Experiments were conducted to determine 14C absorption and translocation by oat (Avena sativa L. ‘Lyon’) foliarly treated with 14C-sethoxydim {(2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one)} and various additives. Safflower (Carthamus tinctorius L.), soybean [Glycine max (L.) Merr.], linseed (Linum usitatissimum L.), and sunflower (Helianthus annuus L.) oil all similarly increased foliar absorption and translocation of 14C more than palm oil (Elaeis quineensis Jacq.) but less than petroleum oil, when applied without an emulsifier. An emulsifier in the oil additive tended to enhance 14C absorption and translocation more in soybean oil than petroleum oil so that 14C absorption and translocation were similar with both oils containing emulsifiers. Absorption and translocation of 14C tended to increase more with an increase in emulsifier concentration in soybean oil than in petroleum oil but not beyond 15% with either oil. Percentage of 14C absorbed and translocated from 14C-sethoxydim applied to oats increased as the amount of soybean oil applied increased from 2.3 to 4.6 L/ha, but the increase was less for sethoxydim at 0.87 kg ai/ha than at 0.03 or 0.17 kg ai/ha.

Previous research has shown that haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} and sethoxydim {2-[1-(ethoxyimino)butyl-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} give less control of quackgrass [Agropyron repens (L.) Beauv. # AGRRE] when applied at the five- to seven-leaf stage compared to the three- to four-leaf stage. Current research indicates that reduced control of quackgrass in the eight-leaf stage, compared to the four-leaf stage, was not due to reduced herbicide retention on leaves or to changes in residual herbicide activity in the soil following postemergence applications. The efficacy of both herbicides on rhizome bud kill did not change between the four- and eight-leaf stages following application to the foliage. However, the efficacy of both herbicides on crown tissue bud viability was less at the eight-leaf stage. Rhizome sink intensity (the capacity to accumulate radiolabel) was similar at both stages of development following 14C-haloxyfop and 14C-sethoxydim application to either upper or lower leaves. Crown tissue sink intensity was significantly less at the eight-leaf stage compared to the four-leaf stage following 14C-sethoxydim application to either upper or lower leaves and following 14C-haloxyfop application to lower leaves. These data suggest that crown bud regrowth contributes substantially to reduced control of quackgrass in advanced stages of growth following applications of haloxyfop and sethoxydim.

Tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane] inhibited growth of seedling corn (Zea mays L. ‘DK T 1100’), wheat (Triticum aesetivum L. ‘Arthur’), and sorghum (Sorghum vulgare Pers. ‘DK 42Y’) in growth chamber experiments. These inhibitions were partially circumvented by simultaneous treatment with OTC (L-2-oxothiazolidine-4-carboxylic acid). Tridiphane, atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine], and OTC each increased levels of low molecular weight thiols (glutathione) in intact roots of treated corn seedlings, but only OTC did in excised roots. Tridiphane and atrazine caused a decrease in thiol content of excised roots. Tridiphane treatments reduced the amount of glutathione S-transferase activity extractable from corn roots, and this reduction was circumvented partially by OTC applied in combination with tridiphane. These data present evidence that tridiphane interference with cysteine or glutathione metabolism can be reversed by increasing cellular content of cysteine.

Detached leaves and whole plants of quackgrass [Agropyron repens (L.) Beauv. # AGRRE] were used to study uptake and translocation of butyl esters of 14C-fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, with or without additional adjuvants. In the absence of adjuvants 3.2% of applied radioactivity entered detached quackgrass leaves by 6 h, and at the end of 24 h, 6.0% had penetrated. The presence of additives increased uptake by leaves significantly. In the presence of the nonionic surfactant Agral (nonyl phenol ethoxylate) at 0.2% (v/v) or the oil-additive Actipron (self-emulsifying adjuvant oil) at 2.0% (v/v), 17.2 and 12.9% of applied radioactivity, respectively, entered the leaves by 24 h. Evidence of dependence of phloem translocation of the radioactivity on source-sink relationships of the plant was obtained in the studies with whole plants. Translocation measured up to 7 days after treatment showed that radioactivity was concentrated in areas such as young developed leaves, young stems, and rhizome apices. Rhizomes appear to be major sinks for the accumulation of radioactivity and at 7 days 0.5% of applied radioactivity was found there. In wholeplant experiments the two adjuvants either individually or in mixture increased the uptake of 14C-fluazifop significantly. However, a corresponding increase in basipetal translocation was found only in one experiment. Much of the increased activity that had entered the leaves in the presence of adjuvants was found to have moved to areas distal to the treated zone or remained within the treated zones. In all experiments, applied 14C was not fully recovered. Evidence of significant volatility losses from treated surfaces was obtained and it is thought that this may be the main reason for the inability to recover all of the applied activity.

