Doses of 1-(2-methylcyclohexyl)-3-phenylurea (siduron), sprayed on seeds of several forage, turf, and weed grasses on the soil surface killed some weed grasses without injuring many desirable grasses. Seeds of tolerant grasses mixed with an excess of a dry siduron formulation and stored for 12 months germinated without injury, but crabgrass (Digitaria sanguinalis (L) Scop.) and barnyardgrass (Echinochloa crusgalli (L.)) were killed during germination. Siduron eliminated seedling weed grasses from seedling perennial turfgrasses when applied on the soil surface or incorporated in the soil just before planting. When applied as a coating on seeds of turfgrasses at planting time, siduron controlled some annual weed grasses without injurying the turfgrasses. Herbicidal action appeared to be localized mainly in the grass roots and differed from that of 1,1-dimethyl-3-phenylurea (fenuron) and isopropyl carbanilate (propham) applied at equimolar doses.

The toxicity, leachability, and site of uptake of the herbicide 2-chloro-2',6'-diethyl-N-(methoxymethyl) acetanilide (hereinafter referred to as CP 50144) were studied in different soils. Two inches of water leached most of the compound to a soil depth of 2 to 3 inches, when applied at rates of 1 and 2 kg/ha. The inherent toxicity of CP 50144 to cotton (Gossypium hirsutum L., var. Acala 4-42) was studied in culture solution. The herbicide was most toxic to cotton when the entire root system of the crop was exposed to soil treated with CP 50144; reduction of weight of seedlings was accompanied by severe inhibition of root growth. On the other hand, only a slight reduction in growth rate was noticed when only the shoot zone of cotton was exposed to the herbicide.

A bioassay standard curve injury rating, using cucumbers (Cucumis sativus L.) as the indicator plant, was developed for quantitatively determining soil residues of 5-bromo-3-sec-butyl-6-methyluracil (bromacil), 6-dichloro-o-anisic acid (dicamba), 3(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), (2,3,6-trichlorophenyl)-acetic acid (fenac), 4-amino-3,5,6-trichloropicolinic acid (picloram), and 2,4-bis(isopropylamino)-6-methoxy-s-triazine (prometone). The herbicide concentrations ranged from 0.001 to 2.187 ppmw. The presence of all the herbicides could be detected at 0.009 ppmw and the herbicides killed cucumbers at 2.187 ppmw. Cucumbers could be used to effectively measure a greater concentration range of fenac than the other herbicides. A highly significant negative correlation existed between injury rating and fresh plant weight. However, concentrations of the herbicides were more easily detected by a visual injury rating on abnormal growth characteristics than by fresh plant weight.

Naturally-established individual specimens of 12 woody plant species occurring in North Carolina were treated with foliar, dormant stem, and basal applications of the propylene glycol butyl ether ester formulation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), the propylene glycol butyl ether ester of 2,4-dichlorophenoxyacetic acid (2,4-D), and the potassium salt of 4-amino-3,5,6-trichloropicolinic acid (picloram). The triethanolamine salt of 2,4,5-T also was applied as a foliar treatment. Three rates of each herbicide were used. Responses measured were percent control of original shoots, percent regrowth, shoot height, and number of live stems per plant. No differences were observed between the amine and ester formulations of 2,4,5-T applied as foliar sprays except on rhododendron (Rhododendron maximum L.) where the ester produced 86% control compared to 28% for the amine salt. Foliar sprays of picloram were effective in controlling all species except white ash (Fraxinus americana L.), sweet gum (Liquidambar styraciflua L.), sweet bay (Magnolia virginiana L.), and rhododendron. Control of these species averaged only 45% compared to 96% on all other species studied. No species was effectively controlled by dormant stem or basal applications of picloram. All species considered, the propylene glycol butyl ether ester of 2,4,5-T applied as a dormant stem or basal application provided the most consistent results, giving 89% and 91% control, respectively.

