAX or Gramoxone INTEON) with bentazon, bentazon plus diclosulam, bentazon plus dimethenamid, bentazon plus imazethapyr, and bentazon plus S-metolachlor was similar to paraquat alone. Peanut injury and pod yield was the same when paraquat (Gramoxone INTEON) was applied alone or with carfentrazone and was similar to carfentrazone alone.

White sweetclover is invading the Alaska glacial river floodplains and roadsides adjacent to natural areas, and control methods are needed. Chlorsulfuron, 2,4-DB, clopyralid, triclopyr, and 2,4-D controlled white sweetclover seedlings below recommended rates in the greenhouse. Biomass of established plants in the field was reduced by chlorsulfuron at recommended (17.6 g ai/ha), 1/2, and 1/4 rates and was reduced by triclopyr and 2,4-D at recommended rates (1,260 and 1,600 g ai/ha). Herbicides were more effective at reducing white sweetclover viable seed production in 2007 than in 2006. Only chlorsulfuron at 17.6 g ai/ha (recommended rate) eliminated seed production in both years. Flaming killed first-year plants, but some second-year plants resprouted and produced viable seed. Cutting at the 2.5 or 10 cm height did not control first-year plants because of regrowth, and second-year plant density and seed production was reduced by cutting at 2.5 cm but not by cutting at 10 cm.

Field experiments were conducted to evaluate the emergence and control of Florida beggarweed in peanut. Diclosulam preemergence (PRE), flumioxazin PRE, and imazapic postemergence (POST) were evaluated at three rates, along with paraquat plus bentazon plus 2,4-DB POST, and a nontreated control. These treatments were applied alone, or followed by chlorimuron applied late postemergence (LPOST). Variable Florida beggarweed control (16 to 90%) was observed when flumioxazin PRE, diclosulam PRE, paraquat plus bentazon plus 2,4-DB EPOST, or imazapic POST were applied alone. The pre-harvest population of Florida beggarweed was significantly reduced by the application of any residual herbicide (flumioxazin, diclosulam, or imazapic) alone at any rate either PRE or POST as compared to the nontreated control. Use of the contact treatment of paraquat plus bentazon plus 2,4-DB EPOST alone did not reduce Florida beggarweed populations as compared to the nontreated control. Adding chlorimuron LPOST to any treatment did not reduce Florida beggarweed populations, but provided suppression and reduced the biomass of existing plants. Consistent Florida beggarweed control (86 to 95%) was achieved with combinations of flumioxazin PRE at 105 g ha−1, diclosulam PRE at 53 g ha−1, and imazapic POST at 71 g ha−1 followed by chlorimuron LPOST at 9 g ha−1. The benefit of chlorimuron LPOST was greatest when early season control was least.

Experiments were conducted during 2000 and 2001 at a total of 13 locations throughout Alabama, Georgia, Florida, North Carolina, and Texas to evaluate efficacy of herbicides at or below the manufacturer's suggested use rate. Herbicide applications included diclosulam and flumioxazin applied PRE alone or followed by imazapic applied early postemergence (EPOST). All possible combinations of diclosulam at 0, 13.5, or 27 g ai/ha and flumioxazin at 0, 53, or 105 g ai/ha applied PRE were included. Imazapic was applied at 35 g ai/ha. Ivyleaf morningglory was controlled more than 87% when imazapic was applied EPOST regardless of PRE herbicide. Pitted morningglory control > 67% was observed with applications of diclosulam (27 g/ha) followed by imazapic, diclosulam (13.5 g/ha) plus flumioxazin (53 g/ha), diclosulam (13.5 g/ha) plus flumioxazin (105 g/ha), and diclosulam (27 g/ha) plus flumioxazin (105 g/ha). Sicklepod was controlled more than 74% with flumioxazin (53 g/ha) followed by imazapic and diclosulam (27 g/ha) plus flumioxazin (105 g/ha) followed by imazapic. Florida beggarweed was controlled more than 84% by all PRE herbicide combinations except flumioxazin (53 g/ha) alone or diclosulam (27 g/ha) alone or with imazapic. Yellow nutsedge was controlled at least 90% with diclosulam at either rate followed by imazapic and by diclosulam plus flumioxazin followed by imazapic regardless of rate. Pod yield was generally higher when herbicides were applied regardless of herbicide combination or rate. Peanut yield was maximized with the lowest rates of flumioxazin or diclosulam PRE followed by imazapic EPOST.

