Caucasian old world bluestem (OWB), seeded for conservation and forage production, has escaped into rangelands in the southern and central Great Plains. Glyphosate, imazapic, imazapyr, imazethapyr, and sulfometuron methyl herbicides were applied at the four- to five-leaf stage and again 8 wk later in 2003 and 2005 to control Caucasian OWB. Glyphosate at 1.14 kg ai/ha at each application was the only treatment that reduced frequency and tiller density of Caucasian OWB, and also controlled over 80% of growth, at 6 wk after the first treatment (WAT) both years. After the first autumn frost, plots treated with glyphosate and imazapyr at 0.28 kg ai/ha at each application had lower frequency and much greater suppression of Caucasian OWB growth than plots treated with other herbicides. Tiller densities and seedhead densities were also less in plots treated with glyphosate and imazapyr compared to other herbicides and the nontreated control. Biomass at the end of the season was near zero for plots treated with glyphosate and imazapyr in 2003, and 26 to 46% of the nontreated control biomass in 2005. Frequency of Caucasian OWB the year following treatment was less than 5% for both glyphosate and imazapyr. Broadcast application of glyphosate and imazapyr also controlled remnant native vegetation in plots, thus different application methods, such as ropewick application, may be useful to avoid native grass injury.

Nomenclature: Glyphosate, imazapic, imazapyr, imazethapyr, >sulfometuron methyl, Caucasian old world bluestem, Bothriochloa bladhii Retz (S.T. Blake) BOTBL

Experiments were conducted in 2004 and 2005 in Virginia to evaluate KIH-485 for shattercane control. KIH-485 was applied to glyphosate-resistant corn at three rates (166, 209, and 250 g ai/ha) and two timings (preemergence [PRE] and postemergence [POST]) and compared to standard rates of S-metolachlor, acetochlor, and pendimethalin. PRE treatments were applied alone, while POST treatments were combined with 1,121 g ai/ha of glyphosate. A single POST application of glyphosate, a nontreated weedy control (WC), and a weed-free control (WFC) were also evaluated. In 2004, at 1 mo after planting (MAP), shattercane was controlled 73, 86, and 93% with the three PRE treatments of KIH-485 compared to only 50, 49, and 48% control with S-metolachlor, acetochlor, and pendimethalin, respectively. Similar levels of shattercane control were also observed with these treatments at 1 MAP in 2005. In both years at 4 MAP, KIH-485 combined with glyphosate applied POST controlled shattercane 96% or greater. However, when glyphosate was combined with S-metolachlor, acetochlor, or pendimethalin, shattercane control was less than 88% in either year. Corn yields with POST applications of KIH-485 plus glyphosate were equivalent to yield from the WFC and greater than yield from any PRE treatment. Early-season shattercane control was promising with KIH-485; however, season-long control only occurred when KIH-485 was applied POST in combination with glyphosate.

Nomenclature: Acetochlor, glyphosate, KIH-485, 3-[(5-difluoromethoxy-1-methyl-3-trifluoromethylpyrazol-4-yl)methylsufonyl]-4,5-dihydro-5,5-dimethylisoxazole, S-metolachlor, pendimethalin, shattercane, Sorghum bicolor (L.) Moench SORVU, corn, Zea mays L. ZEAMX

Rattail fescue, a winter annual grass weed, has been increasing in Pacific Northwest (PNW) dryland cereal producing areas. Although rattail fescue is not a new weed species in the PNW, its incidence is expanding rapidly in circumstances where soil disturbances are minimized such as in direct seed systems. Options for effective rattail fescue control in winter wheat cropping systems have not been adequately investigated and need to be developed. Rattail fescue control with herbicide treatments was investigated in imidazolinone-resistant winter wheat using imazamox and other herbicides. Across multiple sites and two growing seasons, crop injury from herbicide treatments was minor to negligible with some exceptions. Treatments containing imazamox or mesosulfuron produced minor, transient winter wheat crop injury at some locations in some years. With the exception of flufenacet applied preemergence (PRE), control of rattail fescue in wheat was variable with single herbicide applications, but improved with sequential herbicide treatments. Rattail fescue biomass was greatly reduced by several treatments especially those containing flufenacet or from sequential herbicide application. Crop yield varied among sites due to growing season precipitation, and in some cases from rattail fescue control or herbicide related crop injury.

Nomenclature: diuron, flufenacet, imazamox, mesosulfuron, pendimethalin, sulfosulfuron, rattail fescue, Vulpia myuros (L.) K.C. Gmel. VLPMY, winter wheat, Triticum aestivum L. ‘ClearFirst’^®

In previous research, summer annual weeds were successfully controlled in no-till corn with between-row mowing systems that consisted of soil-residual preemergence herbicides banded over corn rows followed by mowing weeds close to the soil surface one or two times later during the growing season. The objective of this research was to determine whether between-row mowing systems could successfully control both winter annual and summer annual weeds as well as broadcast herbicides perform in no-till corn. In two of three years in Missouri, between-row mowing systems controlled and reduced both winter annual and summer annual weed cover and prevented weeds from reducing corn yields. Corn yields for the following no-till weed management systems equaled the weed-free check: winter annual weed control with between-row mowing plus preplant, banded, postemergence-applied glyphosate at 1.1 kg ae/ha and later summer annual weed control with postplant, banded, preemergence-applied atrazine plus S-metolachlor at 2.2 plus 1.8 kg ai/ha followed by between-row mowing. Winter annual weeds growing between rows were controlled with one mowing, and later summer annual weeds were controlled with either one late or “middle” mowing or two mowings (i.e., early and late). Total herbicide use was reduced 50% (i.e., 25 and 25%, respectively) in no-till corn. Commercially acceptable corn stands were needed for between-row mowing systems to adequately control weeds. In one of three years when corn stands were half of those of the other two years, broadcast herbicides performed better than between-row mowing systems in no-till corn.

Nomenclature: Atrazine, S-metolachlor; corn, Zea mays L. ‘Pioneer 33G28’ ZEAMX

Annual ryegrass has been proposed as a cover crop in the corn–soybean cropping systems of the U.S. Midwest because of its low seed cost, rapid establishment, contribution to soil quality, weed suppressive abilities, and susceptibility to common broad-spectrum herbicides. However, cover crops can reduce the subsequent main crop yield by creating unfavorable germination and emergence conditions, harboring pests, and if not controlled, competing with the main crop. This study, conducted in Illinois, Oregon, and Tennessee, investigated the efficacy of glyphosate for annual ryegrass winter cover crop removal. Glyphosate at 415, 830, and 1,660 g ae/ha was applied to annual ryegrass at late tiller, second node, boot, and early flowering stages. Annual ryegrass control was consistently maximized with the highest glyphosate rate applied at the boot or early flower stage. Annual ryegrass biomass was generally the lowest with the highest rate of glyphosate applied at the earlier stages. Overall, no single application timing at any glyphosate rate provided complete control or biomass reduction of the annual ryegrass cover crop. A sequential herbicide program or a glyphosate plus a graminicide tank-mix probably will be needed for adequate annual ryegrass stand removal.

Nomenclature: Glyphosate, annual ryegrass Lolium multiflorum L. LOLMU, corn, Zea mays L, soybean, Glycine max (L.) Merr

Research was conducted to evaluate the residual effect of burning and mechanical removal of sugarcane crop residue on weed control and sugarcane growth and yield. In one study, crop residue was removed in December or January within 3 wk after sugarcane harvest. Mechanical removal of residue from the row top and placement in the row middle using a Sunco Trash Tiger® was compared with burning and a no removal control. Superimposed on each residue removal treatment was tillage of row sides and middles in March and in May and a no-tillage program. Tillage efficiency in March when sugarcane was emerging from the winter dormant period was not negatively affected when residue was removed mechanically. Crop residue on the soil surface did not completely suppress winter weed emergence and growth. Based on sugarcane and sugar yield averaged across locations and tillage programs, mechanical removal of residue was as effective as burning. Sugar yield was reduced 7.9% when residue was not removed from the row top compared with burning or mechanical removal. In another study, crop residue of sugarcane harvested in early December was burned or removed mechanically from the row top 4 d after harvest and also mechanically in January, February, or March. Crop residue ground cover of 79% in March on the row top where residue was not removed provided some suppression of winter weeds. Sugarcane shoot population in April was reduced 16.1% when residue removal was delayed until March compared with December. Averaged across tillage and no-tillage treatments in March, sugarcane yield did not differ when residue was removed by burning in December compared with mechanical removal in December or January. Delaying mechanical removal of residue until February or March compared with residue removal in December decreased sugar yield an average of 13.1%.

