Winter applications of paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) or combinations of paraquat with diquat [6,7-dihydrodipydrido (1,2-α: 2′,1′-c) pyrazinediium ion], propham (isopropyl carbanilate), or pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide], usually controlled both winter annual grass and broadleaf weeds in established white clover (Trifolium repens L. ‘New Zealand,’ ‘Louisiana S-1,’ and ‘Tillman’). Diquat controlled broadleaf weeds, but was less effective than paraquat or combinations of paraquat with diquat, propham, or pronamide for grass control. Dichlobenil (2,6-dichlorobenzonitrile) controlled weeds in some experiments. Pronamide and propham usually controlled grass weeds but not broadleaf weeds. In experiments in which clover seed production differed significantly, paraquat or combinations of paraquat with propham or pronamide usually resulted in higher yields than the check. Yields increased more often where treatments included paraquat.

Field soil studies with 14C-isopropalin (2,6-dinitro-N,N-dipropylcumidine) have demonstrated its biodegradability. None of the recognizable transformation products in soil accumulated beyond 4% of the amount of applied herbicide. After 15 months, approximately 25% of the applied isopropalin remained in soil, and less than 10% was observed after 28 months. Only negligible amounts of radioactivity were detected in crops grown in soil treated with the herbicide. Isopropalin and its recognizable transformation products were not detected in any of the plant tissues examined. Fractionation techniques indicated that the radioactivity was randomly distributed throughout the plant tissue.

A study was made on the absorption and translocation and of the effects of perfluidone [1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl) phenyl] methanesulfonamide] on the morphology and anatomy of cotton (Gossypium hirsutum L.) and yellow nutsedge (Cyperus esculentus L.). Concentrations of 1 μM to 10 μM perfluidone added to the nutrient solutions retarded growth of both species. Necrotic spots appeared on the lamina of cotton leaves which were expanded previous to the treatment. Cotton plants resumed normal growth within 11 days after removal of the herbicide. Yellow nutsedge plants remained stunted 18 days after removal of the herbicide. After 6 days, cotton and yellow nutsedge had absorbed 5.4% and 1.7%, respectively, of the 14C-perfluidone (uniformly labeled in the toluidine ring) added to the nutrient solution. Of the 14C absorbed by the plant, cotton and nutsedge translocated 20% and 30%, respectively, to the shoots. A 10-fold higher concentration of 14C was found at the leaf tips of nutsedge than in the other shoot tissues. In cotton shoots the 14C was distributed evenly. Perfluidone inhibited the mitotic indexes of cotton and nutsedge roots 78% and 100%, respectively, in 5 days.

Four modes of competition were studied in relation to early development of common milkweed (Asclepias syriaca L.) alone and in competition with green foxtail [Setaria viridis (L.) Beauv], redroot pigweed (Amaranthus retroflexus L.), and sorghum [Sorghum bicolor (L.) Moench ‘RS-626’]. The three species were used to study the effect of no competition, light competition, soil competition, and light and soil (full) competition on common milkweed. Common milkweed height was significantly reduced by soil and full competition with the three species, while only green foxtail caused a significant reduction in height due to light competition. Shoot weight of common milkweed was significantly reduced by light, soil, and full competition by the three species. Reproduction percentage of common milkweed roots was most severely reduced by light and full competition from green foxtail and redroot pigweed. An environment conducive to the establishment of the perennial common milkweed from seed exists when annual weeds are removed by herbicides.

Following foliar application of 14C-bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide], a promising selective postemergence herbicide for the control of broadleaf weeds in soybean [Glycine max (L.) Merr.] and navy bean (Phaseolus vulgaris L.), the movement of the 14C-label was primarily acropetal in both species, with some basipetal movement. Metabolism was more rapid in the trifoliate navy bean leaf than in the unifoliate navy bean leaf and the trifoliate soybean leaf. Prior treatment with several other herbicides did not decrease metabolism of bentazon in navy bean. The metabolites in navy bean and soybean appeared similar. Four apparent 14C-conjugates were isolated from soybean plants harvested at full maturity.

Arsenic residues in soil were examined annually over a 5-yr period following annual applications of MSMA (monosodium methanearsonate) at 4.4, 9, 13, 18, 22, 36, 72, 144, and 288 kg/ha. Elemental arsenic did not increase in any plot receiving MSMA rates less than 36 kg/ha. Plots receiving 72, 144, and 288 kg/ha of MSMA for 5 yr showed significant increases in arsenic residues. The arsenic residues for the two heaviest treatments (144 and 288 kg/ha) increased significantly during the first 4 yr, but did not increase in the fifth year.

Perfluidone (1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl]-methanesulfonamide) was chemically stable for 2 to 3 weeks on the surface of three Texas soils either air dry or at field capacity and at temperatures of 22 and 46 C. Perfluidone was susceptible to photodecomposition when applied to glass petri dishes and exposed to ultraviolet irradiation. Perfluidone was readily leached through neutral or slightly alkaline soils, with a tendency toward greater downward movement in soils having low clay and organic matter content. However, leaching was less in an acid loamy sand than in either neutral loamy sand or clay soils.

