A 7-year ecological study of natural infestations of globe-podded (Cardaria pubescens) and lens-podded (C. chalapensis) hoary cresses was conducted under conditions of irrigation and dry land farming in southern Saskatchewan. Density and area measurements were compared annually in competition with grasses, forbs and shrubs in several environments. The hoary cresses are well adapted to moist situations but are not particularly vigorous in dry, semi-arid environments. Globe-podded hoary cress was better able to survive a period of drought than the lens-podded species. Native roses (Rosa spp.), western snowberry (Symphoricarpos occidentalis) and Russian knapweed (Centaurea repens) were the most effective competitors of the hoary cresses. Alfalfa and to a lesser degree, bromegrass were also effective. As these infestations of hoary cress are situated upstream from the Saskatchewan River Irrigation Project, they constitute a serious threat to many acres of irrigable farmland. Control by cultural means is shown to be feasible.

Early spring or late fall treatments of 2,6-dichlorobenzonitrile (dichlobenil) were effective for the control of several annual and perennial sedges, grasses, and broadleaf weeds in cranberry bogs. Isopropyl N-(3-chlorophenyl) carbamate (CIPC) 2,4-dichlorophenoxyacetic acid 2,4-D and 2-chloro-4,6-bis (ethylamino)-s-triazine (simazine) as spring applications were less effective than dichlobenil for the wide spectrum of weeds encountered. Single spring applications of as much as 4 lb/A of dichlobenil, 6 lb/A of 2,4-D, 24 lb/A of CIPC, and 2 lb/A of simazine were tolerated by the cranberry vines. Dichlobenil at 4 and 6 lb/A caused reductions in upright growth and fruit size. Keeping quality of mature fruit was not adversely affected by herbicidal rates of any of the materials.

The effects of various rates of 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid (endothall), isopropyl N-phenylcarbamate (IPC), and 2-methoxy-3,6-dichlorobenzoic acid (dicamba) on Bromus tectorum L. (downy brome) on four soils with surface litter and incorporated organic matter treatments were studied. Significant differences were found in reaction of downy brome seedlings to the herbicides in the four soils. The soil with the highest organic matter content generally inhibited herbicide action to the greatest extent. Straw mulch alone caused a significant decrease in growth of downy brome seedlings. Action of IPC was most inhibited by straw, and endothall the least.

The growth and development of newly-planted red tart cherry trees on a silt loam soil were satisfactory following six annual treatments of 2.5, 5, and 10 lb/A of 2-chloro-4,6-bis (ethylamino)-s-triazine (simazine) or 2.5 lb/A of 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (diuron). Measurements of tree diameter and leaf area gave no evidence of injury. The control of annual and perennial weeds was excellent. In survey experiments, trees which received 80 lb/A of simazine in 4 years were not injured, but 160 lb/A in 4 years produced leaf injury in the fourth and fifth years.

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 following surfactants were prepared at various concentrations in distilled water, with and without 3% W/V technical or formulated 2,2-dichloropropionic acid (dalapon): anionic—Vatsol OT (sodium dioctylsulfosuccinate), sodium lauryl sulfate; nonionic—Dynawet (chemistry undisclosed), X-77 (alkylarylpolyoxyethylene glycols, free fatty acids and isopropanol), Tween 20 (polyoxyethylene sorbitan monolaurate), Tween 80 (polyoxyethylene sorbitan monooleate), T-1947 (polyoxyethylene polyoxypropylene polyols). Contact angles on paraffin coated plexiglas and corn leaf surfaces correlated well with surface tension measurements. With solutions having surface tensions of 31 dynes/cm or less, leaf wetting was complete. Although surfactants differed considerably in their influence on surface tension and wetting, all markedly enhanced herbicidal activity, increasingly with rate. The superiority of Vatsol OT as a surface tension reducer and wetting agent was confirmed. Vatsol OT alone was toxic to corn at 0.5% concentration and higher; T-1947 and sodium lauryl sulfate produced early injury symptoms at 5.0% but caused no lasting effect; all other surfactants were nontoxic at all concentrations used. Minimum surface tensions and contact angles occurred at 0.1–0.5% concentration for all surfactants. However, maximum herbicidal activity was observed at ten times these levels or greater. Thus above 0.1–0.5% surfactant concentration herbicidal enhancement was not correlated with surface tension lowering, contact angle, observed wettability or initial toxicity of the surfactants. This confirms the view that herbicide-surfactant-plant surface interactions, more specific than mere increased wetting, are a part of total surfactant action.

Herbicidal rates (5 to 9 lb/A) of 2-chloroallyl diethyldithiocarbamate (CDEC) retarded emergence of head lettuce (Lactuca sativa L.) reduced both pre- and postthinning plant populations, caused injury symptoms in young plants, affected the subsequent rate of growth, date of maturity, weight of marketable heads, and yield. Decreased yields were attributed to a reduction in plant population, poor head solidity, and small head development. Reductions in yield were in proportion to dosage and of economic importance.

