Field studies were conducted to evaluate weed control in herbicide-resistant canola in Georgia. The resistant canola cultivars and respective herbicides were ‘Pioneer 45A76’ and imazamox, ‘Hyola 357RR’ and glyphosate, and ‘2573 Invigor’ and glufosinate. Weed seed of Italian ryegrass and wild radish were sown simultaneously in October with canola and control of these species was evaluated along with other naturally occurring weeds. Herbicide treatments for the respective herbicide-resistant canola cultivar were imazamox at 0.035 and 0.071 kg ai/ha, glyphosate at 0.84 and 1.64 kg ae/ha, and glufosinate at 0.5 and 1.0 kg ai/ha. Herbicides were applied at one– two-leaf (LF) and three–four-LF canola stages. There was no significant injury to any canola cultivar as a result of herbicide rate or timing of application. By midseason (February), imazamox effectively controlled wild radish, henbit, and shepherd's-purse at both rates and at both timings. When applied to three–four-LF canola, the higher rates of glyphosate and glufosinate were required to provide 75% or greater control of Italian ryegrass, wild garlic, and henbit. Glufosinate did not adequately control wild radish at either rate or application timing. Greenhouse experiments provided similar results.

Nomenclature: Glufosinate; glyphosate; imazamox; henbit, Lamium amplexicaule L. #³ LAMAM; Italian ryegrass, Lolium multiflorum Lam. # LOLMU; wild garlic, Allium vineale L. # ALLVI; wild radish, Raphanus raphanistrum L. # RAPRA; shepherd's-purse Capsella bursa-pastoris (L.) Medicus., # CAPBP; and canola, Brassica napus L. # BRSNS, ‘Pioneer 45A76’, ‘Hyola 357RR’, and ‘2573 Invigor’.

Additional index words: Canola injury, canola yield, susceptibility to herbicides, herbicide resistance, herbicide tolerance.

Abbreviations: LF, leaf stage of growth; DAP, days after planting; IRC, imidazolinone-resistant canola.

Three field trials were established from 2001 to 2003 in Ontario to determine the effect of foramsulfuron POST (35 and 70 g ai/ha), isoxaflutole PRE (105 and 210 g ai/ha), and isoxaflutole plus atrazine PRE (105 1063 and 210 2126 g ai/ha) applied in the previous years to field corn on cranberry, black, kidney, and white (navy) bean. Foramsulfuron residues did not cause visible injury, or reductions in shoot dry weight or yield of dry bean 1 yr after application in corn. In contrast, visual injury across the four market classes varied from 4 to 37% 1 yr after application of isoxaflutole, and from 30 to 54% 1 yr after application of isoxaflutole plus atrazine. Isoxaflutole residues reduced shoot dry weight and yield as much as 81 and 44% in cranberry, 52 and 39% in black, 53 and 19% in kidney, and 42 and 19% in white bean, respectively. Isoxaflutole plus atrazine residues reduced shoot dry weight and yield as much as 87 and 64% in cranberry, 75 and 61% in black, 71 and 46% in kidney, and 65 and 33% in white navy bean, respectively. Injury was not detected regardless of market classes 2 yr after application of isoxaflutole alone or in tank mix with atrazine. Based on these results, it is recommended that none of the market classes of dry bean tested in this study should be grown 1 year after an application of isoxaflutole or isoxaflutole plus atrazine. A recropping interval of 2 years is currently recommended following applications of isoxaflutole or isoxaflutole plus atrazine for these market classes of dry bean.

Nomenclature: Atrazine; foramsulfuron; isoxaflutole; corn, Zea mays L.; dry bean, Phaseolus vulgaris L.

Additional index words: Black bean, carryover, cranberry bean, foramsulfuron, isoxaflutole, kidney bean, white navy bean.

Abbreviations: DAE, days after emergence; OM, organic matter; PRE, preemergence; POST, postemergence.

Field studies were conducted at three locations during both 2002 and 2003 to evaluate weed control and response of glyphosate-resistant (GR) corn to glyphosate or nicosulfuron plus atrazine applied POST at three application timings with and without alachlor plus atrazine applied PRE. The POST herbicides were applied timely (5- to 9-cm weeds) or applications were delayed 1 or 2 wk. All treatments, except the weedy check, were followed by glyphosate postemergence-directed (PDIR) 4 wk after the timely POST application. Common lambsquarters, common ragweed, Palmer amaranth, prickly sida, and smooth pigweed were controlled at least 94% regardless of PRE or POST treatments. Large crabgrass and fall panicum were controlled at least 96% by glyphosate regardless of PRE herbicide or POST application timing. In contrast, control by nicosulfuron plus atrazine POST in the absence of PRE herbicide decreased as application was delayed. Sicklepod was controlled at least 94% when POST herbicides were applied timely, but control by both POST herbicide treatments decreased with delayed application regardless of PRE herbicide. Tall morningglory was controlled 93% or greater by POST herbicides applied timely. Control by both POST herbicide treatments decreased as application was delayed, with glyphosate being affected more by timing than nicosulfuron plus atrazine. Corn grain yield was similar with glyphosate and nicosulfuron plus atrazine. Yield was unaffected by POST application timing when PRE herbicides were included. Without PRE herbicide, grain yield decreased as POST herbicide application was delayed.

Nomenclature: Alachlor; atrazine; glyphosate; nicosulfuron; common lambsquarters, Chenopodium album L. #³ CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; fall panicum, Panicum dichotomiflorum Michx. # PANDI; large crabgrass, Digitaria sanguinalis (L) Scop. # DIGSA; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; prickly sida, Sida spinosa L. # SIDSP; sicklepod, Senna obtusifolia (L.) Irwin & Barneby # CASOB; smooth pigweed, Amaranthus hybridus L. # AMACH; tall morningglory, Ipomoea purpurea (L.) Roth # PHBPU; corn, Zea mays L. ‘Dekalb (DKC) 687 RR’, ‘Dekalb (DKC) 69-71 RR’.

Additional index words: Crop vigor, herbicide-resistant crops, alachlor, atrazine, nicosulfuron.

Abbreviations: GR, glyphosate-resistant; PDIR, postemergence-directed; WAP, weeks after postemergence herbicide application; WAPD, weeks after postemergence-directed herbicide application.

Dose-response experiments were conducted in a greenhouse on a biotype of johnsongrass from Washington County, Mississippi, to determine the level of resistance to the aryloxyphenoxypropionate (AOPP) herbicide fluazifop-P-butyl and the cyclohexanedione (CHD) herbicides clethodim and sethoxydim. Both seedling and rhizomatous plants were evaluated. Resistant/susceptible (R/S) ratios were calculated based on GR₅₀ values (the rate required to reduce shoot dry biomass, expressed as a percent of the control, 50%). The GR₅₀ values for the resistant and susceptible seedling plants were 110 and 10 g ai/ha for clethodim, 193 and 34 g ai/ha for fluazifop-P-butyl, and 265 and 48 g ai/ha for sethoxydim, resulting in R/S ratios of 11.0, 5.7, and 5.5, respectively. The GR₅₀ values for the resistant and susceptible rhizomatous plants were 609 and 39 g/ha for clethodim, 657 and 29 g/ha for fluazifop-P-butyl, and 668 and 30 g/ha for sethoxydim, resulting in R/S ratios of 15.6, 22.7, and 22.3, respectively.

Nomenclature: Clethodim; fluazifop-P-butyl; sethoxydim; johnsongrass, Sorghum halepense (L.) Pers. #³ SORHA.

Additional index words: ACCase inhibitors, herbicide resistance, graminicides.

Abbreviations: ACCase, acetyl coenzyme-A carboxylase; WAT, weeks after treatment.

Experiments were conducted to determine the inheritance of resistance in crosses between imazethapyr-resistant rice and red rice. Past experiments on red rice control, using the Clearfield rice technology, resulted in outcrossing between Clearfield rice and Stuttgart strawhull red rice. The F₂ generation of these spontaneous crosses were characterized with respect to inheritance of imazethapyr resistance, leaf color and leaf pubescence, and seed shattering, pubescence, color, and size. Agronomic traits of hybrids were also observed in relation to their parents. To determine the segregation of resistance among F₂ phenotypes, the response of three- to four-leaf plants to imazethapyr was scored 3 wk after application as resistant (R, no imazethapyr symptoms), susceptible (S, death of plants), or intermediate (I, stunted plants). R, I, and S phenotypes segregated in a 1:2:1 ratio in the F₂ generation. Two- or three-gene inheritance was documented for leaf and seed characteristics. A wide range in onset of flowering (70 to 130 d after planting) was observed in F₂ families, although 6% of the plants did not flower during the growing season. F₂ plants were taller and had more tillers than any of their parents. Resistance to imazethapyr is associated with a single, incompletely dominant allele.

