In a greenhouse experiment, dosages of 2-methoxy-3,6-dichlorobenzoic acid [dicamba] and 2-methoxy-3,5,6-trichlorobenzoic acid [tricamba] required initially to reduce fresh weights of snap beans (Phaseolus vulgaris L.) 50% (hereinafter referred to as ED50 values) increased as clay and organic matter increased in five soils. In all soils, 2,3,6-trichlorobenzoic acid [2,3,6-TBA] was about equally toxic, but ED50 values for 2,3,6-trichlorophenylacetic acid [fenac] and 2-methoxy-3,6-dichlorophenylacetic acid [hereinafter referred to as methoxy fenac] decreased as clay and organic matter increased. Under experimental conditions of alternately moist and dry soil, phytotoxicity of dicamba, tricamba, and methoxy fenac decreased with time, but that of 2,3,6-TBA and fenac remained approximately the same for about 22 months. When soils were maintained moist throughout the incubation period, 3-amino-2,5-dichlorobenzoic acid [amiben] was least persistent, dicamba intermediate, and 2,3,6-TBA and fenac most; under these conditions, phytotoxic effects of 2,3,6-TBA and fenac decreased with time. In soil-enrichment studies, fenac, methoxy fenac, dicamba, and 2,3,6-TBA, in comparison with 2,4-dichlorophenoxyacetic acid [2,4-D], appeared very resistant to microbial degradation.

Greenhouse studies on control of saltcedar (Tamarix pentandra Pall.), a problem phreatophyte, showed that when one of three hygroscopic compounds, polypropylenediol (a mixture of polypropylenediols with molecular weights ranging from 375 to 425) was added to water solutions of phenoxy herbicides, it significantly increased injury from most treatments. Injury to foliage from all herbicides tested, except the oil-soluble amine formulations (a mixture containing 80% tertiary dodecyl and 20% tertiary tetradecyl amine) of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4,5-trichlorophenoxy) propionic acid (silvex), and 2,4-D plus 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) (1:1), increased when polypropylenediol was added to the spray solution at 5% by volume. The increased activity was affected by the rate of the additive, temperature, humidity, and herbicide formulation.

Requirements for germination and rate of juvenile root and shoot elongation of 23 medusahead (Taeniatherum asperum (Sim.) Nevski) selections were investigated in relation to osmotic stress. These were compared with the germination and elongation characteristics of other grasses. Aqueous solutions of different osmotic pressures were obtained by dissolving polyethylene glycol in water. Successive 4-bar increases in osmotic pressure markedly reduced medusahead germination until germination terminated at 16 bars. Other grass species exhibited higher germination than medusahead under osmotic stress. Medusahead juvenile root and shoot elongation under low and moderate osmotic pressure exceeded all other species tested.

Herbicide tests conducted over a period of 3 years indicated that 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron) at 2.5 lb/A preemergence, or a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 2.0 lb/A preemergence, incorporated, are safe and effective herbicides for weed control in gladiolus (Gladiolus grandiflorus). Applications of dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D) applied as directed sprays at rates of 0.5 to 1.0 lb/A prior to spiking controlled late season weeds without apparent injury to the plants.

The problem in determining the economic feasibility of mechanical, chemical, and combination weed control methods in corn (Zea mays L.) is a complex decision involving many factors. The effects of cost, yield, timeliness, and alternative uses of labor are the factors considered in comparing various methods of weed control in this study. Costs of weed control operations range from $2.84/A for two cultivations to $10.45/A for the most intensive, mechanical-chemical operation studied. Most common weed control methods have costs of approximately $3 to $4/A. Yields range from 83 bu/A for two cultivations to 96 bu/A with the highest cost chemical-mechanical weed control methods. All yields used in this study are supported by agronomic studies and are indexed on the basis of 100 bu/A for weed-free conditions. The consideration of both yields and costs does affect the selection of a weed control method. Considering only these two factors, mechanical methods have a slight advantage over chemical weed control methods. Penalizing mechanical methods because of delay or timeliness characteristics gives chemical methods an advantage by as much as $3.00/A. Alternative uses of labor, even though a common argument in selecting chemical or mechanical methods, is a very small item and has only moderate effects on the changes in net income.

The uptake and transport of carboxyl-labeled and unlabeled butoxyethyl esters and ammonium salts of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) by honey mesquite (Prosopis juliflora (Swartz) DC, var. glandulosa (Torr.) Cockerell) leaves were compared as measured by liquid scintillation counting and gas chromatography. Absorption of 2,4,5-T was determined by assaying leaf-rinsing solutions and extracts of treated leaves. Transport of 2,4,5-T was measured by determining amounts of 2,4,5-T found in stem tissue. The methods of analysis gave comparable results when extraction, cleanup, and analytical procedures were identical. When cleanup and methylation procedures were eliminated for the radioisotopic analyses, radioisotopic analyses gave significantly higher values for extracts of treated leaves than did gas chromatographic analyses. Larger amounts of 2,4,5-T were recovered from leaves treated with the butoxyethyl esters of 2,4,5-T than with ammonium salts.

