Acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} and bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were applied singly, in combination at various rates, with and without a crop oil concentrate to common lambsquarters (Chenopodium album L. # CHEAL), redroot pigweed (Amaranthus retroflexus L. # AMARE), jimsonweed (Datura stramonium L. # DATST), and velvetleaf (Abutilon theophrasti Medic. # ABUTH) grown in containers in the greenhouse and outdoors. Without crop oil concentrate, synergistic responses to the combinations were measured in common lambsquarters and velvetleaf. Antagonistic responses were measured in jimsonweed. Redroot pigweed response was antagonistic in the greenhouse and synergistic outdoors. The addition of a crop oil concentrate tended to mask the interactions. Crop oil concentrate also increased the droplet size for common lambsquarters, velvetleaf, jimsonweed, and redroot pigweed 53, 41, 28, and 27%, respectively. Neither herbicide at any rate or combination influenced droplet size. Radiolabeled studies showed reduced uptake of 14C-acifluorfen when bentazon was present in common lambsquarters and redroot pigweed by 15 and 10%, respectively. Radiolabeled bentazon uptake was reduced 3% in jimsonweed and increased 20% in redroot pigweed when acifluorfen was present.

The effect of site of application on uptake and translocation of the butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoic acid} by quackgrass [Agropyron repens (L.) Beauv. # AGRRE] was investigated using 14C-labeled herbicide and intact plants. Uptake and distribution of the label were significantly greater from the abaxial than from the adaxial surface of leaves. The addition of a nonionic surfactant4 to the treatment solution increased the uptake significantly only through the adaxial surface. Uptake of 14C by the apical, middle, and basal regions of the treated leaf lamina did not differ significantly. However, movement of the 14C-label to stem areas and leaves both above and below treated leaves was greater from lamina base applications than from treatments to the lamina apex and middle. The older leaves absorbed more herbicide than did younger leaves, but the pattern of translocation did not differ. Considerably greater translocation occurred from treatments to the outside of the leaf sheaths in the lower regions of the stem than from applications to the upper leaf sheaths, with the 14C-label moved to young and old leaves, roots, and rhizomes. Uptake from applications to the outside of the upper leaf sheaths also resulted in improved translocation mainly within the stem areas and into upper leaves.

The initial metabolism of acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide] in tolerant and susceptible plants was examined to determine if metabolism is a factor in the selective phytotoxicity of this herbicide. Six crop and ten weed species were used. In every case acetochlor was converted initially to thioether conjugates. In thirteen of the species, initial conjugation was with glutathione (GSH). The homoglutathione (hGSH) conjugate was formed in three legumes. Tolerant plant seedlings metabolized acetochlor more readily than susceptible plant seedlings. Based on these results, acetochlor detoxification is a primary factor in the selective phytotoxicity of this herbicide.

Metabolism of 14C-pronamide [N-(1,1-dimethylpropynyl)-3,5-dichlorobenzamide, carbonyl- 14C] was studied in silt loam soil (located in Louvain-la-Neuve, Belgium) and in lettuce (Lactuca sativa L., ‘Appia′, Clause3) from a crop planted in soil that had been treated before planting. During the experiment, most of the 14C remained in the 0- to 6-cm soil layer. The percentage of 14C-pronamide degraded to 14CO2 during the experiment was less than 10%. The soil-extractable 14C was made up of pronamide and its first ketone metabolite [N-(1,1-dimethylacetonyl)-3,5-dichlorobenzamide]. About 30% of the pronamide present in the soil was bound to the soil. The bound residue, i.e., the 14C that could not be extracted by acetone, at lettuce harvest was about 80% of the 14C contained in the soil at that time; 3,5-dichlorobenzoic acid was the main component of the bound residue. The harvested lettuce also contained pronamide, the ketone, and 3,5-dichlorobenzoic acid. Similar kinetics of metabolism were observed with lettuces grown on loamy sand soil (located in St. Kathelijne-Waver, Belgium). However, pronamide was not bound to this type of soil.