A field trial was conducted for 3 yr (2005 through 2007) near Scottsbluff, NE, to examine weed control, crop safety, forage production, and economics of glyphosate-tolerant and conventional alfalfa establishment systems. Glyphosate applied to alfalfa at the unifoliate growth stage provided 67% weed control and was similar to imazamox applied at the two-trifoliate leaf stage. Delaying glyphosate application until alfalfa had reached the two-trifoliate growth stage improved weed control to 83%, and weed control was similar to imazamox plus 2,4-DB and imazethapyr plus 2,4-DB. Imazamox and imazethapyr caused minor crop injury, and the addition of bromoxynil or 2,4-DB to both herbicides further decreased crop safety. Weeds were most competitive with the first forage harvest and reduced relative feed value, crude protein, and value (dollars per t) of forage compared to forage that had been treated with herbicides. The total forage yield for the season consisted of three forage harvests and was greatest when no herbicides were applied. The total forage yield of plots treated with glyphosate at the two-trifoliate growth stage was greater than that of plots treated with imazamox or imazethapyr in combination with bromoxynil. When glyphosate was applied at the two-trifoliate growth stage, seasonal forage yield was similar to forage treated with imazamox, imazethapyr, or both herbicides in combination with 2,4-DB. When herbicide was applied to alfalfa at the two-trifoliate growth stage, the net return from using glyphosate with a glyphosate-tolerant alfalfa variety or utilizing imazamox with a conventional alfalfa variety were similar at $742 and $743/ha, respectively.

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.

Prohexadione calcium retards peanut vegetative vine growth, improves row visibility, and potentially reduces pod shed, thus increasing pod yield compared with non-treated peanut. Although prohexadione calcium has been registered for use in peanut for the past decade, practitioners continue to express a range of questions about use including banded application, compatibility with other agrichemcials, and interactions of application rate and timing. In experiments over multiple years, applying prohexadione calcium to lateral branches only of peanut increased row visibility compared with banded applications over main stems or broadcast applications over the entire peanut canopy. Similarly, when using different spray nozzle configurations, greater row visibility was noted when the highest rate of prohexadione calcium was applied over lateral branches compared with broadcast applications of a uniform rate across all spray nozzles or when the highest rate was delivered to main stems. Delaying the first of two sequential applications of prohexadione calcium 1 wk after 50% row closure resulted in reduced row visibility regardless of application rate when compared with sequential applications initiated at 50% row closure. Applying prohexadione calcium within 2 to 3 wks prior to digging and vine inversion resulted in minor increases in improved row visibility and did not affect pod yield. Efficacy of prohexadione calcium was not affected by tank mixing with pyraclostrobin or 2,4-DB.

Field studies were conducted during the 2003 through 2005 growing seasons to evaluate soil-applied herbicides alone or in combination with postemergence (POST) herbicides for horse purslane, smellmelon, and Palmer amaranth control in peanut. Pendimethalin alone applied preplant incorporated (PPI) failed to control any of the three weeds (< 70% control). Pendimethalin in combination with diclosulam, followed by imazethapyr applied preemergence (PRE), or followed by either acifluorfen or imazapic applied postemergence (POST) controlled all three weed species at least 80%. The soil-applied herbicides flumioxazin, imazethapyr, S-metolachlor, or dimethenamid applied alone failed to control horse purslane and smellmelon (< 75%). Pendimethalin controlled Palmer amaranth less than 42% while flumioxazin at 0.07 kg/ha or dimethenamid at 1.12 kg/ha controlled Palmer amaranth less than 75%. Imazethapyr alone or pendimethalin applied PPI followed by imazethapyr applied PRE or imazapic applied POST controlled Palmer amaranth at least 99%. Pendimethalin applied PPI was present in all herbicide systems that yielded greater than the untreated check. In addition, 80% or greater control of at least 2 of 3 weed species resulted in the highest yields, with the exception of pendimethalin followed by acifluorfen.

