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Hazelnut naturally grows as a multi-stemmed tree. The basal sprouts, known as suckers, grow throughout the season. Suckers are removed to promote a single trunk that facilitates production mechanization and increased yield. In western Oregon, herbicides are the most common method of sucker control, and at least four applications per season are performed in the spring and summer seasons. This study evaluated the efficacy of foliar-applied herbicides currently registered for sucker control in hazelnuts. Season-long and short-term field studies were conducted to assess the efficacy of herbicides to control hazelnut suckers. In the season-long studies, four consecutive applications of treatments that contained 2,4-D, glufosinate, or paraquat provided 50% to 80% control, maintained sucker height at 50 cm or less as compared to 155 cm for the nontreated control, and reduced sucker biomass by 87% as compared to the nontreated control. The short-term study results confirmed the efficacy of 2,4-D, glufosinate, and paraquat for sucker control, and in this study, carfentrazone and saflufenacil reduced sucker biomass to a level comparable to 2,4-D or glufosinate treatment. These results confirm that 2,4-D, glufosinate, paraquat, carfentrazone, and saflufenacil can be used for sucker control in hazelnut and emphasize the necessity of multiple applications during the growing season to control suckers in hazelnut. Proper herbicide selection is important to control suckers with success.

The adoption of chemical fallow rotations in Pacific Northwest dryland winter wheat production has caused a weed species composition shift in which scouringrush has established in production fields. Thus, there has been interest in identifying herbicides that effectively control scouringrush in winter wheat–chemical fallow cropping systems. Field experiments were established in growers’ fields near Reardan, WA, in 2014, and The Dalles, OR, in 2015. Ten herbicide treatments were applied to mowed and nonmowed plots during chemical fallow rotations. Scouringrush stem densities were quantified the following spring and after wheat harvest at both locations. Chlorsulfuron plus MCPA-ester resulted in nearly 100% control of scouringrush through wheat harvest. Before herbicide application, mowing had no effect on herbicide efficacy. We conclude chlorsulfuron plus MCPA-ester is a commercially acceptable treatment for smooth and intermediate scouringrush control in winter wheat–chemical fallow cropping systems; however, the lack of a positive yield response when scouringrushes were controlled should factor into management decisions.

Tropical signalgrass (TSG) is one of the most problematic weeds found on golf courses, sports fields, and sod farms in south Florida. The recent ban of monosodium methane-arsonate (MSMA), an organic arsenical herbicide, from urban areas in Florida has left turfgrass managers searching for effective management options. In an effort to avoid relying solely on POST chemical control, this research examined the effect of combining a cultural practice, verticutting, along with PRE and POST herbicides as an integrated weed management approach to controlling TSG in hybrid bermudagrass. Field experiments were conducted at multiple locations over 2 yr in south Florida to: (1) determine whether verticutting before herbicide applications increases TSG control and (2) identify herbicide programs that effectively control TSG. No interactions between verticutting and herbicide programs were detected, but verticutting consistently provided a slight reduction (8% averaged across herbicide treatments) in TSG cover. Treatments containing a PRE herbicide resulted in a significant reduction (20% to 50%) in TSG cover at 52 wk after initial treatment (WAIT), while some POST herbicide treatments reduced TSG cover to 80% TSG control at 4, 8, and 12 WAIT, with some reaching 100% TSG control at 4 WAIT. Based on these data, verticutting may provide limited complementary control, but certain combinations of POST herbicides exhibited excellent (>95%) TSG control.

Although primarily used as an effective PRE herbicide, indaziflam has been shown to provide early POST control of some weeds commonly found in nursery production. Previous investigation on the early POST efficacy of indaziflam focused on the liquid formulation, and the ability of the granular formulation to provide early POST weed control is unknown. Nursery trials were conducted to evaluate early POST control of oxalis using two formulations of indaziflam. Oxalis seeds were surface sown to nursery containers at two separate dates and grown until they reached the two- to four-leaf stage (2-4L) and six- to eight-leaf stage. Both growth stages were treated with indaziflam at 12.6, 25.1, 50.2, and 100.4 g ai ha−1using either a granular (G) or liquid (SC) formulation. A chemical control treatment (glyphosate) and a nontreated control were also included for comparison. The SC formulation provided > 90% control of both oxalis growth stages at all four rates and was similar to glyphosate. The G formulation at 12.6 and 25.1 g ha−1only provided marginal control, but overall performed similarly to the SC formulation at the 50.2 and 100.4 g ha−1rate in most experiments. In contrast to the SC formulation, the G formulation is labeled for use over the top of container-grown nursery crops. Results of this research indicate that in areas where oxalis is the primary weed of concern, the G formulation of indaziflam could be applied to control small oxalis up to the 2-4L stage at the currently labeled rate (50.2 g ha−1).

The potential widespread adoption of cotton and soybean varieties with 2,4-D and dicamba resistance traits in the southeastern US will increase the risk of accidental exposure of peanut to these herbicides because of drift or application errors. When such accidents occur, growers must decide between continuing the crop and terminating it. In order to make this decision, growers need to estimate the potential yield reduction caused by 2,4-D or dicamba. Dose-response studies were conducted under field conditions in Citra and Jay, FL in 2012 and 2013 to determine peanut injury and yield reduction after exposure to 70, 140, 280, 560, and 1120 g ae ha−1of 2,4-D or to 35, 70, 140, 280, and 560 g ae ha−1of dicamba at 21 and 42 d after planting (DAP). Only herbicide by rate interactions were significant (P < 0.04). Dicamba caused 2 to 5 times higher peanut injury and 0.5 to 2 times higher yield reductions than 2,4-D. Injury ranged from 0 to 35% when peanut plants were treated with 2,4-D and from 20 to 78% with dicamba. The maximum yield reduction was 41% with 1,120 g ha−1of 2,4-D and 65% with 560 g ha−1of dicamba. Linear regression indicated that the intercept for yield reduction was 12% for 2,4-D and 23% for dicamba, and there was a 2.5% and 7.7% increase in yield reduction per additional 100 g ha−1, respectively. Although high variability was observed for the different variables, there was a positive correlation between injury and peanut yield reduction (P < 0.0001) with Pearson's Rho values ranging from 0.45 to 0.59 for 2,4-D and from 0.27 to 0.55 for dicamba, suggesting that growers can use injury data to make rough projections of yield reduction and decide if they continue their crop, especially when injury is evident.