Nomenclature: Sugarcane, Saccharum spp. hybrids ‘LCP 85-384’

A field study was conducted at Vezaiciai branch of the Lithuanian Institute of Agriculture from 1998 to 2000 to determine weed emergence dynamics in potato and to estimate the effect of different intervals of weed crop competition on potato tuber yield if regular interrow cultivation was applied. Treatments varying in intervals of weed-free conditions and competition were laid out in a randomized complete block design with six replications. The greatest emergence of annual broadleaf such as common lambsquarters and other weeds (62 to 86% of the season total) in the crop was observed in the period from potato planting until flowering. Emergence of winter annuals such as field violet and scentless mayweed was greatest in the period from the 20-cm potato plant height until harvesting. The 20-cm potato height was the most important stage affecting potato yield loss due to weed competition. Potato yield losses due to weed competition were minimized when weeds were removed before the potatoes reached 20 cm or kept clean from this point forward. The results indicated that the critical weed-free period, when weed competition was detrimental to yield, started from planting and lasted until 25 d after flowering.

Nomenclature: Field violet, Viola arvensis Mur VIOAR, scentless mayweed, Tripleurospermum perforatum (Merat) M. Lainz MATIN, common lambsquarters, Chenopodium album L. CHEAL, potato, Solanum tuberosum L. ‘Mirta’

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 influenced by diclosulam rate, although no clear relation was evident. Cultivar and diclosulam rate did not interact with respect to visual injury or pod yield.

Nomenclature: Acifluorfen, bentazon, diclosulam, imazapic, imazethapyr, lactofen, paraquat, 2,4-DB, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L. AMBEL, dogfennel, Eupatorium capillifolium (Lam.) Small EUPCP, eclipta, Eclipta prostrata L. ECLAL, entireleaf morningglory, Ipomoea hederaceae var integriscula Gray IPOHG, marestail, Conyza canadensis (L.) Cronq. ERICA, nodding spurge, Chamaesyce nutans (Lag.) Small EPHNU, smooth pigweed, Amaranthus hybridus L. AMACH, yellow nutsedge, Cyperus esculentus L. #CYPES, peanut, Arachis hypogaea L. ‘NC-V 11’ ‘Perry’

Reducing herbicide rates can reduce production costs and the potential for carryover injury in subsequent crops, but may also compromise residual weed control. When used at the highest recommended rates (0.35 kg ai/ha), fomesafen may cause carryover injury on sweet corn. One of the most valuable attributes of fomesafen use in snap and dry beans is control of common ragweed. Field experiments were conducted in 1999, 2000, and 2002 to investigate both the residual ragweed control from fomesafen at 0.09, 0.18, and 0.36 kg ai/ha and the potential for a second application to extend the duration of residual control, while reducing the total amount applied per season. Results were significantly affected by weather conditions. In a very wet year (2000), with the greatest ragweed pressure, a single application of fomesafen at 0.20 kg/ha was predicted to provide at least 90% control of ragweed throughout snap and dry bean seasons. In the driest year (1999), 0.09 kg ai/ha provided greater than 90% control for the same period. Regardless of whether a single or double application was made, the total amount of fomesafen required per season was less than the manufacturer's recommended rate. Compared with making a single application, two low-rate applications did not reduce the total fomesafen rate required per season. To help insure at least 90% control of ragweed throughout the snap and dry bean seasons a grower should apply 0.20 kg ai/ha early in the season. Lower rates may be used, but in wet seasons, a second application may be needed to prevent yield loss or interference of ragweed with mechanical harvesting.

Nomenclature: Fomesafen, common ragweed, Ambrosia artemisiifolia L. AMBEL, bean (snap or dry), Phaseolus vulgaris L, sweet corn, Zea mays

Experiments were conducted at the Upper Coastal Plain Research Station near Rocky Mount and at the Peanut Belt Research Station near Lewiston-Woodville in 2002 and 2003. Peanut injury was minimal (< 5%) with all soil-applied programs. S-Metolachlor PRE alone or in mixture with sulfentrazone, diclosulam, or flumioxazin controlled annual grasses similarly (66 to 87%). The addition of imazapic plus 2,4-DB POST increased annual grass control (> 93%). Sulfentrazone or diclosulam in mixture with S-metolachlor were the best PRE options, with 94% and 92% control of yellow and purple nutsedge, respectively, with flumioxazin being least effective at 70%. Diclosulam and flumioxazin in mixture with S-metolachlor were the best PRE options, with 99% and 93%, respectively for common ragweed control, whereas sulfentrazone was the least effective at 65%. S-Metolachlor in mixture with sulfentrazone, diclosulam, or flumioxazin PRE were similar (87 to 90%) for common lambsquarters control. S-Metolachlor in mixture with sulfentrazone, diclosulam, or flumioxazin provided similar levels of entireleaf, ivyleaf, pitted, and tall morningglory control (87, 86, and 87%, respectively) and better than S-metolachlor alone at 64%. Flumioxazin in mixture with S-metolachlor was the best PRE option for control of Palmer amaranth at 96%, whereas diclosulam with S-metolachlor was the best PRE option for control of eclipta at 100%. The prepackaged mixture of acifluorfen and bentazon plus 2,4-DB POST and imazapic plus 2,4-DB POST were similar for all morningglory species (> 96%) and Palmer amaranth control (93 and 97%, respectively). Peanut treated with S-metolachlor plus diclosulam PRE numerically yielded the highest at 3,210 kg/ha, but were statistically equivalent to S-metolachlor plus flumioxazin PRE at 3,040 kg/ha. Peanut treated with imazapic plus 2,4-DB POST yielded the most at 3,400 kg/ha, while peanut treated with a prepackaged mixture of acifluorfen and bentazon plus 2,4-DB POST yielded less (3,070 kg/ha).

Nomenclature: 2,4-DB, acifluorfen, bentazon, diclosulam, flumioxazin, imazapic, S-metolachlor, sulfentrazone, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L. AMBEL, eclipta, Eclipta prostrata L. ECLAL, entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray IPOHG, ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE, Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA, pitted morningglory, Ipomoea lacunosa L. IPOLA, purple nutsedge, Cyperus rotundus L. CYPRO, tall morningglory, Ipomoea purpurea (L.) Roth PHBPU, yellow nutsedge, Cyperus esculentus L. CYPES, peanut, Arachis hypogaea L., ‘NCV-11’, ‘VA-98R’

Field research was conducted in southern New Mexico to determine the effect of halosulfuron rate, timing of application, and adjuvant on purple nutsedge suppression and chile pepper injury under cultivated conditions. POST-directed treatments of 36 or 53 g ai/ha were applied 2 or 4 wk after thinning direct-seeded chile pepper. Herbicide treatments included a nonionic surfactant or methylated seed oil plus ammonium sulfate plus polyacrylamide polymer. Herbicide rate, adjuvant, and timing of the application had little effect on overall nutsedge suppression; however, herbicide treatment proved to be an important component for managing purple nutsedge in this experiment. Yields were higher with halosulfuron treatment compared with the weedy control. Whereas halosulfuron treatment with 53 g/ha increased chile yield relative to the weedy control, injury and yield results comparing 36 and 53 g/ha rates consistently suggested that halosulfuron should be applied at rates ≤ 36 g/ha in a single application to avoid possible injury. Halosulfuron treatment combined with cultivation and effective crop rotation may reduce the impact of purple nutsedge interference in chile pepper.

Nomenclature: Halosulfuron, purple nutsedge, Cyperus rotundus L. CYPRO, chile pepper, Capsicum annuum L. ‘Sandia’

Field experiments were conducted at five sites in Nebraska in 2000 and 2001 to determine the effect of planting depth and isoxaflutole rate on the response of an isoxaflutole-sensitive corn hybrid, ‘Pioneer 33-G’ across variable environments. Corn was planted at depths of 2.5 and 5.0 cm, and isoxaflutole was applied PRE at the recommended (1×) and twice the recommended (2×) rate. The effects of planting depth and herbicide rate on injury varied considerably across site–years. When injury was evident, it was generally greater at the high rate of isoxaflutole (2×) and at the shallow planting depth (2.5 cm). In most site–years, corn recovered from early season injury, and yields were not reduced, except at Scottsbluff, NE, and North Platte, NE, where soils were lower in organic matter and higher in pH. Isoxaflutole rates should be carefully selected for soils with low organic matter and high pH.