Presently accepted methods for calculating the expected response for combinations of agents such as herbicides or other growth regulators from the responses of individual agents can lead to unacceptable results. This may be true even if responses within the linear region of the individual response curves are used in such calculations. A solution to this problem is to assign parameters to response curves of individual agents and to define the expected response function for combinations of agents by the weighted algebraic means of these parameters.

Cytokinins break bud dormancy and apical dominance, induce basal bulb formation, and dwarf shoot growth in purple nutsedge (Cyperus rotundus L.). Perfluidone (MBR 8251) [1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl) phenyl] methanesulfonamide] in addition to being phytotoxic, mimics the cytokinins in these aspects. This and other herbicides which have demonstrated effectiveness in nutsedge control may derive their potency from the preconditioning effects of their cytokinin activity combined with their phytotoxicity.

Smutgrass [Sporobolus poiretii (R. & S.) Hitchc.] was selectively controlled in carpetgrass (Axonopus affinis Chase) and common bermudagrass [Cynodon dactylon (L.) Pers.] with atrazine [2-chloro-4-(ethylamino) −6-(isopropylamino)-s-triazine] applied at 2.2 kg/ha in each of two applications. MSMA (monosodium methanearsonate) applied alone or in combination with 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 2.2 + 0.6 kg/ha in each of three applications controlled at least 70% of smutgrass in two of three experiments. The common bermudagrass showed signs of atrazine injury during the first 6 weeks after treatment but the injury was not evident the following year. MSMA alone or in combination with 2,4-D killed carpetgrass in all experiments. Repeated treatments with bromacil (5-bromo-3-sec-butyl-6-methyluracil) applied alone or in combination with diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] controlled smutgrass but severely injured the turfgrasses.

The trifoliate leaf of tolerant navy bean (Phaseolus vulgaris L.) retained less bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] from foliar applications than the unifoliate leaf, or the leaves from susceptible cocklebur (Xanthium pensylvanicum Wallr.) and moderately susceptible black nightshade (Solarium nigrum L.) seedlings. The 14C from 14C-bentazon applied to the foliage of black nightshade moved throughout the entire plant. In cocklebur, the 14C moved throughout the treated leaf, whereas, in the trifoliate leaf of navy bean, very little acropetal movement occurred from the site of application. However, in the unifoliate leaf of navy bean, acropetal and basipetal movement of 14C from the leaf was observed. The species differed in the 14C-metabolites formed from 14C-bentazon 1 and 5 days after treatment. The rapid metabolism of bentazon in the trifoliate leaf of navy bean appears to be related to tolerance.

In five field experiments conducted during 1972 and 1973, yellow nutsedge (Cyperus esculentus L.) was either undisturbed or removed from planting beds by hoeing 0, 2, 4, 6, and 8 weeks after cotton (Gossypium hirsutum L. ‘Acala SJ-1’) emergence. Yellow nutsedge undisturbed in beds increased from 23 plants/m of row at cotton emergence to 100 plants/m at harvest. Nutsedge competing with cotton for more than 4 weeks reduced yield of seed cotton. Nutsedge that competed all season reduced yields 34%, as compared with 20% when it competed for 6 and 8 weeks. Nutsedge that competed with cotton for more than 4 weeks reduced height and number of cotton plants and delayed maturity. Although nutsedge competition reduced yields and delayed maturity, it generally did not alter fiber properties. When nutsedge was removed at cotton emergence and was followed by 14 weekly hoeings, the final tuber population was reduced to 24% of the beginning population. When nutsedge removal was delayed for 6 weeks and was followed by nine weekly hoeings, a fourfold increase in tubers resulted. A further tenfold increase resulted when nutsedge was not removed.

The two isomers of diallate [S-2,3-dichloroallyl)diisopropylthiocarbamate] can be isolated by preparative scale gas chromatography using a Carbowax 20M liquid phase. on the basis of IR and NMR spectroscopic and other evidence the isomer with the shorter retention time is assigned the trans configuration and that with the longer retention time is assigned the cis configuration.

EPTC (S-ethyl dipropylthiocarbamate), 1,8-naphthalic anhydride (NA), N,N-dialryl-2,2-dichloroacetamide (R-25788), CDAA (N,N-diallyl-2-chloroacetamide) and CDEC (2-chloroallyl diethyldithiocarbamate) at concentrations of 10-5 M inhibited the incorporation of acetate-1-14C (Ac∗) into fatty acids of isolated spinach (Spinacia oleracea L.) chloroplasts. Lower concentrations of these chemicals did not affect acetate incorporation into fatty acids. However, the inhibition by EPTC at 10-5 M was counteracted by NA and R-25788 [agriculturally important antidotes for EPTC injury to corn (Zea mays L.)] at 10-7 M.