POST control of grass weed species and contaminant turfgrass species, such as common and hybrid bermudagrass, is a major challenge in zoysiagrass. Fluazifop-P-butyl is a POST herbicide that can provide selective grass weed control with limited injury to zoysiagrass. However, because of the extent of genetic variation among zoysiagrass cultivars, it was proposed that fluazifop-P-butyl tolerance was cultivar dependent. Dose–response field studies were conducted in Jay, FL, in 2012 and 2013, evaluating the tolerance of 11 commercial zoysiagrass cultivars and common bermudagrass to 0, 44, 88, 131, 175, and 263 g ai ha−1of fluazifop-P-butyl. ‘Empire' and ‘Meyer' zoysiagrass were injured 30% or less at 2 wk after treatment (WAT) when treated with 131 g ha−1of fluazifop-P-butyl or less. Conversely, ‘Zeon' and ‘PristineFlora' reached from 30 to more than 50% injury between 2 and 4 WAT with 44 and 88 g ha−1fluazifop-P-butyl. ‘Geo', ‘Crowne', ‘JaMur', and ‘UltimateFlora' showed intermediate injury (i.e. ≤ 60% with 175 and 264 g ha−1) and a recovery period longer than 4 WAT. ‘Emerald', ‘Palisades', and ‘Royal' also showed intermediate injury (i.e., 30 to 65% with 175 and 264 g ha−1), which peaked at 2 WAT and then rapidly declined below 25% injury at 4 WAT. By 8 WAT, all zoysiagrass cultivars had recovered, and no injury was observed. Results from a greenhouse experiment demonstrated that differences observed in the field were cultivar related, especially for the lower tolerance level observed in Zeon and PristineFlora. There is potential to increase fluazifop-P-butyl tolerance in zoysiagrass because of the observed variation among 80 zoysiagrass breeding lines.

The submersed macrophyte, sago pondweed, frequently grows to nuisance levels in water conveyance systems throughout the western United States and can cause problems in lakes, reservoirs, and other water bodies. The liquid dipotassium and dimethylalkylamine salt formulations of endothall were evaluated for controlling sago pondweed using short exposure times (3 to 24 h) under controlled environmental conditions (14 : 10 h light : dark; 21.5 C). Endothall treatments ranged from 1 to 10 mg ai/L (dipotassium salt) and 0.5 to 5 mg ae/L (dimethylalkylamine salt). Sixteen concentration and exposure time (CET) combinations were evaluated in each study. At 4 wk after treatment, all CET combinations significantly reduced shoot biomass (43 to 99%) of sago pondweed compared with the untreated reference. Reduction in shoot biomass was greater in plants that received higher herbicide doses and longer exposure times. In addition, more than half of the endothall CET combinations controlled sago pondweed by at least 90%, ...

Failure of glyphosate to control Palmer amaranth was first reported in Arkansas in Mississippi County in June, 2005. The objectives of this research were to (a) confirm glyphosate-resistant Palmer amaranth in Arkansas, and (b) determine the effectiveness of 15 postemergence- (POST) applied herbicides comprising eight modes of action in controlling the glyphosate-resistant biotype compared to glyphosate-susceptible accessions. The LD50 values were similar among three susceptible Palmer amaranth accessions, ranging from 24.4 to 35.5 g ae/ha glyphosate. The resistant biotype had an LD50 of 2,820 g/ha glyphosate, which was 79- to 115-fold greater than that of the susceptible biotypes and 3.4 times a normal glyphosate-use rate of 840 g/ha. The glyphosate-resistant biotype was effectively controlled with most of the evaluated herbicides, but the use of acetolactate synthase-inhibiting herbicides such as pyrithiobac, trifloxysulfuron, and imazethapyr is not a viable option for control of this Palmer amaranth pop...

Studies were conducted to develop a weed management strategy for common purslane in lettuce based on available cultural and chemical control methods and an understanding of common purslane biology. A wide-band application of bensulide or pronamide reduced common purslane emergence compared with the standard narrow band. Both narrow and wide bands of pronamide as well as a wide band of bensulide reduced the time required to thin and hoe lettuce. The wide-band pronamide treatment reduced thinning time more than did the narrow band. Overall, none of the herbicide weed management expenses were lower for pronamide treatments than for bensulide and the control. Wide-band bensulide reduced weed management expenses compared with the control, whereas narrow bands did not. Common purslane plants uprooted 1 or 2 wk after emergence (WAE) did not produce any viable seed. Plants uprooted 3 WAE produced from 1 to 60 viable seeds, and seed production increased rapidly from 4 to 6 WAE. Flame and 2% (v/v) glyphosate treatm...

Two field experiments were conducted to evaluate the reduction of torpedograss canopy by multiple split applications of quinclorac applied postemergence (POST) to bermudagrass golf course roughs in Florida. In one experiment, quinclorac treatments were reapplied for a second year to the same plots, followed by biomass harvest, to evaluate the reduction of torpedograss rhizomes. Quinclorac sprayed at 1.68 kg/ha/yr visually reduced torpedograss canopy to a varying extent, depending on the number of split applications. The most effective treatment, 0.42 kg/ha quinclorac applied four times each year for 2 yr, reduced torpedograss canopy to 10% compared with 86% torpedograss canopy in the untreated plots, and reduced torpedograss dry weight to 1,570 kg/ha compared with 8,010 kg/ha in the untreated plots. After reapplication for 2 yr with the commercially labeled treatment, quinclorac at 0.84 kg/ha applied twice per year, torpedograss canopy was reduced to 45% and dry weight to 4,640 kg/ha. Visual evaluation of...

Diphenylether herbicides may be viable options for postemergence (POST) control of common waterhemp in soybean. A 2-yr field research project was conducted to determine whether common waterhemp control is influenced by application timing and rate of acifluorfen, fomesafen, and lactofen. Common waterhemp control was 9, 9, and 8% greater 7, 14, and 21 d after treatment, respectively, after the early postemergence (EPOST) application timing compared with the POST application timing. Lactofen provided greater common waterhemp control than did acifluorfen or fomesafen, and only the highest application of lactofen provided greater than 85% common waterhemp control 21 d after POST application. No significant differences in common waterhemp dry weight were determined among the three rates of acifluorfen, fomesafen, and lactofen applied EPOST. The highest application rates of fomesafen and lactofen reduced common waterhemp dry weight more than did the lowest application rates applied POST. The highest application ...

Auxin-type herbicides such as 2,4-D and dicamba are commonly used to control kochia in small grain production areas, but poor kochia control with these herbicides has been reported. Several auxinic herbicide-resistant kochia inbreds were evaluated for their response to 2,4-D or dicamba and to alternative herbicide treatments. Values of the dose of the herbicide causing 50% visible injury to test plants (I50) from week 1 to week 4 after treatment with 2,4-D were unchanged for six of the seven 2,4-D–resistant inbreds, indicating that these plants may recover to produce seeds. In contrast, the corresponding I50 values for dicamba decreased for five of the six dicamba-resistant inbreds, indicating that kochia was not recovering from the treatment. Postemergence treatments with atrazine, carfentrazone, fluroxypyr, bromoxynil plus MCPA, nicosulfuron plus dicamba, and nicosulfuron plus dicamba plus atrazine, all provided adequate to excellent control of resistant kochia inbreds. Alternative chemical control opti...

