Freshly harvested smallflower morningglory [Jacquemontia tamnifolia (L.) Griseb. # IAQTA] seed germinated best after 25 to 60 s of scarification in an electric scarifier equipped with 100 to 120 grit emery cloth. Optimum temperature for germination was 25C. At 10 and 45C no germination occurred for up to 7 days. Eight and 12 days after planting in silt loam soil there was 85 and 98% emergence of smallflower morningglory from depths of 0.5 to 1 cm, whereas no emergence was observed from depths of 6 cm or greater 12 days after seeding.

Butylate [S-ethyl bis(2-methylpropyl)carbamothioate] persistence was compared in three soils that were treated annually with four thiocarbamate herbicides in 1981 and 1982. Butylate degraded faster in soils treated two consecutive years with butylate + dichlormid (2,2-dichloro-N,N-di-2-prophenylacetamide) than in soils treated for 2 yr with EPTC (S-ethyl dipropyl carbamothioate) + dichlormid, cycloate (S-ethyl cyclohexylethylcarbamothioate), vernolate (S-propyl dipropylcarbamothioate) + dichlormid, or from previously untreated soils. Butylate + dichlormid applications in 1981 and 1982 enhanced butylate degradation in 1983 at all locations and reduced weed control at two locations. Previously untreated soil or soil previously treated with two annual applications of butylate + dichlormid was treated with 6 ppmw butylate, incubated for 14 days, analyzed for residual butylate, and bioassayed for herbicide activity. Bioassay indicated higher herbicidal activity than was predicted by the residual butylate concentration. A herbicidally active metabolite may be produced during the soil degradation of butylate.

We studied changes in the concentration of 4-amino-3,5,6-trichloropicolinic acid (picloram) with time in roots, stems, and leaves of 20-day-old seedlings of huisache (Acacia farnesiana (L.) Willd.) and honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell). Exposing root systems to aqueous solutions of picloram (1.0 ppm huisache and 10.0 ppm honey mesquite) for 24 hr killed approximately 60% of the treated plants. In honey mesquite, picloram was redistributed and eventually lost over a 5-day period, whereas neither redistribution nor loss occurred in huisache.

The importance of managing weeds in seminatural habitats that are adjacent to farm fields is unclear. Weedy-margin vegetation may harbor pests or pathogens and may ALSo serve as source populations for ongoing immigration of weeds into the field. It is ALSo possible, however, that margin vegetation provides habitat for organisms that consume weed seeds or suppress the likelihood of pest or pathogen outbreak. We examined the nature of margin habitat using spatial-scaling of Weed-Species richness as an ecological assay. In 2003, we recorded the occurrence of weedy species along the perimeters of 63 fields in Wisconsin. The fields were distributed within six counties that differed in topography, geological history, local climate, and soil type and which spanned the range of variability in the agricultural landscape. We identified seven habitats that differed in geology and land use. The relationship between species richness and margin class was estimated using an analog of the power law. Additionally, we investigated broadscale correlates of habitat heterogeneity at the field level, using a modeling strategy that included additional explanatory factors logically connected to plant diversity. Using a model-confrontation approach, the survey supported the inclusion of two topographical diversity indices, elevation gradient and a field-shape index, into our model. Our broadscale survey provides information on one of a suite of important considerations needed to make decisions about the importance of managing weeds in field margins.

A phytotoxin that inhibited seedling root growth was isolated and purified from rhizomes of quackgrass [Agropyron repens (L.) Beauv.]. Aqueous solutions of the phytotoxin (0.1%, w/v) significantly inhibited the seedling root growth of corn (Zea mays L. ‘New Jersey 8’), oat (Avena sativa L. ‘Clintland 60’), cucumber (Cucumis sativus L. ‘Straight Eight’), and alfalfa (Medicago sativa L. ‘Vernal’). Growth inhibition was not due to extremes of pH or osmotic potential of the inhibitor solutions. The phytotoxin was isolated and purified from a methanol:water extract of dried and ground rhizomes by adsorption and elution from charcoal. A golden-brown, crystalline substance was obtained that was soluble in water, partly soluble in semipolar solvents, and insoluble in nonpolar solvents. Thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) suggested that a single compound was present. Elemental analysis showed that it contained 42.17% carbon, 5.06% hydrogen, 38.28% oxygen, 4.02% nitrogen, 2.03% sulfur, 0.03% chlorine, and 0.03% phosphorus. The compound was tentatively identified as a glycoside with a molecular weight of 460. Its ultraviolet (UV) absorption spectrum showed an intense maximum at 307 nm.

