Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, RO-13-8895 {acetone-O-[d-2-[p-[α,α,α-trifluoro-p-tolyl-oxy]phenoxy] propionyl] oxime}, and KK-80 {4-[4-[4-(trifluoromethyl)phenoxy] phenoxyl]-2-pentenoic} were evaluated for potential use for controlling quackgrass [Agropyron repens (L.) Beauv., # AGRRE] in perennial ryegrass (Lolium perenne L. ‘NK200’), smooth bromegrass (Bromus inermis Leyss. ‘Sac’), orchardgrass (Dactylis glomerata L. ‘Nordstern’), timothy (Phleum pratense L. ‘Climax’), Kentucky bluegrass (Poa pratensis L. ‘Park’), Reed canarygrass (Phalaris arundinaceae L. ‘Rise’), meadow fescue (Festuca elatior L.), and red fescue (Festuca rubra L.). The three herbicides, when applied postemergence at 1.1 kg ai/ha, caused severe injury to all species except red fescue. ‘Pennlawn’, ‘Ruby’, ‘Dawson’, MN67123, MN673, and MN6354 red fescue entries were tolerant to the three herbicides in both greenhouse and field experiments. Sethoxydim and RO-13-8895 effectively controlled quackgrass in Pennlawn red fescue, but KK-80 was not effective.

Cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) at 3 lb/A, 2-chloro-N-isopropylacetanilide (propachlor) at 4 lb/A, and 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) at 4 lb/A were applied by 10 different procedures to moist and dry soil in 2 years. When cycloate was incorporated 3 inches deep in either moist or dry soil, it consistently controlled barnyardgrass (Echinochloa crusgalli (L.) Beauv.) and certain broadleaf weeds and caused only temporary injury to the sugarbeets (Beta vulgaris L.). No method of applying pyrazon and propachlor consistently controlled weeds selectively in sugarbeets. Activity of all herbicides was increased by some means of soil incorporation. Activity was frequently extreme when any of the herbicides was applied as a subsurface layer 1 or 2 inches deep; and sugarbeets, as well as weeds, were killed.

Shade cages admitting three quantities of sunlight were placed in a dense field infestation of Canada thistle (Cirsium arvense (L.) Scop.), and the thistles were sprayed with (2,4-dichlorophenoxy)acetic acid (2,4-D) and with 2,4-D plus glucose in 1968 and again in 1969. Necrosis was greatest under full sunlight and when glucose was added. Regrowth the years after spraying increased with decreasing daylight intensities, but it was not significantly influenced by the addition of glucose. Percentage of necrosis in the year of treatment was not correlated with the percentage of regrowth the following year.

Effects of 4-amino-3,5,6-trichloropicolinic acid (picloram) on mitochondrial volume changes and ATPase activity were studied with isolated barley (Hordeum vulgare L., var. Wong) and safflower (Carthamus tinctorius L., var. U. S. 10) mitochondria. Changes in mitochondrial volume and/or configuration of mitochondrial membranes were recorded in terms of changes in light scattering, which was expressed as absorbance. Picloram caused swelling of mitochondria previously contracted by ATP. Picloram-induced swelling was characterized by a later partial recovery of the mitochondria to a contracted state. Picloram did not affect succinate-induced contraction nor cause any additional swelling of the mitochondria in 0.3 M KCl medium. A high concentration (10−3 M) of picloram enhanced the activity of ATPase by 31%. This result was consistent with an increased rate of picloram-induced swelling in mitochondria contracted earlier by ATP. The action of picloram apparently differs from that of known mitochondrial swelling agents.