Experiments were conducted at three locations in North Carolina in 1999 and 2000 to evaluate weed management systems in strip-tillage peanut. Diclosulam was evaluated with standard preemergence (PRE), early postemergence, and postemergence (POST) herbicide systems in a factorial treatment arrangement. Preemergence treatments that contained diclosulam controlled common lambsquarters, common ragweed, and eclipta by 100%. Diclosulam PRE controlled entireleaf morningglory by 88%, ivyleaf morningglory by ≥ 90%, pitted morningglory by ≥ 81%, and prickly sida by ≥ 94%. Yellow nutsedge control with diclosulam ranged from 65 to 100% depending on location, whereas POST systems containing imazapic controlled yellow nutsedge by at least 89%, regardless of PRE herbicides. Peanut yields and net returns were reflective of levels of weed management. Systems that included diclosulam PRE plus POST herbicides consistently provided high yields and net returns. Clethodim late POST was required for full-season control of annua...

S-metolachlor was compared with metolachlor at four field locations in Texas during the 1996 and 1997 growing seasons in terms of yellow nutsedge control, peanut injury, and peanut yield. S-metolachlor caused peanut injury comparable to metolachlor when either herbicide was applied preplant incorporated or preemergence. Yellow nutsedge control was similar and peanut yields were comparable with the two herbicides. At one location where yellow nutsedge failed to develop, the untreated check produced one of the highest yields. Nomenclature: Metolachlor; S-metolachlor; yellow nutsedge, Cyperus esculentus L. #3 CYPES; peanut, Arachis hypogaea L. ‘Florunner’, ‘AT-120’, ‘GK-7’. Additional index words: Groundnut, herbicide efficacy, peanut stunting. Abbreviations: POST, postemergence; PPI, preplant incorporated; PRE, preemergence.

Field experiments were conducted at three Mississippi locations to evaluate potential antagonism when postemergence graminicides were tank-mixed with CGA-277476 and to determine if the antagonism could be overcome with an increase in graminicide rate. At all locations when the 1 x rate of clethodim, fluazifop-P, or quizalofop was tank-mixed with 79 g ai/ ha CGA-277476, johnsongrass, broadleaf signalgrass, and barnyardgrass control was reduced 5 to 30%. When the graminicide rates were increased to 1.5 X, antagonism was still present for fluazifop-P and quizalofop. However, 156 g ai/ha clethodim overcame the antagonism when tank-mixed with 79 g/ha CGA- 277476 compared to 105 g/ha clethodim. CGA-277476 alone controlled barnyardgrass and broadleaf signalgrass 38 to 63% and johnsongrass 60 to 85%. There were no differences in soybean yields with graminicides applied alone or tank-mixed with CGA-277476. Nomenclature: CGA-277476, 2(((((4,6-dimethyl-2-pyrimidinyl)amino)carbonyl)amino)sulfonyl)-, 3- oxetanyl-ester; clethodim, (E E)-( + )-2-(1 -(((3-chloro-2propenyl)oxy)imino)propyl)-5-(2-(ethyl- thio)propyl)-3-hydroxy-2-cyclohexen- l-one; fluazifop-P, (R)-2-(4-((5-trifluoromethyl)-2-pyridi- nyl)oxy)phenoxy)propanoic acid; quizalofop, (?)-2-(4-((6-chloro-2-quinoxalinyl)oxy)phenoxy)pro- panoic acid; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash # BRAPP; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; soybean, Glycine max (L.) Merr.'Hartz 4994,' 'Pioneer 9592.' Additional index words: Antagonism, Brachiaria platyphylla, Echinochloa crus-galli, Sorghum hal- epense, BRAPP, ECHCG, SORHA. Abbreviations: Gm, Greenville; POST, postemergence; Stk-N, Starkville north; Stk-S, Starkville

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. ...

Hemp sesbania control by chlorimuron applied with crop oil concentrate at 1.0% v/v, BCH 815 at 1.0% v/v, methylated seed oil at 1.0% v/v, a blend of methylated seed oil and organosilicone surfactant at 0.5% v/v, organosilicone-based surfactant at 0.125% v/v, and nonionic surfactant at 0.25% v/v was evaluated in field studies in 1994 and 1995. Control by chlorimuron at 4.5 g ae/ha was greater when applied with BCH 815, organosilicone-based surfactant, and nonionic surfactant than with crop oil concentrate, methylated seed oil, and a blend of methylated seed oil and organosilicone surfactant. When chlorimuron was applied at 4.5 g/ha with BCH 815 or nonionic surfactant, hemp sesbania control was similar to that by chlorimuron at 9 g/ha applied with methylated seed oil, the blend of methylated seed oil and organosilicone surfactant, or organosilicone-based surfactant.

Greenhouse and field experiments were conducted to characterize a synergistic interaction between fluazifop-P and terbacil in strawberry (Fragaria x ananassa Duchesne). In the greenhouse, injury from foliar terbacil applications generally increased two- or more fold when 75 or 150 g/ha fluazifop-P was applied foliarly 24 h later to either a terbacil tolerant ('Veestar') or sensitive ('Kent') strawberry cultivar. Synergism also occurred when terbacil was applied as a soil drench and fluazifop-P was applied 5 d later. There was little difference in effect between tank-mixed and sequential applications made 0.5 and 20 min apart. Increased injury was also observed with intervals up to 6 d between applications in the greenhouse, and the order of herbicide application did not affect injury level. Similar results were obtained in field experiments on newly planted 'Honeoye' and 'Cavendish' strawberry. An interval of 6 d or more between terbacil and fluazifop-P application is suggested to minimize the risk of increased crop injury. Nomenclature: Fluazifop-P, (R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid; terbacil, 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4-(1H,3H)-pyrimidinedione; strawberry, Fragaria x ananassa Duchesne 'Cavendish,' 'Honeoye,''Kent,''Veestar.'

