Herbicide experiments conducted on flowering size gladiolus corms over a four year period have shown that 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at 1 lb/A pre-emergence and 1 lb/A at lay-by; ethyl N,N-di-n-propylthiolcarbamate (EPTC), 6 lb/A preemergence and 6 lb/A at lay-by; or 3(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) either 1 lb/A preemergence and 1 lb/A at lay-by or 2 lb/A at lay-by appear to be safe and effective herbicides for weed control on varieties Spic & Span, Valeria, Hopman's Glory, Spotlight, Elizabeth the Queen, Friendship, and White Excelsior.

C14-ring-labeled 2-chloro-4-diethylamino-6-isopropylamino-s-triazine (ipazine) was soil-applied to young cotton plants or placed in solution cultures. C14-labeled constituents accumulated in the lysigenous glands of roots, stems, and leaves. Retranslocation of C14-labeled components into new growth after removal of C14-ipazine from solution cultures did not occur. No evolution of of C14O2 by C14-ipazine-treated plants was detected, but evolution of C14O2 occurred from C14-ipazine-treated soil. Some unaltered C14-ipazine was present in leaves and stems sampled 3 months after treatment. No C14-ipazine could be detected in seed formed on treated plants. Free hydroxyipazine did not constitute a major degradation product. However, hydroxyipazine and other basic substances appeared to be released upon hydrolysis of a chloroform-soluble, non-distillable component that accumulated in roots and leaves. An ethanol-insoluble, non-dialyzable component also accumulated in leaves and roots.

The effect of ethyl N,N-di-n-propylthiolcarbamate (EPTC) on photosynthesis was determined by C14O2 fixation by red kidney bean, Phaseolus vulgaris L., leaves following root application of this herbicide in a time-course study at various concentrations of the herbicide. EPTC inhibited C14O2 fixation at relatively high concentrations and long exposures of the herbicide, but did not alter the relative distribution of C14 in the various labeled compounds. The effect of EPTC on the respiration of excised embryos of corn and mung bean (Phaseolus aureus Roxb.) following 24 or 48 hr exposures to the herbicide. When the data were expressed on a fresh-weight basis, it indicated that EPTC stimulated respiration, but the same data expressed on an embryo basis did not show this stimulation. EPTC inhibited the growth and the concurrent increase in fresh weight of these embryos. The effect of EPTC on oxidative phosphorylation was determined with cucumber mitochondria. EPTC markedly inhibited both phosphorus uptake and oxygen consumption. Phosphorus esterification was more sentitive than oxygen utilization: this gave a reduced P/O ratio or an uncoupling effect. However, since the concentration of EPTC required to produce these effects was quite high, the physiological significance of the results is questionable.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) is widely used to control broad-leaved weeds in pea fields. Occasionally, peas are severely injured by MCPA. This study was conducted in 1959 and 1960 to determine the relationships, if any, of environmental factors and of chemical constituents of plants at the time of spraying to the tolerance of peas to MCPA. Plants were equally susceptible to MCPA at either the 5- or 10-node stages. The time of day at which plants were sprayed appeared to be the most important factor associated with the tolerance of pea to MCPA. Fresh weights of vines and yields of shelled peas from plants sprayed at noon and 4:00 pm were significantly lower than those from unsprayed plants or plants sprayed at other times of the day. The carbohydrate content of pea plants varied with the time of day (exposure to light). The carbohydrate content was associated with susceptibility to injury by MCPA. A high carbohydrate content at the time of spraying was associated with a high degree of susceptibility to MCPA. High temperature at the time of spraying tended to increase the rate of translocation of MCPA. However, in the absence of prolonged exposure to light prior to treatment, high temperature alone did not predispose peas to injury by MCPA.