The herbicide cinmethylin {exo-1-methyl-4-(1-methylethyl)-2-[(2-methylphenyl)methoxy]-7-oxabicyclo [2.2.1] heptane} inhibited oat (Avena sativa L. ‘Porter’) root growth during the first 6 h of treatment at a concentration of 6.7 × 10-8 M. A concentration of 1 × 10-8 M cinmethylin inhibited root growth within 12 to 18 h. Inhibition of shoot growth was less sensitive, but was inhibited by 36 to 48 h after treatment with 1 × 10-7 M and by 12 to 24 h after treatment with 1 × 10-5 M cinmethylin. Cinmethylin concentrations of 1 × 10-5 M and lower did not inhibit cell elongation in isolated oat coleoptiles during a 24-h exposure. Mitotic frequency in oat root tips was reduced after 12 h of treatment with 1 × 10-7 M cinmethylin. The frequency of all stages of mitosis (prophase, metaphase, and anaphase + telophase) was reduced. Concentrations of 1 × 10-6 M cinmethylin resulted in nearly complete arrest (87% inhibition) of mitosis. These data suggest cinmethylin inhibits growth by inhibiting entry of cells into mitosis. The cause of mitotic arrest is unknown; however, the mechanism appears to be different from other herbicides known to inhibit mitosis.

Field experiments were conducted to select winter wheat (Triticum aestivum L.) cultivar(s) that were competitive to downy brome (Bromus tectorum L. # BROTE). Downy brome significantly reduced winter wheat grain yields of all cultivars by 9 to 21% at Lincoln, while at North Platte yield reduction ranged from 20 to 41% depending upon cultivar. ‘Turkey’ was the most competitive cultivar to downy brome but it had the lowest grain yield. Compared to ‘Centurk 78’, ‘Centura’ at Lincoln and ‘SD 75284’ at North Platte proved to be significantly higher yielding and more competitive to downy brome. Winter wheat tiller number, canopy diameter, and plant height were negatively correlated with downy brome yield, but changes in these growth parameters did not always translate into grain yield advantage in downy brome-infested plots. Based on stepwise regression analysis, wheat height was better correlated with reduction in downy brome yield than were canopy diameter or number of tillers.

Ethylene gas stimulated seed germination of the pearl millet [Pennisetum americanum (L.) K. Schum] strain of Striga hermonthica (Del.) Benth. # STRHE) in two soil types in the North Kordofan Region of Sudan. Soils were the noncracking clay pediplain or ‘Gardud’, in Arabic, and the stabilized sand locally called ‘Qoz’. Ethylene at 1.5 kg ai/ha induced greater seed germination (suicidal seed germination) in the Gardud soil than in the Qoz soil. However, ethylene at 3.0 kg ai/ha was better on Qoz than Gardud soil. The effect of injection depth of ethylene was dependent on soil type. Ethylene was more effective when injected at a 15-cm depth in the Gardud soil and at a 30-cm depth in the Qoz soil. The viable population of S. hermonthica seed was reduced by suicidal seed germination at soil depth to 60 cm and to a horizontal distance of 25 cm from the point of ethylene injection. Ethylene-induced germination reduced seed population by 67 and 34% in Gardud and Qoz soils, respectively. A single injection of ethylene diffused up to 300 cm horizontally and up to 60 cm vertically and caused 12.6 and 8.5% reduction in viable 5. hermonthica seed in Gardud and Qoz soils, respectively. The potential of ethylene gas as an effective tool in striga control operations in a pediplain and stabilized sand soil such as is found in N. Kordofan is dependent upon the availability of the gas and the injection apparatus and the economics of its application.

Seedling vernalization was more effective than seed vernalization in promoting flowering of downy brome (Bromus tectorum L. # BROTE). Vernalizing imbibed downy brome caryopses at 3 C for 0 to 30 days did not induce rapid flowering when the caryopses were planted. Downy brome seedlings were exposed for 30 days to six photoperiod/temperature treatments. After subsequent transfer to long days, plants from the short-day/3 C treatment flowered within 30 days. Flowering was delayed or was absent in treatments with higher temperatures or long days. The shoot apex increased in volume during the short-day/3 C vernalization period. Two days following vernalization, floral initiation had occurred. By day 5, lateral organs had proliferated. Rudimentary glumes and lemmas were visible by day 8.

