Purple nutsedge (Cyperus rotundus L.) control with (2,4-dichlorophenoxy)acetic acid (2,4-D) and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) was increased in greenhouse and growth chamber studies by application of these herbicides in an undiluted isoparaffinic oil carrier rather than water. Two applications of 2,4-D at 2.2 kg/ha in the oil carrier inhibited tuber and shoot production and reduced the number of viable tubers present, but two applications of linuron at 0.6 or 2.2 kg/ha in the oil inhibited only shoot production from repotted tubers. Studies with labeled 2,4-D showed an increase in both rate and quantity of penetration of this herbicide into purple nutsedge when applied in oil rather than water. Labeled linuron was applied to purple nutsedge and to beans (Phaseolus vulgaris L. ‘Improved Tendergreen’) and also showed an increase in penetration with the oil rather than water. Translocation out of treated leaves was not increased for either 2,4-D or linuron by application in the oil carrier.

Uptake of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) as influenced by adjuvants to the treatment medium was studied using both excised leaf sections and leaves of intact plants. Uptake of the 14C-atrazine label by yellow foxtail (Setaria glauca (L.) Beauv.) leaf sections was higher at 35 than at 5 C and at pH 3 and 9 than at 5 or 7. The rapid uptake of 14C-atrazine label by corn (Zea mays L.) leaf sections was attributed to a high rate of atrazine metabolism. However, atrazine metabolism did not explain the greater uptake by common lambsquarters (Chenopodium album L.) leaf sections than by yellow foxtail. Atrazine 14C-label uptake by yellow foxtail leaf sections from exogenous solution was influenced by light, phospholipase D or water pretreatment, atrazine concentration, and oil. The 14C-label of atrazine in the leaf distal to the treated spot was greater when the treatment contained an oil than when applied in only water even though the area of the spot was kept constant. Further, greater uptake of the label occurred at a high than at a low temperature regardless of the application medium.

Triethylamine salts of 4-amino-3,5,6-trichloropicolinic acid (picloram) plus (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) (1:1) sprays were more effective for the control of huisache (Acacia farnesiana (L.) Willd.) than for the control of Macartney rose (Rosa bracteata Wendl.) at 13 dates of application in 1969 and 1970. Both species were more controlled effectively with the application rate of 1.12 than 0.56 kg/ha. Most effective control of huisache was obtained June 18, 1970, although other summer treatments in 1970 were effective. The herbicide was, on the average, more effective on huisache and Macartney rose when applied in the evening than morning or midday. Macartney rose was most effectively controlled by treatments applied in September and October of both years. Poorest control of the two species occurred when internal water stress was highest.

Thirty-six collections of foxtail barley (Hordeum jubatum L.) from North Dakota, South Dakota, Minnesota, Wisconsin, and Montana varied in susceptibility to 1-(2-methylcyclohexyl)-3-phenylurea (siduron) as determined from radicle elongation of treated seeds. Data from F2 seedlings of crosses between tolerant and susceptible selections indicated that three complementary dominant factors control the inheritance of siduron tolerance in foxtail barley. Evolution of siduron-tolerant foxtail barley could occur from selection pressure.

Early spring spray applications of the potassium salt of 4-amino-3,5,6-trichloropicolinic acid (picloram) and certain formulations of 1:1 mixtures of picloram plus (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) controlled yaupon (Ilex vomitoria Ait.). Ester formulations of picloram or picloram plus 2,4,5-T were ineffective. Combinations of surfactant and oil: water carriers usually did not improve herbicide performance over water carriers. Granular picloram was superior to sprays when applied as soil treatments at equal rates and controlled yaupon at most dates of application. Post oak (Quercus stellata Wangenh.) and blackjack oak (Quercus marilandica Muenchh.) were controlled more effectively by picloram or picloram plus 2,4,5-T sprays on the foliage than by granular picloram as a soil treatment. Picloram granules usually killed winged elm (Ulmus alata Michx.) regardless of date of application.