Nomenclature: Isoxaflutole, corn, Zea mays L

A field study was conducted at two sites in southwestern Ontario, Canada, from 2002 to 2005 to assess the cumulative effects of different weed management strategies applied to the same plots over time in a corn–soybean rotation. These strategies included a POST broad-spectrum herbicide applied at recommended or reduced rates and use of a computer decision aid to select the POST herbicide having the greatest net return (economic threshold approach) based on weed populations before treatment or seed-bank estimates. Four years after study initiation, increased weed populations were observed only in the nontreated control. The reduced rate and economic threshold approaches did not lead to increased weed seed banks compared with the recommended rate of a broad-spectrum herbicide. Reductions in herbicide rate were more effective than the use of economic thresholds for reducing the risk of environmental impact in corn and soybeans. Weed populations in this study were generally above threshold levels, and herbicides selected by the computer decision aid tended to be older, less-expensive herbicides with high use rates. Recommendations by the computer decision aid were generally more effective and more profitable when based on weed populations before treatment than when based on seed-bank estimates.

Nomenclature: Corn, Zea mays L, soybean, Glycine max (L.) Merr

Field studies were conducted from 2000 to 2002 to determine whether glyphosate applied during periods of low temperature (< 10 C) provides effective control of garlic mustard without injury to nontarget native herbs. A 1% glyphosate solution was applied on three dates between November and March in 2000 to 2001 and 2001 to 2002, when average daily temperatures ranged from −4.2 to 7 C. Glyphosate reduced the population density of prereproductive springtime garlic mustard infestations, regardless of application timing. During the primary bolting period (April to June), mortality of garlic mustard rosettes in sprayed plots was 87 to 94%, whereas mortality in nontreated plots was 12% in the first year and 41% in the second. Nontarget native herbaceous species were not injured by the cold-weather herbicide applications and exhibited higher springtime densities than in the nontreated plots. By targeting garlic mustard rosettes during the part of the year when most other plant species are dormant, managers can selectively control garlic mustard without damage to native herbs and, thereby, increase forest restoration success.

Nomenclature: Glyphosate, garlic mustard, Alliaria petiolata (Bieb.) Cavara and Grande

Livestock poisoning can occur on short-grass prairies when locoweeds are actively growing in spring before warm-season grasses begin growth. White locoweed grows in early spring, completes flowering and seed production by early summer, and goes dormant. Perennial cool-season grasses may provide competition to suppress locoweed or reduce its reestablishment following control. Furthermore, these grasses may provide alternative palatable forage to livestock early in the spring. The objective of this study was to suppress white locoweed reinvasion by seeding cool-season grasses at two mixed-grass and two short-grass prairie sites. White locoweed and associated species were controlled with glyphosate (1.1 kg ai/ha) and picloram (0.38 kg ae/ha) in 3 by 15 m plots. The plots were seeded to ‘CDII’ crested wheatgrass, ‘Vavilov’ Siberian wheatgrass, ‘Luna’ pubescent wheatgrass, ‘Bozoisky’ Russian wildrye, smooth brome, ‘NewHy’ wheatgrass, sideoats grama, and ‘Immigrant’ forage kochia. In addition, a native grass plot, treated with picloram to control locoweed without harming the native grasses, and a nontreated control plot, were established in each replication. Establishment of crested wheatgrass, Siberian wheatgrass, and Russian wildrye averaged 60% over all sites. The other treatments had establishment rates < 30% and were considered unsuccessful. Forage production of Russian wildrye was 2,962 kg/ha, Siberian wheatgrass was 2,736 kg/ha, and crested wheatgrass was 2,339 kg/ha, compared with 1,051 kg/ha for the nontreated control. Mortality of locoweed seedlings was greatest in the pubescent wheatgrass seeding. All seeded species suppressed reestablishment of indigenous locoweed plants.

Nomenclature: Glyphosate, picloram, white locoweed, Oxytropis sericea Nutt. Ex Torr. & Gray OXRMA, crested wheatgrass, Agropyron cristatum (L.) Gaertner × Agropyron desertorum (Fisch. ex Link) Schultes, forage kochia, Kochia prostrata (L.) Schrader, NewHy wheatgrass, Pseudoroegneria spicata (Pursh) A. Love × Elytrigia repens (L.) Nevski, pubescent wheatgrass, Thinopyrum intermedium (Host) Beauv, Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski, Siberian wheatgrass, Agropyron fragile (Roth) Candargy, sideoats grama, Bouteloua curtipendula (Michx.) Torr, smooth brome, Bromus inermis Leysser

Field and greenhouse studies were conducted in 2000 and 2001 in Mississippi to determine the most effective POST herbicide programs for control of Texasweed in glyphosate-resistant soybean. In the field, Texasweed plants recovered from most POST herbicide treatments, and plant death rarely occurred. A sequential application of 1,100 g ae/ha glyphosate followed by 840 g/ha glyphosate was the only treatment that controlled at least 90% of Texasweed 4 wk after treatment. Texasweed control ranged from 80 to 87% for lower rates of glyphosate applied once or twice and 390 g ai/ha fomesafen. The addition of fomesafen or other herbicides to glyphosate did not improve control compared with glyphosate alone. In the greenhouse, glyphosate at 560 g/ha controlled 93 and 90% of one- and two-leaf plants, respectively, but at least 1,400 g/ha was required to obtain 90% control of four-leaf plants. Fomesafen at 260 g/ha controlled 93 to 99% of one- to four-leaf Texasweed plants in the greenhouse.

Nomenclature: Fomesafen, glyphosate, Texasweed, Caperonia palustris (L.) St. Hil, soybean, Glycine max (L.) Merr

The dissipation of trifloxysulfuron in solution has not been evaluated. The objectives of this study were to evaluate the effect of spray carrier pH (pH values of 5, 7, and 9) on dissipation of trifloxysulfuron during a 21-d period and to evaluate the resulting effects on efficacy on Palmer amaranth. ANOVA of half-life values indicated that hydrolysis occurred more rapidly under acidic spray carrier pH with no differences between neutral and alkaline pH levels. Trifloxysulfuron solutions that were applied to Palmer amaranth significantly decreased dry weights compared with nontreated at all pH levels and time intervals. These results indicated that trifloxysulfuron dissipation was most rapid when the spray tank pH was more acidic, but trifloxysulfuron efficacy was not adversely affected by chemical degradation on Palmer amaranth. Data suggest that pesticide applicators may reduce trifloxysulfuron degradation in spray tanks by using neutral or alkaline spray carriers.

Nomenclature: Trifloxysulfuron, Palmer amaranth, Amaranthus palmeri S. Wats AMAPA

Greenhouse research was conducted to evaluate the effects of POST-applied clopyralid and clopyralid plus additives (surfactants and herbicides) on eight processing spinach varieties for leaf injury and yield. Results demonstrate that when applied alone, clopyralid caused mild injury in the form of slight to moderate leaf malformations and crinkling in all tested spinach varieties. Leaf injury increased significantly 10, 20, and 35 days after treatment (DAT) when additives were mixed with clopyralid compared with when clopyralid was applied alone. Applications of clopyralid phenmedipham increased leaf injury over clopyralid applied alone and all other clopyralid additive treatments. Within varieties, spinach yields recorded 35 DAT were generally not reduced with any clopyralid additive treatment, except when phenmedipham was added to the mixture. The leaf injury associated with clopyralid in this study, though consistent across varieties, generally appears to be cosmetic and may not be detrimental to spinach yields or to the quality of spinach harvested for canning or freezing.