Diclosulam is generally applied either PPI or PRE to peanut to control certain broadleaf weeds and suppress sedges. Research was conducted to determine efficacy and peanut response to POST applications of diclosulam at 9, 13, 18, and 27 g ai/ha. Efficacy of diclosulam was affected by application rate and environment. Common ragweed control ranged from 60 to 100%, entireleaf morningglory control from 56 to 100%, marestail control from 78 to 85%, and nodding spurge from 50 to 97%. Smooth pigweed and common lambsquarters were both controlled less than 35%. Diclosulam controlled yellow nutsedge and eclipta less than 70 and 80%, respectively. In separate experiments, diclosulam and imazapic controlled dogfennel more effectively than acifluorfen, bentazon, imazethapyr, lactofen, paraquat, or 2,4-DB. Visual estimates of peanut injury were 15% or less for all rates during both years. Peanut yield ranged from 3,340 to 3,730 kg/ha in 2002 and 5,230 to 5,820 kg/ha in 2003. Foliar injury and peanut pod yield were inf...

Field studies were conducted during the 2003 through 2005 growing seasons to evaluate postemergence herbicides and timing of application for horse purslane, smellmelon, and Palmer amaranth control in peanut. Acifluorfen provided inconsistent control of the three weed species. Bentazon failed to control Palmer amaranth, horse purslane, and smellmelon (< 65%), whereas 2,4-DB controlled horse purslane and smellmelon less than 70%. Diclosulam applied early postemergence (EPOST) controlled Palmer amaranth at least 77% but horse purslane control varied from 27 to 73% when applied EPOST and was less than 50% with the late postemergence (LPOST) application. Diclosulam controlled smellmelon less than 65%. Imazethapyr and imazapic controlled Palmer amaranth and smellmelon at least 70% but controlled horse purslane less than 65%. Lactofen controlled Palmer amaranth and horse purslane at least 93% with the EPOST application but had inconsistent control (40 to 100%) when applied LPOST. Smellmelon control with lactofen...

Experiments were conducted in Florida in 2000 through 2003 to evaluate weed management systems in single- and twin-row peanut utilizing either conventional or strip tillage. Diclosulam or flumioxazin preemergence (PRE) or 2,4-DB or imazapic mid-postemergence (MPOST) or late-postemergence (LPOST) was needed for greater than 95% common cocklebur control in conventional- and strip-tillage peanut. In both tillage systems, paraquat + bentazon early-postemergence (EPOST) followed by (fb) 2,4-DB or imazapic MPOST, 2,4-DB or chlorimuron LPOST, or both was required for more than 80% late-season control of Florida beggarweed and control in twin-row was 5 to 10 percentage points above that observed with single-row peanut. Paraquat + bentazon EPOST preceded by a diclosulam or flumioxazin PRE or fb MPOST or LPOST applications provided 80% or greater control of ivyleaf morningglory, and no differences were observed between peanut planting pattern. Paraquat + bentazon EPOST fb imazapic MPOST was the only treatment that provided 90% or greater late-season sicklepod control across all years and tillage methods, and, regardless of tillage, sicklepod control was 7 percentage points better in twin- than single-row peanut. Treatments that contained diclosulam or flumioxazin PRE and paraquat + bentazon EPOST fb a MPOST or LPOST herbicide application increased peanut yield compared to nontreated in conventional- and strip-tillage peanut. Averaged over all herbicide treatments, years, and tillage methods, peanut seeded in twin rows yielded 300 kg/ha more than in single rows.

