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.

The atomization of jet streams from circular orifices, 279, 483, and 1016 microns in diameter, was measured under operating pressures less than 5 psi. The jet streams disintegrated into uniform large drops approximately twice the diameter of the jet orifice, and small drops making up less than 1% of the liquid volume from the small jet. About 80% of the spray from a jet discharging horizontally was deposited in a band 2 inches wide. The distribution pattern of horizontal jet streams positioned on a 2 inch spacing was improved by angling the jet streams 10–15° from the direction of travel.

Enhancement of 3(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) toxicity to oat plants was not dependent on type—anionic, cationic, or nonionic—of surfactant. However, specific surfactant and concentration were important. Concentrations of surfactant above 0.1% were required for consistent phytotoxic effects. Concentration of diuron in solution at time of application was not an important factor in phytotoxicity. Lowering the temperature from 72 to 60 F slowed the expression of toxicity and increased the chances of plant recovery.

In greenhouse experiments high levels of phosphorus tended to suppress growth of soybeans, oats, and foxtail in the presence of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) as compared to controls containing no simazine. However, this relationship was not significant, varying with the soil used in the experiment. Emergence of the seedling was delayed and the concentration of ions in solution increased as phosphorus applications were increased. Mineral uptake by soybean shoots was unaffected by phosphorus or simazine alone, but markedly disrupted in the presence of both simazine and phosphorus. Changes in mineral uptake were typical of effects produced by phosphorus toxicity, indicating that simazine reduced the amount of phosphorus required to produce salt injury.

Anionic and cationic surfactants differentially enhanced the phytotoxicities of four herbicides to corn and soybeans in relation to variations in their structure. Thirteen ionic and two related nonionic surfactants were studied in sprays containing water-soluble forms of 2,2-dichloropropionic acid [dalapon], 2,4-dichlorophenoxyacetic acid [2,4-D], 4,6-dinitro-o-sec-butylphenol [DNBP], and 3-amino-1,2,4-triazole [amitrole]. Effects of surfactant structure, type, and concentration on two other spray properties—surface tension and specific conductivity—were measured at three pH conditions.

Appreciable enhancement of herbicide toxicities occurred only at the highest concentration, 1.0 g per 100 ml (1.0 percent). With straight-chain isomers of an alkylbenzenesulfonate (ABS) anionic surfactant, enhancement of all herbicides increased as the position of the benzene ring was moved to the mid-chain (C5 and C6) carbons of an n-dodecyl alkyl group. DNBP toxicity to both species and surfactant toxicities to soybeans were increased progressively in separate odd- and even-carbon series, i.e. a C1,3,5-series and a C2,4,6-series. Other ABS variations which provided marked enhancement were use of a highly-branched dodecyl alkyl and substitution of an ester oxygen atom for the benzene ring. Among ethoxylated alkylamine cationic surfactants, variations in alkyl structure affected differentially the toxicities of the various herbicides at alkaline, neutral, and acid pH. Surfactants caused marked modification of physical-chemical properties of sprays in relation to their structure and concentration. However, no one of the properties studied could be correlated consistently with the herbicidal effectiveness of a spray. Results suggested that spray performance of herbicide formulations can be improved by using more effective surfactants to achieve other desired formulation characteristics. The increased toxicity of 2,4-D in certain alkaline sprays also suggested that the conditions necessary for absorption of 2,4-D should be examined more critically.

Exposures of trifluralin, α. α, α-trifluoro-2,6-dinitro-N, N-dipropyl-p-toluidine, coated on glass and soil surfaces were made to sunlight and to artificial light from a mercury-vapor source having a wavelength range of 300–700 millimicrons. Ultraviolet absorption spectra of irradiated samples exhibited progressive change with time and intensity of exposure. Exposures on a glass surface to sunlight for four to six hours resulted in a decrease in the plant growth inhibitory activity of trifluralin. Exposures on soil surtaces also indicated that photodegradation occurs, but at a much reduced rate.

A mitochondrial fraction isolated from cotyledons of etiolated Cucumis sativus L. (Burpee's Improved Long Green) showed respiratory activity roughly comparable to that of other reported plant mitochondrial systems. Published procedures on extraction, centrifugation, and determination of cofactor requirements were modified for this system to obtain maximum activity as measured by Warburg manometry. Succinic dehydrogenase activity in the fraction was inhibited by known inhibitors such as sodium azide, DNP, and hydroxymalonic acid; α-ketoglutarate utilization was inhibited by sodium azide.