The establishment of common milkweed in corn, soybean, and wheat and rotations of corn-soybean and soybean-wheat was determined in field studies at Rosemount and Morris, MN. Common milkweed seedling density 115 d after initial seedling emergence was 500, 15,000, and 31,300 seedlings ha−1 in corn, soybean, and wheat, respectively, in 1990; 500, 7,300, and 15,600 in 1991 at Rosemount and 2,900, 26,500, and 37,000 in 1990; and 2,200, 6,700, and 8,100 in 1991 at Morris in the year of seedling establishment. Common milkweed seedling defoliation by mon arch butterfly larva was 1,31, and 0% at Rosemount and 20, 78, and 0% at Morris for corn, soybean, and wheat, respectively. In the 2nd and 3rd rotational years, corn-soybean rotations had fewer shoots ha−1 115 d after shoot emergence than soybean wheat rotations. Seedling densities 115 d after initial seedling emergence were greater in corn-soybean rotations where soybean rather than corn was the rotational crop and in soybean-wheat rotations where wheat rather than soybean was the rotational crop immediately following common milkweed seeding. Conventional tillage treatments had lower common milkweed shoot density than conservation tillage in all years of all rotations except in the initial count, when soybean was the first rotational crop in which shoot density was greater in conventional than in conservation tillage treatments. Cyanazine, imazethapyr, or bromoxynil applications in corn, soybean, or wheat rotational crops, respectively, reduced common milkweed shoot density.

Strategies for controlling invasive plants in northern Australian ecosystems must be designed to use limited resources. This paper examines the potential contribution of ecology to develop management strategies for Indian jujube, an invasive shrub in northern Australian tropical woodlands. Its fleshy fruits are dispersed by a variety of birds and mammals. Domestic cattle are the major dispersal vector, whose movements can be controlled at critical times to minimize the risk of new infestations. Containment of Indian jujube must include avoiding cattle movement from infested to weed-free paddocks and from infested to weed-free areas. The species has a capacity to sprout following topkill due to fire or mechanical treatment. This means that current options for effectively treating established plants are limited to the application of herbicides and the more expensive mechanical techniques. In single paddocks, concentrating limited resources on large reproductive plants may be more effective than concentrating on plants spatially peripheral to an infestation. At the property level, the first priority should be to prevent weed-free paddocks from becoming infested, the second should be to minimize increases in lightly infested paddocks, and the third to treat heavily infested paddocks that are major potential sources of new infestations. At the regional level, distributional outliers become important; their control may significantly reduce the length of the front from which local range expansion will occur.

A growth chamber study was conducted to evaluate the effects of temperature and soil moisture on the absorption and translocation of the new sulfonylurea herbicide, MON 37500, in wheat, jointed goatgrass, wild oat, and downy brome. Treatment combinations of temperatures—25/23, 15/13, and 5/3 C—and soil moistures of one-third, two-thirds, and full field capacities were assigned to the germinated plants. Radiolabeled MON 37500 was applied to the second leaf of plants at the three-leaf stage. The plants were then harvested at 6, 24, and 96 h after application. The plants absorbed MON 37500 in the greatest quantity during the first 6 h; however, absorption did continue to increase over time. Absorption was highest in wheat and lowest in wild oat. Temperature influenced absorption, while soil moisture status appeared to have no effect. Translocation of radiolabeled material out of the treated leaf increased over time; however, 90 to 97% of absorbed radioactivity remained in the treated leaf 96 h after treatment. Temperature affected translocation differently in each species, but increasing soil moisture increased translocation.

