Herbicidal activity of foliar-applied oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] was light dependent in buckwheat (Fagopyrum esculentum Moench. ‘Tokyo’). Plants were not injured when placed in the dark for as long as 4 days after herbicide treatment. When these plants were brought to the light, injury occurred, albeit more slowly than when plants were placed in the light immediately after treatment. The rate of injury increased as light intensity increased. The most effective wave length was 565 to 615 ηm, suggesting the involvement of a pigment with its absorption spectrum in this region. Chlorophyll content was not reduced by oxyfluorfen. Preliminary evidence suggests that photosynthesis was affected only after membrane integrity was disrupted.

Postemergence applications of flufenprop-methyl [methyl-N-benzoyl-N (3-chloro-4-fluorophenyl)-2-amino-propionate] for wild oat (Avena fatua L.) control in spring wheat (Triticum aestivum L.), durum wheat (Triticum durum L.), and barley (Hordeum vulgare L.) were evaluated in the field, greenhouse, and controlled environmental chambers. Wild oat control with flufenprop-methyl was greater at the five-leaf stage than three and one-half or two-leaf stage of growth. Wild oat control was not reduced when flufenprop-methyl was tank-mixed with bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4) 3H-one, 2,2-dioxide]. Tolerance of spring and durum wheat cultivars to flufenprop-methyl was acceptable; however, tolerance of barley cultivars was considerably more variable. Air temperature after treatment, soil fertility, and moisture did not influence wild oat control with flufenprop-methyl; however, a simulated rainfall of 1 mm within 1/2 h or 4 mm within 4 h after application reduced wild oat control.

A phenetic classification of 44 ecotypes of common purslane (Portulaca oleracea L.) produced 4 major groups: cool temperate; warm temperate to wet dry subtropic; humid subtropic to tropic; and cultivated. These groups were based on 36 plant characteristics; the ecotypes were collected from 18 countries and are representative of climates inhabited by common purslane. The cultivated group is comprised of robust forms which are raised for culinary purposes. For weed forms, plants of the cool temperate group were small, prostrate plants with size and growth habit increasing to maximum in the humid subtropic to tropic group.

The effect of glyphosate [N-(phosphonomethyl)glycine] on carbon dioxide. (CO2) levels, ethylene production, and cellulase activity was investigated. Production of ethylene increased within 12 h and CO2 increased within 24 h when 12-day-old bean plants (Phaseolus vulgaris L. ‘Red Kidney’) were treated with 20 mM isopropylamine salt of glyphosate. The CO2 cycled for 3 days and then increased around treated plants. Specific activity of cellulase was increased in debladed bean seedlings that had been pretreated with 20 mM isopropylamine salt of glyphosate. Cellulase enhancement was detected 2 days after the pretreated plants were debladed. Glyphosate-enhanced ethylene production may have increased the cellulase activity.

Studies on the development of leafy spurge (Euphorbia esula L.) were conducted in the field and growth room. Sixteen months after planting in field plots, leafy spurge plants arising from underground bud-producing root segments, transplanted seedlings, or seeds averaged 96, 83, and 136 shoots per plant, respectively, when grown free of interference from other vegetation. A number of plants arising from each source flowered the first year, and all plants flowered and produced seed the second year after planting. When grown in a perennial grass sod consisting of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] and smooth brome (Bromus inermis Leyss.), no plant flowered or produced additional shoots. Soil moisture was less where a dense sod was present. In the growth room, total dry matter of tops and roots was greatest at a soil temperature of 18.3 C or higher, and plant height was greatest at 33.3 C. An early emerging crop might suppress leafy spurge by utilizing the available soil moisture early in the growing season.

The effect of temperatures below 0 C and plant maturity on the phytotoxicity of glyphosate [N-(phosphonomethyl)glycine] on rapidly growing alfalfa (Medicago sativa L. ‘Vernal’) and quackgrass [Agropyron repens (L.) Beauv.] plants was studied in a controlled environment. Pretreatment at −4 C partially protected alfalfa from injury by 0.8 kg/ha of glyphosate at six alfalfa maturities. This same treatment had no significant effect on glyphosate phytotoxicity to quackgrass. Pretreatment at −4 C increased translocation of glyphosate in quackgrass but reduced its translocation in alfalfa. A greater reduction in translocation occurred in the smaller alfalfa plants.