Nomenclature: Imazethapyr; red rice, Oryza sativa L. #³ ORYSA; rice, Oryza sativa L.; ‘CL121’, ‘CL161’.

Additional index words: Imazethapyr-tolerant rice, outcrossing.

Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); CL, ‘Clearfield’ rice; DAP, days after planting; RR, red rice; RREC, Rice Research and Extension Center; WAP, weeks after planting; WAT, weeks after treatment.

Field experiments were conducted during 3 yr in Thessaloniki, northern Greece, to determine the efficacy of various herbicides applied alone or in mixtures POST on hoary cress grown in winter wheat. Also, the efficacy of these herbicides on hoary cress generated from seed or root fragments was investigated in pot experiments. All herbicides except for ioxynil plus bromoxynil provided 90 to 100% control of hoary cress generated from seed and root fragments grown in pots. Ioxynil plus bromoxynil gave 84% control of hoary cress generated from seed, but only 66% control of plants generated from root fragments. In the field, mecoprop plus dicamba, imazamethabenz plus mecoprop plus dicamba, and triclopyr applied at the four- to eight-leaf stage provided, respectively, 87, 76, and 83% control of hoary cress (averaged over year and assessment time). Thifensulfuron plus tribenuron provided only 29% control. Chlorsulfuron plus dicamba, clopyralid plus MCPA, 2,4-D plus metosulam, and fluroxypyr provided intermediate hoary cress control. Furthermore, the least hoary cress emergence 52 wk after treatment appeared in plots treated with triclopyr. In addition, wheat grown in plots treated with mecoprop plus dicamba yielded more than wheat treated with the other herbicide treatments, and 55% more than wheat grown in nontreated plots. The results of this study indicate that very good control of hoary cress and high wheat yield can be obtained by the application of mecoprop plus dicamba at the four- to eight-leaf weed growth stage.

Nomenclature: Bromoxynil; chlorsulfuron; clopyralid; dicamba; fluroxypyr; imazamethabenz; ioxynil; MCPA; mecoprop; metosulam; thifensulfuron; tribenuron; triclopyr; 2,4-D; hoary cress, Cardaria draba (L.) Desv.#³ DADDR; winter wheat, Triticum durum L. ‘Mexa’.

Additional index words: Herbicide injury, wheat grain yield, yield components.

Abbreviations: FGS, Feekes growth stage; WAT, weeks after treatment.

The effects of microtopographic position on soil microenvironment and weed populations in ridge-tilled soybean were evaluated on three farms in Iowa in 1989 and 1990. In both years, over all weed species (primarily giant foxtail, green foxtail, yellow foxtail, redroot pigweed, and Pennsylvania smartweed), seedling emergence was highest in late May and early June, with few seedlings emerging after mid-June. Weed populations were highest in May and early June, after which rotary hoeing and cultivation reduced weed numbers in all plots. Microtopographic position (row, shoulder, and furrow) had a large effect on soil microenvironment and weed populations. Furrows were the wettest position through most of the growing season. Rows were the warmest position early in the season and the coolest position late in the season. Cumulative weed emergence early in the season was closely related to growing degree days, which accumulated faster in the row position than the furrow position. Following rotary hoeing and cultivation, the row position had significantly more total weeds than the shoulder and furrow positions on all farms in August of both years.

Nomenclature: Giant foxtail, Setaria faberi Herrm. #³ SETFA; green foxtail, Setaria viridis (L.) Beauv. # SETVI; Pennsylvania smartweed, Polygonum pensylvanicum # POLPY; redroot pigweed, Amaranthus retroflexus L. # AMARE; yellow foxtail, Setaria glauca (L.) Beauv # SETLU; soybean, Glycine max (L.) Merr.

Additional index words: Conservation tillage, mechanical weed control, seedling emergence, weed density, weed population dynamics.

Abbreviations: GDD, growing degree days.

Field experiments were conducted in 2002 and 2003 to evaluate total POST weed control in corn with mixtures of mesotrione, atrazine, and the commercial mixture of nicosulfuron plus rimsulfuron plus atrazine at registered and reduced rates. Treatments were compared with nicosulfuron plus rimsulfuron plus atrazine POST, and S-metolachlor plus atrazine PRE alone and followed by (fb) nicosulfuron plus rimsulfuron plus atrazine POST. All treatments controlled common lambsquarters 8 wk after the postemergence treatments (WAPT). Common ragweed control with POST mesotrione plus nicosulfuron plus rimsulfuron plus atrazine combinations was greater than 89%. Mesotrione plus the registered rate of nicosulfuron plus rimsulfuron plus atrazine POST controlled common ragweed more effectively than the PRE treatment alone. Addition of atrazine to mesotrione improved common ragweed control by at least 38 percentage points over mesotrione alone. Nicosulfuron plus rimsulfuron plus atrazine at the registered rate and in mixtures with mesotrione controlled morningglory species (pitted and ivyleaf morningglory) 89 to 91%. Large crabgrass control varied between 2002 and 2003. In 2002, large crabgrass control was 58 to 76% with all POST treatments, but in 2003, nicosulfuron plus rimsulfuron plus atrazine POST alone controlled large crabgrass greater than 86%. Large crabgrass was more effectively controlled by treatments with S-metolachlor plus atrazine PRE than by the total POST treatments in 2002. Giant foxtail was controlled at least 97% with nicosulfuron plus rimsulfuron plus atrazine treatments. S-metolachlor plus atrazine PRE fb nicosulfuron plus rimsulfuron plus atrazine POST controlled all weed species greater than 85%. Corn yields by total POST treatment combinations of mesotrione plus either rate of nicosulfuron plus rimsulfuron plus atrazine were comparable to S-metolachlor plus atrazine PRE alone or fb nicosulfuron plus rimsulfuron plus atrazine POST.

Nomenclature: Atrazine; mesotrione; nicosulfuron; rimsulfuron; S-metolachlor; common lambsquarters, Chenopodium album L. #³ CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; giant foxtail, Setaria faberi Herrm. # SETFA; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; morningglory species, Ipomoea spp. # IPOSS; pitted morningglory, Ipomoea lacunosa (L.) Roth # IPOLA; corn, Zea mays L. ‘Dekalb DKC60-09 (RR2)’, ‘Pioneer 33B51’, ‘Pioneer 33G56’.

Additional index words: Reduced herbicide rates, total postemergence, sulfonylurea herbicides, triketone herbicides.

Abbreviations: DAP, days after planting; fb, followed by; WATP, weeks after treatment with POST herbicides.

Field studies were conducted to assess the tolerance of seashore paspalum (‘Salam’) to postemergence (POST) herbicides in Florida in 2000 and 2001. POST applications of bentazon (2,200 g/ha), clopyralid (420 g/ha), dicamba (280 g/ha), halosulfuron (70 g/ha), imazaquin (420 g/ha), mecoprop 2,4-D dicamba (160 180 40 g/ha), metsulfuron (30 g/ha), and quinclorac (1,700 g/ha) resulted in ≤10% injury 7 and 15 d after treatment (DAT), indicating their safety for POST application. Clethodim (280 g/ha) and sethoxydim (310 g/ha) caused 67 and 46% injury, respectively, 15 DAT averaged across 2000 and 2001. Ethofumesate was inconsistent between years, causing 30 and 60% injury 7 and 15 DAT, respectively, in 2000, but only 5 and 13% 7 and 15 DAT, respectively, in 2001. Imazapic and trifloxysulfuron-sodium caused an average of 47% injury 7 DAT in 2000 and 45% injury 15 DAT in 2001. Clethodim, ethofumesate, imazapic, sethoxydim, and trifloxysulfuron-sodium can not be safely applied POST to Salam seashore paspalum; however, bentazon, clopyralid, dicamba, halosulfuron, imazaquin, mecoprop 2,4-D dicamba, metsulfuron, and quinclorac are safe.

