In field studies, surfactant and phytobland oil were compared as additives to herbicides and herbicide combinations for postemergence weed control in cotton (Gossypium hirsutum L. ‘Stoneville 7A’). Addition of phytobland oil to MSMA (monosodium methanearsonate) and MSMA + fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea], dinoseb (2-sec-butyl-4,6-dinitrophenol), or norea [3-(hexadydro-4,7-methanoindan-5-yl)-1,1-dimethyl-urea] had no significant effect on weed control when applied as directed treatments to weeds in cotton 7 to 15 cm tall. In cotton 15 to 23 cm tall, addition of phytobland oil to MSMA + linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and MSMA + linuron + prometryne [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] increased weed control when compared to the same treatments with surfactant. MSMA + linuron + phytobland oil decreased cotton yields. Addition of phytobland oil to DSMA (disodium methanearsonate) and DSMA combinations had no effect on weed control when compared to the same treatments with surfactant. There were no differences in several paraffinic phytobland oils or surfactant when used as additives to MSMA + fluometuron for weed control in cotton 7 to 15 cm tall.

Two methods of controlling weeds during the establishment of crownvetch (Coronilla varia L. ‘Chemung’) were studied. The first involved broadcast-incorporated spray treatments with either EPTC (S-ethyl dipropylthiocarbamate) or benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) before planting. At planting, simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] or bromacil (5-bromo-3-sec-butyl-6-methyluracil) was applied in bands between seeded rows of crownvetch. Excellent weed control and good crownvetch establishment were obtained consistently, but in some years bromacil damaged seedling crownvetch excessively. In the second, weed control and subsequent crownvetch establishment were successful for 4 consecutive years after broadcastpreplanting treatments of EPTC or benefin, followed by a postemergence spraying with dinoseb (2-sec-butyl-4,6-dinitrophenol).

The adsorption-desorption equilibria of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] were studied; a slurry technique with soil at 0-bar moisture tension was used. The equilibria established with Bosket very fine sandy loam (VFSL) were evaluated by three equations. The equation best describing the adsorption isotherm was x/m = K1Ce + K2Ce2. Successive equilibrations resulted in a shift in the equilibria toward the adsorbed state, most likeiy due to a physical change in the adsorption capacity of the soil with repeated agitation. Desorption studies with seven additional soils indicated the importance of soil organic matter content in the adsorption-desorption equilibria of fluometuron. The relationship between soil organic matter contents and the adsorption-desorption equilibrium constants was characterized by a highly significant linear correlation (r = 0.93) and the resulting regression equation: K1 = 0.46 + 0.45(O.M.%). Clay content of these soils was not significantly correlated with fluometuron equilibrium constants.

Field experiments were conducted to study the feasibility of using trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline] for the selective control of johnsongrass [Sorghum halepense (L.) Pers.] from rhizomes and seed in soybeans [Glycine max (L.) Merr. ‘Lee’]. Both herbicides were incorporated into the soil at 0.56 to 3.36 kg/ha with two disk cultivations immediately after application. Most effective johnsongrass control on Dundee silty clay loam (sicl) followed treatments of nitralin or trifluralin at 1.68 to 3.36 kg/ha, but 2 years or more of continuous treatment were required for acceptable control. Trifluralin at 1.12 and 2.24 kg/ha on Sharkey clay and at 0.56 to 2.24 kg/ha on Bosket fine sandy loam (fsl) provided better average johnsongrass control over a 2-year period than nitralin at the same rates, but soybean yields after both herbicides at the same rates were equal. Immediate incorporation of trifluralin or nitralin in all three soils at 1.12 to 2.24 kg/ha for 2 successive years effectively controlled johnsongrass from rhizomes without soybean injury and with greatly increased soybean yields.