During the planting of alfalfa (Medicago sativa L.), ethyl N,N-dipropylthiocarbamate (EPTC) was applied in subsurface bands beneath the legume seed and each of three triazine herbicides or EPTC was placed in subsurface bands between the rows. Triazines used were 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), 2-chloro-4-ethylamino-6-isopropylamino-5-triazine (atrazine), and 2-isopropylamino-4-methoxyethylamino-6-methylmercapto-s-triazine (hereinafter referred to as G-36393). EPTC applied between and within the rows, as well as simazine between the rows and EPTC within the rows, gave superior weed control with little chronic effect on alfalfa. Alfalfa yields following both treatments were increased. Other treatments were unsatisfactory because of poor weed control or because of serious damage to alfalfa.

The hydrogen bonding of 2,2-dichloropropionic acid (dalapon) to N-methylacetamide (NMA) as a model protein was studied using infrared spectra. Changes in the spectra indicated that the dalapon carboxyl-OH, hydrogen bonds significantly to the model amide carbonyl.

The herbicide O-(2,4-dichlorophenyl) O-methyl isopropylphosphoramidothioate (DMPA) contains an asymmetric tetracovalent phosphorus. The d-isomer is much less active and the l-isomer more active than dl-DMPA in inhibiting seedling grass growth. Furthermore, low levels of dl-DMPA stimulate root growth of seedling wheat (Triticum vulgare L., var. Soft winter).

Discs of potato (Solanum tuberosum L.) tuber tissue were immersed in buffered (pH 4.0 to 8.0) solutions of 4-amino-3,5,6-trichloropicolinic acid (picloram) (5 × 10−4M to 5 × 10−3M) for 1 to 36 hr. Uptake of picloram during incubation, and leakage after return of the discs to untreated buffer, were determined by gas chromatographic analysis of extracts of the tissue and ambient buffer. Picloram absorption increased with concentration and with time up to 24 hr. Maximum uptake occurred at pH 4.0 and very little picloram was absorbed at pH 7.0 and 8.0. Both absorption and leakage were temperature dependent. The rate and extent of leakage was greatest at the highest concentration. Typically, more than 90% of the picloram absorbed from 5 × 10−3M was lost to fresh buffer within 12 hr.

On Tifton loamy sand, N-1-naphthylphthalamic acid (naptalam) controlled weeds much better, and injured soybeans [Glycine max (L.) Merr.] much less, when mixed with 2-sec-butyl-4,6-dinitrophenol (dinoseb) and applied as a delayed preemergence treatment, than when it was applied alone immediately after planting. Differences attributable to either timing of application or to mixing with dinoseb were not as marked for 3-amino-2,5-dichlorobenzoic acid (amiben) as for naptalam. Neither amiben, naptalam, nor mixtures of these two herbicides with dinoseb adversely affected germination, weight per seed, or total oil and protein content of the harvested soybean seed.

We studied the inactivation of herbicides applied to the soil by activated carbon in the greenhouse and field. Degree of inactivation depended upon herbicide type, dosage, plant species, and quantity of activated carbon applied. In greenhouse experiments with Toa silty clay, 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine) was inactivated at activated carbon: herbicide ratios of 66:1, whereas 4-amino-3,5,6-trichloropicolinic acid (picloram) required ratios of 3600:1. Beans (Phaseolus vulgaris L., var. Black Valentine) were used as a bioassay. In the field, activated carbon rates up to 600 lb/A did not completely prevent injury to oats (Avena sativa L., var. Markton), cucumbers (Cucumis sativus L., var. Ashly), and Black Valentine beans by propazine at 2.5 lb/A in Toa silty clay 0, 37, 72, and 93 days after herbicide application. Activated carbon protected oats from picloram at 0.5 lb/A but did not completely protect cucumbers or beans at rates up to 600 lb/A. Activated carbon in untreated herbicide soils was not harmful to growth of beans, oats, and cucumbers in Toa silty clay.