Soil-active herbicides were investigated for control of live oak (Quercus virginiana Mill.) on the Texas Coastal Prairie and Claypan areas with and without mechanical treatment. Roller chopping before, during, or after herbicide application had very little influence on mortality of live oak compared to the herbicide applied alone. Roller chopping did allow increased grazing of livestock for at least 3 yr after knockdown of the brush. Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} was generally the most effective herbicide for live oak control; bromacil (5-bromo-3-sec-butyl-6-methyluracil), karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1,1-dimethylurea], and picloram (4-amino-3,5,6-trichloropicolinic acid) were somewhat less effective, especailly at 2.2 kg/ha. Limited data suggested that hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl]-1,3,5-triazine-2,4(1H,3H)-dione] also was highly effective for control of live oak. Primary invaders on either mechanically or chemically treated areas were American beautyberry (Callicarpa americana L.), southern dewberry (Rubus trivialis Michx.), boneset (Eupatorium perfoliatum L.), yankeeweed (Eupatorium compositifolium Walt.), brownseed paspalum (Paspalum plicatulum Michx.), and carpetgrass (Axonopus affinis Chase). A herbicide was generally equally effective for live oak control whether applied broadcast or in rows as granules, or applied as sprays to the soil surface or subsurface.

Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] applied early enough for large crabgrass [Digitaria sanguinalis (L.) Scop.] control provided full season goosegrass [Eleusine indica (L.) Gaertn.] control during bermudagrass [Cynodon dactylon (L.) Pers. ‘Midiron’ and ‘Tufcoat’] establishment from sod strips. Prosulfalin {N-[[4-(dipropylamino)-3,5-dinitrophenyl]sulfonyl]-S,S-dimethylsulfilimine}, DCPA (dimethyl tetrachloroterephthalate), pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] and bensulide [0,0-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] gave full season goosegrass control in well-established Midiron bermudagrass, but not during the initial establishment period where open bare soil was present. Napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] provided long term residual control of goosegrass with some interference with rooting of bermudagrass from stolon nodes. Winter survival of Midiron bermudagrass was superior to Tufcoat bermudagrass. Controlling annual grasses permitted superior bermudagrass growth, and winter survival was improved tremendously. Postemergence goosegrass control was obtained with MSMA (monosodium methanearsonate) and methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] when repeated several times during the season. A mixture of MSMA and methazole was superior to either used alone. The rate of bermudagrass establishment was increased through the control of goosegrass with herbicides.

Glyphosate [N-(phosphonomethyl)glycine] consistently controls many winter annual weeds in dormant bermudagrass [Cynodon dactylon (L.) Pers.] but injures actively growing turf. Experiments were conducted to determine the effects of dates of glyphosate treatments on control of winter annuals in different stages of maturity and on the tolerance of bermudagrass when applied to the turf at different stages of greenness from dormant turf in the winter to actively growing turf in the spring. Glyphosate was applied at rates of 0, 0.3, 0.6, 1.1, and 2.2 kg/ha to different plots of winter annuals and bermudagrass at 3-week intervals from February 13 to May 3. Glyphosate at 0.3 kg/ha controlled at least 90% of annual bluegrass (Poa annua L.), spur weed (Soliva sessilis P. & K.), and corn speedwell (Veronica arvensis L.) within a 6-week period regardless of the date of treatment. All glyphosate treatments injured bermudagrass when applied to semi-dormant or actively growing turf. Bermudagrass treated with glyphosate at 0.3 kg/ha was injured the least and the turf had essentially recovered by 6 weeks after treatment. However, the injury from higher rates (0.6 to 2.2 kg/ha) was too severe to be acceptable in turf areas. Glyphosate did not severely injure bermudagrass when applied to dormant turf.

Waterhyacinth [Eichornia crassipes (Mart.) Solms.] was partially controlled with 10.6 nm laser radiation. Radiation levels of < 1 J/cm2 for individually irradiated plants and 69 J/cm2 for group-irradiated plants significantly inhibited growth. Photosynthesis in treated plant-leaf tissue was inhibited about 50% by an exposure level of 4 J/cm2. 14C-labeled compounds fixed by plant-leaf tissue following laser treatment were found to be normally distributed.