Nomenclature: Clethodim, clopyralid, phenmedipham, sethoxydim, s-metolachlor, spinach, Spinacia oleracea L. ‘DMC 66-09’, ‘DMC 66-07’, ‘DMC 66-16’, ‘F415’, ‘17047’, ‘Avon’, ‘157’, ‘Padre’

Studies were initiated to evaluate absorption, translocation, and distribution of ¹⁴C-quinclorac in propanil- and quinclorac-resistant (R-BYG) and -susceptible (S-BYG) barnyardgrass. No differential absorption of ¹⁴C-quinclorac was observed between R-BYG and S-BYG, but more ¹⁴C remained in the treated leaf of S-BYG (57% of total absorbed) compared with the R-BYG leaf (34% of total absorbed) at 72 h after treatment (HAT). After 12 HAT, 20 and 15% of the amount absorbed had been translocated basipetally by R-BYG and S-BYG, respectively. At 72 HAT, 27 and 17% of the total absorbed ¹⁴C had been translocated acropetally by R-BYG and S-BYG, respectively. The levels of ¹⁴C above the treated leaf continued to increase throughout the duration of the experiment in R-BYG while levels of ¹⁴C above the treated leaf in S-BYG remained relatively constant. Seven percent more of the total absorbed ¹⁴C was exuded from roots of R-BYG than S-BYG at 72 HAT. Although differential translocation was observed between R-BYG and S-BYG, it is unclear whether this difference is a cause of quinclorac resistance or an effect of some other physiological process. Further research is needed to determine if differential translocation is due to metabolism or other physiological factors.

Nomenclature: Quinclorac, barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG

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 was also inconsistent. Removal of weed interference with all herbicides except bentazon provided peanut yields greater than the nontreated check.

Nomenclature: Acifluorfen, bentazon, diclosulam, imazapic, imazethapyr, lactofen, 2,4-DB, horse purslane, Trianthema portulacastrum L. TRTPO, Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA, smellmelon, Cucumis melo L. var. Dudaim Naud. CUMME, peanut, Arachis hypogaea L. ‘Tamrun 96.’

Bird vetch is a perennial Eurasian plant which, unlike many exotic weed species, can invade low fertility areas that have not been disturbed. It also is common in pastures, woodland, and tall forb communities. Bird vetch is expanding along Alaskan roadsides, in urbanized areas, and in low density forests. A greenhouse study was conducted to determine efficacy of six herbicide treatments applied at reduced rates in 2005 and again in 2006 for bird vetch seedling control. Bird vetch seedlings were tolerant of reduced rates of chlorsulfuron and 2,4-DB; however, complete control was achieved with rates of clopyralid, dicamba plus diflufenzopyr, triclopyr, and 2,4-D that were a fourth to an eighth of the full registered rate. These results will be important for developing effective, low-cost methods for controlling bird vetch in Alaska, especially on the outer margins of infestations.

Nomenclature: Chlorsulfuron, clopyralid, dicamba, diflufenzopyr, triclopyr, 2,4-D, 2,4-DB, bird vetch, Vicia cracca L. VICCR

Field studies were conducted near Clayton, Goldsboro, Kinston, and Rocky Mount, NC in 2003 to evaluate weed control and cotton response to postemergence (POST) treatments of glufosinate applied alone or in tank mixtures with s-metolachlor, pyrithiobac, or trifloxysulfuron. Late-season control of common lambsquarters, common ragweed, entireleaf morningglory, ivyleaf morningglory, jimsonweed, pitted morningglory, purple nutsedge, and sicklepod with glufosinate early postemergence (EPOST) was ≥90%. The addition of S-metolachlor to glufosinate EPOST improved control of all weeds except sicklepod, ivyleaf morningglory, and entireleaf morningglory. When applied POST, glufosinate provided ≥90% late season control of common lambsquarters, common ragweed, entireleaf morningglory, ivyleaf morningglory, jimsonweed, large crabgrass, pitted morningglory, purple nutsedge, and sicklepod. Control of goosegrass and Palmer amaranth was 81 and 84%, respectively. When pyrithiobac or trifloxysulfuron were added in POST tank mixtures, control of Palmer amaranth improved 6 and 9 percentage points, respectively. Control of goosegrass remained near 80% regardless of herbicide treatment used. The addition of a late post-directed (LAYBY) tank-mixture of glufosinate plus prometryn provided ≥88% late season control of all weeds. Reduced control of goosegrass and Palmer amaranth was observed with the LAYBY tank mixture of glufosinate plus MSMA when compared to other LAYBY tank mixtures. Cotton lint yields in plots receiving any herbicide application were significantly higher than plots receiving no herbicide application for all application timings. Cotton lint yields were ≥ 740 kg/ha where an EPOST was applied and ≥ 680 kg/ha when a POST herbicide was applied. Cotton lint yields were at least 200 kg/ha greater on plots receiving a LAYBY application when compared to plots where no LAYBY treatment was applied.

Nomenclature: Glufosinate, MSMA, prometryn, pyrithiobac, S-metolachlor, trifloxysulfuron, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L. AMBEL, entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray IPOHG, goosegrass, Eleusine indica ELEIN, ivyleaf morningglory, Ipomoea hederacea Jacq. IPOHE, jimsonweed, Datura stramonium L. DATST, large crabgrass, Digitaria sanguinalis L. DIGSA, Palmer amaranth, Amaranthus palmeri S. Wats AMAPA, pitted morningglory, Ipomoea lacunosa L. IPOLA, purple nutsedge, Cyperus rotundus L. CYPRO, sicklepod, Senna obtusifolia L. Irwin and Barnaby CASOB, cotton, Gossypium hirsutum L

Annual bluegrass is a troublesome weed of Kentucky bluegrass because of a lack of selective POST herbicides for control. Field experiments were conducted in New Jersey to investigate the potential of bispyribac-sodium, primisulfuron, and sulfosulfuron for selective annual bluegrass control in Kentucky bluegrass. Primisulfuron provided the best combination of Kentucky bluegrass safety and annual bluegrass control with greater efficacy in summer than fall. Bispyribac-sodium also provided substantial annual bluegrass control, especially in the summer, but caused unacceptable (> 20%) Kentucky bluegrass injury, whereas annual bluegrass control with sulfosulfuron was inconsistent. Growth chamber experiments confirmed that greater primisulfuron efficacy in summer than fall may be attributed to higher temperatures. Overall, primisulfuron has promising implications for future use in Kentucky bluegrass for annual bluegrass control whereas bispyribac-sodium will likely be more applicable in other cool-season turfgrasses.

Nomenclature: Bispyribac-sodium, primisulfuron, sulfosulfuron, annual bluegrass, Poa annua L. POANN, Kentucky bluegrass, Poa pratensis L. ‘Baron’, ‘Midnight’

In 2004 and 2005, glyphosate diuron and flumioxazin MSMA were applied POST-directed to cotton at 20, 30, 40, and 50 cm in height. Herbicides were directed to either the lower 2 cm of the cotton stem or to the lower 50% of the cotton stem to determine the impact of application timing and placement on cotton response. Glyphosate diuron resulted ≤ 22% injury when applied high on the stem and ≤ 8% injury when applied low on the stem. Regardless of application placement or timing, no yield reductions were observed as a result of glyphosate diuron application. Conversely, flumioxazin MSMA applications resulted in 93 and 64% injury when applied high POST-directed (HPD) to 20- and 30-cm cotton, respectively. Low POST-directed (LPD) applications caused 33 and 23% injury to 20- and 30-cm cotton, respectively. In both years, HPD applications of flumioxazin MSMA on 20-cm cotton resulted in excessive yield loss (94 to 87%), whereas yield loss was only noted in 30-cm cotton in 2004. No yield loss was observed in 40- or 50-cm cotton. Additionally, LPD applications of flumioxazin MSMA, though causing significant visual injury, did not result in a yield reduction at any application timing. Although cotton became more tolerant to flumioxazin MSMA as the season progressed, the research suggests that applications of flumioxazin should be made with precision or delayed until cotton reaches 40 cm in height.

Nomenclature: Diuron, flumioxazin, glyphosate, MSMA, Cotton, Gossypium hirsutum L. ‘DPL 555’, GOSHI

Only two spinach herbicides are currently available to producers, and with limited choices in herbicide mode of action (MOA), overuse of the current herbicides can result in dominance of uncontrolled weeds. Therefore, spinach producers need more herbicide options. Trials were conducted in processing spinach to evaluate the crop safety of dimethenamid-p (0.56 kg ai/ha), EPTC (2.94 to 3.40 kg ai/ha), or ethofumesate (0.84, 1.12 or 2.24 kg ai/ha) applied pre-emergent (PRE), and ethofumesate (0.09 or 0.18 kg ai/ha) applied early postemergent (EPOST) for potential use as alternatives to s-metolachlor (0.73 kg ai/ha) and cycloate (2.52 kg ai/ha). The control of London rocket was excellent with s-metolachlor, dimethenamid-p, and ethofumesate. Weed control with cycloate and EPTC was fair, and generally inferior to all others. Cycloate and s-metolachlor were safe to spinach, and only minor crop injury was observed with all other herbicides, except the high rate of ethofumesate PRE, which resulted in high levels of injury. Spinach outgrew all early herbicide injury with no significant yield losses. Ethofumesate applied EPOST caused no injury in year 1, although in year 2 injury was higher in all plots where it was applied twice, regardless of rate. In high-density plantings, dimethenamid-p caused significant crop injury to spinach, but only at one location on a sandy loam soil. In that trial, yields in dimethenamid-p plots were reduced an average 30% compared to the hand-weeded and s-metolachlor plots. As a result of this research, dimethenamid-p, EPTC, and ethofumesate should be considered candidates for expanded-use registrations in processing spinach production. More research is needed to determine additional rates and use patterns for improved crop safety, as well as an evaluation of soil types and spinach varieties.