No effect was shown of 3-amino-l,2,4-triazole (amitrole) upon the incorporation of alanine or histidine into soluble protein in bean (Phaseolus vulgaris L.) hypocotyls grown in darkness. The metabolic derivative of amitrole, β-(3-amino-1,2,4-triazolyl-l-)α-ala-nine (hereinafter referred to as 3-ATAL), also had no effect upon histidine incorporation. Serine incorporation was increased 56% in the presence of amitrole, but this may result from a reduction of endogenous serine pools. No evidence indicates a general disruption of protein synthesis. Activity from amitrole-5-14C was readily incorporated into bean protein, but hydrolysis revealed no 3-ATAL. Most of the activity was recovered as amitrole. Amitrole in the presence of riboflavin and light attacked bovine serum albumin, probably by free radical formation. Hydrolysis of bovine serum albumin revealed mainly amitrole. Apparently, the entry of amitrole into bean protein is by free radical formation.

Emulsions of aromatic solvent or dimethylbenzene (xylene) are used to control submersed aquatic weeds in irrigation systems. A procedure was developed for analyzing the concentrations of xylene in irrigation water. Samples of xylene emulsions were collected in glass bottles containing tetrachloromethane (CCl4). Xylene and emulsifier were partitioned into the CCl4. After addition of sodium chloride (NaCl) to remove the emulsifier from the CCl4, aliquots of the CCl4 were analyzed for xylene content by gas chromatography. Extraction of xylene from the water was complete and quantities of xylene as small as 10 ng were readily detected.

We evaluated 214 lines of wild oat (Avena fatua L.) for response to S-2,3-dichloroallyl N,N-diisopropylthiolcarbamate (diallate), S-2,3,3-trichloroaHyl N,N-diisopropylthiolcarbamate (triallate), and 4-chloro-2-butynl m-chlorocarbanilate (barban). We found large differences among the lines in response to these herbicides and some lines that might not be controlled by recommended rates of these herbicides. Frequency distributions of response to herbicides suggest that reaction to these three herbicides is quantitatively inherited. We were unable to establish a relationship between morphological characteristics and plant response to these herbicides.

A fast and efficient method of evaluating soil incorporators consists of incorporating a fluorescent dye into the soil, taking soil samples, removing the dye by a solvent, and determining the dye concentration. Pontacyl Brilliant Pink B was the best dye for incorporation studies and a fluorometer was the analytical instrument.

Initial and residual phytotoxicity of 3-(m-trifluoromethylphenyl)-1, 1-dimethylurea (fluometuron) in seven soils was studied under greenhouse condition, using oats (Avena sativa L., var. Brave) as the bioassay species. The phytotoxicity of fluometuron in four of the soils, with an organic matter range of 1.0 to 5.0%, was not different at any one of the five cropping periods. Inactivation of fluometuron was more rapid in Eden silty clay loam with 3.3% organic matter than in Maury silty clay loam/silt loam with 7.2% organic matter. Phytotoxicity was significantly correlated with organic matter and soluble phosphorus during the first two cropping periods, and with cation exchange capacity, exchangeable calcium, total exchangeable bases, and soluble phosphorus during the last three croppings.

Requirements for germination of 23 medusahead (Taeniatherum asperum (Sim.) Nevski) selections were investigated in relation to temperature and afterripening requirements, and were compared with the germination characteristics of other grasses. Medusahead germinated best at 10 to 15 C. Germination percentages were markedly lower at 20 and 25 C. Unlike medusahead, germination of all competing or replacement species tested was markedly decreased at lower temperatures (10 C). Above 15 C, medusahead selections had strong afterripening requirements which decreased over time. Shortly after maturity, medusahead caryopses germinated only at low temperatures (10 and 15 C). Germination temperatures became less dominant after a 180-day afterripening period.

Safer methods of herbicide application are needed for irregular planting areas. The herbicide 2,6-dichlorobenzonitrile (dichlobenil) was incorporated into various organic mulches so that a specified depth of mulch delivered the desired concentration of herbicide. The incorporation technique provided equal or better weed control than either the dichlobenil or mulch used alone. In addition, prolonged effect of the dichlobenil was realized into the second year when it was incorporated into the mulch. Increasing the mulch depth to 4 inches increased the weed control. A nutrient supplemented mulch in conjunction with the dichlobenil increased the growth of many woody ornamental plants as much as 300 to 400%.