Seed of 41 accessions of Crotalaria representing 35 species were analyzed for the concentration of total pyrrolizidine alkaloids (PAs) and for oral toxicity to 1-week-old chicks. All accessions were assayed for the presence of monocrotaline and spectabiline by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). High concentrations of PA were found in the seed of Crotalaria spectabilis Roth # CVTSP (3.85%), C. retusa L. (2.69%), C. alata Leveille (1.60%), C. quinquefolia L. (1.19%), and C. argyrolobioides Bak. (1.01%). The seed of Crotalaria argyrolobioides produced toxic signs but no deaths when fed at 10 mg/g of body weight, whereas the seed of the other four species were 100% lethal when fed to chicks in one dose at 2 to 6 mg/g of body weight. Seed of other species contained less than 0.6% PA and were nontoxic to chicks fed one dose at 10 mg/g of body weight. Monocrotaline was identified in 17 accessions and spectabiline in 7. No species contained both monocrotaline and spectabiline.

Net (apparent) photosynthesis rate (Pn) of jointed goatgrass (Aegilops cylindrica Host # AEGCY) leaves in the greenhouse became light saturated at a photosynthetic photon flux density (PPFD) of about 1000 μE·m–1-2·s–1 with a maximum Pn of 27 mg CO2 ·dm–2 ·h–1. Diffusive resistance to water vapor (rl) of adaxial leaf surfaces was 43% that of abaxial surfaces, in part, because stomatal density was 50% greater on adaxial leaf surfaces than on abaxial surfaces. Dark respiration rate (Rd) was 1.6 mg CO2 ·dm−2·h−1. Light compensation point (CPl) was 21 μE·m−2·s−1 and CO2 compensation point (CPc) was 32 ppmv. In the field, where light intensity and temperature were greater than in the greenhouse, leaves became light saturated for Pn at a higher intensity, and Rd and CPl were three times greater than in the greenhouse. Pn and Rd of spikes at anthesis were at least 30% less and 200% greater, respectively, than the values for leaves.

Seeds of false cleavers (Galium spurium L.) grown in mid-May germinated 12 to 14 days after planting in central Alberta. The plants flowered from early July to late August and developed fruits from mid-July to early September. Plants from the late-June sowing date developed fruits until early October unless early fall frost killed the plants. Plants from seeds sown after mid-July remained in a vegetative state until late September and did not flower. Seedlings that emerged in August and September survived a mild prairie winter and resumed growth the following spring. Under greenhouse conditions, plant height ranged from 77 to 113 cm and the number of branches at first node ranged from 6 to 14, as plant density decreased from 16 to 1 plant/pot. Shoot dry weight decreased by 50% as plant population doubled, 46 days after emergence. The number of seeds produced/plant decreased from 3500 to 175 as plant density increased from 1 to 16 plants/pot. In growth chamber studies, plant growth was greatest at 20 compared to 16 or 24C.

An accession of velvetleaf (Abutilon theophrasti Medik. # ABUTH) known to be highly tolerant of atrazine [6-chloro-N-ethyl-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine] and a normal susceptible accession were crossed reciprocally. F1 plants were intermediate in response to atrazine, but they were more like the tolerant parent than the susceptible parent. The response of F1 plants was the same for each reciprocal cross, indicating that atrazine tolerance was not cytoplasmically inherited. Response of F2 plants to atrazine was consistent with a ratio of one tolerant: two intermediate: one susceptible. These results and further evaluations of F3 plants indicated that atrazine tolerance was controlled by a single, partially dominant gene.