Nomenclature: Cycloate, dimethenamid-p, EPTC, ethofumesate, s-metolachlor, London rocket, Sisymbrium irio L. SSYIR, spinach, Spinacia oleracea L., ‘DMC 66-09’, ‘Baker’

Field studies were conducted near Oxnard, CA and in two locations near Salinas, CA in 2002 and 2003 to evaluate efficacy and safety of six herbicides in celery. s-metolachlor at 0.6 and 0.7 kg ai/ha and flufenacet at 0.5, 0.6, and 0.7 kg ai/ha PRE were safe to celery and controlled 81 to 94% of yellow nutsedge at densities < 20 plants/m². At yellow nutsedge densities > 20 plants/m², the most efficacious treatments were 1.1 kg/ha of s-metolachlor or 0.7 kg/ha of flufenacet, which reduced nutsedge densities by 71 or 53%, respectively; however, both resulted in slight injury to celery. All other herbicides generally did not injure celery and none reduced marketable crop yield. Flumioxazin pretransplant (PRE) at 0.1 and 0.2 kg ai/ha controlled broadleaf weeds near 100% at all locations, suggesting that it can be an effective alternative to standard linuron and prometryn, which are applied post-transplant (POST) in celery.

Nomenclature: S-metolachlor, flufenacet, flumioxazin, prometryn, linuron, oxyfluorfen, yellow nutsedge, Cyperus esculentus L. CYPES, celery, Apium graveolens L

Field trials were initiated at three Missouri locations in the fall of 2004 and 2005 to compare the efficacy of fall and early spring herbicide applications on winter and summer annual weed populations in no-till soybean. All three experiments received applications of chlorimuron plus sulfentrazone plus 2,4-D; chlorimuron plus tribenuron plus 2,4-D; and glyphosate plus 2,4-D in the fall, 60 d prior to planting (60 PP), 30 days prior to planting (30 PP), and 7 d prior to planting (7 PP). Good control of all winter annual weeds, except for common chickweed, was observed at planting from fall applications of chlorimuron plus sulfentrazone plus 2,4-D and chlorimuron plus tribenuron plus 2,4-D. Fall, 60 PP, and 30 PP applications of chlorimuron plus sulfentrazone plus 2,4-D provided relatively poor control of common chickweed. Glyphosate plus 2,4-D applied in the fall and 60 PP provided adequate control of early fall germinating winter annuals, such as common chickweed and henbit. However, these treatments provided poor control of winter annual species that exhibited some degree of spring germination. Control of summer annual weed species 7 wk after planting (WAP) was highly variable. Relatively poor control of common waterhemp was obtained from all treatments except chlorimuron plus sulfentrazone plus 2,4-D applied at all three spring timings. Giant foxtail control was highly variable ranging from 0 to 95%. Measurements of weed biomass collected 7 WAP revealed larger amounts of biomass present in the fall application timing of each herbicide treatment. Emergence of winter and summer annual weed species from early March to 7 WAP varied by herbicide treatment. Emergence of total winter and summer annual weed species was reduced with both residual herbicide treatments when compared with glyphosate plus 2,4-D and the untreated control.

Nomenclature: Chlorimuron, 2,4-D, glyphosate, sulfentrazone, tribenuron, common chickweed, Stellaria media (L.) Vill. STEME, common waterhemp, Amaranthus rudis Sauer AMATA, giant foxtail, Setaria faberi Herrm. SETFA, henbit, Lamium amplexicaule L. LAMAM, soybean, Glycine max (L.) Merr. ‘Dekalb 38-52’

Field and greenhouse studies examined glyphosate and several ACCase-inhibitor herbicides for control of wirestem muhly. A field study evaluated application rate and timing for control in glyphosate-resistant soybean. Herbicides were applied at two rates, 4 and 6 wk after planting (WAP) of soybean when wirestem muhly was about 30 and 50 cm tall, respectively. A complimentary greenhouse experiment with the same herbicides examined wirestem muhly rhizome viability 30 days after herbicide application. A second field study examined optimum glyphosate application timing for control of wirestem muhly during a fallow rotation period. Glyphosate was applied at 14-day intervals from mid-May through early October. In the first field study, glyphosate, fluazifop, and clethodim provided better control of wirestem muhly than sethoxydim and quizalofop. Clethodim, fluazifop, and glyphosate provided 74 to 92% control over both rates and application timings, whereas quizalofop and sethoxydim were the least effective, providing only 52 to 64% control regardless of rate or timing. In the greenhouse, glyphosate was the most effective herbicide, providing at least 97% control and an 87% reduction in shoot biomass; sethoxydim and fluazifop were the least effective herbicides. All of the herbicides reduced rhizome viability compared to nontreated plants up to 71%, but no difference between herbicides was observed. In the second field study, end-of-season ratings revealed that glyphosate provided 95 to 100% control of wirestem muhly from applications made between late June and early September. The year following application, glyphosate provided 91 to 99% control of wirestem muhly from applications made between mid-June and early September. Applications earlier than mid-June or after early September resulted in less than 90% control. Overall, results show that (1) glyphosate was the most effective herbicide; (2) the ACCase-inhibitor herbicides differ in their effectiveness; and (3) rate and application timing can impact control.

Nomenclature: Clethodim, fluazifop, glyphosate, sethoxydim, quizalofop, wirestem muhly, Muhlenbergia frondosa (Poir.) Fern. MUHFR, soybean, Glycine max (L.) Merr. ‘A5403: 40-3-2’

Mesotrione is under evaluation for registration in turfgrass for weed control, but often requires repeat treatments. Previous research in agricultural crops indicates tank mixtures with mesotrione improve weed control. Greenhouse trials were conducted in Blacksburg, VA, with 7 mo-old white clover, and field trials in Knoxville, TN, evaluated control of 5-yr old white clover in a stand of common bermudagrass. Data from both field and greenhouse trials indicate mesotrione applied in combination with bromoxynil, carfentrazone, or simazine control white clover better than any of these herbicides applied alone. Combinations of bromoxynil, carfentrazone, and simazine with mesotrione also decreased relative chlorophyll index and white clover fresh weights in agreement with visually estimated control.

Nomenclature: Bromoxynil, carfentrazone, mesotrione, simazine, white clover, Trifolium repens L. TRFRE, common bermudagrass, Cynodon dactylon (L.) Pers. ‘Vamont’

Field studies were conducted in 2004 and 2005 to determine the effect of soybean row width and population on weeds, canopy closure, crop yield, and economic return in glyphosate-resistant soybean. Soybean leaf area index (LAI) was greater in 19- and 38-cm, compared with 76-cm rows from 8 to 12 wk after planting in the low, moderate, and high soybean populations. Canopy closure was delayed by 2 wk in the moderate population in 76-cm rows compared with the high population in 19-cm rows. Fewer weeds emerged in 19-cm, compared with 76-cm rows following glyphosate application, and increasing the soybean population within a row width did not influence late-season weed emergence. Weed biomass in the weedy control was greater in the very low soybean population compared with the high soybean population within each row width; however, weed biomass in the weedy control was similar in the high and moderate soybean populations. Soybean yield in the weed-free and 10-cm glyphosate treatment did not differ, and yield was greater in 19-cm rows planted at moderate or high, compared with low populations. There was no difference in weed-free soybean yield at low, moderate, and high populations within 38- and 76-cm rows. Gross margins were usually greater in 19- and 38-cm, compared with 76-cm rows. The gross margin for soybean planted in 19-cm rows was usually greater at moderate or high soybean populations compared with lower populations. In 76-cm rows, the gross margin was greatest at the low and moderate soybean populations. When rainfall or other factors limited soybean yield, increasing the soybean population from approximately 300,000 plants/ha to 445,000 plants/ha in 19-, 38-, and 76-cm rows did not result in quicker canopy closure, reduced weed emergence, or greater soybean yield and gross margins.