The effect of mono-and dichlorophenyl analogs of N-phenyl-2-methylpentanamide (PMP) and N-(3,4-dichlorophenyl)-alkylamides on the photolytic activity (Hill reaction) of chloroplasts isolated from turnip greens (Brassica spp.) was studied. Photochemical activity was measured potentiometrically with ferricyanide as the electron acceptor. PMP inhibited the Hill reaction by 50 percent (I50) at 4.5 × 10-5 M. Monochlorination in the meta and para ring positions enhanced the inhibitory activity whereas chlorination in the ortho position negated inhibitory activity of the parent chemical (PMP). N-(3,4-dichlorophenyl)-2-methylpentanamide (3,4-DCPMP) was the most inhibitory of the 6 dichlorinated isomers (I50 = 5.8 × 10-7 M). Replacement of the imino hydrogen of 3,4-DCPMP with a methyl group reduced inhibitory activity below that of the unsubstituted parent compound (PMP). Of the straight-chain N-(3,4-dichlorophenyl)alkylamides studied, the propanamide expressed maximum inhibition. 2-Methylalkylamides were more inhibitory than the corresponding straight-chain alkylamides. Maximum inhibition in the branched series was obtained with 3,4-DCPMP. Kinetic studies performed with 3,4-DCPMP at different light intensities indicated that both light and dark reactions were inhibited. However, the light reaction was more sensitive to the effects of the chemical.

The apparent solubility in water of 2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine [ametryne], 3-(3,4-dichlorophenyl)-1,1-dimethyl urea [diuron], and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine [atrazine] was increased when a surfactant was added to the water. At 0.5% surfactant concentrations, considerable variation in solubility was found, both as regards the herbicide and surfactant used, as measured by ultraviolet absorption spectrophotometry. The two triazines were more soluble in cationic surfactants, followed by anionic and nonionic; diuron was more soluble in cationic followed by nonionic and anionic types.

Minimum lethal levels of surfactant in water for 2 week old cucumber plants varied from about 0.1% for the cationic to 0.2% for most nonionic and 1.0% or more for anionics of the alkyl aryl sulfonate type.

The absorption and translocation of labeled herbicides by submersed weeds was studied by sealing the immersed root system in a 60 ml polyethylene bottle and immersing the bottle and shoots in water in a 500 ml graduate. The medium for either roots or tops could be treated without affecting the other. Simazine [2-chloro-4,6-bis(ethylamino-1-C14)-s-triazine] and fenac [2, 3, 6-trichlorophenylacetic acid-1-C14 (mixed isomers)] were absorbed by both roots and shoots of waterstargrass (Heteranthera dubia) and translocated to the untreated portion (root or shoot) of the plant. The distribution patterns of C14-labeled simazine and fenac in bluegills (Lepomis macrohirus) were studied by gross autoradiography. The viscera of the fish contained the greatest amount of activity.

The injurious effects of different rates of fenuron (3-peynyl-1,1-dimethylurea) on four species of brush were recorded for two years in two different types of southwestern brushlands, the Oak-chaparral and the Chihuahuan Desert Shrub. Fenuron was more injurious to fire sprouts than to mature plants of turbinella oak (Quercus turbinella Greene) in the Oak- chaparral type especially at 2 to 8 lb/A ai. The effects of fenuron on mature plants were reduced by burning, suggesting that much of the fenuron absorbed was residual in the stems, twigs, and leaves where it was destroyed by the fire. The effect of fenuron on the fire sprouts changed only slightly between six months and two years. Gibberellic acid was applied to sprouts and mature oak plants appeared to slightly reduce the injurious effects of some rates of fenuron during the first six months but no gibberellin induced differences were observed after two years. In the Chihuahuan Desert shrub type, tarbush (Flourencia cernua DC.) and whitethorn (Acacia constricta Benth.) were about equally susceptible to injury by fenuron with creosotebush (Larrea tridentata (DC.) Cov.) slightly more resistant. Summer applications just before the rainy season were most effective and 4 lb/A combined high shrub kill with greatest grass growth.

Although 8 and 16 lb/A ai killed and injured both grasses and shrubs on the oak plots, grass naturally reseeded into these plots within six months after treatment, but on the Chihuahuan Desert area grass had not recovered on the plots treated at 8 lb/A after two years. This difference in grass re-establishment was probably due to rainfall differences which would give differences in leaching of fenuron. Palatability of the grasses in the oak plots increased due to fenuron treatments, particularly on the heavily treated plots. These studies indicate that moderate rates of fenuron, applied just prior to favorable seasonal rains and repeated at several-year intervals, may be used to control turbinella oak sprouts and mature Chihuahuan Desert shrubs. However, treatments would only be economical where high forage and watershed values would result.