A comparative study of the growth and development of several populations of dinitroaniline-susceptible (DS) and -resistant (DR) goosegrass [Eleusine indica (L.) Gaertn. # ELEIN] biotypes was conducted under noncompetitive field conditions. Plant height and width, number of tillers, aboveground dry weight, relative growth rate (RGR), number of inflorescences/plant, total inflorescence dry weight, individual inflorescence dry weight, number of spicate branches/inflorescence, and flag leaf length and width were recorded periodically during the growing season. There were no significant differences between biotypes in most characteristics with the exception of total inflorescence dry weight. The DS biotype produced more total inflorescence dry weight than the DR biotype at 8 and 13 weeks after transplanting. Significant variation among DS and DR populations occurred in 37 and 33 of 56 evaluations, respectively. When variation existed within a biotype, populations exhibited broad ranges of response for the various growth parameters. With the exception of total inflorescence dry weight, DS and DR biotypes generally exhibited similar ranges of variability.

‘Ransom’, ‘Govan’, and ‘Bragg’ soybeans [Glycine max (L.) Merr.] were seeded in 30-, 61-, and 91-cm row spacings to achieve a uniform population of 323 000 plants/ha. In 1979 and 1980, shade development within the row was similar for all row spacings, but 15 cm from the row the inflection point occurred earlier when soybeans were seeded at the 30-cm row spacing. In 1979, shading 30 cm from the row was similar with the 61- and 91-cm row spacings, but in 1980 the 61-cm row spacing provided earlier shading. Shading within the row and 15 and 30 cm from the row was similar for all cultivars in 1979, but Govan and Bragg shaded row middles earlier than Ransom at the 91-cm row spacing. In 1980, shade development in the row was similar for all cultivars, but delayed shading was observed between the rows with Ransom. In 1979, maximum soybean seed yields were produced with 2, 2, and 0 weed-free weeks at the 30-, 61-, and 91-cm row spacings, respectively. In 1980, 2 weed-free weeks prevented soybean seed yield reductions at all row spacings. In 1979, Ransom, Bragg, and Govan required 4, 2, and 0 weed-free weeks, respectively, for maximum seed yields. In 1980, all cultivars achieved maximum seed yields with 2 weed-free weeks.

The response of wild garlic (Allium vineale L. # ALLVI) to fall and spring applications of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino] carbonyl] benzenesulfonamide} was evaluated in the field in 1982 and 1983. In natural stands, application of 20 g ai/ha in the spring reduced aerial bulblet production by 99%. Applications in the fall were much less effective (20 g/ha reduced aerial bulblet production by 59%), but were still better than the standard treatment of 2,4-D applied in the spring (840 g ae/ha reduced aerial bulblet production by only 45%). In planted stands, chlorsulfuron was applied preemergence at two locations at 10 and 20 g/ha in the fall, and postemergence in early fall, late fall, early spring, and late spring. All treatments reduced aerial and underground bulb production, but spring applications were much more effective than any of the fall treatments. Application of 20 g/ha of chlorsulfuron in late spring (mid-to-late April) reduced aerial and underground bulb production by greater than 95%. At this time the old bulb reserves were exhausted, and the scape and new bulbs were at an early and rapid stage of development.

Field experiments designed to determine the efficacy and interaction of hexazinone [(3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] and nitrogen on weeds and lowbush blueberry [Vaccinium angustifolium (Ait.)] growth and yield were established at five locations in 1980 and 13 locations in 1981. Hexazinone was applied after pruning, preemergence with nitrogen, using a split-block design, with locations serving as replications. Grasses, goldenrod (Solidago spp.), and meadowsweet [Spiraea latifolia (Ait.) Borkh. # SPVLF] were reduced significantly as the rate of hexazinone was increased. Blueberry injury, plant stand, number of flower buds, and yield all increased with increases in hexazinone rate. Variations in blueberry yields occurred among locations due to differences in plant stand and productivity, as well as climatic and edaphic factors. Within each nitrogen rate, increases in the rate of hexazinone resulted in a quadratic increase in blueberry yield. Within the hexazinone treatments, increasing nitrogen had no effect on yield. Blueberry yield reached a maximum of 3926 kg/ha at a hexazinone rate of 1.83 kg/ha. Partial budgeting was used to evaluate the effect of combinations of hexazinone and nitrogen on net income. Response function analysis determined yield and profit-maximizing combinations of hexazinone and nitrogen. Partial budgeting indicated that hexazinone alone or combined with nitrogen increased net income, but nitrogen without hexazinone decreased net income. Response function analysis indicated that hexazinone at 1.79 kg/ha without nitrogen maximized profits.