Metabolic incorporation of adenine-2-14C by Saccharomyces cerevisiae was examined for alterations produced by 3-amino-1,2,4-triazole (amitrole) and histidine. The radioactivity recovered from cells after a 4-hour incubation was found predominantly in ethanol-insoluble components (nucleic acids and proteins) of untreated cultures. Amitrole inhibited incorporation of 14C into insoluble components. Carbon-labeled imidazoleglycerol phosphate, a precursor of histidine, and labeled imidazoleglycerol accumulated in the ethanol-soluble fraction of amitrole treated cells. Imidazoleglycerol accumulated in the external medium. Histidine prevented 14C incorporation into the hot trichloroacetic acid-insoluble residue (protein), prevented amitrole-induced imidazoleglycerol and imidazoleglycerol phosphate accumulation, and circumvented amitrole inhibition of 14C incorporation into the hot trichloroacetic acid-soluble (nucleic acids) fraction.

It was shown that less sprouting of blue oak (Quercus douglasii) and California black oak (Q. kelloggii) occurred when treated stumps were (a) cut 30 cm rather than 90 cm high, (b) treated at once after cutting rather than after 7 days, (c) treated with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) amine rather than with 2,4-dichlorophenoxyacetic acid (2,4-D) amine, and (d) left uncovered rather than covered. The differences between treatments eventually disappeared because of the death of the sprouts, possibly due to the levels of herbicide used in making the treatments.

The downward movement of carboxyl C14-labeled 2,4-D and 2,4,5-T, 3-amino-1,2,4-triazole-5-C14, and C14-labeled urea in interior live oak (Q. wislizenii) stumps was studied. Rainfall, level of 2,4-D applied, and time interval all appeared to influence downward movement.

Dicamba (dimethylamine salt of 2-methoxy-3,6-dichlorobenzoic acid) followed slightly behind the forward penetration of added water in both loam and sandy loam soils. Dicamba persisted longer than 2,4-D butyl ester in autoclaved and not-autoclaved loam and sandy loam soils. Tartary buckwheat, Fagopyrum tataricum (L.) Gaertn. planted at intervals in the autoclaved soils showed no injury from the 2,4-D at 16 oz/A after 4 weeks but was completely killed by dicamba at 8 oz/A after 12 weeks of incubation. In the not-autoclaved soils there was no visible effect on the buckwheat plants from 2,4-D after 2 weeks but nearly all of the plants were killed by dicamba after 12 weeks of incubation. Oxygen consumption in the loam soil was greatly reduced by dicamba at concentrations of 10,000 ppm or higher. Similar concentrations of 2,4-D butyl ester had only a slight and sometimes no effect on oxygen uptake. These concentrations are well in excess of those suggested for selective weed control in grain crops.

A study was conducted to determine the effects of five densities each of rough pigweed (Amaranthus retroflexus L.), green foxtail (Setaria viridis (L.) Beauv.), and combinations of the two upon sugar beet yields, top weights, percent sucrose, and total vegetation weights. Green foxtail was less competitive per plant than rough pigweed. Foxtail densities of less than one plant per beet did not reduce beet yields significantly. Rough pigweed alone or combined with green foxtail reduced the beet root yields significantly at all densities in this study. Root yields were reduced 80 percent by two pigweeds and two foxtails per sugar beet. Beet top weights were consistently higher than those of the roots and were reduced approximately in proportion to those of the roots by the various weed densities. The diameter and length of the sugar beets were significantly reduced by competition, the diameter being more affected than the length. The percent sucrose of sugar beets was not affected by weed competition.

Nemaha oats and 3-amino-2,5-dichlorobenzoic acid (amiben) were effective in reducing weed growth during sweetclover establishment. Hubam and Madrid sweetclover, as well as Nemaha oats, were tolerant of amiben rates necessary for annual weed control. Second-year Madrid sweetclover hay yields were increased from amiben applications the previous year.

Some seeds of Cicuta douglasii (DC.) Coult. & Rose (western waterhemlock), Cuscuta planiflora Tenore (smallseed dodder), Cuscuta indecora Choisy (largeseed dodder), Linaria dalmatica Mill. (Dalmatian toadflax), Asclepias speciosa Torr. (showy milkweed), and Halogeton glomeratus (M. Bieb.) C. A. Mey (halogeton) (brown seeds) still germinated after 12 months of submergence at 12- and 48-inch depths in canal water. Black seeds of halogeton were not viable after 6 months. In another test, 35 percent of the seeds of Polygonum persicaria L. (ladysthumb) remained firm and 24 percent germinated after 5 years. Seeds of Cichorium intybus L. (chicory) and Swainsona salsula (Pall.) Taub. (swainsonpea) were not decomposed and devitalized in toto until after 5 years. No seeds of Avena fatua L. (wild oat), Bassia hyssopifolia (Pall.) Kuntze (fivehook bassia), and Rumex crispus L. (curly dock) sprouted after 6, 18, and 42 months, respectively. No seeds of Salsola kali L. var. tenuifolia Tausch (Russian thistle) and few seeds of Sonchus arvensis L. (perennial sowthistle) germinated after 3 months.