Nomenclature: Glyphosate potassium salt, glyphosate-resistant soybean, Glycine max (L.) Merr., ‘AG2701’

Field trials were established in Fayetteville, AR, to determine the effects of glyphosate on biomass and seed production of spurred anoda, entireleaf morningglory, hemp sesbania, and Florida pusley. Inconsistent control of these species by glyphosate allows them to enrich the soil seedbank. Glyphosate rates of 0.42, 0.84, and 1.68 kg ae/ha were applied at 3, 6, and 9 wk after emergence (WAE) and were compared with a nonsprayed control. Spurred anoda seed production was reduced 99.9% by glyphosate at 1.68 kg/ha averaged over application timings and 99.7% by glyphosate applied at 6 WAE averaged over rates. Entireleaf morningglory seed production was reduced 100% by glyphosate at 1.68 kg/ha at 3 WAE and > 93% by the same rate applied at 6 or 9 WAE. Hemp sesbania seed production was reduced 100% by glyphosate at 1.68 kg/ha at 3 WAE and > 96% by glyphosate at 0.42, 0.84, and 1.68 kg/ha applied at 6 or 9 WAE. Florida pusley seed production was reduced 99.9% by glyphosate at 1.68 kg/ha averaged over application timings and 99.4% by application at 3 or 6 WAE averaged over rates. Biomass accumulation for all species was reduced most by early applications, particularly at 1.68 kg/ha.

Nomenclature: Glyphosate, entireleaf morningglory, Ipomoea hederacea var. integriuscula (L.) Jacq. A. Gray IPOHG, Florida pusley, Richardia scabra L. RCHSC, hemp sesbania, Sesbania exaltata (Raf.) Cory SEBEX, spurred anoda, Anoda cristata(L.) Schlecht ANVCR

Dallisgrass response to various MSMA and foramsulfuron herbicide combinations was evaluated from 2004 through 2006 in North Carolina. Dallisgrass control declined with herbicide rates; therefore, only the highest rates (foramsulfuron, 0.15 kg ai/ha; MSMA, 2.5 kg ai/ha) are discussed. Foramsulfuron followed by (fb) foramsulfuron 1 wk after initial treatment (WAIT) provided 60% control of dallisgrass 1 mo after initial treatment (MAIT), but control declined to 40% 3 MAIT. MSMA (2.5 kg ai/ha) applied three times provided 89% dallisgrass control 1 MAIT, but control declined to 71% 3 MAIT. Among 22 MSMA and foramsulfuron sequential application programs, MSMA fb foramsulfuron 2 WAIT fb MSMA 3 WAIT provided the highest control (94%) of dallisgrass 1 MAIT, and control levels remained high (93%) 3 MAIT. This herbicide program provided 85% control 1 yr after initial treatment (YAIT), whereas no other treatment provided greater than 37% control 1 YAIT. Timing of foramsulfuron application following the initial MSMA application affected the control of dallisgrass. Waiting 2 WAIT, rather than 1 WAIT, before applying foramsulfuron increased control of dallisgrass by 20% 1 MAIT and 19% 3 MAIT. However, the increase in control 1 YAIT was only 5% regardless of herbicide rate. The addition of a second application of MSMA following the application of foramsulfuron 2 WAIT of MSMA further increased control by 10% 1 MAIT, 37% 3 MAIT, and 48% 1 YAIT. Results from this study suggest dallisgrass may be controlled with applications of MSMA fb foramsulfuron 2 WAIT fb MSMA 3 WAIT applied during early to midsummer. The use of MSMA was required to achieve dallisgrass control, however, the relatively high level of control achieved 1 YAIT with a program including sequential applications of MSMA and foramsulfuron may help reduce the total amount of arsenical herbicides used to control dallisgrass infestations over time.

Nomenclature: Dallisgrass Paspalum dilatatum Poir. PASDI, hybrid bermudagrass, Cynodon transvaalensis × Cynodon dactylon ‘Tifway’

Field experiments were conducted to evaluate the influence of three nitrogen fertilizer application timings on corn and giant ragweed dry weight, corn and giant ragweed nitrogen accumulation, and corn grain yield. By the V8 growth stage, corn plants in treatments which included nitrogen at planting accumulated up to 27% more dry weight and 26% more leaf area than corn in sidedress-only treatments that had not yet received any fertilizer nitrogen. Nitrogen fertilizer application timing did not influence early-season giant ragweed dry weight, but did influence N accumulation. Giant ragweed at 0.5 plants/m² accumulated up to 16 kg N/ha in 40-cm-tall plants by the V8 corn growth stage and up to 104 kg N/ha when allowed to remain in corn until the end of the growing season. At this density of giant ragweed, corn yields were not reduced if removed by the V8 corn growth stage. However, season-long interference reduced corn yields by up to 19% regardless of nitrogen application timing. Early-season giant ragweed growth was less responsive to nitrogen application timing than corn, suggesting that nitrogen management programs should not be altered significantly to influence giant ragweed competitiveness in corn. However, giant ragweed should be removed in a timely manner to minimize nitrogen accumulation in nitrogen-limiting corn production situations.

Nomenclature: Giant ragweed, Ambrosia trifida L. AMBTR, corn, Zea mays L. ‘DKC60-09RR2/YGCB’ and ‘DKC61-45RR/YGCB’

Path rush can become problematic on golf course fairways, especially on roughs where continuous golf cart or maintenance equipment traffic occurs. Research trials conducted in 2003 and 2004 compared the efficacy of 2,4-D and mixtures containing 2,4-D in single or sequential applications to herbicides without 2,4-D for path rush control in bermudagrass roughs. Sequential applications of 1.1 kg ae/ha 2,4-D or 0.8 0.2 0.1 kg ae/ha 2,4-D MCPP dicamba provided 95% path rush control with no injury to bermudagrass, 15 wk after initial treatment (WAIT). Single applications of 1.1 0.3 0.1 kg/ha 2,4-D MCPP dicamba or 1.1 kg/ha 2,4-D provided at least 81% path rush control, 15 WAIT. Treatments without 2,4-D did not provide acceptable levels of control (34% or less, 15 WAIT). 2,4-D applied alone or in preformulated mixtures provided excellent path rush control compared to treatments without 2,4-D. Sequential applications of these treatments provided greater path rush control than single applications. However, only the sequential application of 0.8 0.2 0.1 kg/ha 2,4-D MCPP dicamba provided greater path rush control than the single application. Results from these studies suggest that 2,4-D is a key herbicide for path rush control.

Nomenclature: 2,4-D, MCPP, dicamba, carfentrazone, foramsulfuron, triclopyr, clopyralid, trifloxysulfuron-sodium, path rush, Juncus tenuis Willd. JUNTE, bermudagrass, Cynodon dactylon (L.) Pers. CYNDA

Experiments were conducted in 2005 and 2006 near Huntley, Montana to evaluate two formulations of mesosulfuron-methyl for the control of wild oat in malt barley. The two formulations differed due to the amount of safener, mefenpyr-diethyl, that each contained. Formulation 1 and 2 contained mesosulfuron-methyl and mefenpyr-diethyl at a 1 : 2 and 1 : 6 ratio, respectively. The two formulations were applied alone at two rates or in combination with other small grain herbicides that are typically used for broadleaf weed control. The low and high rate of formulation 1 contained 7.8 and 10.1 g ai/ha of mesosulfuron-methyl and 15.6 and 20.2 g ai/ha of mefenpyr-diethyl, respectively. The low and high rate of formulation 2 contained 2.5 and 3.1 g ai/ha of mesosulfuron-methyl and 15 and 18.6 g ai/ha of mefenpyr-diethyl, respectively. These treatments were compared to a standard treatment of fenoxaprop and a nontreated control. In 2005, formulation 2 applied alone at the low and high rates caused barley injury of 7 and 11% at 21 days after treatment (DAT) and 4 and 7% at 56 DAT, respectively. Applications of formulation 1 caused barley injury that was 9 and 17 percentage points greater at 21 DAT and 12 and 18 percentage points greater at 56 DAT than barley injury from applications of formulation 2 when these herbicides were applied alone at the low and high rate, respectively, in 2005. In both years, formulation 1 applied alone at either rate injured barley more than fenoxaprop at 21 and 56 DAT. In both years, formulation 1 and 2 applied alone controlled wild oat between 85 and 96% at 21 DAT and between 92 and 98% at 56 DAT. Regardless of rate, wild oat control with either formulation was similar to that provided by fenoxaprop at 56 DAT. In 2005 and 2006, barley yield was equivalent between treatments of formulation 1 or 2 and that produced by barley treated with fenoxaprop. No difference in the percentage of plump kernels occurred between treatments of formulation 2 and fenoxaprop. The percentage of plump kernels was reduced 6 to 7 percentage points with treatments containing formulation 1 compared to treatments containing formulation 2. Overall, formulation 2 was effective for the control of wild oat in malt barley. Low levels of malt barley injury occurred with this treatment; however, barley successfully recovered by harvest, and yield and kernel size were equivalent to barley treated with fenoxaprop.