In a 3-year study on four soil types, subsurface application just ahead of a planter with a device that removed the top from the bed, applied a band of spray, and covered the band with soil reduced weed control in cotton (Gossypium hirsutum L.) obtained with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne), 3-(hexahydro-4,7-methanoindan-5-yl)-1,1-dimethylurea (norea), dimethyl-2,3,5,6-tetrachloroterephthalate (DCPA), and 1,1-dimethyl-3(α,α,α,-trifluoro-m-tolyl)urea (fluometuron) compared to applications on the soil surface. This machine improved weed control with α,α,α,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). Shallow incorporation, with two helical blades, after planting increased weed control with trifluralin, diuron, and DCPA by 10% or more over the surface applications. This incorporator increased weed control obtained with prometryne and norea 5%. Very shallow incorporation, with metal tines, after planting improved weed control obtained with trifluralin and DCPA 18 and 11%, respectively. Weed control with norea was increased 7%, but metal tines did not appreciably affect weed control obtained with prometryne, diuron, or fluometuron. Compared to surface applications, incorporation increased cotton injury with diuron, norea, prometryne, and fluometuron on sandy loam soil.

Distribution and degradation of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at 5, 10, 15, and 20 ppmw in red pine (Pinus resinosa Ait.) seedlings were investigated using 14C-ring-labeled simazine dispersed in agar medium. Simazine readily entered red pine roots and moved rapidly into stem and needles. Accumulation was greatest in roots, next in stems, and least in needles. Significant differences in simazine uptake by roots were observed among concentrations between 5 and 20 ppmw in the incubation medium. Radiochromatographic scans revealed that a small amount of simazine was degraded to three unknown compounds by both fresh and boiled homogenates from whole plants, needles, stems, and roots. There were no observable differences in the amount of simazine degraded by homogenates of each separate plant part.

The hypothesis that plants treated with 2,4-dichlorophenoxyacetic acid (2,4-D) die as a consequence of abnormal growth has been examined. Cocklebur (Xanthium sp) plants spot treated on one leaf with 2,4-D show three phases of growth toward death. For the first 2 days after treatment, there is a net weight increase, largely due to abnormal growth of the axis (apex, stem, and tap root). Root and leaf growth are drastically curtailed. Between 2 and 7 days, axis growth continues primarily at the expense of leaf tissue which is induced to senesce, especially the cotyledons. The last phase between 7 and 10 days leads to collapse and withering of plants, and was not examined in detail.

Analyses for nitrogenous constituents show the usual mobilization to the axis, with early and large increases in nucleic acid. Both photosynthesis and ion absorption are initially stimulated but decline sharply after the first day. Translocation to leaves and roots is drastically reduced in favor of the proliferating axis.

The death of the plant appears to be due to suppression of normal apical growth coupled with induction of abnormal axis growth. Failure to produce new root and leaf tissue plus inadequate nutritional maintenance of existing roots and leaves lead to lack of autotrophism and eventual death. The biochemical basis for these responses appears to be with aberrant nucleic acid metabolism.

Electronmicrographs of barnyardgrass (Echinochloa crusgalli (L.) Beauv.) grown under controlled conditions and treated with 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) at the one to three-leaf stages show that degradation of the chloroplast starts as a swelling of the fret system followed by swelling and disruption of the granal discs. In advanced stages of breakdown, the membranes of the grana and chloroplast envelope were ruptured. These changes were initiated 2 hr after treatment with rates of 2, 5, 10, and 20 ppm atrazine. The incidence of starch grains greatly decreased as the duration of treatment exceeded 4 hr. The mitochondria appeared normal throughout, not being affected by concentration or duration of treatment. The stage of growth at which plants were treated was insignificant in determining changes at the ultrastructural level. The ultrastructural changes preceded any macroscopically discernable symptoms of tissue breakdown.

Corn (Zea mays L.) plots receiving broadcast spray applications of triazine herbicides without cultivation yielded as much as plots receiving the standard two cultivations for weed control. One cultivation resulted in an average 6% increase in corn grain yield on herbicide treated plots. This yield increase probably was due to improved weed control. Weed growth reduced grain yields an average of 1.23 bu/A for each 100 lb/A of dry weeds. In some experiments, increases in corn yield due to improved weed control by cultivation on plots treated with herbicides were less than increases expected based on weed growth reductions. This disparity may have been due to injury to the corn by cultivation.

Laboratory experiments and field observations were made to study reproduction and overwintering of cabomba (Cabomba caroliniana Gray) in New Jersey. Flowering begins in late June and continues until frost. Overwintering is accomplished chiefly by means of vegetative portions of the plant. No evidence of reproduction by seed was found in the field. No seeds germinated in the laboratory under any of the environmental conditions imposed on them. Microscopic sections of seeds were prepared and examined; no embryos were present in these sections.

Ethylene production was stimulated by 2,4-dichlorophenoxyacetic acid (2,4-D) from light-grown corn (Zea mays L., var. XL-15) and soybeans (Glycine max Merr., var. Hawkeye). Ethylene had an inhibitory effect on the growth of corn and soybeans, but a reversal of the ethylene effect could not be clearly demonstrated using the competitive inhibitor, carbon dioxide. Ethylene did not mimic the ability of 2,4-D to cause growth curvatures. It was concluded that ethylene played a role in the activity of sublethal amounts of 2,4-D.