Giant foxtail (Setaria faberii Herrm.) was grown from seed in controlled climate rooms at temperatures of 50, 60, 70, and 80 F and photoperiods of 8, 12, 16, and 20 hours. An inherently poor primary root system resulted in slow and uniform growth during the first few weeks under all environmental conditions. Giant foxtail produced the most dry matter at the highest temperatures and longest photoperiods. No photoperiod inhibited flowering but photoperiod produced differences in development of inflorescences. Within any temperature, the longer the photoperiod the greater the size of panicle and number of seeds produced. Seed viability was high at 80 and 70 F, low at 60 F and zero at 50 F within all photoperiods.

Recrystallized 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 3-phenyl-1,1-dimethyl-urea (fenuron), 1-n-butyl-3-(3,4-dichlorophenyl)-1-methylurea (neburon), 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), 5-bromo-3-isopropyl-6-methyluracil (isocil), and 5-bromo-3-sec-butyl-6-methyluracil (bromacil) were deposited in thin layers on aluminum planchets, irradiated with far, middle, and near ultraviolet light and collected in ethanol. Spectral changes in the ultraviolet region and losses were determined spectrophotometrically. The greatest changes and losses occurred with far ultraviolet and the least with near ultraviolet irradiation. Little or no spectral changes occurred in the dark, but there was some loss of each herbicide.

The extent of adsorption of five C14-labeled s-triazines, 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine), 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone), and 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) from aqueous solutions by soil constituents was expressed as a distribution coefficient (Kd), which is the ratio of the amount of herbicide adsorbed to the amount in the equilibrium solution. The Kd value for a given s-triazine and exchanger remained relatively constant over a range of concentrations. The adsorption reaction was essentially at equilibrium within 1 hour. Increasing the temperature and pH resulted in decreased adsorption of simazine and atrazine. The order of increasing adsorption of these compounds by soils was propazine, atrazine, simazine, prometone and prometryne. Increased amounts of organic matter and/or clay in a soil generally were associated with increased adsorption of these s-triazines. No adsorption of simazine or atrazine was detected with kaolinite. Putnam clay, illite, and montmorillonite were increasingly adsorptive in that order. The organic materials were generally much more adsorptive than the clays. The adsorption reaction was reversible by increasing temperatures, water elution, and elution with various organic solvents. Fifty percent ethanol plus heat was very effective in eluting the chloro-s-triazines from soil.

During a 2-year study corn exhibited relatively good tolerance to flaming at a speed of 4 mph. Soybeans were more susceptible to injury by flaming at early growth stages than was corn. For weed control conventional cultivation and preemergence herbicides were superior to flaming. Damage to crop or weeds was influenced by morphology of the plant, size of plant, adjustment of equipment, number of flamings, and speed or length of exposure.

This study suggests that flame cultivation would not be very competitive in areas where preemergence herbicides and conventional cultivation give satisfactory control of weeds. Although cost of gas would be about equal to cost of herbicide, cost of flame cultivation equipment is about five times greater, and flame cultivation would require 2 to 4 more trips over the field. Flame cultivation may have more potential in the drier areas where preemergence herbicides have been less effective.

The phytotoxicities of three phenylurea herbicides applied annually to cotton at rates used for selective weed control were studied in irrigated soils of the southwestern United States. Yields of seed cotton were generally not affected by annual applications of 3-(p-chlorophenyl-1)-1,1-dimethylurea (monuron) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron). Annual applications of 3-phenyl-1,1-dimethylurea (fenuron) often reduced seed cotton yields. Mild chlorosis of foliage of cotton seedlings was occasionally observed when monuron was used annually. Although diuron affected the growth of oats and barley 6 to 12 months after application, it caused no adverse effect on cotton seedlings. Monuron residues affected barley and oats more severely than did diuron residues. Accumulation of diuron and monuron from annual applications at rates used for selective weed control in cotton appears unlikely.

Giant foxtail (Setaria faberii Herrm.) germinated, emerged, and produced panicles containing viable seeds when sown during the greater part of the growing season. The height of the plant, size of panicle, and number of seeds produced depended on date of planting. Cutting to 2 inches at various stages of growth did not prevent further growth and reflowering but reduced the size of the panicle and the number of seeds. Mowing in May and June allowed giant foxtail to produce two crops of viable seeds.

Methionine-methyl-C14 administered to seedling tissue produces radioactive polymers consisting primarily of protein. Formation of polymer was inhibited within half an hour in susceptible species by 1, 10, and 50 ppm concentrations of isopropyl N-phenylcarbamate (IPC), isopropyl N-(3-chlorophenyl)carbamate (CIPC), methyl N-(3,4-dichlorophenyl)carbamate (swep), and 4-chloro-2-butynyl N-(3-chlorophenyl)carbamate (barban). Resistance to inhibition varied with plant species, and was in accord with previously observed responses in field work. Inhibition of amino acid utilization may be a fundamental cause of carbamate phytotoxicity. Formation of material tentatively described as lignin is also inhibited.