Nomenclature: Bentazon, clethodim, clopyralid, dicamba, ethofumesate, halosulfuron, imazapic, imazaquin, mecoprop 2,4-D dicamba, metsulfuron, quinclorac, sethoxydim, trifloxysulfuron-sodium; seashore paspalum, Paspalum vaginatum Swartz ‘Salam’ #³ PASVA.

Additional index words: Turfgrass tolerance, turfgrass injury.

Abbreviations: DAT, days after treatment; OCGC, Old Collier Golf Club; WFREC, West Florida Research and Education Center.

Response of ‘Dixie’, ‘Lemondrop’, ‘Multipik’, ‘Superpik’, and ‘Seneca Prolific’ summer squash to halosulfuron PRE or POST at 0.036, 0.053, and 0.072 kg ai/ha, or halosulfuron PRE fb halosulfuron POST at 0.018 fb 0.018, 0.027 fb 0.027, and 0.036 fb 0.036 kg/ha was field evaluated in 1997 and 1998. All halosulfuron treatments and rates reduced the height of cultivars 17–19% at 6 WAP (weeks after planting) and summer-squash injury (chlorosis and necrosis of crop foliage) was 6, 14, and 11% from halosulfuron PRE, POST, and PRE fb POST, respectively. Early summer-squash flowering was reduced 32–82% by halosulfuron, resulting in reduced early yields. Dixie was the cultivar most tolerant to halosulfuron. Early flowering of Dixie was reduced 32–36% compared to 32–82% for the other cultivars. Marketable yield of summer squash was reduced 20–30% by all rates of halosulfuron when averaged over all application timings. Marketable yield of Seneca Prolific, Superpik, Dixie, Multipik, and Lemondrop was reduced 0–17% by halosulfuron PRE. Halosulfuron POST or PRE fb POST reduced marketable yield of all summer-squash cultivars by 25–46%. Thus, summer squash was not tolerant of POST halosulfuron; however, Dixie, Multipik, Seneca Prolific, and Superpik exhibited tolerance to halosulfuron PRE.

Nomenclature: Halosulfuron; summer squash, Cucurbita pepo L. ‘Dixie’, ‘Multipik’, ‘Superpik’, ‘Seneca Prolific’ and ‘Lemondrop’.

Additional index words: Sulfonylurea, vegetable tolerance to herbicides.

Abbreviations: WAP, weeks after planting.

Field experiments were conducted during 2003 and 2004 to compare the effectiveness of KIH-485 and S-metolachlor for PRE weed control in no-tillage and conventional-tillage corn. Longspine sandbur control increased as KIH-485 or S-metolachlor rates increased in conventional-tillage corn, but control did not exceed 75% when averaged over experiments. Both herbicides controlled at least 87% of green foxtail with the exception of no-tillage corn in 2004, when KIH-485 was more effective than S-metolachlor at lower rates. Palmer amaranth control ranged from 85 to 100% in 2003 and 80 to 100% in 2004, with the exception of only 57 to 76% control at the lowest two S-metolachlor rates in 2004. Puncturevine control exceeded 94% with all treatments in 2003. In 2004, KIH-485 controlled 86 to 96% of the puncturevine, whereas S-metolachlor controlled only 70 to 81%. Mixtures of atrazine with KIH-485 or S-metolachlor generally provided the most effective control of broadleaf weeds studied.

Nomenclature: Atrazine; KIH-485; S-metolachlor; Palmer amaranth, Amaranthus palmeri S. Wats. #³ AMAPA; green foxtail, Setaria viridis (L.) Beauv. # SETVI; puncturevine, Tribulus terrestris L. # TRBTE; longspine sandbur, Cenchrus longispinus (Hack.) Fern. # CCHPA; corn, Zea mays L.

Additional index words: Tillage systems, best management practices.

Abbreviations: BMP, best management practices; DAT, days after herbicide treatment; K_ow, herbicide adsorption coefficient.

Field experiments were conducted at the Caddo Research Station near Ft. Cobb, OK and at the Agronomy Research Station near Perkins, OK to measure the effects of seven crownbeard (Verbesina encelioides) densities on peanut (Arachis hypogaea) yield. The seven densities evaluated were 0 (the weed-free check), 0.2, 0.4, 0.8, 1.6, 2.4, and 3.2 weeds/m of row. Data collected consisted of dry weed biomass and peanut yields. Correlation between weed density and dry weed biomass, dry weed biomass and peanut yield (kg/ha), dry weed biomass and peanut yield loss (percentage of check), weed density and peanut yield (kg/ha), and weed density and peanut yield loss (percentage of check) were evaluated. For each weed/m of row, dry weed biomass increased by 0.34 kg/m row. Dry weed biomass was a good predictor of peanut yield. For each kilogram of dry weed biomass/ m row, a 1900-kg/ha or 46.3% reduction in peanut yield occurred. Weed density was also a good predictor of peanut yield. A 559-kg/ha reduction or 16% increase in peanut yield loss occurred for each weed/m row. Peanut yield was reduced approximately 50% when crownbeard density increased to 3.2 weeds/m row.

Nomenclature: Crownbeard, Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray #³ VEEEN; peanut, Arachis hypogaea L.

Additional index words: Competition, dry weed biomass.

Field studies were conducted at four locations over a 2-year period to evaluate the utility of soil-applied herbicides and glyphosate timing for weed control and soybean yield. Pendimethalin, S-metolachlor plus metribuzin, and flufenacet plus metribuzin were applied pre-emergence (PRE) alone or followed by glyphosate applied early postemergence (EPOST), late postemergence (LPOST), or EPOST plus LPOST. Soil-applied herbicides or glyphosate alone failed to control (<45%) broadleaf signalgrass in 2003 due to late-season rainfall, which accounted for a late flush of growth. In 2004, soil-applied herbicides alone controlled 79–100% broadleaf signalgrass, whereas glyphosate alone or in combination with soil-applied herbicides controlled at least 99%. Barnyardgrass and tall waterhemp were controlled at least 87% with soil-applied herbicides alone and at least 95% when glyphosate was used alone or in combination with a soil-applied herbicide. Soybean yield varied, but at only one location did herbicide treatments produce higher yields than the untreated check. Under low to moderate weed pressure, the use of a soil-applied herbicide followed by glyphosate failed to increase net returns over soil-applied herbicides alone.

Nomenclature: Flufenacet metribuzin; glyphosate; S-metolachlor metribuzin; pendimethalin; broadleaf signalgrass; Brachiaria platyphylla (Griseb.) Nash #³ BRAPP; barnyardgrass; Echinochloa crus-galli (L.) Beauv. # ECHCG; tall waterhemp, Amaranthus tuberculatus (Moq.) J. D. Sauer # AMATU; soybean, Glycine max (L.) Merr. ‘HBK 5123RR, DP 5110RR’.

Additional index words: Application window, sequential.

Abbreviations: EPOST, early postemergence; fb, followed by; LPOST, late postemergence; POST, postemergence; PRE, preemergence.

Field studies were conducted at Shiraz, Iran, during 2000 and 2001 to investigate the effect of separate and combined herbicide treatments on weed control and corn yield. Separate and combined herbicide treatments included 14 combinations applied at two rates. Herbicides reduced weed biomass compared with the weedy check. In both years, maximum reduction in weed biomass was observed with atrazine plus alachlor at 1 2.44 and 1.5 1.92 kg ai/ha and minimum reduction in weed biomass was observed with rimsulfuron at 0.02 and 0.04 kg/ha. In 2000 and 2001, 2,4-D plus MCPA at 0.36 0.31 and 0.54 0.46 kg/ha, and alachlor plus 2,4-D plus MCPA at 1.92 0.54 0.46 kg/ha, and 2.44 0.36 0.31 kg/ha, controlled 80 to 100% of field bindweed and rimsulfuron at 0.02 and 0.04 kg/ha controlled 17 to 70% of field bindweed. All herbicide treatments controlled redroot pigweed 60 to 100%. In 2000, at 6 and 17 WAP, minimum biomass reduction of Chinese-lantern-plant was observed with 2,4-D plus MCPA at 0.36 0.31 and 0.54 0.46 kg/ha, and primisulfuron plus prosulfuron at 0.02 0.02 and 0.03 0.03 kg/ha. Rimsulfuron plus primisulfuron plus prosulfuron at 0.02 0.03 0.03 and 0.04 0.02 0.02 kg/ha reduced johnsongrass biomass 96 to 100% and the efficacy of rimsulfuron increased when tank mixed with primisulfuron plus prosulfuron. Results of both years showed that all herbicide treatments increased corn grain yield as compared with the weedy check. Maximum corn grain yield was obtained with combinations of atrazine plus alachlor at 1 2.44 and 1.5 1.92 kg/ha.