Experiments were conducted in North Carolina during 2002 and 2003 to evaluate entireleaf morningglory control by 2,4-DB applied alone or with seven fungicides. In a separate group of experiments, tall morningglory control by 2,4-DB was evaluated when applied in four-way mixtures with the following: the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, or tebuconazole; the insecticide lambda-cyhalothrin; and the foliar fertilizer disodium octaborate or the plant growth regulator (PGR) prohexadione calcium plus urea ammonium nitrate. Pyraclostrobin, but not azoxystrobin, boscalid, chlorothalonil, fluazinam, propiconazole plus trifloxystrobin, or tebuconazole, reduced entireleaf morningglory control by 2,4-DB. Mixtures of fungicides, insecticides, and foliar fertilizer/ PGR did not affect tall morningglory control by 2,4-DB. Placing artificial morningglory in the peanut canopy when fungicides were applied did not intercept enough fungicide to increase peanut defoliation by early leaf spot and web blot...

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 us...

A promising approach for the control of parasitic weeds is herbicide seed priming, which consists of soaking crop seeds in a herbicide solution such that the herbicide is later present in the crop seedling to inhibit growth of attaching parasites. This technique is effective where selectivity exists between crop and parasite; for example, varieties of imidazolinone-resistant maize. However, seed priming has not been reported for sorghum or pearl millet, two crops that are greatly affected by purple witchweed. Research was initiated to evaluate herbicides for potential use as seed priming agents in these crops. Auxin-mimic and acetolactate synthase-inhibitor class herbicides were evaluated; specifically, clopyralid, 2,4-DB, dicamba, picloram, and prosulfuron. For sorghum, immersion of seed in 0.5% (w/v) ae 2,4-DB for 5 min 1 d before planting reduced purple witchweed densities to levels 20 to 50% of nontreated controls. However, this concentration was at the threshold of crop toxicity and reduced sorghum yields in some experiments. None of the herbicides tested consistently reduced purple witchweed on pearl millet. This research illustrates both the potential and limitations of adapting seed priming technology for sorghum and pearl millet.

Alfalfa seed producers have a limited number of herbicide options to manage weed problems. MON-37500 (proposed name sulfosulfuron) is a sulfonylurea herbicide that controls dandelion and quackgrass, two common weeds in alfalfa fields. A study was conducted in two alfalfa fields at Valparaiso and Carrot River, Saskatchewan, Canada, from 1999 to 2001 to evaluate perennial weed control and alfalfa production responses with 0.5×, 1×, and 1.5× label-recommended rates of MON-37500 and also 2,4-DB and hexazinone. MON-37500 applied at the 1× and 1.5× rates at both locations reduced mid-May alfalfa vigor from 100% to between 80 and 90% and increased early-season control of dandelion and quackgrass by about 10 to 40 percentage units, when compared with other herbicide treatments. Improved weed control with 1× and 1.5× MON-37500 rates was sustained into mid-June only at Carrot River and was completely eliminated (100% vigor and 0% weed control), or almost so, by mid-July. MON-37500 did not control Canada thistle. Improved early-season weed control with the 1× MON-37500 rate apparently compensated for the loss of alfalfa vigor at Valparaiso, thus resulting in 27% (57 kg/ha) greater seed yield than with the other herbicide treatments. At Carrot River, hexazinone generally provided levels of weed control similar to MON-37500 but did not injure alfalfa. Consequently, alfalfa yields were highest and the proportion of dead (decaying) seed was least with this treatment. The 0.5× MON-37500 rate often resulted in inferior weed control relative to the 1× and 1.5× rates and never was among the herbicide treatments providing the greatest seed yield. Managing the residual activity of MON-37500 and its negative effect on alfalfa growth, especially at locations with soils having coarse texture and low organic matter content, represents the greatest challenge in making MON-37500 a reliable weed management tool for alfalfa seed producers.