Field experiments were established to evaluate coffee senna control in cotton with registered PRE, early POST-directed (EPD), and late POST-directed (LPD) herbicides and with pyrithiobac applied PRE and early POST. Fluometuron and norflurazon applied PRE controlled coffee senna 87 and 65%, respectively, 6 wk after planting (WAP). Methazole applied EPD controlled coffee senna 96% 2 wk after application, whereas fluometuron and MSMA applied EPD controlled 70 and 16%, respectively. LPD applications of cyanazine, diuron, and prometryn averaged only 45% control 8 WAP. MSMA applied LPD controlled coffee senna only 12%. Fluometuron and norflurazon applied PRE followed by methazole applied EPD and cyanazine applied LPD controlled coffee senna 98 and 99% 6 WAP, respectively. PRE, early POST, and PRE followed by early POST applications of pyrithiobac controlled coffee senna 88, 89, and 95% 6 WAP, respectively. Seed cotton yields were similar to weed-free cotton with all treatments except MSMA applied EPD and the LPD treatments, all of which provided unacceptable (12 to 49%) control 8 WAP.

Acifluorfen, lactofen, chlorimuron, thifensulfuron, imazethapyr, and imazaquin were evaluated for control of Palmer amaranth, common waterhemp, redroot pigweed, and tumble pigweed at three application timings in field and greenhouse experiments. Results from field studies indicated that most herbicides provided greater than 90% control of common waterhemp, redroot pigweed, and tumble pigweed regardless of time of application. Palmer amaranth was the most difficult species to control, and only thifensulfuron and imazethapyr provided greater than 80% control at all application timings. In the greenhouse experiment, herbicides were applied when pigweeds averaged 10 cm, 20 cm, and 30 cm in height. Results were similar to the field experiment, except that common waterhemp was more difficult to control.

The effects of metribuzin herbicide and phorate insecticide were studied on summer harvest chipping-potatoes at Muscatine, IA, from 1989 to 1991. Phorate at 1.5 kg/ha increased total and ‘A’-size tuber yield and tuber specific gravity. Metribuzin applied at 0.56 kg/ha postemergence decreased total and ‘A’-size tuber yield. Metribuzin applied at 0.56 kg/ha preemergence and 0.28 kg/ha postemergence did not reduce Atlantic cultivar yield. Metribuzin did not affect ‘B’-size tuber yield or specific gravity. Phorate in combination with metribuzin did not increase plant injury or reduce tuber yield.

Metham was applied in the dormant season to established cranberry for the control of false lily-of-the-valley. Rates of 108 to 214 kg ai/ha controlled false lily-of the-valley, but there were inconsistent results between years and fields. Soil temperature, organic matter content, and amount of water used for incorporation appeared to be important factors in determining results. The phytotoxicity of metham sodium to cranberry was sporadic, ranging from moderate at 214 kg ai/ha to severe at 108 kg ai/ha. The 142 kg ai/ha rate usually resulted in an acceptable level of crop injury. Sanding the bog after application reduced phytotoxicity and heat stress increased it.

Phenmedipham was registered for use at 1.1 to 1.7 kg ai/ha in 1970 and desmedipham at 1.1 to 1.4 kg ai/ha in 1974 for postemergence control of broadleaf weeds in sugarbeet. Phenmedipham was sold from 1970 through 1981 and desmedipham plus phenmedipham (1:1), as a premixed product, has been sold since 1982. Development of multiple applications of reduced rates began in 1972 primarily to reduce sugarbeet injury. The technique was promoted to farmers after 1976. A half-rate of phenmedipham and/or desmedipham applied twice at a 5to 7-d interval controlled weeds better and caused less sugarbeet injury than a single full-rate application, and allowed application to smaller than four-leaf sugarbeet. Suggested sugarbeet size for the first application changed from 4-leaf in 1970 to cotyledon to two-leaf in 1992. Earlier application to more susceptible small weeds allowed a further rate reduction. The use of soil-applied herbicides prior to phenmedipham and/or desmedipham increased weed control and sugarbeet injury. Application to small weeds and sugarbeet by air or by ground sprayers at spray pressures over 1040 kPa controlled weeds better and injured sugarbeet more than when applied by ground sprayers at 280 kPa. Desmedipham and phenmedipham rates presently are adjusted for sugarbeet size, application method, soil-applied herbicide, and environment. The suggested initial application rate of phenmedipham and/or desmedipham in 1992 was 0.13 to 0.28 kg/ha as compared with 1.1 to 1.7 kg/ha in 1970. A typical rate of desmedipham or desmedipham plus phenmedipham applied in 1992, including multiple application, was approximately 0.7 kg/ha less than typical rates from 1970 through 1977. Nomenclature: Desmedipham, ethyl { 3-[[(phenylamino)carbonyl]oxy]phenyl]carbamate, phenmedipham, 3-[(methoxycarbonyl)amino]phenyl (3-methylphenyl)carbamate, sugarbeet, Beta vulgaris L. Additional index words: Weed control, agrichemicals, environmental safety, phenmedipham, desmedipham, application technology.

Torpedograss has invaded fine turfgrasses in the Southern U.S. due to its tolerance to most commonly used turfgrass herbicides. Research was conducted to determine torpedograss and 'Tifway' bermudagrass tolerance to quinclorac and tank-mix combinations with other turf herbicides. Quinclorac rates in excess of 2.2 kg ai/ha were required for control (2 80%) of torpedograss. Sequential applications were more effective than single applications. Generally, sequential applications made 3 wk after the initial were more effective than delaying sequential applications until 4 wk after the initial application. Tifway bermudagrass injury from quinclorac applied at 4.5 kg/ha, or at 2.2 kg/ha followed by a sequential application of 1.1 or 2.2 kg/ha, was observed at 4 to 10 wk; however, turf recovered thereafter. Sequential applications of quinclorac plus imazaquin (1.1 + 0.6 kg/ha) increased torpedograss control (approximate 35%) as compared to quinclorac plus MSMA (1.1 + 1.1 kg/ha) but also decreased turf quality versus quinclorac applied alone or in combination with MSMA. Quinclorac applied at 2.2 kg/ha followed by 1.1 kg/ha applied 3 or 6 wk after the initial controlled torpedograss best with least reduction in bermudagrass quality. Quinclorac is the first herbicide reported to selectively control torpedograss in bermudagrass turf. Nomenclature: Imazaquin, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-lH-imidazol-2-yl]-3-quinolinecarboxylic acid: MSMA, monosodium salt of methylarsonic acid; quinclorac, 3,7-dichloro-8-quinolinecarboxylic acid; torpedograss, Panicum repens L. #3 PANRE; 'Tifway' bermudagrass, Cynodon dactylon (L.) Pers. x C. transvaalensis Burt-Davy. Additional index words: Golf course, BAS 514, imazaquin, MSMA, quinclorac, PANRE.