Nomenclature: Atrazine; alachlor; bentazon; bromoxynil; 2,4-D; MCPA; primisulfuron; prosulfuron; rimsulfuron; chinese-lantern-plant, Physalis alkekengii L. #³ PHYAL; field bindweed, Convolvulus arvensis L. # CONAR; johnsongrass, Sorghum halepense L. # SORHA; redroot pigweed, Amaranthus retroflexus L. # AMARE; corn, Zea mays L.

Additional index words: Corn grain yield, weed biomass, herbicides.

Abbreviation: WAP, weeks after planting.

Weed management is often difficult and expensive in organic production systems. Clove oil is an essential oil that functions as a contact herbicide and may provide an additional weed management tool for use on organic farms. Burning nettle, purslane, and rye responses to 5, 10, 20, 40, and 80% v/v clove oil mixture applied in spray volumes of 281 and 468 L/ha were examined. Log-logistic curves were fitted to the nettle and purslane data to determine the herbicide dose required to reduce plant dry weight 50% (GR₅₀) and 90% (GR₉₀). A three-parameter Gaussian curve was fitted to the rye data. The GR₅₀ and GR₉₀ were largely unaffected by spray volume. Nettle dry weight was reduced by 90% with 12 to 61 L clove oil/ha, whereas 21 to 38 L clove oil/ha were required to reduce purslane biomass to the same level. Rye was not effectively controlled by clove oil. Clove oil controls broadleaf weeds at high concentrations, but its cost makes broadcast applications prohibitive, even in high-value vegetable production systems.

Nomenclature: Burning nettle, Urtica urens L. URTUR; purslane, Portulaca oleracea L. POROL; rye, Secale cereale L. ‘Merced’.

Additional index words: Log-logistic, spray volume, contact herbicide, organic.

Abbreviations: GDD, growing degree days; OMRI, organic materials review institute.

Field studies were conducted at Lewiston–Woodville and Rocky Mount, NC in 2001 and 2002 to evaluate weed control and peanut response to POST treatments of diclosulam at various rates and application timings. Diclosulam controlled common ragweed and entireleaf morningglory when applied within 35 d after planting (DAP). Common ragweed 61 cm tall was controlled ≥92% with 4 to 13 g ai/ha diclosulam and larger common ragweed (107 to 137 cm tall) were controlled ≥97% with 27 g/ha diclosulam. Common lambsquarters was controlled 62% or less with all diclosulam POST treatments following metolachlor applied PRE, which provided 48% control. Peanut injury was less than 15% with all diclosulam POST treatments and was transitory. In separate studies, POST diclosulam treatments did not affect peanut yield in a weed-free environment. Peanut yield in weedy environments was reduced as the diclosulam application timing was delayed because of early season weed interference. A linear relationship was observed between yield and application timing with yield decreasing as application timing was delayed. This yield response documents the importance of early season weed management for maximizing peanut yield potential. Virginia peanut varieties were not affected by different POST rates of diclosulam; however, early season peanut injury showed a linear and quadratic relationship with diclosulam rate and was less than 14% at rates as high as 71 g/ha, and was not apparent by late season.

Nomenclature: Diclosulam; common lambsquarters, Chenopodium album L. #³ CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray # IPOHG; peanut, Arachis hypogaea L., NCV-11, Gregory, Perry, and VA-98 R.

Additional index words: Herbicide injury, weed control, yield, diclosulam.

Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); COC, crop oil concentrate; DAT, days after treatment; EPOST, early POST; NIS, nonionic surfactant; RCBD, randomized complete block design; WAP, weeks after planting; WAT, weeks after treatment.

No-till cropping is an option for growers needing to reduce soil erosion in the Palouse annual-cropped region of the Pacific Northwest, which is well suited for wheat production. A 6-yr field study was conducted to determine optimum levels of fertilizer and herbicide inputs in a no-till continuous wheat crop production system. Three levels of nitrogen (N) and two weed management levels (WML) were compared in a spring wheat (SW)–winter wheat (WW)–WW rotation through two rotation cycles. The high WML reduced weed densities about 50% compared with the low WML. In general, herbicide treatments were more effective on broadleaf weeds and may have facilitated a shift toward grass weeds. The high WML reduced grass weed biomass only at the reduced N levels, whereas the high WML reduced broadleaf weed density at all N levels. Variable environmental conditions affected wheat yield; however, yield tended to be highest where winter wheat immediately followed spring wheat. Nitrogen had little effect on weed density but increased crop yield about 13% with each increased N level. Crop yield was greater at the high versus low WML at each N level, even though weed density and biomass were reduced least between WMLs at the highest N level. The highest crop yield and net returns were obtained with the highest N and WML; however, none of the N and WML combinations were profitable.

Nomenclature: Winter wheat, Triticum aestivum L., ‘Waverly’, ‘Daws’, ‘Edwall’, ‘Hill 81’.

Additional index words: Crop rotation, nitrogen fertilizer, weed/crop interaction.

Field experiments were conducted to study the effects of oxadiazon and oxyfluorfen on weeds and Syrian marjoram (Origanum syriacum L.) in the central Jordan Valley during the period from 1998 to 2001. Results showed that weed competition with marjoram for the whole growing period resulted in almost complete crop failure. Oxyfluorfen and oxadiazon applied preplanting or postplanting to marjoram controlled weeds effectively, resulted in significant increase in marjoram shoot fresh and dry weight yields and in more branches per plant compared with the weed-infested control. High marjoram yield was obtained with oxyfluorfen applied at 0.72 kg ai/ha in preplanting treatment and with oxadiazon at 1.25 and 0.75 kg ai/ha in pre- and postplanting treatments, respectively. In preplanting treatment, 0.36 kg ai/ha of oxyfluorfen was highly selective, but 1.44 kg ai/ha reduced marjoram yield. Conflicting results were obtained with oxadiazon under the same treatments. In postplanting, oxyfluorfen at 0.24 and 0.96 kg ai/ha significantly increased marjoram yield over the weed-infested control. However, the highest shoot dry weight of marjoram was obtained at 0.96 kg ai/ha of this herbicide. In contrast, the low rate (0.38 kg ai/ha) of oxadiazon was highly selective and increased marjoram yield, but the herbicide failed to increase yield beyond the weed-infested control when the higher rate (1.5 kg ai/ha) was used. Results showed that both oxyfluorfen and oxadiazon herbicides were highly selective and effective for weed control in Syrian marjoram, providing normal rates of both are used, although high rates of the two herbicides were also selective and increased marjoram yield over the weed-infested control.

Nomenclature: Oxadiazon; oxyfluorfen; Syrian marjoram; Origanum syriacum L.; weeds.

Additional index words: Crop injury, medicinal crop, weed competition.

The objectives of this research were to determine if adjuvants with water-repellent properties could reduce herbicide retention on foliage, and thereby absorption, of the spray solution and to determine if herbicide activity was maintained with a reduction in herbicide retention. Water-repellent adjuvants, DC 2-1322, DC 1-6184, and DC 772, were evaluated with three herbicides, isoxaflutole, pendimethalin, and flumioxazin, and on three crop species, cabbage, tomato, and wheat. The water repellents DC 2-1322 and DC 772 were ineffective with these herbicides and these crop species. DC 1-6184 effectively reduced spray retention for all three herbicides evaluated, regardless of formulation, on all three species. The efficacy of DC 1-6184 was more evident if the spray application was restricted to the plant foliage. The water-repellent DC 1-6184 has potential to decrease injury while maintaining weed control with certain herbicides.

Nomenclature: Flumioxazin; isoxaflutole; pendimethalin; cabbage, Brassica oleracea L. ‘Megaton F1’; tomato, Lycopersicon esculentum Mill., ‘Sunny hybrid’; wheat, Triticum aestivum L. ‘Harus’.