Light from sunlight, incandescent, and fluorescent sources was filtered through fresh tobacco (Nicotiana tabaccum L.), corn (Zea mays L.), and soybean (Glycine max (L.) Merrill) leaves. The spectral quality of the leaf-filtered light showed that much more of the incident red energy was absorbed than the far-red. The effect of the leaf-filtered light on the phytochrome-controlled germination of six weed species was generally to inhibit germination of seeds given a stimulatory pre-irradiation of red light from a standard source. Germination of seeds with no pre-irradiation was either not promoted or promoted to various degrees. Unfiltered light, at intensities equivalent to those under the leaf filters, caused no comparable effects. These results indicate an effect of altered spectral quality of the leaf-filtered light on the ratio of inactive/active phytochrome (Pr/Pfr) in the underlying seeds. We suggest that such phenomena could influence the germination of weed seeds in the field.

The influence of repeated clipping of the shoots on the translocation of 14C-assimilates and 2,2-dichloropropionic acid 2-14C (dalapon) into the rhizome system of established johnsongrass (Sorghum halepense (L.) Pers.) was studied when regrowth was in the preboot, boot, and flowering stages. Radioautography and radio-assay procedures were used to follow the distribution of label within the plants. Plants defoliated three times prior to treatment showed no increase in basipetal translocation over plants defoliated once. As plants matured to the flowering stage, assimilate translocation into rhizomes increased. This increase was closely related to the degree of secondary rhizome growth occurring at time of label application. During preboot, assimilate movement was restricted to rhizome apices with very little retention in intervening tissue. Labeled dalapon followed a similar translocation pattern to that of assimilates. The role of assimilate translocation and storage as correlated with life cycle changes in carbohydrate nutrition of established johnsongrass is discussed.

The toxicity of 1,1'-dimethyl-4,4'-bipyridinium ion (paraquat) in soil can be related to the degree of bonding strength to the soil aggregates. Tightly bound material is unavailable to plants, while loosely bound material can be potentially available to plants. On the basis of growth of corn (Zea mays L., var. Golden Cross Bantam) and beans (Phaseolus vulgaris L., var. Idaho 1-11) in sand, loamy sand, loam, and muck treated with paraquat, it is concluded that planned and careful application would not lead to accumulation of lethal dosages in medium to heavy soils.

Absorption of the isooctyl ester of (2,4,5-trichlorophenoxy)-acetic acid varied more than 20% in four woody species when incident light intensity was increased from 40 to 4,000 ft-c. Variations in translocation of the herbicide of 45 to 50% in post oak (Quercus stellata Wangenh.) and water oak (Quercus nigra L.) accompanied changes in illumination. Light intensity did not affect translocation in longleaf pine (Pinus palustris Mill.) or American holly (Ilex opaca Ait.)

Experiments were conducted to determine the effect of 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron) and 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) on oxygen consumption by mitochondria isolated from the hypocotyls of soybean (Glycine max L., var. Lee) seedlings. Prometryne caused a decrease in second state 3 oxidation of both malate and succinate, but the decrease was overcome by 2,4-dinitrophenol (hereinafter referred to as DNP), indicating a response similar to that of oligomycin. Fluometuron caused an increase in second state 4 oxidation of both malate and succinate and overcame the inhibition of oxidative phosphorylation caused by oligomycin, indicating an uncoupling response similar to DNP. Fluometuron was also shown to reverse the inhibition of oxidative phosphorylation caused by prometryne. Concentrations of prometryne causing the 50% inhibitory response were somewhat higher than those reported for s-triazines on other tissues, while those for fluometuron were well within the inhibitory range reported for other substituted ureas.