Experiments were conducted to compare control of entireleaf morningglory with POST applications of DPX-PE350 applied with no adjuvant, a nonionic surfactant, or crop oil concentrate in spray volumes of 94, 235, and 375 L ha−1. Control was greater with a nonionic surfactant or crop oil concentrate than with no adjuvant and control with crop oil concentrate exceeded control with the nonionic surfactant. Spray volume had no effect on efficacy. DPX-PE350 was more effective when applied to foliage only or to soil plus foliage than when applied to soil only after emergence of entireleaf morningglory. Control from soil-only applications was lower on a silty clay soil than on a silt loam soil. Except for sicklepod, mixing DPX-PE350 with fluometuron or MSMA had little effect on weed control.

Field studies were conducted from 1986 through 1989 to evaluate the tolerance of three clover species to selected POST herbicides. 2,4-D at 0.8 and 1.7 kg ha−1injured rose and berseem clovers while the high rate injured subterranean clover. Bentazon and pronamide did not injure rose or subterranean clover; however, pronamide at 3.4 kg ha−1injured berseem clover 18% when rated 72 days after treatment.

Chlorimuron applied alone and in combination with acifluorfen or thifensulfuron was evaluated for POST control of common lambsquarters, common ragweed, common cocklebur, and a mixture of pitted, ivyleaf, entireleaf, and tall morningglory in soybean. Common cocklebur control was similar with thifensulfuron at 3 and 4 g ae ha−1and with chlorimuron at 7 and 9 g ae ha−1, Common ragweed and morningglory control was greater with chlorimuron while common lambsquarters control was greater with thifensulfuron. Control of all species was good with combinations of chlorimuron at 7 g ha−1plus thifensulfuron at 2 g ha−1or acifluorfen at 140 g ae ha−1and similar to or greater than the control with chlorimuron at 9 g ha−1. Soybean yields with all POST herbicide treatments were equivalent to that of the weed-free check.

Greenhouse and field studies were conducted to characterize wild poinsettia growth response to imazaquin (140 g ai ha-'), fomesafen and acifluorfen (420 g ai ha-'), and chlorimuron (9 g ai ha-1) applied at 5 to 7 cm (POSTI), 8 to 10 cm (POST2), and 15 to 20 cm (POST3). Based on reductions in weed height and lateral branch number 28 DAT, wild poinsettia was controlled more effectively in both greenhouse and field studies for all herbicides applied at POSTI than at POST3. In the greenhouse studies, reduction in wild poinsettia biomass with the herbicides 28 DAT was similar when applied at POSTI and POST2 and, with the exception of chlorimuron, was higher at POST2 than at POST3. In the field study, weed biomass reduction measured approximately 4 mo after herbicide application was higher for imazaquin, acifluorfen, and chlorimuron applied at POST2 than at POSTI. Wild poinsettia biomass was reduced more with imazaquin applied at POST3 than at POST1. Increased lateral branch production, indicative of decreased weed control, was often manifested in higher seed production per plant. With application of all herbicides at POST3 seed production was equal to the untreated check. Nomenclature: Acifluorfen, 5-[2-chloro4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid; chlorimuron, 2-[[[[(4-chloro-6-methoxy-2pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid; fomesafen, 5-[2-chloro-4(trifluoromethyl)phenoxy]-N-(methylsulfonyl)-2-nitrobenzamide; imazaquin, 2-[4,5-dihydro-4methyl-4-(1-methylethyl)-5-oxo-lH-imidazol-2-yl]-3-quinolinecarboxylic acid; wild poinsettia, Euphorbia heterophylla L. #3 EPHHL. Additional index words: Growth characteristics, regrowth, seed production, EPHHL.

The successful introduction of a new crop depends upon the availability of economical, safe, and effective herbicides for that crop. Greenhouse trials identified PRE herbicide applications of 4.5 kg ai ha−1 of metolachlor and of alachlor, 2.2 kg ai ha−1 of linuron and of pendimethalin, and 1.1 kg ai ha−1 of desmediphan as noninjurious to sweet white lupin. POST applications of 0.28 kg ai ha−1 of sethoxydim and of fluazifop and 0.22 kg ai ha−1 of haloxyfop also did not injure the sweet white lupin. Field trials indicated that safe and effective weed control could be obtained with combinations of linuron with metolachlor, alachlor, or pendimethalin depending on weed species present.

Field studies were conducted at Charleston, SC to evaluate the effects of six chemical treatments on bahiagrass and the potential of these treatments to reduce mowing operations. Sulfometuron, maleic hydrazide, and imazethapyr plus imazapyr, in decreasing order of effectiveness, were the most consistent treatments evaluated during the 2-yr study. Sulfometuron reduced bahiagrass vegetative height (23%) for 6 to 8 WAT and suppressed 87 to 92% of seedheads without adversely affecting turf quality. All treatments temporarily discolored turf; however, effects were not objectionable for medium- to low-quality turf settings. Sulfometuron, maleic hydrazide, and imazethapyr plus imazapyr controlled growth and maintained acceptable turf quality for an average of 9, 9, and 8 wk, respectively; thereby reducing mowing operations by an average 29%. Mefluidide plus fluazifop-P, mefluidide plus sulfometuron, and chlorosulfuron were the least effective and/or consistent treatments evaluated.

Dicamba, 2,4-D, picloram, and commercially available premixes of glyphosate plus 2,4-D or glyphosate plus dicamba were evaluated alone and in combination for field bindweed control in a winter wheat-fallow system in Colorado, Wyoming, Kansas, and Montana. Approximately one year after application, herbicide mixtures containing picloram at 0.14 or 0.28 kg ai ha-1provided the best control. In five of seven locations, the control provided by picloram in herbicide mixtures was greater than the control provided by glyphosate plus 2,4-D, 2,4-D, or dicamba when these products were mixed with picloram. Glyphosate plus 2,4-D or glyphosate plus dicamba premixes, or 2,4-D added to dicamba were less effective for long-term control of field bindweed than mixtures containing 0.14 kg ai ha-1or more of picloram. Under drought conditions in Kansas in 1988, picloram did not control field bindweed as well as in Colorado, Wyoming, or Montana where rainfall was normal.

Field experiments were conducted during 1982 to 1988 in Virginia to evaluate BAS 517, CGA 82725, clethodim, cloproxydim, fenoxaprop, fluazifop, fluazifop-P, haloxyfop, paraquat, quizalofop, SC-1084, sethoxydim, sethoxydim plus thifensulfuron, and terbacil for control of annual grasses in alfalfa. Herbicides were applied to alfalfa and grasses 2 to 30 cm in height after the first and/or second cuttings. Overall, the herbicides were highly effective in controlling fall panicum, giant foxtail, barnyardgrass, and large crabgrass. Alfalfa yields were not increased with herbicide treatments in several experiments. Only paraquat, applied later than recommended after cutting in one experiment, and sethoxydim plus thifensulfuron at one location reduced alfalfa yields.