Reserve polysaccharides were stored at high levels in rhizomes of mugwort (Artemisia vulgaris L.). Polysaccharide level in the rhizome dropped within 24 hr after treatment with 2,3,6-trichlorophenylacetic acid (fenac). Fructosans were hydrolyzed to yield increased levels of simple sugar. Sucrose concentration was slightly lower in treated rhizomes. Glucose was low in untreated rhizomes, and fenac treatment resulted in slight increases in glucose levels. Rhizomes became enlarged, the epidermis was disrupted, and “root primordia” were observed in rows parallel to the main rhizome axis after 1 to 5 days in 10 ppmw of fenac solution. The new primordial growth occurred through activation of the interfascicular cambium.

An oil soluble formulation of the dodecyl (51% w/w) and the tetradecyl (13% w/w) amine salts of (2,4-dichlorophenoxy)acetic acid (2,4-D) was diluted with diesel oil and applied in homogeneous sprays of 100, 200, and 400-μ. droplets to seedlings of sunflower (Helianthus annuus L. ‘Peredovik’). At each droplet size all combinations of five dosage levels and five spray volumes were compared. For the same applied dosage the amount of stem curvature increased as droplet-size was decreased. When compared with 100-μ droplets, approximately three times and six times as much active ingredient was needed to produce the same effect with 200-μ and 400-μ droplets, respectively. For a fixed droplet-size, the effective dosage could be increased equally well by increasing the concentration or by increasing the number of droplets per unit area.

We investigated the forces involved in the adsorption and desorption of 4-amino-3,5-6-trichloropicolinic acid (picloram), 1,1-dimethyl-4,4′-bipyridinium ion (paraquat), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) using cationic, anionic, and nonionic exchange resins. The anionic resin (Cl-form) adsorbed 375, 0.08, and 0.67 mg of picloram, paraquat, and trifluralin, respectively, per gram of oven-dry resin. The nonionic resin adsorbed 4.0, 0.34, and 10.0 mg of picloram, paraquat, and trifluralin, respectively, per gram of oven-dry resin, while the cationic resin (H-form) adsorbed 2.3, 226, and 0.17 mg of picloram, paraquat, and trifluralin, respectively. Other cationic resins (Na-form and Ca-form) performed similarly to the hydrogen form. Desorption studies indicated that picloram was adsorbed mainly in the anionic form by coulombic forces (electrostatic) and to a lesser degree by weak physical bonding (van der Waal's forces). Paraquat was adsorbed as a cation through coulombic forces. Trifluralin was mainly absorbed by physical bonds at sites on the resins where there were no coulombic forces.

Preemergence herbicidal activities of 27 3-phenoxypyridazine derivatives were evaluated in pots under upland and submerged conditions. Each of the compounds containing an alkyl or halogen at the ortho position of the benzene ring showed marked herbicidal effects. The activity of some disubstituted compounds carrying one of the substituents at the ortho position was the next. Among the compounds tested, 3-(2-methylphenoxy)-, 3-(2,3-dimethylphenoxy)-, 3-(2,4-dimethylphenoxy)-, and 3-(2,6-dimethylphenoxy)-pyridazines exhibited an excellent margin of selectivity for tomato (Lycopersicum esculentum Mill.), cotton (Gossypium hirsutum L.), soybean (Glycine max (L.) Merr.), and Azuki bean (Phaseolus angularis Wight). For transplanted rice (Oryza sativa L. ‘Norin No. 29′) under submerged conditions, 3-(2-isopropylphenoxy)-and 3-(2-n-butylphenoxy)-pyridazines showed a remarkable margin of selectivity, though the herbicidal activity of both compounds was slightly inferior to that of 3-(2-methylphenoxy)-pyridazine.

A laboratory spray cabinet was constructed of stainless steel with three compartments for separate dosage applications. Overhead spraying is accomplished in all three compartments by a single mobile nozzle activated by an air cylinder and cable drive. The system was designed so that test compounds could be applied safely and accurately at various rates on plants up to 1 m high. The cabinet has an air exchange and filtration system to prevent possible contamination of spray equipment, untreated test materials and the atmosphere.