Dichlobenil (2,6-dichlorobenzonitrile) consistently increased respiration (up to 162% of the controls, using 1.45 × 10-4 M dichlobenil in a succinate substrate mixture); 2,5-diiodo-4-hydroxybenzonitrile (ioxynil) consistently reduced O2 uptake at 0.75 × 10-6 to 0.75 × 10-3 M concentrations. Picloram (4-amino-3,5,6-trichloropicolinic acid) performed in a manner generally similar to the five following substituted benzoic acids: 2,3,6-trichlorobenzoic acid (2,3,6-TBA); 3-amino-2,5-dichlorobenzoic acid (amiben); 3-nitro-2,5-dichlorobenzoic acid (dinoben); 2-methoxy-3,6-dichlorobenzoic acid (dicamba); and 2-methoxy-3,5,6-trichlorobenzoic acid (tricamba). Using succinate as substrate, stepwise inhibition occurred in the range of 10-5 to 10-3 M herbicide; however, the α-ketoglutarate system was much less sensitive to all compounds. For example, the effects of 10-3 M amiben and dicamba on α-ketoglutarate utilization were essentially negligible. Six other herbicides studied showed either no effect or varying degrees of inhibition, depending upon concentration and substrate employed. Dichlobenil uncoupled oxidative phosphorylation at a 1.45 × 10-4 M concentration.

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.

Diuron, 3-(3,4-dichlorophenyl)-1,1-dimethylurea-C14, moved primarily in the apoplast with the transpiration stream, and did not move with the plant assimilates of red kidney bean, soybean, and barley plants. There did not appear to be a species difference in absorption, distribution, and accumulation. Uptake and distribution increased progressively as duration of treatments increased from 6 hours to 16 days. No phloem movement and distribution was observed in the 16-day treatment time. The addition of a surfactant did not alter the translocation pattern of diuron.

The evidence obtained from gross autoradiographs did not eliminate the possibility that very small amounts of diuron may get into the symplast. However, it did indicate that if diuron moved into the symplast, it was restricted and the movement of diuron out of the area of application by phloem was very limited.

Giant foxtail (Setaria faberii Herrm.) was seeded the day the crop was planted and 3, 6, 9, and 12 weeks later. Foxtail that began growing with the crop and was left to maturity reduced corn yields 13% and soybean yields 27%. Foxtail seeded 3 weeks or later after the crop was planted did not cause yield reductions in corn or soybeans. Although not competitive, foxtail seeded 3 weeks after corn was planted produced 500 pounds of dry matter per acre, and all seedings in corn produced seed. Soybeans produced more shade than corn, and foxtail from the 3-week or later seedings in soybeans produced little or no dry matter or seed.

Structural characteristics of surfactants and a herbicide were incorporated in the same molecule by forming long-chain alkylamine salts of 2,4-dichlorophenoxyacetic acid [2,4-D]. In water sprays, all of the 2,4-D salts showed surface activities characteristic of surfactants. The application rate of 2,4-D was held constant at 1/16 lb ae/A; salt concentration was varied by varying spray volume. Seventeen salts were herbicidally active on soybeans at a high concentration (1/16 lb ae in 10 gpa of spray) and a few were also active at a lower concentration (1/16 lb ae in 40 gpa). The remaining thirteen salts were relatively inactive in water. Structural features associated with water-active salts of 2,4-D were those which contribute to hydrophilic characteristics of surfactants. Lipophilic structural features contributed to inactivity in water.

The 2,4-D toxicity of fourteen water-active and water-inactive salts of 2,4-D was maximally and equally elicited in one or more of six water and oil spray systems. Differential activities of the salts permitted their classification into six distinct classes—three hydrophilic and three lipophilic. No one of five solution properties—surface tension, interfacial tension, turbidity, specific conductivity, or pH—could be correlated with herbicidal toxicity of a spray. However, a combination of three properties—interfacial tension, turbidity, and specific conductivity—provided some indication of the relative hydrophilic or lipophilic character of a salt and of the 2,4-D toxicity in different sprays. Data suggested that herbicides move into plants by two distinct pathways—one hydrophilic and the other lipophilic.