Canada thistle (Cirsium arvense L.) plants containing one elongated and one recently emerged shoot from the same root segment were treated with 14C-ring labeled atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Fourteen days after atrazine application to the elongated shoot 98% of the recovered activity remained in this shoot. The distribution pattern of 14C suggested movement with the transpiration stream. Of the 14C in the treated shoot, 82% was in the form of unaltered atrazine at 14 days after application. Greenhouse studies with nonlabeled atrazine indicated that this herbicide had only an indirect effect on portions of the plant located basipetally to the area of application.

Studies were conducted to determine both the extent and relative strengths of adsorption of twelve dinitroaniline herbicides to a Piano silt loam soil. The effects of soil on the growth of foxtail millet [Setaria italica (L.) Beauv.] in vitro on agar media containing 1.0 and 0.1-μM concentrations of the various herbicides and on the relative phytotoxicities of herbicide vapors arising from the agar media to the same species were also measured. Although considerable differences in the extents and strengths of adsorption of the respective herbicides to soil were noted, correlations with herbicide performance under field conditions were low. Extrapolation of laboratory results to a Piano silt loam soil under field conditions suggests that field applications of 0.32 kg/ha of the respective herbicides might result in herbicide concentrations between 0.00062 and 0.026 ppmw in the soil solution. These concentrations appeared to be less than those necessary to produce substantial plant injury from most of the dinitroaniline herbicides. High correlations between the effects of herbicide vapors on growth of the foxtail millet under laboratory conditions and the relative effectiveness of seven of the herbicides under field conditions suggest that absorption of vapors of the dinitroaniline herbicides by plants may be more important than absorption of the herbicides from soil solutions.

At early stages of canopy development net carbon exchange (NCE) values for redroot pigweed (Amaranthus retroflexus L.), prickly sida (Sida spinosa L.), and birdsfoot trefoil (Lotus corniculatus L.) were determined in an air-sealed leaf chamber. Regardless of light intensity, temperature, CO2 concentration, or competition level, redroot pigweed had a NCE at least 10 mg CO2/dm2 per hr higher than that of birdsfoot trefoil or prickly sida. On a total leaf area basis, CO2 utilization changed as the heteroculture canopies developed and as the microenvironmental parameters changed. Redroot pigweed's rapid attainment of leaf area and leaf display coupled with a high photosynthetic (P) rate greatly enhance its utilization of available CO2. Direct competition for CO2 does not occur between plants with low and high (P) rates under field conditions because CO2 concentrations are always greater than the CO2 compensation point (r) of plants with low (P) rates. More efficient utilization of available CO2 by weeds such as redroot pigweed with greater (P) capacity contributes to more rapid growth and development of these weeds to the ultimate detriment of a plant such as birdsfoot trefoil with lower (P) capacity.

Effects of barban (4-chloro-2-butynl m-chlorocarbanilate) were investigated on the growth and metabolism of oat (Avena sativa L. ‘Victoria’) (susceptible) and wheat (Triticum aestivum L. ‘Ushio’) (tolerant) plants. Barban remarkably retarded the growth of oat seedlings but not that of wheat seedlings. Respiration and photosynthesis of both plant species were not inhibited. Protein and RNA synthesis of oat seedlings were remarkably inhibited even 1 day after the barban treatment, while the protein and RNA synthesis of wheat seedlings were inhibited less.