Artemisinin (qinghaosu), a sesquiterpenoid lactone peroxide constituent of annual wormwood (Artemisia annua L. # ARTAN) that is used as an antimalarial drug, was tested for phytotoxic properties. It inhibited germination of lettuce (Lactuca sativa L.) and annual wormwood, and growth of roots and shoots of lettuce, redroot pigweed (Amaranthus retroflexus L. # AMARE), pitted morningglory (Ipomoea lacunosa L. # IPOLA), annual wormwood, and common purslane (Portulaca oleracea L. # POROL) was inhibited at 33 μM. No effects of 33 μM artemisinin were detected on growth of velvetleaf (Abutilon theophrasti Medik. # ABUTH) and grain sorghum [Sorghum bicolor (L.) Moench.]. Chlorophyll content was not affected in lettuce, and chlorosis was not observed in any species tested. The probable biosynthetic precursors of artemisinin, arteannuin B and qinghao acid, had no effect on growth or chlorophyll content of lettuce; however, they inhibited lettuce seed germination. Artemisinin and cinmethylin {exo-1-methyl-4-(1-methylethyl)-2-[(2-methylphenyl)methoxy]-7-oxabicyclo [2.2.1] heptane} were equally effective in reducing growth of lettuce; however, cinmethylin had no effect on germination. Respiration of lettuce roots or cotyledons was not inhibited by artemisinin. Artemisinin only marginally increased the mitotic index of lettuce root tips at 33 μM. At the ultrastructural level, however, chromosomes were less condensed during mitosis in artemisinin-treated than control meristematic cells. The growth-inhibiting ability of artemisinin could not be reduced by feeding the plants with hydrolyzed protein or treatment with putrescine. Artemisinin is a selective phytotoxin that reduces growth by a mechanism other than mitotic disruption or inhibition of protein synthesis.

Genetic diversity within and among populations of yellow nutsedge (Cyperus esculentus L. # CYPES) was analyzed to evaluate and quantify the genetic consequences of the reported predominance of asexually-produced tubers as colonizing agents. Ten populations were examined using starch gel electrophoresis for allozyme analysis. Four populations of purple nutsedge (Cyperus rotundus L. # CYPRO) were surveyed for comparison. Twelve loci were identified in yellow nutsedge among the eight enzyme systems examined; ten of these loci were found in purple nutsedge. Yellow nutsedge showed relatively low genetic diversity. Most of the genetic diversity occurred as differences among individuals within populations (Hs), compared to differences among populations (Dst) for the four variable loci identified in this species. Thus, most genetic distances between its populations were small. Generally, only a few genotypes occurred within each population. Purple nutsedge was found to possess even lower within- and among-population gene and genotypic diversity. This study supports the view that tubers account for most of the establishment of new populations of both species.

Crownbeard [Verbesina encelioides (Cav.) Benth. & Hook. f. ex. A. Gray # VEEEN (Compositae)] exhibited rapid seedling, vegetative, and reproductive growth. Seed germination under ideal conditions was high and occurred in varying soils except in gravel. It was significantly suppressed under drought and waterlogged conditions and was maximum at 21% moisture regimes. Larger and heavier seeds which exhibited higher germination were produced by the plants growing in open and sand dune habitats. Seedling emergence was highest from surface-sown seeds and least in those sown at 2.5-cm soil depth, beyond which no emergence occurred. High phenotypic plasticity, ecological variability, phenological diversity, seed germination in varied soils and under diverse moisture regimes, quick seedling growth and subsequent establishment, coupled with versatile breeding system, contribute to the successful growth, propagation, and spread of this species in nature in India.

The optimum pH for germination of smallflower morningglory (Jacquemontia tamnifolia (L.) Griseb. # IAQTA] seed was 8.0. A scarification time of 25 to 60 s using a drum scarifier with medium grit provided the best germination, and the optimum temperature for germination was 35 to 40C. However, the optimum temperature for growth was 25 to 35C, with reductions in growth occurring above or below this range. Emergence after 14 days was 81 and 49% at planting depths of 1.5 and 10 cm, respectively. Shade levels of 30 to 92% reduced smallflower morningglory growth by 38 to 87% compared to plants grown in full sunlight.