Additional index words: Retention, surfactant.

Abbreviations: CS, capsule suspension; DAT, days after treatment; EC, emulsifiable concentrate; SC, soluble concentrate; WDG, water-dispersible granule.

Centipedegrass is a warm-season turf grass that has increased in popularity in recent years. However, more information is needed on the use of herbicides during centipedegrass establishment from seed, particularly in seed and sod production systems. The intent of this study was to evaluate turf-grass injury and weed control when atrazine, imazapic, imazethapyr, and simazine are applied immediately after seeding centipedegrass. Atrazine and simazine (applied at 1.1, 2.2, and 4.4 kg ai/ ha) injured centipedegrass less than 15% at 5 wk after treatment (WAT) in 2001. Imazethapyr and imazapic (applied at 0.04, 0.07, and 0.1 kg ai/ha) injured centipedegrass between 7 and 13%, 5 WAT, in 2001 and from 30 to 77% in 2002. Herbicide and application rate also affected centipedegrass cover. At 3 WAT, cover decreased with all herbicides as application rate increased. At 12 WAT in both years, centipedegrass cover increased as atrazine application rate increased and imazethapyr application rate decreased. Imazapic and simazine were less consistent, causing increases in cover one year and decreases, or no change, the next. Imazapic controlled Texas panicum 80 to 89% and was more effective than any other herbicide. Atrazine and simazine controlled crowfootgrass better than any other herbicide. Imazethapyr often injured centipedegrass and failed to control weeds. Atrazine effectively controlled grass and broadleaf weeds with minimal centipedegrass injury. Imazethapyr and imazapic were too injurious to permit usage during centipedegrass establishment from seed.

Nomenclature: Atrazine; imazapic; imazethapyr; simazine; centipedegrass, Eremochloa ophiuroides Munro., ‘Tifblair’ #³ ERLOP; crowfootgrass, Dactyloctenium aegyptium (L.) Willd., # DTTAE; Texas panicum, Panicum texanum Buckl., # PANTE.

Additional index words: Turf cover.

Abbreviation: DAT, days after treatment.

Weed interference experiments have not been extensively conducted in Oklahoma peanut. Research was conducted in three environments to evaluate usefulness of single-weed density experiments with the use of several weeds to measure their relative competitive abilities with a crop. These data can be used to validate current competitive indices (CIs) used by a model to predict peanut yield loss due to weeds. This model is used by the Herbicide Application Decision Support System (HADSS) and Pesticide Economic and Environmental Tradeoffs (PEET), two decision-support systems (DSSs) available for Oklahoma peanut. Six weeds common in Oklahoma peanut were used: crownbeard, eclipta, ivyleaf morningglory, johnsongrass, Palmer amaranth, and prickly sida plus two others, barnyardgrass and common cocklebur, as benchmark species. Each weed was planted into peanut uniformly at eight weeds/10 m of row. Dry weed biomass accounted for 77 to 90% of variation in in-shell peanut yield loss; however, model parameters only allow for weed number. Yield losses from these experiments were compared to those predicted by the model to test original CI accuracy. Treatment means were compared to the prediction model with the use of protected LSD. Several significant differences were noted, and the CIs for those weed species were adjusted accordingly. Adjusting CIs improved actual yield data goodness of fit to model predictions specific to environment in question, but not necessarily in different environments. The CI changed at Ft. Cobb were eclipta from 1.8 to 4.5 and ivyleaf morningglory from 3.4 to 5.0. CI adjustments at Perkins were common cocklebur from 10.0 to 5.8 and johnsongrass from 3.0 to 4.6. Collecting data for several weed species at uniform density in a crop provides a more time-efficient method for obtaining accurate relative weed interference data; this method is useful in validating or establishing CI lists in areas and/or crops with limited data.

Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv. #³ ECHCG; common cocklebur, Xanthium strumarium L. # XANST; crownbeard, Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray # VEEEN; eclipta, Eclipta prostrata L. # ECLAL; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; prickly sida, Sida spinosa L. # SIDSP; peanut, Arachis hypogaea L. ‘Tamspan 90’.

Additional index words: Competition, decision-support system, interference, yield-loss prediction model.

Abbreviations: TCL, total competitive load.

The response of the sugarcane cultivars HoCP 91-555, HoCP 85-845, and LCP 85-384 to flumioxazin during the first (plant cane) and second (first ratoon) production years was evaluated within two identical experiments, the first starting in 2000 and the second in 2001. In the plant-cane crop, flumioxazin application timings were PRE immediately following planting, fall postemergence (FPOST) 6 wk after planting, early spring postemergence (ESPOST), postemergence-directed spray (PDS) following layby cultivation, and sequential applications of FPOST followed by ESPOST. During the first-ratoon crop, flumioxazin was applied ESPOST, late-spring (LSPOST), PDS following layby cultivation, and sequentially LSPOST followed by PDS. Flumioxazin injury to sugarcane consisted mainly of stunted growth and reddening and necrosis of treated leaves. In plant cane, injury was 28% 2 wk after treatment (WAT) when applied ESPOST in one experiment but less than 10% in the other, and was no more than 13% in either experiment at 6 WAT. In the first-ratoon crop, injury was around 15% when applied ESPOST in the first experiment, but no injury was observed 6 WAT. However, in the first ratoon, injury to all cultivars was 25 to 30% when following a LSPOST application. When applied as a PDS, injury was no more than 15% 4 WAT in either plant-cane or first-ratoon sugarcane. Stalk height was reduced 15 cm compared to the nontreated control when flumioxazin was applied as a sequential application (FPOST followed by ESPOST) in plant cane and by 23 cm (LSPOST followed by PDS) in first-ratoon sugarcane. In plant cane ESPOST applications of flumioxazin reduced sugar yield (9 to 28%) within all three cultivars used in this study in both experiments with only one exception. Sequential (FPOST followed by ESPOST) applications reduced sugar yield within all cultivars (6 to 37%). PDS applications at layby reduced yields (7 to 12%) in the first experiment, but not in the second experiment. In the first-ratoon crop, LSPOST applications of flumioxazin reduced sugar yield (7 to 11%), sequential flumioxazin applications (LSPOST followed by PDS) reduced sugar yields (8 to 19%), and PDS applications at layby did not reduce yield. It appears that there is little if any difference in tolerance to flumioxazin for the cultivars used in this experiment. To avoid risk of yield loss, flumioxazin should not be applied as an over-top POST treatment to weeds in actively growing sugarcane, and care should be taken to minimize spray contact with sugarcane leaves when applying flumioxazin as a PDS at layby.

Nomenclature: Flumioxazin; sugarcane, Saccharum interspecific hybrids, ‘LCP 85-384’, ‘HoCP 85-845’, and ‘HoCP 91-555’.

Additional index words: Crop injury, application timing.

Abbreviations: EXP1, experiment one; EXP2, experiment two; TRS, theoretically recoverable sugar; USDA-ARS, U.S. Department of Agriculture, Agricultural Research Service.

Studies were conducted for 12 wk from June 16 to September 8, 2003 and July 10 to October 4, 2004 with the objective of evaluating growth regulation, lateral regrowth, and injury of Tifway bermudagrass [Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy Tifway] in response to two GA-inhibiting plant growth regulators, trinexapac-ethyl and flurprimidol. Trinexapac-ethyl was applied alone at 0, 0.052, and 0.104 kg ai/ha and flurprimidol alone at 0, 0.14, and 0.28 kg ai/ ha, plus all combinations. Applications were made every 3 wk for the duration of the study. Tifway bermudagrass clipping yield was reduced 33% and 54% by trinexapac-ethyl at 0.104 kg/ha at 4 and 8 wk after initial treatment (WAIT), respectively. Flurprimidol at 0.28 kg/ha reduced clipping yield 49% 8 WAIT. Lateral regrowth was reduced 20% 2 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 26% 2 WAIT by flurprimidol at 0.28 kg/ha. Lateral regrowth was reduced 13% 4 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 15% 4 WAIT by flurprimidol at 0.28 kg/ha. Overall, acceptable injury (<30%) was observed with a trinexapac-ethyl and flurprimidol tank mixture; however, this evaluation did not indicate an advantage in growth regulation when using a tank mixture of these products, compared to using them alone.

Nomenclature: Flurprimidol; trinexapac-ethyl; Tifway bermudagrass, Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy Tifway.