Phytotoxicity of five substituted urea herbicides 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (fenuron), 3-hexahydro-4,7-methanoindan-5-yl) −1,1-dimethylurea (norea), and 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron) at 0, 10, 100, and 1000 ppm were determined in factorial combination at four urea nitrogen levels of 0, 45, 450, and 900 ppm with three Aspergilli: A. niger, A. sydowi, and A. tamarii. Response interactions were apparent, with all three fungi most tolerant for fenuron and least for diuron. Apparent tolerance order of the three intermediates were: A. niger, norea > fluometuron > monuron; A. sydowi, fluometuron > monuron > norea; and A. tamarii, fluometuron > norea > monuron. Oat (Avena sativa L.) bioassay for residual herbicide toxicity indicated significant differences in herbicide degradation rates between these three fungi at 5, 10, and 20 ppm in Eufaula sand. Diuron was more rapidly degraded than monuron at these levels with fluometuron and norea somewhat intermediate. A. niger was most effective in degradation of these herbicides with A. tamarii greater than A. sydowi. High nitrogen levels in soil organic matter amendment generally favored increased rates of urea herbicide degradation.

Simazine (2-chloro-4,6-bis(ethylamino)-s-triazine) at 0.12 to 1.0 ppmw in nutrient cultures of common duckweed (Lemna minor L.), elodea (Elodea canadensis Michx.), and parrotfeather (Myriophyllum brasiliense Camb.) inhibited oxygen evolution within 24 hr. Of the plants studied, the submersed form of parrotfeather exhibited the greatest reduction in apparent photosynthesis as measured by dissolved oxygen in the water. Simazine in nutrient culture without plants remained relatively stable during the treatment period; a slight, but not significant, diminution of chemical was detected after 4 days. Each species, elodea or emersed parrotfeather, reduced the concentration of simazine in solution within 48 hr after treatment.

The disappearance of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) from soil was studied using Brassica species for bioassay and the spectrophotometer and chromogenic reagents for chemical determination. Loss of pyrazon from soil appeared to be an exponential function of time characteristic of the activity of soil microorganisms. On the other hand, non-biological degradation appeared negligible. Leaching of pyrazon appeared to be insignificant or minor. The greater part of the herbicide remained in the top 3 inches of soil.

Herbicides applied shortly after wheat (Triticum aestivum L.) harvest combined with no tillage or with several minimum tillage treatments were compared with conventional tillage for weed control from wheat harvest 1 year through sorghum (Sorghum bicolor (L.) Moench) production the next year. Three lb/A of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) with no tillage did not completely control weeds, but over 4 years of sorghum grain yields on the atrazine-no tillage plots and on conventional tillage plots were not significantly different. One tillage either immediately before or immediately after application of 3 lb/A atrazine controlled essentially all weeds from wheat harvest until fall, but in some years grass weeds emerged in the spring. One pre-planting tillage or one cultivation after sorghum emergence reduced weed competition so that no additional weed control measures were needed. Sorghum yields from those plots were substantially above yields resulting from conventional tillage.

An application of potassium nitrate or urea to the soil of detopped potted tomato plants [Lycopersicon esculentum Mill.] increased the rate of exudation from the stumps of the plants from 100 to over 300% and increased the concentration of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine [atrazine] in this augmented exudate from 9 to 40%. Atrazine applied to the soil at 2:00 PM was detected in the stump exudate within 10 min and with an application of 3500 μg per pot it was approaching its maximum concentration by the end of 3 hr. The build-up in the concentration of atrazine in the exudate occurred at a faster rate in plants treated with potassium nitrate than in water control plants. Increasing the soil temperature from 10 to 30 C increased the rate of exudation and at each temperature an application of potassium nitrate or of urea increased the concentration of atrazine in the augmented exudate. In addition to atrazine, 2-chloro-4,6-bis(isopropylamino)-s-triazine [propazine], 2-methoxy-4,6-bis(isopropylamino)-s-triazine [prometone], and 2-methoxy-4-ethylamino-6-isopropylamino-s-triazine [atratone] were applied at 1750 and 3500 μg/pot. The concentration of these triazines in the exudate increased directly with their solubility in water. An application of urea increased the concentration of all four triazines in the exudate.