Dicamba (3,6-dichloro-o-anisic acid), 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], 3,6-dichloropicolinic acid, picloram (4-amino-3,5,6-trichloropicolinic acid), triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] were applied at rates of 0.3, 0.6, 1.1, and 2.2 kg/ha pre- and postemergence to greenhouse-grown common buffelgrass (Cenchrus ciliaris L. ♯3 PESCI). Buffelgrass tolerated preemergence sprays of 3,6-dichloropicolinic acid up to and including 1.1 kg/ha. All other treatments except picloram and 2,4,5-T at 0.3 kg/ha were phytotoxic to emerging buffelgrass. Buffelgrass tolerated early postemergence applications of 2,4-D, picloram, and tebuthiuron at 0.3 kg/ha; dicamba and 2,4,5-T at 0.6 kg/ha; and 3,6-dichloropicolinic acid at 2.2 kg/ha based on oven-dry shoot production 1 month after treatment. Regrowth of buffelgrass from stubble 1 month after original harvest of the early postemergence treatment occurred only with all rates of 3,6-dichloropicolinic acid and 2,4,5-T at 0.3 kg/ha. When treated at 45 days after planting, buffelgrass tolerated dicamba, 2,4-D, 2,4,5-T, 3,6-dichloropicolinic acid, and picloram at 2.2 kg/ha, but top growth production was significantly reduced by most rates of hexazinone and tebuthiuron. Relative differences in regrowth of buffelgrass 1 month after the original harvest were similar to those of the original harvest. Mature buffelgrass (90 or 150 days old) responded similarly to herbicides as the 45-day-old buffelgrass.

Gibberellin-enhanced response of bean plants (Phaseolus vulgaris L. ‘Black Valentine’) and Canada thistle [Cirsium arvense (L.) Scop.] to bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and glyphosate [N-(phosphonomethyl)glycine] was determined on both species under controlled photoperiods in the growth chamber and on Canada thistle under natural conditions in the field. Pretreatment of bean plants in the growth chamber with 10 mg/L gibberellin (GA3 or GA4/7) more than doubled the herbicidal effect of 1600 mg/L bentazon treatments. Pretreatment of Canada thistle plants in the growth chamber with 100 mg/L GA4/7 increased the herbicidal effect of 50 mg/L bentazon applications more than four-fold, and that of 400 mg/L glyphosate applications by more than two-fold. The phytotoxicity of bentazon to field-grown Canada thistle increased 10% or more in populations pretreated with 25 g/ha gibberellin; and that of 840 g/ha glyphosate was similarly increased. The effectiveness of a higher glyphosate dosage (1680 g/ha) was not significantly increased by GA pretreatment. Plants induced to bolt with gibberellin (GA4/7) were injured more by bentazon than were plants that bolted naturally.

Death of the apical shoot and subsequent compensatory growth from previously inhibited axillary buds is a possible result of POST weed control practices. The objective of this research was to determine the efficacy of glyphosate and lactofen on ivyleaf morningglory, common waterhemp, and giant ragweed during mechanically stimulated compensatory growth. Plants were grown in the greenhouse to a height (or lateral growth) of 15 cm; at which time, the apical shoots were removed by cutting just above the cotyledonary node. Plants were allowed to regrow to 15 cm and treated with lactofen or glyphosate. Herbicide treatments were also applied to intact plants that were 15 cm in height for comparison. Weed response to herbicides during mechanically stimulated compensatory growth varied by weed species and herbicide. Giant ragweed under compensatory growth was less sensitive to both glyphosate and lactofen compared with intact plants. Comparison of GR50 (the herbicide dose that reduced dry weight by 50%) values indicated that ivyleaf morningglory under compensatory growth was 1.5 times more sensitive to glyphosate than intact plants. Conversely, previously injured ivyleaf morningglory plants were less sensitive to lactofen than intact plants. The GR50 for glyphosate applied to intact common waterhemp plants and plants under compensatory growth was similar. However, common waterhemp plants under compensatory growth were more sensitive to lactofen at the three lowest rates evaluated compared with intact plants. In summary, the efficacy of foliar herbicides applied to weeds that exhibit compensatory growth may be different from weeds under a normal growth state.

Foliar applications of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) at 0.05 to 1.0 lb/A caused characteristic injury symptoms on cucumber (Cucumis sativus L.) plants. Analytical methods were evaluated and found suitable in detecting atrazine in cucumber leaves sprayed at a low rate of 0.005 lb/A. For analytical detection, tissue samples should be taken as soon as necrotic symptoms appear, 4 to 7 days after suspected drift, and frozen immediately.