Numerous cations were evaluated as possible substitutes for copper in mixtures with diquat (6,7-dihydrodipyrido[1,2-α:2′,1′-c] pyrazinediium ion) for control of hydrilla [Hydrilla verticillata (L.f.) Royle]. Several cations, including ferrous and ferric iron, when substituted for equal weights of copper in the mixtures, were as effective as copper in enhancing the phytotoxicity of diquat to hydrilla. In most instances, death of the test plants occurred more rapidly when the substitutes were used. Ferric chloride, because of its apparent innocuous behavior in the aquatic environment, is a desirable substitute for the more toxic copper. Bluegill sunfish (Lepomis macrochirus RAf.) were unaffected by week-long exposure to ferric chloride at concentrations as high as 100 ppmw. Since ferric chloride alone exhibited no toxicity to hydrilla in the range of concentrations tested, the greater phytotoxicity of the mixtures probably was due to the increased toxicity of diquat. In evaluations using other species of aquatic weeds, neither the addition of copper nor the addition of other cations increased the phytotoxicity of diquat. In most tests, the mixtures of diquat with other cations reduced the level of activity of diquat on weeds other than hydrilla.

Dalapon (2,2-dichloropropionic acid), TCA ester [ethyleneglycol bis(trichloroacetate)], MSMA (monosodium methanearsonate), and glyphosate [N-(phosphonomethyl)glycine] were evaluated for their effectiveness as spot spray treatments to johnsongrass [Sorghum halepense (L.) Pers.] 30, 75, or 100 cm tall from rhizomes. Glyphosate was also applied as a spot spray to soybeans [Glycine max (L.) Merr. ‘Pickett 71′] to determine its effect on stand losses and subsequent soybean yields. Glyphosate at a concentration of 6 or 12 g/L of water was the most effective treatment regardless of johnsongrass height. A single application provided excellent-to-complete seasonal control within 2 weeks after application. Repeated applications of dalapon, MSMA, and TCA ester would be needed for season-long control. Glyphosate at a concentration of 6 g/L of water applied to 0.5 m long spots of soybeans in late August reduced soybean yields 9, 17, and 28% while the stand was reduced 5,10, and 20%, respectively.

Hydroponic treatment with EPTC (S-ethyl dipropylthiocarbamate) inhibited leaf growth and stimulated stem growth of hybrid corn (Zea mays L. ‘Wisconsin 473′). Root treatment with GA3 (gibberellic acid) prevented leaf stunting from EPTC. Most abnormalities in foliar display and height from treatment with 50 μM EPTC were prevented by increasing GA3 levels from 0.5 μM to 10 μM over a week. The effect of EPTC on endogenous gibberellin activity was measured by bioassay of shoot extracts. EPTC (6.7 kg/ha) reduced the levels of total endogenous gibberellin-like substances in eight-day-old seedlings grown in treated soil. Under the environmental condtions of the experiment, this corresponded to the first discernable signs of injury. In addition EPTC induced an abnormal distribution of endogenous gibberellins in the shoots of older corn plants. Leaves of two-week-old EPTC-treated plants contained less gibberellin activity than the leaves of controls. Stems of herbicide-treated plants contained the same levels of gibberellin-like substances as the controls.

Fall applications of pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] control or suppress quackgrass [Agropyron repens (L.) Beauv.] in established alfalfa (Medicago sativa L.). Studies were initiated to evaluate benefits of pronamide usage in areas where quackgrass is a problem. Alfalfa swards severely infested with quackgrass were treated with pronamide. Forage quality of first cutting alfalfa was significantly improved with pronamide usage, but second and third cutting forage quality was not greatly affected. First cutting hay from pronamide-treated and untreated areas was fed to goats and dairy cows in feeding trials. Animal intake of total forage dry matter, digestible dry matter, and digestible crude protein was increased with pronamide usage. A reduction in need for supplemental protein, an increase in efficiency in dry matter conversion into milk, and a 20% increase in milk production resulted from controlling quackgrass in alfalfa with pronamide.

Viable cutleaf groundcherry (Physalis angulata L. var. angulata) seed were produced 4 weeks after flowering began. Constant temperatures of 10 and 40 C totally inhibited germination. Varying photoperiods had no effect on the germination. Seedling emergence decreased (89% to 0%) as planting depth increased (0 to 10 cm). Greater than 97% preemergence control of cutleaf groundcherry was obtained with metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2 -1,3,4-oxadiazolin-5-one], oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene], and bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate]. Postemergence applications of dinoseb (2-sec-butyl-4,6-dinitrophenol), chloroxuron {3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea}, naptalam (N-1-naphthylphthalamic acid) plus dinoseb, oxyfluorfen, and acifluorfen {sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate} linuron plus 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid], metribuzin plus 2,4-DB, and bifenox resulted in 96 to 100% control of cutleaf groundcherry. When confined to the soybean [Glycine max (L.) Merr.] drill, no significant reductions in soybean leaf area index (LAI), plant height, dry weight accumulation, crop growth rate (CGR), or seed yield were obtained from cutleaf groundcherry competition at densities as high as 60 plants/m of row. Presently, cutleaf groundcherry does not appear to be a major weed problem in soybean production.