A linear uptake of 14C-labeled 6,7-dihydrodipyrido (1,2-a:2′,1′-c)pyrazinediium ion (diquat-14C) at 1 ppmw by hydrilla (Hydrilla verticillata Casp.) occurred during a 10-day period under controlled conditions. Plant tissue contained higher amounts of radioactivity after treatment with combinations of 0.1 or 0.5 ppmw of diquat-14C plus 1 ppmw of copper than did tissue of plants in solutions of diquat-14C alone. Plants in a 1 ppmw of diquat-14C solution contained 2,123 cpm/mg after 8 days; however, 5,857 cpm/mg were measured in plant tissue taken after the same period from solutions containing diquat-14C plus 2 ppmw copper as copper sulfate pentahydrate (CSP). An increase in CSP from 3 to 10 ppmw did not significantly increase the uptake of diquat-14C over the 2 ppmw. Results with an organic copper complex (copper sulfate triethanolamine) in combination with diquat-14C were the same as those obtained with diquat-14C plus CSP.

Approximately 80% of the johnsongrass (Sorghum halepense (L.) Pers.) rhizomes produced in clay soil were in the top 7.5 cm, but 80% of the rhizomes in sandy loam occurred in the top 12.5 cm. Distribution of rhizomes within the top 20 cm of soil was more uniform in sandy loam than in clay; yet, 5% of the rhizomes produced in clay occurred deeper than 20 cm, but only 1% of the rhizomes in sandy loam occurred deeper than 20 cm. Incorporation of a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-/7-toluidine (trifluralin) in soil at 0.84 kg/ha reduced rhizome production approximately 50% throughout the soil profile but reduced rhizome production most in the top 6 cm. More plants emerged from rhizomes when planted in sandy loam than in clay. More plants emerged from short rhizomes (76 mm) than from long rhizomes (152 mm) when planted at depths to 7.6 cm, but the opposite trend was obtained when rhizomes were planted deeper. Percentage germination of rhizome buds increased as rhizomes were cut into smaller pieces. Exposure of rhizomes to temperatures of 50 to 60 C killed buds within 1 to 3 days. Rhizomes usually survived temperatures of −3 to −5 C for only a few hours.

Anionic herbicide transport properties of lipids were measured using the Schulman model of liquid-liquid membrane and parenchymateous tissue from potato (Solarium tuberosum L. ‘Russet’) tubers. The more polar lipids, lecithin and monogalactosyl dilinolenate, increased (2,4-dichlorophenoxy)acetic acid (2,4-D) exchange from the hydrophilic phase (buffered H2O:2,4-D solution) to the lipophilic phase (n-pentanol) more rapidly than the less polar triglycerides: tristearate, trioleate, and trilinolenate. The rate of 2,4-D exchange decreased with increased acidity of the hydrophilic phase indicating that polar lipids increased exchange of anionic herbicides through the liquid-liquid interface in the dissociated form. Potato tuber slices treated with lecithin accumulated more 2,4-D than did tissue receiving no lecithin, indicating that lecithin treatments increased 2,4-D accumulation by parenchymateous tissue when compared with untreated tissue.

Seed fields of white clover (Trifolium repens L. ‘New Zealand’ and ‘Louisiana S-1′) were treated with the dimethylamine salt and the isooctyl ester of 4-(2,4-dichlorophenoxy)-butyric acid (2,4-DB). Rates of application were 0.56, 1.12, and 1.68 kg/ha. Applications were made at the vegetative, bud, and flowering stages of growth. All treatments applied at the vegetative and bud stages of growth significantly reduced white clover seed production. Reductions in clover seed production usually became more severe as the rate of 2,4-DB increased.

Six Setaria species and varieties and three Panicum species were allowed to absorb 14C-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine), and/or 2-chloro-4,6-bis (ethylamino)-s-triazine (simazine). The grasses metabolized the herbicides to water-soluble derivatives. Peptide conjugates were the only major metabolites formed by each species or variety; however, hydroxyderivatives of the herbicides were detected. The order of ability of the Setaria and Panicum species and varieties to metabolize atrazine and/or propazine was similar to the order of their tolerance to atrazine and/or propazine. Several Setaria and Panicum species and varieties formed peptide conjugates of atrazine and/or propazine to which they are resistant, more rapidly than they formed peptide conjugates of simazine, to which they are susceptible.