Most of the elongation responsible for barnyardgrass seedling emergence occurred in the first internode. The developing foliar leaves within the coleoptile were the consistent site of EPTC injury. Injury symptoms were never observed in the roots. The first internodes of EPTC-injured seedlings seemed to function normally, although they were sometimes kinked into zig-zag patterns. This kinking was a secondary rather than a direct effect of EPTC injury. Seed germination was not affected by EPTC. Injury occurred after germination. Exposing the seed and primary root to EPTC did not lead to injury, whereas exposing the shoot or only the coleoptile did. It was concluded that leaf tissue is the main site of EPTC uptake in barnyardgrass as well as the prime site of injury.

Herbicide performance was markedly altered by soil incorporation, depth of incorporation, crop seed placement, soil type, and rainfall. Of the 25 herbicides studied, 2-chloro-N,N-diallylacetamide (CDAA) and isopropyl-N-(3-chlorophenyl)carbamate (CIPC) and mixtures of them showed most promise. Herbicide-placement studies showed that the selectivity of these herbicides in cotton largely depends on herbicide placement in relation to the crop seed and on rainfall. Without rainfall, CDAA incorporated in moist soil above the cotton seed provided excellent weed control with minimal injury to cotton. CDAA was readily leached from the zone of germinating weed seed by rain or irrigation on coarse-textured soils. Without rainfall, CIPC was slightly inferior to CDAA in weed control but more stable in performance over a wider range of environmental conditions. Mixtures of CDAA and CIPC were somewhat superior to either alone. Commercial usage of these herbicides in moist soil depends on the development of suitable equipment for application.

Application of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) generally reduced dry weight of tops and roots of corn and Pinus radiata seedlings. Simazine always increased top-root ratios of corn but generally decreased those of pine seedlings. Simazine increased significantly the uptake of N by corn in all soils; of Mg and P in limed, and of K in acidified soils. Aluminum sulfate decreased injury from simazine. Lime at 3 tons per acre mixed into the soil exerted a synergistic effect on the activity of 12 pounds per acre of simazine and killed all pine seedlings in the 7th or 8th week after sowing. The death of the seedlings was. caused by excess calcium ions and not by pH.

Ten herbicides were applied preemergence to proso millet (Panicum miliaceum), three Amaranthus species, and Chenopodium album L. The herbicides were either incorporated or left on the soil surface and plots were either sprinkler or furrow irrigated. The phytotoxicity of some herbicides was increased by soil incorporation and/or sprinkler irrigation. Some were unaffected by method of irrigation, and others were not affected by incorporation. Grass and broadleaf weed control were affected differently by incorporation and irrigation. When incorporated with furrow irrigation, five herbicides developed weed control patterns indicating a movement similar to salt movement. A more complex pattern occurred with non-incorporated herbicides.

Foliar applications using volumes of 100 to 500 ml per acre were used to determine the effect of droplet size on herbicide toxicity to five plant species. Several types of plant response were used to indicate effectiveness. Herbicide toxicity increased as the particle diameter decreased from 0.3 mm to 0.1 mm.

Three-quarter inch seedlings of northern nutsedge (Cyperus esculentus L.) were transplanted into the field where numbers of plants, inflorescences and the rate of spread were recorded. Seed was collected from each plot and germination tests conducted. During one growing season, a single seedling developed into a stand of plants that produced a yield of 90,000 seeds with a germination of 51%.

Rhizome sections of ironweed from which the fleshy roots had been pruned made less than half as much growth in the greenhouse as sections which had three inches of fleshy roots attached. Rhizome sections at least two inches long with portions of the fleshy roots intact should be used for asexual reproduction of ironweed. Ironweed plants in the field after 8 and 9 years of mowing treatments at 2 dates were approximately ⅔ as tall as untreated plants. No significant reduction in stand was obtained by 9 successive years of mowing.