In field studies, bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] was applied as postemergence sprays over the top of weeds and soybeans [Glycine max (L.) Merr.]. Bentazon at 0.84 to 1.68 kg/ha applied as an early postemergence treatment controlled wild mustard [Brassica kaber (DC.) L.C. Wheeler var. pinnatifida (Stokes) L.C. Wheeler], common ragweed (Ambrosia artemisiifolia L.), velvetleaf (Abutilon theophrasti Medic.), Pennsylvania smartweed, (Polygonum pensylvanicum L.), common cocklebur (Xanthium pensylvanicum Wallr.), and wild common sunflower (Helianthus annuus L.). Pigweeds (Amaranthus sp.) were controlled by applications in the three true-leaf stage but became more resistant at later stages. Control of common lambsquarters (Chenopodium album L.) was erratic. The optimum time for controlling weeds with bentazon was around the first trifoliolate stage of soybeans. Rainfall within several hours after treatment reduced weed control. Eight yield studies, two of which included eight cultivars, were conducted on weed-free soybeans. In none were yields reduced significantly by bentazon at 3.36 kg/ha (the highest rate studied). Eight yield studies were conducted on soybeans infested with common cocklebur or velvetleaf. Weed control was generally excellent with 0.84 kg/ha of bentazon. Where infestations were sufficient to reduce yields, bentazon treatments increased the yields to levels generally comparable with those of the handweeded checks. One exception was an application of bentazon to soybeans growing in a low area that was periodically flooded by heavy rains. In that experiment the benefit of controlling common cocklebur was offset by bentazon injury to the soybeans, and yields from the treated plots were about the same as those of the weedy check.

The selective action of chloroxuron [3-(p-(p-chlorophenoxy)phenyl)-1,1-dimethylurea] on tolerant soybean [Glycine max (L.) Merr. ‘Kent’] and susceptible tall morningglory [Ipomea purpurea (L.) Roth] was studied using root and foliar applications. In root uptake studies with carbonyl-14C-chloroxuron, soybean roots contained greater than 90% of the total absorbed radioactivity; whereas tall morningglory roots contained approximately 60% of the total absorbed radioactivity. Leaves of 1, 2, and 3-wk old soybean plants contained 0.8, 3.7, and 3.5% of the total radioactivity, respectively; whereas leaves of tall morningglory plants of corresponding age contained 29.1, 33.0, and 37.4% of the total radioactivity. Metabolism from root uptake of both species was similar; and metabolites were identified as approximately 85% chloroxuron, 13% 3-(p-(p-chlorophenoxy)phenyl-1-methylurea (Compound II), and 2.5% 3-(p-(p-chlorophenoxy)phenylurea (Compound III) in 3-wk old plants. In a nutrient solution containing 5.6 × 10−6M chloroxuron, soybean plants with roots intact were tolerant; whereas plants with roots detached were susceptible indicating the importance of differential translocation for selective action from root uptake. Following foliar spray and washing of 2-wk old plants, tall morningglory foliage absorbed about two times more radioactivity than soybean foliage. Further, 18 hr after foliar application, chloroplasts isolated from tall morningglory contained twice as much 14C-chloroxuron as soybean chloroplasts. Metabolite concentrations recovered from foliar treatment of both species were similar; and metabolites were identified as 88.1 to 92.2% chloroxuron, 6.4 to 8.6 % Compound II and 0.5 to 1.7% Compound III.

Seeds of common cocklebur (Xanthium pensylvanicum Wallr.), jimsonweed (Datura stramonium L.), ivyleaf morningglory [Ipomoea hederacea (L.) Jacq.], giant ragweed (Ambrosia trifida L.), yellow foxtail [Setaria lutescens (Weigel) Hubb.], and velvetleaf (Abutilon theophrasti Medic.) were buried in the soil at depths down to 15.2 cm in November 1966. Seeds of jimsonweed, ivyleaf morningglory, giant ragweed, yellow foxtail, velvetleaf, common ragweed (Ambrosia artemisiifolia L.), and Pennsylvania smartweed (Polygonum pensylvanicum L.) were buried 2.5 and 10.2 cm below the surface in October 1968. Seeds were exhumed for periodic laboratory analyses of dormancy changes. All species except ivyleaf morningglory and common cocklebur germinated better in light than in darkness after at least one winter of burial in the soil. Seeds decayed faster at 2.5 cm below the soil surface than at 10.2 cm, but some viable seeds of all species were recovered from both depths after 3 years. The development or maintenance of hard seeds was considered the principle mechanism for seed survival for 3 years in these species.