Additional index words: Plant growth regulator, fairways, injury, clipping reduction, percent lateral regrowth, turfgrass.

Abbreviations: GA, gibberellic acid; PGRs, plant growth regulators.

The potential for future commercialization of glyphosate-resistant wheat necessitates evaluation of agronomic merits of this technology. Experiments were established to evaluate glyphosate-resistant wheat and weed responses to glyphosate rate, application timing, and tank mixtures. Glyphosate at 1,680 g/ha did not injure wheat. Wheat response to glyphosate applied to one- to three- or three- to five-leaf wheat was not different from that of untreated wheat. Wheat was injured more from glyphosate plus thifensulfuron or glyphosate plus dicamba than from individual herbicides at one of six locations, but grain yield was not affected by glyphosate tank mixtures. Glyphosate application timing did not affect control of wild oat or common lambsquarters 56 d after treatment. Glyphosate when applied to one- to three-leaf wheat provided better control of wild buckwheat than later glyphosate application, whereas glyphosate applied to three- to five-leaf wheat provided the best control of green and yellow foxtail, redroot pigweed, and Canada thistle. Weed control with glyphosate tended to be better than with conventional herbicides, and wheat treated with glyphosate produced approximately 10% more grain than wheat treated with conventional herbicide tank mixes.

Nomenclature: Dicamba; glyphosate; thifensulfuron; Canada thistle, Cirsium arvense (L.) Scop. #³ CIRAR; green foxtail, Setaria viridis (L.) Beauv. # SETVI; redroot pigweed, Amaranthus retroflexus L. # AMARE; wild buckwheat, Polygonum convolvulus L. # POLCO; yellow foxtail, S. glauca (L.) Beauv. # SETLU; spring wheat, Triticum aestivum L.

Additional index words: Genetically modified organism, GMO, herbicide injury, herbicide-resistant crops, transgenic wheat, wheat yield.

Abbreviations: DAT, days after treatment; GMO, genetically modified organism.

During routine use of fluazifop-P-butyl for grass control, county extension agents in Georgia observed control of bristly starbur in grower fields. Experiments to characterize the activity of fluazifop-P-butyl on bristly starbur were conducted under greenhouse conditions in Gainesville, FL, during 2001 and 2002. Fluazifop-P-butyl activity was characterized as a function of herbicide rate and time after application. Commercially available fluazifop-P-butyl was compared to technical fluazifop-P-butyl as a function of herbicide rate and bristly starbur height. Finally, injury to bristly starbur was evaluated when clethodim, diclofop, fluazifop-P-butyl, haloxyfop, quizalofop-p, and sethoxydim were applied at two growth stages. Fluazifop-P-butyl caused >90% injury to bristly starbur with all other post graminicides displaying <8% injury. Nonlinear regression revealed a sigmoidal response of bristly starbur injury to fluazifop-P-butyl. Estimates for 50 and 90% bristly starbur injury (I₅₀ and I₉₀) were 0.07 and 0.14 kg ai/ha, respectively. There was no difference in activity of technical and commercial fluazifop-P-butyl formulations. There was a differential response of bristly starbur to fluazifop-P-butyl over time as a function of plant height at the time of treatment. However, 14 days after treatment (DAT) all treatments displayed >89% injury. Bristly starbur response to fluazifop-P-butyl was similar to injury associated with contact-type herbicides.

Nomenclature: Clethodim; diclofop; fluazifop-P-butyl, Fusilade DX; haloxyfop; quizalofop-p; sethoxydim; bristly starbur, Acanthospermum hispidum DC #³ ACNHI.

Additional index words: ACCase, aryloxyphenoxy, cyclohexanedione, protoporhyrinogen oxidase, PROTOX, Arachis hypogaea L., Gossypium hirsutum L.

Abbreviations: ACCase, acetyl-CoA carboxylase; POST, postemergence; WAE, weeks after emergence.

Studies were conducted in 2002 and 2003 on a golf course fairway in New Jersey to compare spring, summer, and fall treatments of bispyribac-sodium for annual bluegrass control and creeping bentgrass tolerance. Single applications at 74, 111, or 148 g ai/ha were applied in May, August, or October. Split applications of 37 followed by (fb) 37 or 74 fb 74 g/ha applied 3 wk apart were also evaluated. Summer-applied bispyribac-sodium did not reduce bentgrass quality, whereas spring and fall treatments reduced turf quality at 3 wk after treatment and fall treatments in 2002 substantially reduced bentgrass quality. Summer treatments were more effective than spring or fall treatments in reducing annual bluegrass cover. Final evaluations revealed 36, 31, 21, and 26% annual bluegrass cover averaged across nontreated, spring-treated, summer-treated, and fall-treated plots, respectively. This study demonstrates that two split applications of bispyribac-sodium at 74 g/ha in summer can effectively reduce annual bluegrass cover while minimizing creeping bentgrass injury.

Nomenclature: Bispyribac-sodium, 2,6 bis[(4,6-dimethoxy-2-pyrmidinyl)oxy] benzoic acid; annual bluegrass, Poa annua var. annua (L.) Timm, var. reptans (Hausskn.) Timm #³ POAAN; creeping bentgrass, Agrostis stolonifera L. ‘L-93’ and ‘Penncross’.

Additional index words: Turf-grass tolerance.

Abbreviations: ALS, acetolactate synthase (EC 2.2.1.6); fb, followed by; WAT, weeks after treatment.

Bispyribac-sodium is a POST herbicide that selectively controls annual bluegrass in creeping bentgrass, but inconsistent results with seasonal applications are believed to occur from temperature influences on bispyribac-sodium efficacy. Growth chamber experiments at the New Jersey Experimental Greenhouse Research Complex, New Brunswick, NJ, investigated three temperature regimes on ‘L-93’ creeping bentgrass and annual bluegrass responses to bispyribac-sodium. Annual bluegrass and creeping bentgrass exhibited contrasting responses to bispyribac-sodium as temperature increased from 10 to 30 C. Regressions of 4 week after treatment (WAT) data revealed as temperature increased from 10 to 30 C, required bispyribac-sodium rates for 50% clipping reduction (CR₅₀) of annual bluegrass decreased from 85 to 31 g ai/ha and required rates for 50% leaf chlorosis decreased from greater than 296 to 98, indicating increased herbicidal efficacy at higher temperatures. In contrast, required bispyribac-sodium rates for creeping bentgrass CR₅₀ increased from 200 to greater than 296 as temperature increased from 10 to 30 C. Bispyribac-sodium discolored creeping bentgrass 0 to 20% at 20 and 30 C and discoloration increased 10 to 50% at 10 C. Thus, warmer temperatures (20 and 30 C) increase bispyribac-sodium efficacy for annual bluegrass control with minimal bentgrass discoloration; however, cooler temperatures (10 C) have minimal efficacy on annual bluegrass and increase bentgrass chlorosis.

Nomenclature: Bispyribac-sodium; annual bluegrass Poa annua L. #³ POANN; creeping bentgrass, Agrostis stolonifera L. # AGSST, ‘L-93’.

Additional index words: Chlorosis, efficacy, turfgrass.

Substantial weed growth often occurs in legume-cereal cover-crop mixes commonly grown on organic vegetable farms. A 2-yr study at the USDA-ARS in Salinas, CA, was conducted to test the effect of zero, one, and two passes with a rotary hoe on weed control in a mixed cover crop of 10% rye, 15% common vetch, 15% purple vetch, 25% peas, and 35% bell bean. Rotary hoeing occurred 14–15 days after planting (DAP) in the one-pass treatment, and 14 and 28 DAP in the two-pass treatment. Rotary hoeing did not affect total cover-crop density or biomass in either year, but reduced rye density and biomass in year 2. One pass reduced total weed density by 69% in year 1 and 49% in year 2. A second pass did not affect weed density in year 1 but reduced weed density an additional 33% in year 2. One pass decreased weed biomass in year 1, whereas two passes were required to reduce weed biomass in year 2. Rotary hoeing reduced seed shed by chickweed and shepherd's-purse seeds, the two predominant weed species, by 80 to 95% in both years. Rotary hoe efficacy depended on weather conditions directly before and after cultivation. The decision to repeat rotary hoeing should be based upon field scouting and weather conditions following the initial pass with the rotary hoe.