Several field studies have observed increased foramsulfuron efficacy for the control of dallisgrass when foramsulfuron is applied after MSMA. Therefore, laboratory studies were conducted with mature dallisgrass to study the absorption and translocation of 14C-foramsulfuron, and then examine the impact of preliminary applications (preapplications) of MSMA or foramsulfuron on herbicide absorption and movement. Herbicide absorption increased rapidly through 4 h, and by 8 h, differences in absorption between pretreated and control plants were evident. After 48 h, foramsulfuron absorption in non-pretreated plants was 55%, whereas plants that received either pretreatment absorbed 70% of the herbicide. Translocation above (younger tissue) and below (older tissue) the treated leaf was 0.65 and 0.62% for non-pretreated plants, respectively. Pretreatment with foramsulfuron resulted in the translocation of 2.12 and 1.55% of applied radioactivity above and below the treated leaf, respectively. Pretreatment with MSMA resulted in the translocation of 2.33 and 2.34% of applied radioactivity above and below the treated leaf, respectively. These data indicated that pretreatment of mature dallisgrass with either foramsulfuron or MSMA results in an increase in both uptake and translocation of foramsulfuron applied 2 wk after pretreatment. The increase in absorption and translocation of foramsulfuron in the pre–MSMA-treated plants may explain the increase in control observed in the field when comparing it to the pre–foramsulfuron-treated dallisgrass plants.

To determine simazine movement and dissipation in a drip-irrigated Vitis vinifera vineyard under two irrigation schedules [ grower standard (GS) and current evaporation/transpiration (CET)], field experiments were conducted in a Hanford fine sandy loam, a soil type prone to leaching. In experiment 1, simazine was surface-applied in a 1.7-m swath down the vine row, and chloride was applied as a tracer. Total recovery of simazine was < 1.0% under the irrigation emitters 51 and 57 d after simazine application in 1997 and 1999, respectively. Simazine was not detected in the soil profile from 0 to 150 cm deep, 1.0 m from the emitters. A chloride tracer moved to a soil depth of 90 cm but not deeper. In experiment 2, simazine moved 75 cm under the emitters in 7 d but did not move deeper into the soil. Under the emitter, 28% of applied simazine was found 0 to 45 cm deep and 3% was > 45 cm deep. In experiment 3, which was conducted in the absence of irrigation, total recovery of simazine was 30% when sheltered from rain and 8% when exposed to rain. Rapid dissipation and proper irrigation management were key factors preventing deep percolation of simazine in these studies.

Lanceleaved waterplantain is an exotic weed of rice that was introduced into Australia in the 1930s. Since its introduction, it has spread throughout much of the rice-growing region in southeastern Australia. The variability of lanceleaved waterplantain in these regions was studied using polymerase chain reaction-based, inter simple sequence repeat (ISSR) analysis. Deoxyribonucleic acid fingerprints from samples of the weed from southeastern Australia were compared between locations and with two samples of common waterplantain, a closely related species. The analysis indicated that there were two distinct groups of lanceleaved waterplantain that correlated with location. From the results of multidimensional scaling analysis, it is hypothesized that the Griffith group did not arise from hybridization between lanceleaved waterplantain and common waterplantain, and that it is more likely that the group arose from a separate introduction into the area. It is also suggested that there is seed movement between areas in the Murray Valley and Colleambally Irrigation areas. The implications of this variation for biological control of the weed are discussed.

Response of weeds and sugarbeets (Beta vulgaris L. ‘Mono Hy D2′) to preplanting treatments of mixtures of cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) and ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] was evaluated in five field studies. A mixture containing 1.7 kg/ha of each herbicide reduced the stand of common lambsquarters (Chenopodium album L.) 90%, green foxtail [Setaria viridis (L.) Beauv.] and yellow foxtail [Setaria lutescens (Weigel) Hubb.] 97 to 99%, kochia [Kochia scoparia (L.) Schrad.] 64 to 77%, and redroot pigweed (Amaranthus retroflexus L.) 82 to 99%. The response of weeds to preplanting applications of mixtures of cycloate and ethofumesate was independent of soil texture, whereas response of sugarbeets was dependent on soil texture. The herbicide mixtures significantly reduced the pre-thinning stand of sugarbeets and root and sucrose yields on two sandy loams, but not on a clay loam.