Experiments were conducted from 1988 through 1991 to evaluate the effectiveness of imazethapyr alone and in combination with metolachlor for control of yellow and purple nutsedge. Inazethapyr alone at 0.07 kg ha-1 controlled yellow nutsedge irregularly while the addition of metolachlor greatly improved control. Metolachlor preplant incorporated (PPI) followed by imazethapyr at ground-crack (GC) or postemergence (POST) controlled 72 to 96% of yellow nutsedge, whereas a tank-mix of metolachlor plus imazethapyr PPI controlled 85 to 96%. The addition of metolachlor to imazethapyr did not result in any improvement in control of purple nutsedge. Metolachlor plus imazethapyr PPI controlled > 85% of purple nutsedge PPI, whereas imazethapyr POST controlled ? 94%. Nomenclature: linazethapyr, (?)-2-[4,5-dihydro-4-methyl-4-(l-methylethyl)-5-oxolH-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid; metolachlor, 2-chloro-N-(2ethyl-6-methylphenyl)-N-(2-methoxyl-methylethyl)acetamide; peanut, Arachis hypogaea L. 'Florunner'; purple nutsedge, Cyperus rotundus L. #3 CYPRO; yellow nutsedge, Cyperus esculentus L. # CYPES. Additional index words: Metolachlor, timing of application, purple nutsedge, yellow nutsedge

Fluazifop-P, applied in the spring or fall and pronamide, applied in the fall only, reduced quackgrass infestation in established alfalfa and increased the dry matter yield of alfalfa. Herbicides did not improve alfalfa in vitro digestibility or crude protein content. Average residues of fluazifopP in alfalfa treated with rates of 0.25 or 0.5 kg ai ha7l, were 0.1 mg kgl when harvested 280 d after application, and 0.06 mg kg-1 when harvested 295 d after application. Average residues in alfalfa harvested 41 and 55 d after application were 0.13 mg kgjl and 0.1 mg kg-1, respectively, with a 0.25 kg ha-' treatment and 0.19 mg kg-1 and 0.05 mg kg-1, respectively, with a 0.5 kg ha-l treatment. Nomenclature: Fluazifop-P, (R)-2[4[[5 -(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid; pronamide, 3, 5-dichloro(N-l,l-dimethyl-2-propynyl)benzamide; alfalfa (Medicago sativa L.); quackgrass [Elytrigia repens (L.) Nevski #3 AGGRE]. Additional index words: Alfalfa yield and quality, fluazifop-P, pronamide, AGGRE.

A practical and objective system is needed to determine the lowest rates of the most efficacious herbicides to meet each producer's specific weed control problems. Determining which method of weed control to utilize is difficult today with increasing product choices, the growing use and complexity of herbicide mixtures, regulatory pressures to reduce rates, and the closer integration of weed control with other crop decisions. Expert computer systems could improve current practices and use herbicide mixtures as a tool to increase herbicide efficiency. Such systems would account for herbicide dose and mixture responses; select most economical herbicides; optimize adjuvants; recommend control at economic thresholds; and vary rates according to weed spectrum, density, and local environmental conditions. An example using chlorimuron and thifensulfuron illustrates how these systems could use quantitative dose response and mixture information. Nomenclature: Chlorimuron, 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid; thifensulfuron, 3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2yl)amino]carbonyl]-amino]sulfonyl]-2-thiophenecarboxylic acid. Additional index words: Herbicide interaction, dose response, LISA, environment, chlorimuron

In the greenhouse, soil applications of primisulfuron (40 g ai ha–1) reduced growth of emerged rhizome johnsongrass plants more than nicosulfuron (40 g ai ha–1). Both herbicides reduced growth more when applied to foliage only; a further decrease in growth did not occur for applications to both soil and foliage. Primisulfuron did not completely prevent regrowth of johnsongrass with any application method. Nicosulfuron prevented regrowth when applied to the foliage and to both soil and foliage. In single-year field studies in corn at four dryland sites and two irrigated sites, 50:50 split applications of primisulfuron (40 g ai ha–1) and nicosulfuron (35 g ai ha–1) approximately 2 wk apart provided the most consistent rhizome johnsongrass control compared with early or late single applications when visually rated 8 wk after the first application. Nicosulfuron treatments were more effective than primisulfuron treatments at both dryland sites the first year and at one of two dryland sites the second year. Primisulfuron and nicosulfuron at the irrigated site the first year were equivalent in efficacy. Nicosulfuron was more effective than primisulfuron at the irrigated site the second year. Primisulfuron or nicosulfuron treatments more than doubled corn yields at the dryland sites both years regardless of application timing. Split applications of primisulfuron or nicosulfuron provided the highest yields (approximately 80% increase over untreated plots) at the irrigated site the first year. All treatments provided equivalent yield increases (approximately 50%) the second year.

In the field, 14 soft red winter wheat cultivars responded differently to 1.1 kg ai ha–1diclofop, 1.7 kg ai ha–1BAY SMY 1500, and 0.42 kg ai ha–1metribuzin applied POST. Diclofop and metribuzin did not injure any cultivar more than 10% on a silty clay soil. However, BAY SMY 1500 injured ‘Pioneer 2551’ and ‘Coker 983’ 39 and 21%, respectively, in March. All other cultivars were injured less than 10% by BAY SMY 1500. Early injury did not translate into yield loss in the cultivar tolerance study. In an application timing study for Italian ryegrass control, late-season ratings indicated better control with two-leaf applications than with PRE applications for all treatments. Delaying application to the three-tiller stage reduced control with BAY SMY 1500 or metribuzin, but not with diclofop. On the sandier soil at this location, wheat injury with 0.28 or 0.43 kg ha–1metribuzin or 2.2 kg ha–1BAY SMY 1500 was sufficient to reduce wheat yield compared with other treatments, despite good Italian ryegrass control.

Sicklepod control with seven chemical treatments was evaluated in 25-cm and 97-cm soybean row widths. Metribuzin applied preplant incorporated followed by metribuzin applied preemergence, and metribuzin applied preplant incorporated followed by either imazaquin or chlorimuron applied postemergence controlled sicklepod over 90% early in the season, and row spacing did not influence control at that evaluation. In late season ratings, all herbicide treatments controlled sicklepod better in 25-cm rows than in 97-cm rows. However, only imazaquin applied sequentially or metribuzin followed by chlorimuron in 25-cm rows controlled sicklepod greater than 80% late in the season. Sicklepod control in 25-cm row soybean with either imazaquin or metribuzin plus chlorimuron applied preplant incorporated was equivalent to or better than sequential preemergence and postemergence treatments of these three herbicides in 97-cm rows. All treatments resulted in lower yields than the weed-free check in the 97-cm rows, whereas all herbicide treatments except the sequential application of metribuzin gave yields equivalent to the weed free check in 25-cm rows.