The herbicide 3’,4′-dichloropropionanilide (propanil) effectively controlled barnyardgrass [Echinochloa crusgalli (L.) Beauv.], brachiaria [Brachiaria platyphylla (Griseb.) Nash], crab-grass [Digitaria spp.], sesbania [Sesbania exaltata (Raf.) Cory], curly indigo [Aeschynomene virginica (L.) B.S.P.], spikerush [Eleocharis spp.], and umbrellasedge [Cyperus spp.] in the 1- to 4-leaf stages without significant injury to commercial varieties of rice in the 1- to 2-leaf stages. It was ineffective for control of ducksalad [Heteranthera spp.], redstem [Ammannia coccinea Rottb.], morningglory [Ipomoea spp.], sprangletop [Leptochloa panicoides (Presl.) Hitchc.], and red rice [Oryza sativa L.]. Mixtures of propanil and a blended surfactant, containing petroleum sulfonate, free and combined fatty acids, and petroleum oil, and mixtures of propanil and isopropyl N-(3-chlorophenyl)carbamate (CIPC) and methyl 2,4-dichlorocarbanilate (swep), controlled barnyardgrass better than propanil alone. Propanil sometimes injured the rice, but it recovered in 5 to 10 days after treatment and yield and quality were unaffected.

Castorbeans (Ricinus communis L.) are extremely tolerant of the rotary hoe. Its timely use plus cultivation gave effective weed control in castorbeans. The preemergence herbicides, used either alone or in combination, that appeared most promising for selective control of weeds in castorbeans were: 2-chloro-N,N-diallylacetamide (CDAA), dimethyl-2,3,5,6-tetrachloroterephthalic acid (DCPA), ethyl N,N-dipropylthiolcarbamate (EPTC), N-1-naphthylphthalamic acid (NPA), 2,6-dinitro-N,N-dipropyl-alpha, alpha, alpha-trifluoro-p-toluidine (trifluralin), and propyl dipropylthiolcarbamate (R-1607). The most dependable weed control practice in castorbeans was the use of preemergence herbicides in combination with rotary hoeings plus cultivation.

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.

There were usually no significant differences in weed and crop yields between plots receiving aerial and ground applications of herbicides. Where differences were found, aerial application was the more effective.

Soybeans treated preemergence with carboxyl-labeled C14 amiben (3-amino-2,5-dichlorobenzoic acid) were harvested at 7-day intervals. The C14 activity per gram of dry plant matter decreased with later harvest dates but the activity per plant increased over the period. The cotyledons had considerable radioactivity. Both rates contained the same amount of C14 amiben but the soybeans exposed to 6 lb/A contained a significantly higher C14 count than did those exposed to 3 lb/A. All of the identifiable C14 components were amiben.

Most of the activity in soybeans from seed imbibed with C14 amiben remained in the cotyledons. That which did translocate was evenly distributed. Most (98.1%) of the radioactivity in plants grown in treated nutrient solution remained in the roots. Translocated C14 amiben appeared about 8 days after exposure and was evenly distributed in the top of the plant. Plant-respired CO2 had no radioactivity present.

Tissue abnormalities in colonial bentgrass (Agrostis tenuis Sibth.) were observed after foliage applications at normal doses of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2, 4, 5-trichlorophenoxy)propionic acid (silvex), or 4-(2,4-dichlorophenoxy)-butyric acid [4-(2,4-DB)]. They included proliferations of the pericycle, hypertrophic cortical cells, and massed lateral root and root hair formations. The abnormalities usually resulting from phenoxy rates of 1, 1-½, or 3 pounds active per acre were often followed by death of the bentgrass within 20 days after treatment.

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.

Effective control of Artemisia vulgaris L. (mugwort) was obtained with 2,3,6-trichlorophenylacetic acid (fenac) and 4-amino-3,5,6-trichloropicolinic acid (picloram). Dimethylamine salt of 2-methoxy-3,6-dichlorobenzoic acid (dicamba) gave control when applied in April when mugwort shoots were small. Dicamba was less effective later in the season even after clipping to obtain small new shoots. The amount of fenac necessary for effective control was reduced by mixing with dicamba, the butoxyethanol ester of 2,4-dichlorophenoxyacetic acid (2,4-D) or oleyl-1,3-propylenediamine salt of 2,4-D. Late in the season, fenac was more effective when applied after mowing than when applied to large mugwort. Soil incorporated ethyl N,N-dipropylthiolcarbamate and propyl dipropylthiolcarbamate reduced mugwort stands and rhizome weight; however, regrowth occurred in the same season.