A 50-yr buried-seed study was initiated at Fairbanks, AK, in 1984. Seed of 17 weed species important in Alaskan agriculture were collected and buried 2 and 15 cm deep. Seed viability was determined initially and after recovery from the soil through a combination of germination tests and 2,3,5-triphenyltetrazolium chloride (TTC) treatments. Seed exhumed at 9 and 21 months were tested for viability and dormancy. Burial depth had a significant effect on seed longevity of corn spurry (Spergula arvensis L. # SPRAR), wild oats (Avena fatua L. # AVEFA), pineappleweed [Matricaria matricarioides (Less.) C. L. Porter # MATMT], and bluejoint reedgrass [Calamagrostis canadensis (Michx.) Nutt.]. Viability was higher for seed buried at 15 than at 2 cm. Viability of shepherdspurse [Capsella bursapastoris (L.) Medik. #CAPBP] and pineappleweed seed did not decrease significantly over the 21-month burial period. In contrast, seed viability of wild buckwheat (Polygonum convolvulus L. # POLCO), common hempnettle (Galeopsis tetrahit L. # GAETE), wild oats, quackgrass [Agropyron repens (L.) Beauv. # AGRRE], and foxtail barley (Hordeum jubatum L. # HORJU) was less than 11% at the end of 21 months. There was no significant relationship between initial seed dormancy and viability after 21 months of burial.

Cotton (Gossypium hirsutum L.) was grown in the presence of common cocklebur (Xanthium strumarium L. # XANST) on a Lucedale fine sandy loam. Cotton was maintained weed free or allowed to compete with common cocklebur for 0, 3, 5, 7, 9, or 11 weeks after planting. Mathematical predictions of seed cotton yield were optimum when maintained free from common cocklebur interference for 8 weeks or more after cotton emergence in 1981 and 1982, and 10 weeks or more in 1980. Common cocklebur adversely affected yield when allowed to compete longer than 4 weeks in 1981 and 1982, and 2 weeks in 1980.

Field, greenhouse, and laboratory studies were conducted to evaluate the performance of starch xanthide (SX), sludge polymer (SP), and coventional formulations (CF) of benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine], oxadiazon {3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H-one}, and prosulfalin {N-[[4-dipropylamino)-3,5-dinitrophenyl] sulfonyl]-5,5-dimethylsulfilimine} for the control of large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] in Kentucky bluegrass (Poa pratensis L.) turf. Turf injury was greatest with SP oxadiazon and prosulfalin formulations, while SX formulations of oxadiazon and prosulfalin caused decreased and /or delayed injury and provided control comparable to conventional formulations. Coarse SX granules containing prosulfalin caused less turf injury than fine granules, while the opposite effect sometimes occurred with SX oxadiazon. Differences in control were observed in the greenhouse when SX benefin formulations which varied in cross-linking agent and/or degree of substitution were compared to the conventional formulation on sandy and silt loam soils. Benefin SX formulations also demonstrated controlled-release properties, which improved large crabgrass control when compared to the conventional formulation in the greenhouse. This effect was short lived on silt loam but persisted on sand. SX granules cross-linked with Fe3+ extended benefin activity longer than H2O2 cross-linked materials on sandy soil only. Release of 14C-labeled benefin from SX matrices was altered by the extent of water imbibition, solvent characteristics, and granule size.