The following species of arthropods were exported from California to the U.S.S.R. for the biological control of ragweed (Ambrosia spp.): Tarachidia candefacta Hübner (Lepidoptera: Noctuidae); Coleophora sp. near annulatella Braun (Lepidoptera: Coleophoridae); and Eriophyes boycei Keifer (Acarina: Eriophyidae). Tarachidia candefacta represents the first insect species intentionally introduced from North America into Europe and established for biological weed control.

Studies were conducted to characterize qualitatively and quantitatively the water-soluble carbohydrates in johnsongrass [Sorghum halepense (L.) Pers.]. Glucose, fructose, and sucrose were the only sugars detected in other than trace amounts in leaves, culms, or rhizomes. Sucrose was the major storage carbohydrate, although glucose and fructose were present throughout most of the life cycle in both leaves and rhizomes. Levels of glucose, fructose, and sucrose in rhizomes were maximum when plants began flowering and minimum at 10 to 30 days after plant emergence. Glucose, fructose, and sucrose were at a maximum in leaves within 30 days after plant emergence. Glucose was present only in trace amounts in leaves for about 10 days during initial flowering; fructose was at a maximum at that time. Sucrose in leaves occurred in greatest quantities soon after plant emergence, immediately before flowering, and after flowering. Leaf blades and sheaths contained nearly equal concentrations of carbohydrates, but stems contained greater concentrations than leaves. Basal shoots and secondary culms from nodes on primary culms contained greater concentrations of carbohydrates than leaves on primary culms. Regrowth from clipped shoots had significantly higher concentrations of glucose and sucrose than did unclipped shoots. Rhizomes of clipped plants had significantly less sucrose but more glucose than rhizomes of unclipped plants.

The effects of eight s-triazines on respiration of (Phaseolus vulgaris L. ‘Black Valentine’) bean and rat liver mitochondria and on cyclic photophosphorylation of pea (Pisum sativum L. ‘Thomas Laxton’) chloroplasts were determined. All triazines inhibited state 3 respiration and cyclic photophosphorylation. The degree of inhibition was similar in both rat liver and bean mitochondria. Prometryne [2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine] was the most potent inhibitor of both respiration and cyclic photophosphorylation. Triazines with the methylthio group showed the most activity, followed by those with the methoxy and chloro substituents in that order.

The translocation of foliar-applied 14C-labelled 2,4-D [(2,4-dichlorophenoxy)acetic acid] in seedlings of leafy spurge (Euphorbia esula L.) was investigated. Approximately 90% of the tracer was extracted from the tissues with 80% ethanol. Seven days after treatment 48% of the 14C in the shoot extract and 75% of that extracted from the root were identified chromatographically as 2,4-D. Translocation out of the treated leaves and into the shoot, root, and root buds was significantly increased both by decapitation of the shoot and by increasing the nitrogen supply. This effect is attributed to the marked promotion of bud growth produced by both of these treatments.

In a 3 year herbicide-crop rotation involving corn (Zea mays L. ‘Coker 811A’), cotton (Gossypium hirsutum L. ‘Carolina Queen’), and peanuts (Arachis hypogaea L. ‘Argentine’), uncontrolled yellow nutsedge (Cyperus esculentus L.) and annual weeds drastically reduced all crop yields. By the end of the rotation sequences, intensive cultivation throughout the rotation killed 97 to 99% of the nutsedge tubers, but this level of control depended on hand-weeding the cotton. Moderate application of herbicides killed from 78 to over 99% of the yellow nutsedge tubers, while intensive treatment with herbicides produced at least 99% kill. In addition, all annual weeds present when the experiment was initiated were controlled satisfactorily by intensive herbicide applications except Florida beggarweed [Desmodium tortuosum (Sw.) DC.] in peanuts. The major change in composition of the weed population was a reduction in yellow nutsedge and in the total number of weeds; however, certain other population shifts also seemed affected by the weed control treatments. Compared to intensive cultivation, the investment in intensive herbicide treatment produced maximum yields and highest gross profit per acre. None of the treatments affected the market grade or organoleptic characteristics of peanuts. The fatty acid content of corn and cotton changed significantly only in 1967.