A 3-yr experiment and a 1-yr experiment in continuous winter wheat (Triticum aestivum L. ‘Newton’) and two 3-yr experiments in continuous grain sorghum [Sorghum bicolor L. (Moench.) ‘Co-op SG-10’ or ‘DeKalb DX-42Y’] were conducted to evaluate selected foliage-applied herbicides for control of honeyvine milkweed [Ampelamus albidus (Nutt.) Britt # AMPAL]. Glyphosate [N-(phosphonomethyl)-glycine] applied at 3.4 kg ae/ha, glyphosate plus dicamba (3,6-dichloro-2-methoxybenzoic acid) applied at 1.7 plus 0.6 kg ae/ha, and glyphosate plus 2,4-D [(2,4-dichlorophenoxy)acetic acid] applied at 1.7 plus 1.1 kg ae/ha in summer between harvesting and planting winter wheat and in spring prior to planting grain sorghum effectively reduced honeyvine milkweed regrowth 1 yr after initial application in both cropping systems. One or two additional annual applications did not provide complete control in either cropping system. Applications of 2,4-D at 2.2 kg ae/ha dicamba at 1.1 kg ae/ha and 2,4-D plus dicamba at 1.1 plus 0.6 kg ae/ha were effective if applied consecutively for 3 yr in continuous winter wheat but not in continuous grain sorghum.

A field experiment was conducted to determine the influence of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] and/or chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl)benzenesulfonamide} on germination, coleoptile growth, and mineral accumulation of seed from treated parent plants. The herbicides were applied postemergence in the spring to ‘Vona’ and ‘Centurk’ winter wheat (Triticum aestivum L.). The rate of metribuzin was 360 g ai/ha, with chlorsulfuron applied at 18, 35, or 70 g/ha. Metribuzin reduced grain yields of both varieties approximately 40%, whereas chlorsulfuron at the higher rates reduced grain yields of only Vona. Seed germination was not affected by either herbicide, but metribuzin, when applied alone, reduced coleoptile growth of Vona seed. The addition of chlorsulfuron to metribuzin eliminated this growth reduction. The mineral concentration of the seed of both varieties indicated that metribuzin and chlorsulfuron did not affect mineral translocation to the seed by the parent plant.

Field experiments were conducted to determine the effects of various densities of four fall-seeded small grain mulches and diphenamid (N,N-dimethyl-α-phenyl benzeneacetamide) on weed control, yield, and quality in no-till flue-cured tobacco (Nicotiana tabacum L. ‘McNair 944’). A greenhouse study investigated the effects of non-soil-incorporated mulch from the same small grains plus alfalfa (Medicago sativa L.) on various growth parameters of tobacco (‘Speight G-70’). None of the mulches used in the greenhouse study adversely affected growth of the tobacco. Mulch from rye (Secale cereale L. ‘Abruzzi’) killed about 2 weeks before transplanting plus diphenamid provided better annual broadleaf weed control (85%) than wheat (Triticum aestivum L. ‘McNair’), barley (Hordeum vulgare L. ‘Keowee’), and no mulch. Oat (Avena sativa L. ‘Brooks’) mulch resulted in 80% broadleaf weed control. There were no differences in annual grass control (which was short lived) among mulches but control was lower in the no-mulch treatment. Rye mulch resulted in a 22% increase in the control of broadleaf weeds compared to no-mulch. Yield of the no-till tobacco did not differ among mulches and averaged 82% of that conventionally grown. The quality was not affected. The rye mulch did not affect the yield or quality of tobacco when compared to a nonmulch, noncultivated treatment. The 18% decrease in the no-till yield was apparently the result of the lack of tillage and increased weed interference and was not due to adverse effects from the rye.