The effect of spray carrier volume on the antagonism of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} by bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] was investigated under greenhouse and field conditions. In the laboratory, the spray droplet overlap between components of a sequential spray application increased from 17 to 50% as carrier volume was increased from 94 to 374 L/ha, respectively. Carrier volume had a significant influence on treatments of sethoxydim alone and sethoxydim sequentially applied with bentazon, but not on the tank mixture of the two herbicides. Carrier volumes of 94 and 187 L/ha used to deliver sethoxydim alone and the sethoxydim/bentazon sequential treatment were superior to the use of 374 L/ha for the control of large crabgrass [Digitaria sanquinalis (L.) Scop. # DIGSA], fall panicum (Panicum dichotomiflorum Michx. # PANDI), and goosegrass (Eleusine indica Gaertn. # ELEIN). There was no difference in grass control between sethoxydim alone and the sequential treatment except at carrier volumes of 187 L/ha or more with which the sequential treatment was less effective. Rates of 0.06 and 0.11 kg ai/ha of sethoxydim were influenced more by changes in carrier volume than 0.22 kg/ha in both the alone and sequential treatments.

Field and greenhouse experiments were conducted during 1984 through 1986 to examine the efficacy of the seed protectants CGA-92194 {α-[(1,3-dioxolan-2-yl-methyl)imino]benzacetonitrile} and flurazole [2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylic acid] for protecting grain sorghum [Sorghum bicolor (L.) Moench.] from alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and propachlor [2-chloro-N-(1-methylethyl)-N-phenylacetamide] injury. In the field, CGA-92194 and flurazole protected sorghum from injury, stand reduction, and yield loss due to alachlor and metolachlor. In general, sorghum was protected with either antidote, and protected response to alachlor or metolachlor was similar to sorghum subjected to propachlor. Greenhouse experiments were conducted to examine the response of bronze and yellow pericarp color to seed protectants, six sorghum hybrids to these antidotes, and the effects of cool soil temperature on the early seedling vigor of sorghum protected with the antidotes. The response of sorghum with yellow and bronze pericarp color was similar when compared across antidotes. However, there were differences among the sorghum hybrids when compared across protectants. The potential of CGA-92194 and flurazole to protect against alachlor injury was reduced when sorghum was grown in cool soil.

Field and laboratory studies were conducted to evaluate the efficacy of several herbicides applied after small-grain harvest on Russian thistle (Salsola iberica Sennen and Pau # SASKR) control and subsequent seed germination. Best postharvest control of Russian thistle was with chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} treatments, paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), and bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) plus metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], where control ranged from 73 to 96%. During the summer-fallow year, chlorsulfuron and paraquat decreased Russian thistle population and biomass compared to the untreated control. Germination of large seeds from plants treated with paraquat and both rates of chlorsulfuron was reduced at least 64% compared to seeds of similar size from untreated plants.

Cucumber [Cucumis sativus L. ‘Calypso′] susceptibility to the ethyl ester of quizalofop {2-[4-[(6-chloro-2-quinoxyalinyl)oxy] phenoxy] propanoic acid} was investigated under field and greenhouse conditions. Cucumber yield was significantly reduced under field conditions with a single or repeated application of quizalofop at 0.14 or 0.28 kg ai/ha. Under greenhouse conditions, quizalofop significantly suppressed cucumber plant fresh weight with or without the presence of an adjuvant. Enhancement of herbicide activity was related to the concentration of adjuvant. At a higher rate of quizalofop, addition of the lower concentration of an adjuvant increased the herbicidal effect (growth suppression and visually estimated phytotoxicity). At a lower concentration, increasing adjuvant concentration enhanced visually estimated phytotoxicity.

The effects of weed control measures in established alfalfa (Medicago sativa L.) on forage yield and quality were investigated at three sites with varying alfalfa densities and weed populations. Herbicide treatments were 0.56 and 1.12 kg/ha metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] applied in fall or spring, respectively, 1.68 kg/ha pronamide [3,5-dichloro (N-1,1-dimethyl-2-propynyl)benzamide] applied in fall, and combinations of these treatments. First-harvest forage yields (weeds plus alfalfa) were either reduced or unchanged by herbicide treatments. Total forage yield was not altered by the herbicide treatments, but first-harvest and total alfalfa yield as well as first-harvest forage protein content were increased by several treatments, depending on stand density and weed pressure. Little effect was observed on in vitro digestible dry matter or acid detergent fiber content.