Field studies were conducted in 1987 and 1988 at Fayetteville and Clarkedale, AR, to evaluate various herbicide treatmnents for johnsongrass control in soybeans. Herbicide treatments were postemergence applications of sethoxydim, fenoxaprop, fluazifop-P, haloxyfop, quizalofop, imazethapyr, and clethodim. No significant soybean injury was noted in 1987 or 1988 at either location in the johnsongrass experiments. All treatments except those with fenoxaprop and imazethapyr, provided 70 to 90% johnsongrass control. Generally, soybean yields were reduced from treatments that controlled less than 60% of the johnsongrass. Nomenclature: Clethodim, (E,E)-(?)-2-[l-[[(3-chloro-2-propenyl)oxy]imino]propy1]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-l-one; fenoxaprop, (?)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid; fluazifop-P, (R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid; haloxyfop, 2-[4-[[3chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid; imazethapyr, (?)-2-[4,5-dihydro-4-methyl-4-( 1-methylethyl)-5-oxolH-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid; quizalofop, (?)-2-[4-[(6-chloro-2-quinoxalinyl)oxy]phenoxy]propanoic acid; sethoxydim, 2-[1(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one; johnsongrass, Sorghum halepense (L.) Pers. #3 SORHA; soybeans Glycine max (L.) Merr. 'Centennial' and 'Forrest'. Additional index words: Clethodim, fenoxaprop, fluazifop-P, haloxyfop, imazethapyr, quizalofop

Several precision postemergence-directed sprayers with different nozzle designs and arrangements were evaluated for potential use in sweet corn for wild-proso millet (PANMI) control in field trials from 1987 to 1989. Ametryn at 2270 g ha-1plus oil-emulsifier mixture (OEM) at 1.3% v/v and sethoxydim alone or plus OEM applied postemergence-directed selectively controlled PANMI in sweet corn. Sethoxydim at 220 g ha-1plus OEM controlled PANMI best when averaged over the 3-yr period. Ametryn plus OEM did not injure corn and sethoxydim at 110 g ha-1plus OEM caused little or no corn injury and no yield reductions when applied with any of the sprayers. Generally, only sethoxydim at 220 g ha-1plus OEM injured corn. The amount of injury was different among sprayers, with the nozzle designs and arrangements responsible for corn injury. Injury was minimized when sethoxydim was applied with a sprayer equipped with 150 degree dual orifice nozzles spaced 38 cm apart and mounted on skids that contacted the soil to assure constant nozzle height. This sprayer, or sprayers of similar nozzle design, show the most potential for use by sweet corn growers.

A heavy, uncontrolled infestation of field dodder and largeseed dodder suppressed newly seeded alfalfa severely and killed many of the plants. Glyphosate at 75 or 150 g ae ha-1, sprayed over the top of the dodder-infested alfalfa, stopped the growth of dodder and did not injure alfalfa significantly. Treated dodder began to grow normally again 2 to 3 wk after treatment. This regrowth injured the alfalfa severely in spite of earlier control. Glyphosate at 75 or 150 g ha-1applied two or three times controlled dodder effectively and protected the alfalfa. A rate of 40 g ha-1was not effective.

Field experiments were conducted to evaluate the influence of application timing of imazethapyr and fluazifop-P on rhizome johnsongrass and pitted morningglory control in soybean. Herbicides were applied at three timings keyed to johnsongrass heights of 15, 30, and 60 cm and 3-, 6-, and 9-leaf pitted morningglory. Evaluations 6 wk after the fmal treatment indicated imazethapyr controlled both species best when applied at the 15-cm johnsongrass growth stage. Increasing imazethapyr rate did not increase control of pitted momingglory, but did increase johnsongrass control at the 15-cm application timing. However, at the 30-cm johnsongrass application timing, increasing the rate from 0.07 to 0.10 kg ha-1 improved control of both species. Johnsongrass control with imazethapyr was no more than 64% when applications were delayed to 30-cm or larger johnsongrass. Fluazifop-P controlled johnsongrass well at all timings. Nomenclature: Fluazifop-P, (R)-2-[4-[[5-trifluoromethyl)-2-pyridinyl]oxy]phenoxylpropanic acid; imazethapyr, (?)-2-[4,5-dihdyro-4-methyl-4-(l-methylethyl)-5-oxo-lH-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid; johnsongrass, Sorghum halepense (L.) Pers. #3 SORHA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; soybean, Glycine max (L.) Merr. Additional index words: Fluazifop-P, growth stage, imazethapyr, postemergence, Glycine max.

Research was conducted on a sandy clay loam in Georgia during 1987-88 and 1988-89 to detennine winter wheat, oats, barley, and Italian ryegrass tolerance to flurtamone. Flurtamone was applied PPI, PRE, and early POST at 0.28, 0.56, and 1.1 kg ai ha-'. Order of tolerance of the four species was barley > wheat > oat > Italian ryegrass. Flurtamone potentially can be used to control Italian ryegrass in winter wheat and barley, but not in oats. In general, wheat and oat injury with flurtamone was PPI > PRE ? early POST, particularly at 1.1 kg ha-'. Nomenclature: Flurtamone, 5-(methylamino-2-phenyl]-4-[3-(tifluoromethyl)phenyl]-3(2H)-furanone; winter wheat, Triticum aestivum L.; winter barley, Hordeum vulgare L.; winter oats, Avena sativa L; Italian ryegrass, Lolium multiflorum Lam. #3 LOLMU. Additional index words: Diclofop, Avena sativa, Hordeum vulgare L., Triticum aestivum, LOLMU.

An established alfalfa stand infested with quackgrass received fluazifop-P, haloxyfop, or quizalofop at single applications of 0.28 ae kg ha-1and sequential applications of 0.14 plus 0.14 ae kg ha-1with the second treatment being made 16 d after the first. All herbicide treatments increased diffusive resistance and decreased transpiration of quackgrass compared to control plants. These effects became apparent 16 d or more after spraying. Visual injury symptoms were noted 8 to 10 d after treatment, several days prior to changes in diffusive resistance or transpiration. The alfalfa content of the first cutting was increased from herbicide treatment; however, total forage yield was reduced. Yields and composition of later cuttings were unaffected by the various herbicide treatments.