Nineteen different genera of weeds encompassing twelve plant families were surveyed for hydrolytic enzymes which were able to metabolize the amide bonds in several groups of herbicides. Propanil (3′,4′-dichloropropionanilide), 1,1-dimethyl-3-phenylurea (fenuron), and isopropyl carbanilate (propham) were employed as enzyme substrates, representing the amide, urea, and carbamate classes. Propanil was hydrolyzed at widely diverse rates by approximately 70% of the plants tested. Only one plant showed a hydrolysis of propham and fenuron. The study demonstrates a widespread distribution of hydrolytic enzymes capable of degrading the herbicide, propanil. An apparent lack of hydrolytic enzymes able to metabolize propham and fenuron was also noted.

The effect of 67 g ai/ha chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-amino] carbonyl] benzenesulfonamide} on Canada thistle [Cirsium arvense (L.) Scop. ♯ CIRAR] root bud growth was examined in a series of greenhouse trials in which potted plants were treated with foliar sprays. Injury to root buds was assayed by determining their ability to form secondary shoots. Added surfactant, 0.2% (v/v) oxysorbic [oxysorbic (20 POE) polyethylene sorbitan monooleate], did not enhance chlorsulfuron-induced inhibition of parent shoot growth, but it increased root bud injury from foliarly applied chlorsulfuron. Cuttings taken from controls formed more secondary shoots than did chlorsulfuron-treated plants 2 weeks following spraying. However, root fresh weight and final secondary shoot growth from cut roots were unchanged 3 weeks after chlorsulfuron treatment compared to the time of spraying. Foliar treatment or a combination of foliar and soil treatment inhibited root fresh weight accumulation and secondary shoot growth equally 1 month following treatment relative to harvest controls. Soil treatment alone did not reduce either root fresh weight gains or secondary shoot outgrowth from root buds. Foliar treatment of vegetative Canada thistle with chlorsulfuron inhibited subsequent secondary shoot outgrowth from root buds more than did treatment at flowering.

Barnyardgrass [Echinochloa crus-galli (L.) Beauv. # ECHCG] spikelets were collected from greenhouse-grown plants at various developmental stages. Caryopses contained in a single spikelet were dormant at maturity, but dormancy was overcome when the spikelets were dry afterripened at 23 C or were treated with high temperatures, acid scarification, or punctured with a scalpel. The season at which anthesis occurred affected the length of time for afterripening. Enhanced germination due to puncturing and scarification was not related to removal of a restriction to water entry. The effectiveness of puncturing in overcoming dormancy depended on moisture content of the spikelets at the time of puncturing. Above 18% moisture content germination percentage was low regardless of the dormancy-releasing treatment.

Pitted morningglory is an adaptable species with an indigenous range encompassing the southern Midwest and southeast United States. In 2000 through 2002, 64 pitted morningglory accessions from 11 states were grown in Fayetteville, AR, to compare their morphology in a common environment to document potential morphological variation and to determine whether variation proves the existence of pitted morningglory morphological ecotypes. Accessions were evaluated for leaf size and vine length 8 wk after emergence (WAE), date of flower initiation, flower color, leaf pubescence 12 WAE, capsule and sepal pubescence, sepal length and width, plant weight, and seed number at physiological maturity. Morphological variables were standardized and analyzed with cluster analysis to differentiate the morphological variation among accessions. Documented variation was best described by eight clusters. Four clusters distinguished themselves morphologically. Accessions within these distinct clusters were originally from Arkansas, Delaware, Kentucky, Louisiana, Mississippi, and Missouri and were documented with leaf size, vine length, and day of flower initiation generally increasing with decreasing latitude. The other four clusters were nondistinct because most variables differed very little, but characteristics such as capsule pubescence separated these clusters. Accessions within these nondistinct clusters originated from Arkansas, Georgia, Louisiana, North Carolina, Oklahoma, and Tennessee. Leaf shapes of arrow, heart, an arrow and heart mixture, and heart with pointed projections and white or purple flower colors were documented. Documented differences indicate the existence of pitted morningglory morphological ecotypes.