Nomenclature: Chickweed, Stellaria media (L.) Vill. #³ STEME; shepherd's purse, Capsella bursa-pastoris (L.) Medic. # CAPBP; rye, ‘Merced’ Secale Cereale L.; common vetch, Vicia sativa L.; purple vetch, Vicia benghalensis L.; peas ‘magnus’, Pisum sativum L.; bell bean, Vicia faba L.

Additional index words: Weed seed, organic, Senecio vulgaris, Lamium amplexicaule, Solanum sarrachoides, Poa annua.

Abbreviations: GDD, growing degree days

Field studies were conducted to evaluate rice injury and control of propanil-resistant and -susceptible (natural infestation) barnyardgrass, broadleaf signalgrass, and Amazon sprangletop with BAS 625, cyhalofop, and fenoxaprop plus the safener isoxadifen in rice. BAS 625 at 100 g ai/ha applied to two- to three-leaf rice resulted in 19 to 72% injury in three of four experiments. Fenoxaprop plus isoxadifen at 90 98 g ai/ha injured rice 11 to 31%, and cyhalofop at 280 g ai/ha consistently resulted in minimal rice injury. The most effective control (84 to 99%) of propanil-resistant and propanil-susceptible barnyardgrass across all experiments was achieved with sequential applications of the BAS 625 at 75 and 100 g ai/ha, cyhalofop at 210 and 280 g ai/ha, and fenoxaprop plus isoxadifen at 68 74 and 90 98 g ai/ha. When the graminicides were applied to four- to six-leaf rice (one tiller), propanil-resistant and propanil-susceptible barnyardgrass control was generally very poor. Fenoxaprop plus isoxadifen controlled broadleaf signalgrass 91 to 100%, even when applied once to four- to six-leaf rice. BAS 625 at 75 and 100 g ai/ha and cyhalofop at 210 and 280 g ai/ha applied sequentially provided consistent broadleaf signalgrass control (≥98%). Amazon sprangletop control was good (85 to 99%) with fenoxaprop plus isoxadifen at 45 49, 68 74, and 90 98 g ai/ha (applied in a single application or sequentially), BAS 625 at 100 g ai/ha applied to two- to three-leaf and four- to six-leaf rice or 50, 75, and 100 g ai/ha applied sequentially, and cyhalofop at 140, 210, and 280 g ai/ha applied to two- to three-leaf rice or sequentially.

Nomenclature: BAS 625, 2-[1-[2-(4-chlorophenoxy)propoxyimino]-butyl]3-oxo-5-thian-3-ylcyclohex-1-enol; cyhalofop; fenoxaprop; isoxadifen (4,5-dihydro-5,5-diphenyl-3-isoxazolecarboxylic acid); Amazon sprangletop, Leptochloa panicoides (Presl.) Hitchc. # LEFPA; barnyardgrass Echinochloa crus-galli (L.) Beauv. #³ ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash. # BRAPP; rice, Oryza sativa L.

Additional index words: Application timing.

Abbreviations: ACCase, acetyl-CoA carboxylase; WAT, weeks after treatment.

Texas wheat producers have observed reduced efficacy and failure to control Italian ryegrass with registered rates of sulfonylurea herbicides that were previously effective. Growth chamber studies were conducted to quantify the sensitivity and distribution of Italian ryegrass ecotypes in Texas to triasulfuron and to determine alternative herbicide management options. Italian ryegrass seed samples were collected from over 40 wheat fields in 13 central and north Texas counties where declining Italian ryegrass control was reported by farmers following sulfonylurea herbicide application(s). Two-leaf Italian ryegrass was screened with an application of 150 g ai/ha triasulfuron, a rate five times the registered herbicide use rate. Sensitivity was determined by the response of an ecotype to that of a known susceptible population. Of the 48 Italian ryegrass ecotypes sampled, nine were comparable to susceptible standard, while the remaining 39 ecotypes were less sensitive to triasulfuron. Four of the least sensitive ecotypes to triasulfuron plus the susceptible standard were selected for a subsequent study. Diclofop, clodinafop, and metribuzin reduced fresh weights by at least 69, 71, and 62% across all ecotypes. No imazamox or triasulfuron treatment reduced fresh weights more than 60%.

Nomenclature: Clodinafop; diclofop; imazamox; metribuzin; triasulfuron; Italian ryegrass, Lolium multiflorum L. #³ LOLMU; wheat, Triticum aestivum L.

Additional index words: ALS inhibitor, cross-resistance, herbicide resistance, imidazolinone, resistance survey, sulfonylurea.

Abbreviations: ALS, acetolactate synthase; ACCase, acetyl-CoA carboxylase; DAT, days after treatment; LTSE, low triasulfuron-sensitivity ecotypes.

Corn and soybean growers across Indiana were surveyed in 2003 to determine their perceptions of the importance of weed problems in various crop rotations. Growers were asked to list the three most problematic weeds in the following rotation systems: soybean and corn planted in alternate years (SC) and corn (CC) or soybean (SS) planted to the same field for 2 or more years. Although some summer annuals and perennials (common lambsquarters, Canada thistle, and common cocklebur) and winter annuals (chickweed and henbit) were considered problematic by at least 10% of growers in all three systems, there were differences among systems in the relative importance of weed species. Giant ragweed was considered problematic by at least 30% of SC and CC growers but by less than 10% of SS growers. Horseweed was listed as a problematic summer annual by 13% of SS growers but by only 3% of CC growers. Purple deadnettle was listed by 15% of CC growers but by less than 6% of SC and SS growers. Perennial dicots were more problematic in SS than in CC. Annual and perennial grasses were more problematic in CC than in SC or SS. Despite these differences, the results of this survey suggest that the cumulative effect of weed management practices in corn and soybean rotation systems in Indiana has been the promotion of larger seeded, broadleaf, summer annual species.

Nomenclature: Canada thistle, Cirsium arvense (L.) Scop. #³ CIRAR; chickweed, Stellaria media (L.) Vill. # STEME; common cocklebur, Xanthium strumarium L. # XANTH; common lambsquarters, Chenopodium album L. # CHEAL; giant ragweed, Ambrosia trifidia L. # AMBTR; henbit, Lamium amplexicaule L. # LAMAM; horseweed, Conyza canadensis (L.) Cronq. # ERICA; purple deadnettle, Lamium purpureum L.; corn, Zea mays L.; soybean, Glycine max (L.) Merr.

Additional index words: pests, weed rankings, winter annual, summer annual, perennial.

Abbreviations: ALS, acetolactate synthase; CC, continuous corn rotation; CTIC, Conservation Technology Information Center; fb, followed by; GR, glyphosate-resistant; IASS, Indiana Agricultural Statistics Service; SC, soybean/corn rotation; SS, continuous soybean rotation.

Agronomic research and extension personnel generally recognize the benefits of integrated pest management (IPM) but IPM practices have not been rapidly adopted by farmers. In order for applied research and extension programs to be as influential as possible, strategies and tactics must be evaluated in the context of the real-world constraints experienced by farmers. We investigated the linkage between farmers' pest management behaviors, attitudes, and constraints by analyzing an extensive corn pest management survey distributed throughout Wisconsin in 2002. Our objectives were to (1) create a benchmark against which future changes in pest management practices could be detected and (2) explore potential associations between practices and farm characteristics, e.g., farm size or commodity produced. A total of 213 farmers responded with descriptions of their operations; weed, insect, and disease pest management practices; crop consultant usage; interactions with their local agrichemical dealer; and attitudes regarding pest management decision-making. We compared the relative responses of cash-grain and dairy farmers as well as managers of large and small farms. Larger farm size and percentage of operation in cash-grain production were associated with an increased frequency of rotating crops, rotating herbicide families, and use of a broadcast herbicide application. Managers of large farms and/or cash-grain crops also more frequently indicated considering the level of pest control, price, carryover potential, weed resistance management, environmental safety, and risk to the applicator than did dairy or small-sized operations. Cash-grain farmers had significantly higher scores on a calculated IPM index than did dairy farmers (P < 0.0001). We also found a significant positive relationship between farm size and IPM score (P < 0.0001). Our results provide a benchmark for future comparisons of IPM adoption rates in Wisconsin and highlight the association between IPM research/extension and farmers' management behavior.

Nomenclature: corn, Zea mays L.