Nomenclature: mefenpyr-diethyl, [diethyl 1-(2,4-dichlorophenyl)-5-methyl-2-pyrazoline-3, 5-dicarboxylate], mesosulfuron-methyl, [methyl-2-[3-(4,6-dimethoxypyrimidin-2-yl)ureidosulfonyl]-4-methane-sulfonamidomethylbenzoate], Wild oat, Avena fatua L. AVEFA, barley, Hordeum vulgare L. HORVX, ‘Moravian 37’

Field studies were conducted during the 2004 and 2005 growing seasons to evaluate the effects of various herbicides on smellmelon control and soybean yield response. Pendimethalin applied pre-emergence (PRE) alone controlled smellmelon no better than 70%, whereas pendimethalin plus imazethapyr, flumioxazin, or cloransulam applied PRE provided almost complete smellmelon control (99%). Pendimethalin applied PRE followed by acifluorfen applied early postemergence (EPOST) provided similar control. Glyphosate alone applied late postemergence (LPOST) provided complete control (100%), and pendimethalin followed by glyphosate applied EPOST controlled smellmelon at least 95%. Most herbicides increased soybean yield over the nontreated check.

Nomenclature: Acifluorfen, cloransulam, flumioxazin, glyphosate, imazethapyr, pendimethalin, smellmelon, Cucumis melo L. var. Dudaim Naud. CUMME, soybean, ‘HBK 5123’

Field experiments were conducted in 2003 and 2004 to evaluate the effects of reduced rates of glufosinate on development and yield of three nonglufosinate-resistant cotton varieties. The varieties evaluated were selected on their relative maturity with PayMaster (PM) 1218, early maturity; FiberMax (FM) 960, medium maturity; and Delta and Pine Land (DP) 555, late maturity. Rates of 47, 23, and 4.7 g ai/ha were applied, representing 10, 5, and 1% of the typical use rate per application of 467 g ai/ha, respectively. As might be expected, when averaged over varieties, the 10% rate showed more injury than the 5%, and the 5% rate caused more visual injury than the 1% rate. Pooled over timing and rate, PM1218 showed more injury (18%) than FM960 (7%), which showed more injury than DP555 (1%) 7 days after application (DAA) at the 10% rate. However, although PM1218 showed the most visual injury, this did not translate into delay in maturity or loss of lint yield. DP555 showed 70 kg ai/ha and 50 kg ai/ha lint yield loss when glufosinate was applied at the 10% rate on the fifth and eighth node stage, respectively. DP555 was delayed in maturity when glufosinate was applied at the 10% rate on the eighth node stage. FM960 showed 30 kg/ha lint yield loss when glufosinate was applied at the 10 and 5% rates at the fifth node stage. Maturity of FM960 was delayed with the 10 and 5% rates applied at the fifth node stage.

Nomenclature: Glufosinate, cotton, Gossypium hirsutum L., ‘Delta & Pine Land’ (DP555), ‘FiberMax’ (FM960), ‘PayMaster’ (PM1218)

A study was established to evaluate herbicides registered for barnyardgrass control in rice for activity on creeping rivergrass. Treatments included 208 g ai/ha cyhalofop early POST (EPOST) followed by (fb) 315 g/ha cyhalofop late POST (LPOST), 22 g ai/ha bispyribac EPOST fb 22 g/ha bispyribac LPOST, 66 g ai/ha fenoxaprop EPOST fb 86 g/ha fenoxaprop LPOST, 70 g ai/ha imazethapyr EPOST fb 70 g/ha imazethapyr LPOST and 50 g ai/ha penoxsulam mid-POST (MPOST). Each POST program was evaluated with and without 448 g ai/ha clomazone PRE. Barnyardgrass control, averaged over days after treatment (DAT), was 88 to 92% with the addition of clomazone PRE. Clomazone applied PRE followed by two applications of cyhalofop controlled creeping rivergrass at 91%. Creeping rivergrass control was less than 75% at 35 to 49 DAT. This response indicates only suppression of creeping rivergrass is achieved with the herbicide programs evaluated in this study.

Nomenclature: Bispyribac, clomazone, cyhalofop, fenoxaprop, imazethapyr, penoxsulam, barnyardgrass, Echinochloa crus-galli (L.) Beauv, creeping rivergrass, Echinochloa polystachya (Kunth) A.S. Hitchc, rice, Oryza sativa L

Field and greenhouse studies were conducted from 1996 to 2000 to determine tropical soda apple fruit size required for mature seed, overwintering survival potential of seeds, and growth and fruit production in a containment area near Stoneville, MS (latitude 33°25′N). Seedling emergence was ≥ 50% from tropical soda apple fruit > 1.8 cm in diameter. Tropical soda apple overwintering emergence was 14, 10, 48, 42, and 13% from seed alone and 86, 83, 48, 41, and 18% for seeds in tropical soda apple fruit overwintering at 100, 0, −5, −10, and −15 cm from the soil surface, respectively. Before frost (early November), average tropical soda apple plant heights were 0.8, 0.6, and 0.7 m; plant diameters were 2.6, 1.7, and 2 m; fruit produced per tropical soda apple plant were 415, 342, 128; and plant weights were 9.9, 9.5, and 4.9 kg at 27 wk after transplanting (WATP) for 1996, 1997, and 1998, respectively. Regeneration from overwintering tropical soda apple roots varied depending on the winter conditions. These results suggest that tropical soda apple plants can survive mild winters.

Nomenclature: Tropical soda apple, Solanum viarum Dun. SOLVI

Sulfentrazone adsorption and mobility in six soils with varying soil properties were evaluated under laboratory conditions. Adsorption was evaluated using a modified slurry technique. Mobility was evaluated using packed-soil columns under saturated flow conditions. The order of adsorption to soil was Sequatchie loam > Dothan loamy sand  =  Bosket fine sandy loam > Malden loamy sand > Commerce silty clay loam > Harkey clay loam. Greater sulfentrazone adsorption occurred in soils with lower pH. Sulfentrazone movement under saturated flow conditions in 27-cm soil-packed columns was greater in soils with low adsorption, high pH, and coarse texture. Sulfentrazone movement was limited in the Sequatchie loam but was greater in the other soils examined. No clear relationship was evident between sulfentrazone mobility and adsorption in these soils.

Nomenclature: Sulfentrazone

Field research was conducted to evaluate plant growth-regulator efficacy for tall fescue growth and seedhead suppression applied using application placement equipment. Specially designed equipment outfitted with fluid application systems applies low-volume plant growth regulator directly on plant foliage, reducing opportunity for drift and visible application. Wet-blade mowers are equipped to apply plant growth regulators and mow in a single pass, whereas rotary-wick applicators simply wipe chemicals directly on uncut vegetation. Therefore, a wet-blade, rotary-wick, and broadcast sprayer system were chosen to apply imazapic at three rates (9, 35, and 53 g ai/ha), and a mefluidide chlorsulfuron tank mix at 7 140 g ai/ha to tall fescue roadsides for vegetative growth and seedhead suppression. Experiments were conducted during the spring and summer of 2004 in central and western North Carolina. Tall fescue was slightly injured and discolored by all treatments but fully recovered by 2 mo after treatment. Imazapic suppressed new vegetative growth 3 mo after treatment compared with the nonmowed–nontreated control (16.1 cm of growth) and the mowed–nontreated control (21.1 cm) when applied with the rotary-wick applicator (8.5 cm) and broadcast sprayer (6.2 cm). However, differences in vegetative height primarily occurred when application placement equipment treatments were compared with nontreated vegetation as opposed to mowed–nontreated plants. Although mowed–nontreated and wet-blade–treated plots had more new vegetative growth, nonmowed–nontreated plots still consistently had the greatest vegetative height. Seedhead suppression ranged from 87 to 100% when compared with the nonmowed–nontreated control, with wet-blade treatments consistently providing the least-effective seedhead suppression. Overall, application placement equipment did not improve plant growth-regulator efficacy when compared with the foliar broadcast spray.