The translocation of disodium methanearsonate (DSMA) and amine methanearsonate (hereinafter referred to as AMA) in purple nutsedge (Cyperus rotundus L.) was studied following foliar applications. Tracer techniques with DSMA-14C and chemical analyses for elemental arsenic (hereinafter referred to as As) suggested apoplastic and symplastic movement of both arsenicals. Chromatographic studies of extracts from DSMA-14C-treated plants indicated that the compound was not readily broken down. The carbon-arsenic bond appeared to remain largely intact, although some 14C activity was found in respiratory CO2 several days after treatment. A comparison between the Rf value of the radioactive plant extract to that of standard DSMA-14C suggested that a plant extract-DSMA complex may have been formed. Over 85% of the material applied to the plant remained in the treated shoots. DSMA moved in both acropetal and basipetal directions, and such movement within a single leaf was not influenced by relative leaf age. The arsenicals were not redistributed in the shoot or in the tuber system, but As was accumulated in terminal tubers following repeated applications.

The mode of action of quinclorac was investigated in broadleaf and grass species. Quinclorac induced characteristic auxinlike symptoms in broadleaf species but not in susceptible grasses. In susceptible grasses, quinclorac caused necrotic bands near the zones of elongation in shoots and roots. Electrolyte leakage was induced by quinclorac in smooth crabgrass and other susceptible grasses but not in tolerant grass or susceptible broadleaf species. In smooth crabgrass, increased electrolyte leakage and reduced fresh weight were rate dependent, and initially specific to young tissues. An inhibitory effect on elongation in the youngest leaf of smooth crabgrass and in primary roots of corn was detected 6 and 3 h after quinclorac treatment, respectively. Electrolyte leakage required more than 12 and 6 h in the leaf and root, respectively. Depolarization of corn root cell membrane potential was not observed in a 6-h treatment period. Results presented here provide additional evidence that quinclorac activity differs between susceptible broadleaf and grass species. In addition, the action of quinclorac appears to be similar in both shoot and root tissues of susceptible grasses. It is proposed that quinclorac-induced electrolyte leakage in susceptible grasses is a secondary response and that the primary mechanism of action involves inhibition of an as yet unknown metabolic process associated with cell expansion.

Field studies were conducted near Tifton, GA, from 1995 to 1997 to measure Cyperus esculentus (yellow nutsedge) interference with ‘Fancipack’ Cucumis sativus (cucumber) using a response prediction experiment with a natural infestation of C. esculentus. Cucumis sativus was direct-seeded each year. Plots (1.8 by 1.8 m) were established immediately after crop emergence. Cyperus esculentus plants were counted 2 wk after crop emergence in each plot, at which time four weed-free plots were randomly established. C. esculentus densities ranged from 0 to 955 plants m−2. Total yield, plant biomass, and C. sativus stand were regressed against C. esculentus density and biomass. Regression analysis showed a 5% reduction in C. sativus yield with a C esculentus infestation of approximately 15 plants m−2. A uniform C. sativus stand maximized its competitive ability and minimized interference from C. esculentus. Cyperus esculentus was more competitive and reduced C. sativus yields when C. sativus stands were low and nonuniform.

Eight herbicide postemergence treatments were applied to proso millet (Panicum milaceum L.) at three growth stages. The dimethylamine salt of (2,4-dichlorophenoxy)acetic acid (2,4-D) at 0.56 kg/ha had significantly higher grain yields than the weedy check. All herbicides except the amine of 2,4-D at 0.28 kg/ha appeared to injure proso millet plants by varying degrees; however, yields were not greatly affected. All herbicides gave excellent control of redroot pigweed (Amaranthus retroflexus L.) when applied to proso millet in the 4 to 6-leaf stage. Weed control was poorer when spraying was delayed until proso millet was in pre-boot and post-flower stages.