Additional index words: Integrated weed management, survey.

Abbreviations: CPMS, corn pest management survey; HRC, herbicide-resistant crops; MP, most productive; USDA, United States Department of Agriculture.

Corn and soybean growers across Indiana were surveyed during winter 2003/2004 to assess their perceptions about the importance of glyphosate-resistant weeds and management tactics to prevent development of resistant populations. The survey showed two intriguing observations. First, 65% of survey respondents expressed moderate or low levels of concern about weeds developing resistance to glyphosate, whereas 36% expressed a high level of concern. Second, when asked an open-ended question regarding the factors that contribute to development of glyphosate-resistant weeds, 58% of the responses included repeated use of the same mode of action. Other factors such as poor application techniques or timing (33%), unique weed characteristics (8%) and changes in tillage practices (1%) were also mentioned. The survey showed that even though a relatively low percentage of respondents were highly concerned about resistance, they still expressed a willingness to use field scouting, tank-mix partners with glyphosate for burn-down and postemergence weed control, and soil-applied residual herbicides as resistance management strategies. This survey also showed that growers who farm 800 ha or more were more concerned about glyphosate resistance and more likely to adopt resistance management strategies than smaller growers.

Nomenclature: Glyphosate; corn, Zea mays; soybean, Glycine max (L.) Merr.

Additional index words: Survey.

Abbreviations: GR, glyphosate-resistant.

Chinese yam is an exotic perennial vine that invades natural areas in the temperate regions of the eastern United States. Research was conducted from 2001 to 2004 to evaluate growth, reproduction, and management options for this weed. Vine length, lateral shoot production, and reproductive capacity were lower in the first year of growth compared to 2 subsequent years. During the second and third growing season, plants were more mature and tended to flower earlier and produce larger bulbils compared to the first growing season. Maximum vine length was not reached prior to frost in the first year and was approximately 480 cm in each of the subsequent years. Both glyphosate and triclopyr were effective in controlling plants growing from bulbils and plants growing from tubers. Triclopyr did not display acropetal translocation, in that only the treated tissue died. However, both products displayed excellent basipetal translocation resulting in elimination of tubers and no shoot regrowth the year following treatment. Native area managers should attempt to eradicate small populations of Chinese yam prior to establishment of an extensive tuber system.

Nomenclature: Chinese yam, Dioscorea oppositifolia L.; glyphosate, triclopyr.

Additional index words: Cinnamon vine, Dioscorea batatas, exotic plants, invasive plants, nagaimo, natural areas.

Abbreviations: GDD, growing degree days; NIS, nonionic surfactant.

Greenhouse, growth chamber, and winter survival studies were conducted at Stoneville, MS from 1996 to 2002 to determine growth, time to first flower, and winter survival of wetland nightshade. At 12 wk after emergence, wetland nightshade plants had 58-, 45-, 48-, and 4-cm heights, respectively; 24, 21, 21, and 12 nodes/plant, respectively; 62, 31, 36, and 21 leaves/plant, respectively; and 7.1, 3.9, 5.1, and 0.3 g/plant dry weights, respectively, at temperatures of 26/36, 20/30, 14/24, and 8/18 (±0.5) C at the 14/10 day/night length. Flowering occurred at 79, 85, and 85 days after emergence at 26/36, 20/30, and 14/24 C night/day, respectively at the 14/10 day/night cycle. Wetland nightshade plants did not flower at 8/18 C. Wetland nightshade growth was adequate for flowering and fruit production in additional areas of the southeastern United States with night/day temperatures greater than or equal to 14/24 C. Winter survival was greater than or equal to 33% for established wetland nightshade plants in 5 of 6(1996 to 2002) above water levels and 82% from 20 cm below the water surface. Based on these results, wetland nightshade has the potential to continue to spread in the United States.

Nomenclature: Wetland nightshade, Solanum tampicense Dunal #³.

Additional index words: Solanum tampicense Dunal.

Cogongrass is a serious weed in small-scale farms in the lowland humid zone of West Africa. This study evaluated the response of cogongrass to herbicides and the legume cover crop velvetbean in cassava and white Guinea yam. In 2001/2002, cassava tuber yields and gross returns in treatments that received glyphosate alone were higher than in plots that received fluazifop-P-butyl once. In 2002/2003, treatments that received fluazifop-P-butyl once, glyphosate alone, glyphosate integrated with sowing velvetbean, or hoeing only, had higher cassava tuber yields than other treatments. Gross returns were higher in treatments that received glyphosate followed by sowing velvetbean or those hoed only than in other treatments. Fluazifop-P-butyl applied twice, glyphosate alone, or glyphosate followed by sowing velvetbean reduced cogongrass shoot biomass more than other treatments. Rhizome biomass was lower in plots that received glyphosate alone than in all fluazifop-P-butyl treatments. In 2002, white Guinea yam tuber yields were highest in plots that received glyphosate alone and lowest in plots where fluazifop-P-butyl was applied alone or followed by sowing velvetbean. The highest gross return was obtained in plots that received glyphosate alone while the lowest was obtained in plots that received fluazifop-P-butyl once followed by sowing velvetbean. In 2003, the highest tuber yields and gross returns were from plots that received glyphosate alone, fluazifop-P-butyl alone, or those hoed only. The hoed-only plots had 14 times higher cogongrass shoot biomass and 7 times higher rhizome biomass than other treatments. In both crops, hoeing alone or followed by sowing velvetbean was more costly than chemical control. The highest margin over hoeing was obtained from plots that received glyphosate alone. Sensitivity analysis showed that using glyphosate was more cost effective than fluazifop-P-butyl, even if the cost of the herbicide increased by 100% or the cost of labor decreased by 30%.

Nomenclature: Fluazifop-P-butyl; gyphosate; cogongrass, Imperata cylindrica L. (Beauv.) #³ IMPCY; cassava, Manihot esculenta Crantz ‘TMS30572’; white Guinea yam, Dioscorea rotundata Poir ‘Dan-Anacha TDr 93-31’; velvetbean, Mucuna cochinchinensis (Lour.) A. Chev. MUCCO.

Additional index words: Chemical control, cover crop, sensitivity analysis, weed management cost.

Abbreviations: MAP, months after planting; WAP, weeks after planting.

In input-intensive cropping systems around the world, farmers rarely proactively manage weeds to prevent or delay the selection for herbicide resistance. Farmers usually increase the adoption of integrated weed management practices only after herbicide resistance has evolved, although herbicides continue to be the dominant method of weed control. Intergroup herbicide resistance in various weed species has been the main impetus for changes in management practices and adoption of cropping systems that reduce selection for resistance. The effectiveness and adoption of herbicide and nonherbicide tactics and practices for the proactive and reactive management of herbicide-resistant (HR) weeds are reviewed. Herbicide tactics include sequences and rotations, mixtures, application rates, site-specific application, and use of HR crops. Nonherbicide weed-management practices or nonselective herbicides applied preplant or in crop, integrated with less-frequent selective herbicide use in diversified cropping systems, have mitigated the evolution, spread, and economic impact of HR weeds.

Additional index words: Herbicide resistance, integrated weed management.

Abbreviations: ACCase, acetyl-CoA carboxylase; ALS, acetolactate synthase; APP, aryloxyphenoxypropionate; CHD, cyclohexanedione; DSS, decision-support system; EPSPS, enolpyruvylshikimate-3-phosphate synthase; HR, herbicide resistant; HS, herbicide susceptible; IWM, integrated weed management.

Feral rye, commonly referred to as cereal, winter, common, or volunteer rye, is an important weed in winter wheat production in many parts of the United States and the world. Feral rye reduces net profits in the United States by more than $27 million due to lower grain yields, increased dockage, and reduced land values. To date, limited research has been conducted on components that make feral rye a problem in various cropping systems. Herbicide-tolerant wheat technology can be used to manage feral rye, but current efficacy levels are not adequate for high feral rye densities. In addition, the long-term effects that individual management strategies may have on feral rye populations are unknown. This review addresses the physical, environmental, and genetic characteristics of Secale cereale. Current economic impact, management, and research data gaps are also discussed.

Nomenclature: Feral rye, Secale cereale L. #³ SECCE; wheat, Triticum aestivum L.

Additional index words: Integrated pest management, winter wheat, winter annual grasses, best management practices.