Corn (Zea mays L.) was grown continuously without tillage (no-tillage) and with conventional tillage for 7 years to evaluate several herbicides for use in both crop culture systems. The only consistently satisfactory herbicide combinations for the no-tillage corn were 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 1,1′-dimethyl-4,4′bipyridinium ion (paraquat) or 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), simazine, and paraquat. Annual weed population shifted rapidly with different herbicide systems; fall panicum (Panicum dichotomiflorum Michx.) was the major annual weed where triazines were used as the residual herbicide. After several years of corn grown with no-tillage, hempdogbane (Apocynum cannabinum L.) became a significant problem in some plots. Corn yields with no-tillage were equal to yields in tilled areas provided weed control was satisfactory.

Growth of green foxtail (Setaria viridis (L.) Beauv.) was effectively controlled in the greenhouse by applying the sodium salt of trichloroacetic acid (TCA) as a postemergence treatment, when a rate of 0.84 kg/ha was used; when application preceded the two-leaf stage; and when 2.54 mm of water were available daily for moving TCA into the soil. There were significant interactions of TCA rate with light intensity, temperature, and source of seeds on the response of green foxtail. Seedhead production was curtailed at rates of 0.56 kg/ha or above when plants were grown under high light intensities (19,250 to 22,000 lux) and at moderate temperatures (20 to 22 C). Rates of 1.68 kg/ha or more were required to stop heading of foxtail grown at high temperature (27 C).

Rapid absorption and acropetal translocation of 14C from p-nitrophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (fluorodifen) labeled with 14C at either the 1 position of the p-nitrophenyl ring (fluorodifen-1′-14C) or the trifluoromethyl carbon (fluorodifen-14CF3) were observed in cucumber (Cucumis sativus L. ‘Ashley’) seedlings after root treatment via nutrient solution. The major degradative products of fluorodifen-1′-14C were p-nitrophenol and Unknown I (possibly a conjugate of p-nitrophenol). Some p-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether (2-amino-fluorodifen), p-aminophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether (p,2-diamino-fluorodifen), p-aminophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (p-amino-fluorodifen), and several minor unknowns also were detected. The major degradative product of fluorodifen−14CF3 was Unknown II (possibly a conjugate of 2-amino-4-trifluoromethylphenol). Also detected were some 2-amino-fluorodifen, 2-amino-4-trifluoromethylphenol, p-amino-fluorodifen, p2-diamino-fluorodifen, 2-nitro-4-trifluoromethylphenol, and several minor unknowns. The basic difference in susceptibility to fluorodifen of cucumber and peanut (Arachis hypogaea L. ‘Starr’) appears to be due to the rate of acropetal translocation (cucumber translocates more than peanut) and the rate of degradation (peanut degrades fluorodifen much more rapidly than cucumber).

Field studies were conducted with giant foxtail (Setaria faberii Herrm.) under shade intensities of 0, 30, 60, 70, 80, and 98%. Seed weight, dry weight of plant tops exclusive of seed, and total dry weight per plant decreased linearly with increasing shade intensities. These decreases were due primarily to decreases in number of leaves, number of stems per plant, and number of heads per plant. Height of main culm was less affected than other morphological characteristics. Shading affected the length of internodes but had little influence on number of internodes on the main culm. The amount of shade required to control giant foxtail completely, once it is established, appears to be above 95%. Expressed as 2-year means, plants grew to as much as 135 cm, had as many as 188 leaves, 41 stems, and 31 heads, and produced 73 g of dry matter per plant including 6 g of seed. Maximum number of seeds per head was 1405.

The control of grasses and broadleaf weeds in sunflowers (Helianthus annuus L. ‘Peredovik’) generally was as good with one or two cultivations during the 3-year period as with chemicals applied alone or in sequence with cultivation. Plant injury was not evident from mechanical treatments or from α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). However, plant injury occurred when plots were treated with 2-chloro-2′6-diethyl-N-(methoxymethyl) acetanilide (alachlor) plus 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) as a preemergence application in 1 year and from postemergence applications of 2-tertiobutyl-4-(2,4-dichloro-5-isopropyloxyphenyl)-5-oxo-1,3,4-oxodiazoline (RP 17623) and 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) in 2 years. Seed yields from plots cultivated once were as good as yields from plots that received multiple cultivation or herbicide treatments. Other agronomic characteristics were favorable from plots that received one cultivation.