A method was developed for the quantitative determination of trace levels of the widely used herbicide sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} and its metabolites in an aqueous solution using reversed-phase high-performance liquid chromatography (HPLC). Optimum extraction of sethoxydim was with dichloromethane and was only 15% efficient at pH 3. The limit of detection by HPLC for sethoxydim was 5 ng on column and <5 ppb in soil. At least five different compounds were detected in the commercial formulation, in EPA reference standards, and in commercial sethoxydim standards. Sethoxydim undergoes a rapid decomposition in the presence of water to form more polar products, which accounts for the low extraction efficiency. Decomposition was greatest under alkaline conditions. Acid pH and soil inhibited decomposition and gave greater recoveries of parent compound. At least one breakdown product cochromatographed with a known sulfone derivative. The procedures are directly applicable to soils, environmental waters, and plant and animal tissues.

Fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine], pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine], and trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] either alone or in combination with fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, or sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} were evaluated for johnsongrass [Sorghum halepense (L.) Pers. # SORHA] control in reduced-tillage soybean [Glycine max (L.) Merr.] production systems. Data obtained in 1983 and 1984 near Lexington and Princeton, KY, indicated that johnsongrass could be effectively controlled. A single discing before application of the soil-active herbicides usually had no effect on johnsongrass control. Johnsongrass control was primarily dependent on foliarly applied herbicides. Preplant-incorporated treatments did not provide adequate johnsongrass control when used alone. Johnsongrass panicle numbers recorded in September corresponded to visual evaluations of control recorded earlier in the growing season. Soybean yield with all herbicide treatments was greater than with a nontreated control and was closely associated with the degree of johnsongrass control.

The residual effect of three cotton (Gossypium hirsutum L.) herbicide programs, including the use of no herbicides, a minimum program consisting of fluometuron {N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl] urea} and MSMA (monosodium salt of methylarsonic acid), and an intensive program consisting of trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], fluometuron, MSMA, and linuron [N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea], were evaluated from 1976 to 1982. Herbicide injury to wheat (Triticum aestivum L.) and hairy vetch (Vicia villosa Roth.) on three soils showed carryover effects in the following sequence: Sharkey silty clay > Dundee silt loam > Loring silt loam. The intensive program was the most injurious on the Sharkey silty clay. The effects of the two herbicide programs were nearly equal on the Dundee and Loring silt loams. Possible replacement crops for cotton, such as grain sorghum [Sorghum bicolor (L.) Moench.] and corn (Zea mays L.) suffered the least damage from carryover; rice (Oryza sativa L.), soybeans [Glycine max (L.) Merr.] and cucumber (Cucumis sativis L.) suffered severe damage. Greenhouse bioassays generally confirmed field results, and fluometuron appeared to be the major component of carryover.

Field experiments were conducted over a 3-yr period to evaluate the efficacy of herbicides for the control of volunteer Jerusalem artichoke [Helianthus tuberosus (L.) # HELTU] in barley (Hordeum vulgare L.) and on summer fallow. In barley, Jerusalem artichoke was controlled with a single postemergence application of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) at 1 kg ae/ha, or at 0.5 kg/ha when combined with 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 0.5 kg ae/ha. Dicamba (3,6-dichloro-2-methoxybenzoic acid) at 0.2 kg ae/ha plus 2,4-D at 0.4 kg/ha was also an effective combination. Split applications of 2,4-D at 0.4 kg/ha each were more effective than a single treatment at 0.8 kg/ha. On summer fallow, glyphosate [N-(phosphonomethyl)glycine] applied at 0.5 to 2 kg ai/ha, as a single or repeated treatment, provided only marginal control of Jerusalem artichoke during the season of treatment and, in one of three experiments, reduced regrowth in the year following treatment.

In field experiments at Prosser, WA, black nightshade (Solanum nigrum L. # SOLNI), eastern black nightshade (S. ptycanthum Dun. # SOLPT), American black nightshade (S. americanum Mill. # SOLAM), hairy nightshade (S. sarrachoides Sendtner # SOLSA), and sometimes accessions within a species responded differentially to herbicides applied preplant incorporated, preemergence, or postemergence. Also, the response of the nightshades to some of the herbicides varied significantly between years. Generally, black nightshade was more tolerant of herbicides than were the other three species. An accession of black nightshade from England and an accession of eastern black nightshade from Minnesota were the most tolerant of herbicides of eight accessions evaluated. Of the 25 herbicides evaluated, preplant-incorporated applications of ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl) benzenamine] and preemergence applications of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], chloramben (3-amino-2,5-dichlorobenzoic acid), lactofen [1′-(carboethoxy)ethyl 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl] acetamide] controlled all species best. These herbicides reduced the oven-dry weights of both accessions of all four species of nightshades by 93% or more. Nightshades varied widely in their response to the thiocarbamates.