An overview of bioinformatics is presented with an emphasis on describing a set of tools, databases, and ontologies useful to the weed science community. These tools can be used to identify genes whose product may be the target site of a herbicide or in the degradation pathway of a xenobiotic. They may identify receptors responsible for pathogen recognition or enzymes in the metabolic pathway for allelopathic compounds. Whatever the gene of interest, bioinformatics allows researchers to assemble complete or partial genes from expressed sequence tags (ESTs), complete cDNAs, or complete genomes and then translate them into their corresponding amino acid sequences. Similarity searches can be used to find other proteins with homology to the gene of interest, which can provide clues to its function from the annotation of these database hits. The use of protein domain databases can also provide insight into the functional capabilities of the protein in question and delineate those portions essential for activity. Enzyme Commission (EZ) numbers or gene ontology (GO) descriptors allow placement of the protein within the larger network context of a biological system. These capabilities allow the scientist to probe deeper into the function of their protein of interest to gain a novel understanding of the biology.

Weeds can infest management-intensive grazed pastures and impact forage quantity, forage quality, and animal health. Common burdock, plumeless thistle, and Canada thistle are three common pasture weeds in the midwestern United States that are managed to avoid these impacts. Experiments were established at two sites to determine if increasing grazing heights from fall through summer would reduce emergence and survival of burdock, plumeless thistle, and Canada thistle seedlings. Five simulated grazing heights (5, 10, 15, and 20 cm and a not-clipped treatment) were implemented in October 2008 and repeated in May through August. Density of all species was reduced from May to September, with reductions ranging from 65 to 78%, regardless of treatment. Treatments that left at least 15 cm of residual grass had reduced densities of burdock and Canada thistle compared to the 10-cm treatment. Regression analysis demonstrated that reduction in burdock and summed planted weed density was related to increased intercepted photosynthetically active radiation from forage in April. However, total biomass yield was reduced up to 60% when grazing heights were increased from 5 to 20 cm, although differences were only observed at the fall and early spring grazing events. Relative forage quality (RFQ) was similar across treatments, except at the third grazing event for which the 15 and 20-cm treatments had reduced RFQ compared with other treatments. Results suggest that increasing grazing heights can reduce emergence and survival of burdock and Canada thistle but can also result in a reduction in forage quantity in the fall and early spring.

Although Russian knapweed is not as widespread as some of the other deep-rooted perennial weeds, thousands of acres of farmland are infested and it is spreading. It is generally called Centaurea repens L., according to Fernald and Stevens, though it also is referred to as C. picris Pall. Stevens states that there is some question about the identity of C. repens.

When one talks about Latin America, one is talking about approximately 200 million people of a variable kind disproportionately divided among 20 republics comprising an area about 2.6 times the size of Continental United States, not including Alaska.

The control of undesirable woody plants is one of the biggest land management problems on non-crop land in the South. There are more than six million acres of pine sites in Louisiana alone that are in need of cull hardwood control (12). Large acreages of similar stands and sites are located in other southern states. Because of the competition for land and increased demand for raw materials, many landowners have realized the necessity of utilizing their land to the fullest extent.

Germination of dormant crabgrass seed, Digitaria ischaemum (Schreb.) Muhl. and D. sanguinalis L., was increased by treatment with the nematocides 1,2-dibromo-3-chloropropane and ethylene dibromide.

The effects of haloxyfop on elongation, mitotic index, and morphology of sorghum and unicorn-plant primary roots were examined. Elongation of sorghum roots was completely inhibited by haloxyfop concentrations of 10–6 M or greater 24 h after treatment, whereas unicorn-plant root elongation was unaffected by the same concentrations 72 h after treatment. Mitotic indices of sorghum roots were reduced by both 10–6 and 10–8 M haloxyfop, with the higher concentration reducing the index to near zero by 24 h of exposure. The mitotic indices of unicorn-plant roots were unaffected by the same levels of the herbicide after both 24- and 48-h treatment. Histological analyses showed that after 24 h exposure to 10–6 M haloxyfop, large vacuoles were present in cells at the root apex that normally did not exhibit these organelles. After 48 h of exposure many cells in the apical region appeared to lack visible cytoplasm and/or nuclei, and by 72 h only cell walls remained visibly evident, and many cells had collapsed. These changes are similar to those that occur in tissues undergoing senescence. Treatment of sorghum roots with 10–8 M haloxyfop did not cause discernible changes after 72 h. Unicorn-plant roots treated with 10–6 M haloxyfop appeared unaffected after 72 h.