In greenhouse studies root absorption after postemergence applications of cyanazine 2-[[4-chloro-6-(ethylamino)-s-triazine-2-yl] amino]-2-methylpropionitrile enhanced phytotoxicity to fall panicum (Panicum dichotomiflorum Michx.), green foxtail (Setaria viridis L.), and corn (Zea mays L.). Less 14C-cyanazine was taken up by the foliage of corn than by the weed species. A lower concentration of parent cyanazine in corn leaves was also evident. The addition of a phytobland oil to the treatment solution increased foliar cyanazine absorption 1 and 5 days following treatment. Although rapid metabolism occurred in corn roots, the large amount of cyanazine absorbed via the root system resulted in internal concentrations of parent cyanazine similar to that observed in the weed species. Cyanazine translocation was mainly acropetal from the point of application. The basis of selectivity is not solely based on the differential foliar uptake of cyanazine, but also on the proportion taken up by the foliage and roots. Under conditions favoring uptake by roots, the margin of selectivity may be reduced.

One-year-old and 3-month-old black walnut (Juglans nigra L.) and yellowpoplar (Liriodendron tulipifera L.) seedlings were treated with ring-labeled 14C-simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] in nutrient culture. Simazine uptake was measured and the levels of simazine and its degradation products monitored at 3, 6, and 9 days following treatment for 1-year-old seedlings and at 3, 8, and 13 days for 3-month-old seedlings. Concentration of simazine and the phytotoxic degradation product monodealkylated simazine [2-chloro-4-amino-6-(ethylamino)-s-triazine] were significantly higher in yellowpoplar than in black walnut leaves. For 1-year-old seedlings, higher concentrations of phytotoxic compounds in yellowpoplar than in black walnut were attributed to greater simazine degradation by black walnut. For 3-month-old seedlings, higher concentrations in yellowpoplar were attributed to greater simazine uptake by yellowpoplar and greater degradation in black walnut. Simazine degradation proceeded rapidly in both species and N-dealkylation was a major pathway. Monodealkylated simazine and 2-chloro-4,6-diamino-s-triazine were isolated from various tissues of black walnut and yellowpoplar. Hydroxysimazine [2-hydroxy-4,6-bis(ethylamino)-s-triazine] was found in yellowpoplar roots but not in any black walnut extracts. Two other degradation products were isolated but not identified.

Field and greenhouse experiments were conducted on bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)one 2,2-dioxide] at 2.2 and 4.4 kg/ha and perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl) phenyl] methanesulfonamide} at 4.5 and 9.0 kg/ha for purple nutsedge (Cyperus rotundus L.) control and tolerance of five turfgrasses. A single application of each herbicide was applied to purple nutsedge, but single and repeated applications were applied to turfgrasses. Purple nutsedge control during the initial year of treatment was 98 to 100% when bentazon was applied in late spring, but the control was only 28 to 68% when applied in mid or late summer. Perfluidone controlled 76 to 87% of purple nutsedge when applied in late spring and 95 to 100% when applied in late summer. Bentazon treatments generally did not cause turf injury. In the field, perfluidone treatments injured St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], zoysia grass (Zoysia japonica × Z. teniuflolia ‘Emerald’), centipedegrass [Erenoehloa ophiuroides (Munro) Hack.], and common bermudagrass [Cynodon dactylon (L.) Pers.]. ‘Tifway’ bermudagrass was generally tolerant to perfluidone treatments. In the greenhouse, perfluidone reduced the root growth of all turfgrasses except centipedegrass when compared with untreated checks.

Purple nutsedge (Cyperus rotundus L.) from single tubers was grown for 3 months at 24, 32, and 40 C and 9, 13, and 19 klux illumination. Growth in number and dry weight of shoots, bulbs, and tubers were determined at monthly intervals. Maximum growth for all portions of the plant occurred after 3 months at 32 C and 19 klux illumination. Minimum growth occurred at 40 C and 9 klux illumination. Growth at 24 C was not significantly affected by increased illumination above 9 klux.

At intervals of 3 to 56 days, propanil (3′,4′-dichloropropionanilide) at 4.5 kg/ha was applied after treatments of carbofuran (2,3-dihydro-2,2- dimethyl-7-benzofuranylmethyl carbamate) at 0.7 kg/ha. Their interaction injured rice (Oryza sativa L., ‘Starbonnet’) vegetatively, but did not reduce grain yields, milling quality, or seed viability. Leaf chlorosis and necrosis developed within 7 days after propanil treatment and lasted for 2 to 4 weeks. As the time interval between carbofuran and propanil treatments increased, leaf injury decreased. Older rice recovered more quickly than younger rice. Interaction of carbofuran and propanil did not cause chlorosis or necrosis of rice leaves when the insecticide was applied 5 days after the herbicide. Propanil alone, applied once at 4.5 kg/ha, or applied sequentially at 4.5 kg/ha each time, caused only slight chlorosis of rice leaves.