Preplant applied herbicides were compared for their effect on three varieties of sugarbeets when seeds were planted at six depths during 1987 through 1989. More sugarbeet seedlings emerged and at a faster rate as the depth of seeding decreased from 4.5 to 1.6 cm. Herbicide injury to sugarbeet seedlings increased as depth of seeding increased from less than to greater than 2.5 cm. Herbicide treatments reduced sugarbeet stand and decreased early season sugarbeet height but had little effect on root yield or sucrose content. Nomenclature: Sugarbeet, Beta vulgaris L. Additional index words: Cycloate, diethatyl, ethofumesate.

Five field experiments were conducted at two locations in Virginia during 1988-89 to evaluate DPX-V9360 and CGA-136872 for postemergence control of johnsongrass in field corn grown under no-till and conventional conditions. DPX-V9360 at rates of 35 (except in no-till plots), 52, and 69 g ai ha-1 applied to 8-leaf johnsongrass was 88 to 98% effective in 1988. CGA-136872 at 25, 49, and 99 g ha-1 was 80% effective at the highest rate. Applications of these herbicides to 6-leaf johnsongrass resulted in 69% or less control. DPX-V9360 at 35, 52, and 69 g ha-1 and CGA136872 at 20 and 40 g ha-1 applied to johnsongrass up to 48 cm in height provided 77 to 97% control at 7 WAT3 in an excellent stand of conventionally planted corn during 1989. Crop yields were more than doubled with herbicide treatments relative to yields in control plots. At a second location where crop damage caused by other factors resulted in a weak stand, DPX-V9360 provided 61 to 96% control compared to 29 to 56% control with CGA-136872. Nomenclature: CGA136872, 2-[[[[[4,6-bis(difluoromethoxy)-2-pyrimidinyl]amino]carbonyl]amino]sulfonyl] benzoic acid methyl ester; DPX-V9360, 3-pyridinecarboxamide, 2-(((4,6-dimethoxy-pyrimidin-2-yl)aminocarbonyl))aminosulfonyl)))-N,N-dimethyl; corn, Zea mays L.; johnsongrass, Sorghum halepense (L.) Pers. #4 SORHA. Additional index words: Adjuvant, no-till, conventional tillage, SORHA.

Research was conducted to determine environmental and cultural factors influencing triallate phytotoxicity to hard red spring wheat. Triallate injured ‘Alex’ wheat more than ‘Coteau’ but injury was not influenced by triallate application date. Wild oat control was greater when triallate was applied immediately before seeding compared to 12 d before seeding. Triallate tolerance in wheat did not relate to solid stem characteristic. Injury was highest when wheat was seeded in a 4-cm incorporated triallate layer and least when wheat was seeded below the treated layer. However, triallate injury to wheat was similar at both seeding depths within the 8-cm incorporated triallate layer. Triallate at 1.1 kg ai ha-1reduced wheat fresh weight approximately 33% with a soil at 8 C but over 84% with a soil at 24 C.

The effect of the isopropylamine salt of glyphosate and the ethyl ester of quizalofop on the rhizome bud viability of five quackgrass biotypes was tested. Two bioassays used were: direct measure of the growth of the bud on an agar medium and determination of the respiratory activity with tetrazolium chloride. The response to herbicide treatments differed among biotypes. The growth bioassay showed lower viability than the tetrazolium bioassay. Quizalofop reduced viability more than glyphosate. Viability of untreated buds increased with increasing distance from the base of the rhizome. The viability of herbicide-treated buds was more or less equal regardless of the position. It appeared that both herbicides were translocated to all the rhizome buds.

Selective postemergence herbicides were applied broadcast to control wild-proso millet in soybeans early postemergence (early post), postemergence (post), and late postemergence (late post) when wild-proso millet was 2 to 8 cm tall, 3 to 15 cm tall, and 3 to 31 cm tall, respectively. CGA-82725, fluazifop, haloxyfop, and sethoxydim applied early post controlled 75% or less lateseason wild-proso millet. Intefrow cultivation following early post fluazifop applications improved wild-proso millet control and soybean yields. Higher rates of CGA-82725, haloxyfop, and sethoxydim applied post controlled 91 to 98% late-season millet, but resulting soybean yields were less than the hand-weeded check. Fenoxaprop, fluazifop, fluazifop-P, haloxyfop, quizalofop, and sethoxydim applied late post provided 93 to 99% late-season millet control and soybean yields equal to hand-weeded checks. Wild-proso millet emerging after early post or post herbicide applications contributed to reduced effectiveness from those treatments. However, most wild-proso millet emerged before late post applications and were controlled. Other herbicides including BAS51702, clethodim, cloproxydim, and SC-1084 applied late post also controlled wild-proso millet in soybeans. Nomenclature: BAS-51702, 2-[1-(ethoxyimino)butyl]-3-hydroxy-5-(2Htetrahydrothiopyran-3-yl)-2-cyclohexenl-one; CGA-82725, 2-propynyl 2-[4-j(3,5-dichloro-2pyridinyl)oxy]phenoxy]propionate; clethodim, (E,E)-(?)-2-[1-[[(3-chloro-2-propenyl)oxy]imino] propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one; cloproxydim, (E,EK)-2-[l-[[(3chloro-2-propenyl)oxylimino]butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one; pyridinyl]oxy] phenoxy]propanoic acid; haloxyfop, 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid; quizalofop, (?)-2-[4-[(6-chloro-2-quinoxalinyl) oxy] phenoxy]propanoic acid; SC-1084, 3-hydroxy-4-[4-[[5-(trifluoromethyl)-2-pyr-idinyl]oxy]phenoxy]pentanoic acid; sethoxydim, 2-[1-(ethoxyinino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen1-one; wild-proso miret, Panicum miliaceum L. ssp. ruderale (Kitagawa) Tzevelev. #3 PANMI; soybean, Glycine max (L.)Merr. Additional index words: Application timing, BAS-51702, CGA-82725, clethodim, cloproxydim, fenoxaprop, fluazifop, haloxyfop, quizalofop, SC-1084, sethoxydim, PANMI.

Picloram was applied to leafy spurge using flexible and rigid ropewick applicators for 3 yr at each of two upland pasture sites. The ropewick applicators were a cost-effective way to apply picloram to control leafy spurge compared to broadcast application, but minimal advantage was demonstrated for the segmented, flexible unit compared to the rigid applicator. Picloram applied as an 80 g ae/L solution through ropewick applicators controlled leafy spurge equal to broadcast picloram at 1.1 kg/ha while using 36% as much picloram. Nomenclature: Picloram, 4-amino3,5,6-trichloro-2-pyridinecarboxylic acid; leafy spurge, Euphorbia esula L. #3 EPHES. Additional index words: Selective applicators, rangeland weed control, pasture weed control, EPHES.