In tests conducted from 1951 to 1961 in the Peace River section of Alberta, 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) was applied to vigorous quackgrass (Agropyron repens (L.) Beauv.) sods on different soils. These tests showed: 1) tillage either before or after application of monuron strongly reduced its effect; 2) when used without tillage it did not matter whether monuron was applied in the early summer or early autumn, but when used with tillage it was best applied in the early summer; 3) 40 lb/A applied without tillage eradicated quackgrass under all conditions except when it was established in an unusually deep and loamy soil; 4) killing quackgrass by monuron usually took 2 years; and 5) lethal rates of monuron prevented quackgrass re-establishment for from 1 to 7 years and satisfactory growth of cereal crops for 10 years or more.

The disodium salt of 3,6-endoxohexahydrophthalic acid (disodium endothal) and the derivative identified by the manufacturer as the di-N,N′-dimethylococoamine salt of endothal (coded as TD-47) were particularly effective upon submersed species of aquatic vegetation as contact herbicides. Disodium endothal at concentrations of 0.5 to 10.0 ppmw was effective in controlling approximately 50 per cent of the 19 species of plants involved in 270 tests. TD-47 at concentrations of 0.02 to 10.0 ppmw trolled 77 per cent of the 11 plant species in 94 tests.

Algae (Chara, Cladophora, Pithophora, and Spirogyra) were more effectively controlled by TD-47 than by disodium endothal. Although TD-47 was at least 10 times more herbicidal than disodium endothal, it was about 100 times more toxic to fish. Disodium endothal was more than 50 per cent effective on submersed aquatic plants at rates in excess of 2.5 ppmw with a wide margin of safety in fish (4- to 10-fold). Disodium endothal had a median tolerance limit ranging from 95 to 150 ppmw in the aggregate of nine fish species tested extensively. Median tolerance limits for TD-47 ranged from about 0.06 to 0.3 ppmw for five species of fish. TD-47 applied at a concentration lethal to fish (0.3 to 1.0 ppmw) was effective as a dual management tool in controlling vegetation and achieving partial or complete renovation of stunted fish populations.

Young, growing vegetation was most susceptible to control, and best results were achieved at water temperatures exceeding 60 F. Higher rates were required to kill plants as they matured and stands became dense. Endothal liquid formulations were superior to granules in controlling algal mats, floating and emergent plants. Granules were more effective on submersed rooted plants.

TD-47 residues were of short duration. The rate of disappearance depended on time and concentration. Detectable residues disappeared within 8 days following application of 0.3 ppmw and within 2 weeks for 0.6 ppmw. However, 1.0 to 3.0 ppmw took up to 25 days to disappear. Some residues were found in fish-food organisms from treated enclosures 3 weeks after application. Fish flesh showed no absorption of endothal-armeens at sublethal concentrations. Intraperitoneal injection of endothal into fish produced a disturbance of the osmoregulation. The physiological effect of endothal was measured by chemical analysis of blood serum.

Isopropyl N-(3-chlorophenyl)carbamate (CIPC), 2-chloroallyl diethyldithiocarbamate (CDEC), ethyl N,N-di-n-propylthiolcarbamate (EPTC), sodium 2,4-dichlorophenoxyethyl sulfate (sesone), and N-1-naphthylphthalamic acid (NPA) controlled Amaranthus palmeri S. Wats., (Palmer amaranth) Echinochloa colonum (L.) Link, (junglerice) and Sorghum vulgare Pers. var. sudanense Hitchc. (sudangrass) more efficiently when applications were followed by overhead irrigation, except in a few instances where weeds were controlled regardless of the irrigation method. More CIPC, sesone, CDEC, and EPTC penetrated below ¼ inch into soils, and they penetrated deeper with overhead irrigation.

During the vegetative phase of barnyardgrass (Echinochloa crusgalli (L.) Beauv.) development, the leaves, axillary buds (tillers) and permanent root system were initiated and developed. First adventitious roots appeared on the 6th day after germination. Internode elongation, which was coincident with a change from a vegetative phase to a reproductive phase of the plant, was observed in the field about 30 days after germination. At this time the main stem had 4–5 maturing leaves. Typically, barnyardgrass formed 8 leaves on the main axis from primordia which were initiated during the first two weeks after germination. The first tiller primordium appeared in the axil of either the 1st or 2nd leaf on the day of emergence from the soil. In the field, tillering was observed from the twelfth day. Heading began on the 40th day and the first mature seeds were formed about 64 days after germination.