Nomenclature: Chlorsulfuron; imazapic; mefluidide; tall fescue, Lolium arundinaceum (Schreb.) S.J. Darbyshire, ‘Kentucky 31’

New hybrid bluegrass cultivars have been bred for increased heat and drought tolerance compared with traditional Kentucky bluegrass cultivars. Research was conducted to evaluate hybrid bluegrass tolerance and smooth crabgrass and goosegrass control with mesotrione and quinclorac during seeded establishment. Mesotrione applied as a single application 14, 28, or 42 d after emergence (DAE) injured hybrid bluegrass acceptably from 1 to 11% 7 d after treatment (DAT). A sequential mesotrione application at 0.14 kg/ha 28 DAE did not injure hybrid bluegrass greater than the initial 14 DAE application; however, a sequential application at 0.28 kg/ha 28 DAE injured hybrid bluegrass greater than the initial 14 DAE application. Three sequential mesotrione applications did not reduce hybrid bluegrass ground cover 63 DAE. Quinclorac applied singly at 1.68 kg/ha 14 DAE and sequentially at 0.84 kg/ha 14 and 28 DAE injured hybrid bluegrass that continued throughout the rating period resulting in decreased ground cover at 63 DAE. Quinclorac at 0.84 kg/ha plus mesotrione at 0.28 kg/ha injured hybrid bluegrass < 20% throughout the rating period but reduced ground cover 63 DAE. All quinclorac-containing treatments controlled smooth crabgrass ≥ 92%. All mesotrione sequential-application treatments controlled smooth crabgrass and goosegrass ≥ 87%. These data indicate that sequential mesotrione applications can be used for smooth crabgrass and goosegrass control during seeded hybrid bluegrass establishment. Quinclorac should be applied according to label recommendations at 0.84 kg/ha no earlier than 28 DAE.

Nomenclature: Mesotrione, quinclorac, goosegrass, Eleusine indica (L.) Gaertn. ELEIN, smooth crabgrass, Digitaria ischaemum (Schreb.) Schreb. ex Muhl. DIGIS, hybrid bluegrass, Poa pratensis L. × Poa arachnifera Torr. ‘Solar Green’, ‘Durablue’, and ‘Thermal Blue’, Kentucky bluegrass, Poa pratensis L. POAPR

Cogongrass is a highly invasive perennial grass that threatens agriculture, forestry, and native plant assemblages in many regions of the world. Cogongrass is a prolific seed producer, but the ecological importance of seeds as a vector of invasion has not been adequately addressed. Propagule pressure plays a key role in many successful invasions and the relative importance of propagule pressure across environmental gradients is an area of research that is quickly becoming important in understanding invasion success. The present study was conducted to test the effects of varying propagule density upon the ability of cogongrass seedlings to grow and establish across experimentally manipulated light and soil gradients. Seedlings growing in high-nutrient soil performed the best regardless of the amount of available light, but overall biomass was always greatest in high-light environments. Cogongrass showed a very strong trend in biomass allocation, with seedlings in reduced light environments partitioning more biomass to aboveground tissue. The data provided no evidence that initial propagule density affected the growth and establishment of cogongrass seedlings, but growth and biomass production were positively correlated with final seedling density.

Nomenclature: Cogongrass [Imperata cylindrica (L.) Beauv.] IMPCY

The difficulty of monitoring growth parameters of climbing invasive plants subjected to different control options can be overcome by using standardized support structures (trellises). The utility of such support structures on aboveground biomass accumulation and fruit production was demonstrated using the invasive climber, bridal creeper in three invaded nature reserves near Perth in Western Australia. Mean above-ground plant biomass for plots provided with trellises ranged from 204 ± 38 g/m² to 336 ± 31 g/m², whereas it ranged from 66 ± 10 g/m² to 118 ± 10 g/m² in plots with no trellises. The mean number of fruits/m² produced on shoots in plots provided with trellises ranged from 424 ± 159 to 3,787 ± 873 and was up to almost four orders of magnitude greater than the number of fruits produced on plants in plots with no trellis (ranging from 0 to 5.25 ± 7.9). The use of standardized trellises also showed that fruit volume and fruit seed number can vary significantly between sites. Standardized trellises have been installed at sites across Australia to assess the long-term impact of biological control agents introduced to manage bridal creeper.

Nomenclature: Bridal creeper, Asparagus asparagoides (L.) Druce

Certified Crop Advisors of Arkansas and members of the Arkansas Crop Consultants Association were surveyed in Fall 2006 through direct mail to assess current weed management practices and needs in cotton from both a research and educational perspective. Consultants reported scouting 162,300 of the possible 473,700 ha of cotton grown in Arkansas. Collectively, glyphosate-resistant and enhanced glyphosate-resistant cultivars were reported grown on 98% of the cotton hectares. Ninety-five percent of the consultants believe the planting of enhanced glyphosate-resistant cultivars will increase over the next 5 yr. All consultants indicated a “moderate” to “high” level of concern with herbicide-resistant weeds in cotton, and 79% of the consultants suspect herbicide resistance in the fields they scout, predominately glyphosate-resistant horseweed. Horseweed, Palmer amaranth, and morningglories were the three most problematic weeds in cotton. A continued focus on resistant weed management was the most frequent research and educational request by consultants.

Nomenclature: Horseweed, Conyza canadensis (L.) Cronq. ERICA, morningglories, Ipomoea spp, Palmer amaranth, Amaranthus palmeri S. Wats AMAPA, cotton, Gossypium hirsutum L

Certified Crop Advisors of Arkansas and members of the Arkansas Crop Consultants Association were surveyed in Fall 2006 through direct mail to assess current weed management practices and needs in rice from both a research and educational perspective. Consultants reported scouting 228.2 of the possible 567 thousand hectares (40%) of rice grown in Arkansas. Pre-emergence herbicides most often recommended were clomazone (93%) and quinclorac (40%). Propanil (55%) and quinclorac (47%) were the two most commonly recommended postemergence herbicides. Thirty-two percent of the consultants often recommend three or more herbicide applications per field. An average of 37% of the fields were believed to have “serious” or “very serious” weed infestations, and fields were scouted for weeds on average 11 times per growing season. Ninety-two percent of the consultants had “moderate” to “high” concerns with herbicide-resistant weeds. The perceived average additional expense associated with managing a resistant weed in rice was $65.60/ha. Propanil-resistant and quinclorac-resistant barnyardgrass were believed to be infesting 24 and 7% of the scouted rice hectares, respectively. Barnyardgrass was the most problematic weed of rice followed by red rice. Northern jointvetch and smartweeds were the two most problematic broadleaf weeds. The number one research need was improved broadleaf weed control. Respondents indicated that research and educational efforts should continue to focus on herbicide performance and development of economical weed control programs.

Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG, northern jointvetch, Aeschynomene virginica (L.) B.S.P. AESVI, red rice, Oryza sativa L. ORYSA, smartweeds, Polygonum spp, rice, Oryza sativa L

Advances in statistical software allow statistical methods for nonlinear regression analysis of dose-response curves to be carried out conveniently by non-statisticians. One such statistical software is the program R with the drc extension package. The drc package can: (1) simultaneously fit multiple dose-response curves; (2) compare curve parameters for significant differences; (3) calculate any point along the curve at the response level of interest, commonly known as an effective dose (e.g., ED30, ED50, ED90), and determine its significance; and (4) generate graphs for publications or presentations. We believe that the drc package has advantages that include: the ability to relatively simply and quickly compare multiple curves and select ED-levels easily along the curve with relevant statistics; the package is free of charge and does not require licensing fees, and the size of the package is only 70 MB. Therefore, our objectives are to: (1) provide a review of a few common issues in dose-response-curve fitting, and (2) facilitate the use of up-to-date statistical techniques for analysis of dose-response curves with this software. The methods described can be utilized to evaluate chemical and non-chemical weed control options. Benefits to the practitioners and academics are also presented.