Cogongrass [Imperata cylindrica (L.) Beauv.] was introduced into the Mobile Bay area of Alabama in 1911 or 1912. During the ensuing 60 years this rhizomatous weedy grass has spread into most of the southern portion of the state. Cogongrass has become a problem in agronomic and horticultural crops which are not intensively cultivated. Several currently available herbicides show promise of control.

The basis for selectivity of phenmedipham (methyl-m-hydroxycarbanilate m-methylcarbanilate) and desmedipham (ethyl m-hydroxycarbanilate carbanilate) on wild mustard [Brassica kaber (DC.) L.C. Wheeler ‘pinnatifida’ (Stokes) L.C. Wheeler], redroot pigweed (Amaranthus retroflexus L.), and sugar beet (Beta vulgaris L.) was studied by evaluating spray retention, absorption, translocation, and metabolism. Total photosynthesis in wild mustard was severely inhibited in less than 5 hr after foliar application of either herbicide and did not recover. Total photosynthesis in sugar beet was slightly inhibited but recovered after 24 hr. Photosynthesis in redroot pigweed recovered from a treatment of phenmedipham but did not recover when treated with desmedipham. Differences in spray retention or foliar absorption did not explain selectivity. Within 5 hr after herbicide application, redroot pigweed had translocated more desmedipham than phenmedipham from the site of absorption and had metabolized a large amount of the phenmedipham but little desmedipham. The key factor explaining selectivity appeared to be at the initial detoxication reaction of the parent compound.

Three annual plant species — erect plantain (Plantago erecta Morris), common chickweed [Stellaria media (L.) Cyrill.], and silver hairgrass (Aira caryophyllea L.)—are commonly found and may dominate a unique flora on areas sprayed with paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) in cismontane rangelands of California. The basis of this phenomenon is shown to be temperature-related germination requirements, novel seed characteristics, and lack of competition.

The toxicity of several toluidine and thiocarbamate herbicides to johnsongrass [Sorghum halepense (L.) Pers.] rhizome tissue was determined by a triphenyl tetrazolium chloride (TTC) assay. Rhizome sections were incubated in herbicide solutions for 24 hr and then in TTC solution for 24 hr. The amount of reduced TTC was a quantitative measure of herbicide toxicity. Concentrations of the different herbicides required to cause 100% tissue injury indicated that the order of decreasing herbicide toxicity was: USB-3584 (N3,N3-diethyl-2,4-dinitro-6-trifluoromethyl-1,3-phenylendiamine); trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine); benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2-6-dinitro-p-toluidine); nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline]; San-9789 [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazione]; and A-820 (Nsec-butyl-4-tert-butyl-2,6-dinitroaniline). In another study CGA-11607 (N-ethyl-N-tetrahydrofurfuryl-4-trifluoromethyl-2,6-dinitroaniline); AN-5647 [N,N-bis(2-chloroethyl)-2,6-dinitro-p-toluidine]; and CGA-10832 (Nn-propyl-N-cyclopropylmethyl-4-trifluoromethyl-2,6-dinitroaniline) were less toxic than trifluralin to johnsongrass rhizomes. Complete tissue injury caused by the thiocarbamates occurred in the same concentration range (10−3 to 10−2M) as the toluidine herbicides. At a concentration required for complete kill the toxicity in decreasing order was: EPTC (S-ethyl dipropylthiocarbamate); vernolate (S-propyl dipropylthiocarbamate); butylate (S-ethyl diisobutylthiocarbamate); and pebulate (S-propyl butylethylthiocarbamate). R-25788 (N,N-diallyl-2,2-dichloroacetamide) at 6.7 × 10−5 M had no effect on vernolate, EPTC, or pebulate activity; but it increased the toxicity of butylate to johnsongrass rhizome tissue.