Low recoveries of total applied 14C in translocation studies and erratic control of hemp dogbane (Apocynum cannabinum L.) in the field showed a need for a balance-sheet study of absorption, translocation, and metabolism of 14C-2,4-D [(2,4-dichlorophenoxy) acetic acid] and 14C-glyphosate [N-(phosphonomethyl)glycine]. Total recovery of 14C-herbicides applied to hemp dogbane in the laboratory was 97% for 2,4-D and 105% for glyphosate. Of the 14C recovered after 12 days in the hemp dogbane, 34 to 55% was parent-2,4-D after 2,4-D treatment, and 93 to 96% was parent glyphosate after glyphosate treatment. Only negligible amounts of 14C were lost via volatilization or evolution as 14CO2. A broadcast treatment with unlabeled herbicide did not significantly affect subsequent absorption, translocation, or metabolism of either herbicide. Total herbicide absorbed and translocated out of the treated area of the leaf generally increased during the subsequent 12 days for 2,4-D but only 3 days for glyphosate. A greater percentage of the total applied 2,4-D (31 vs. 14%) and glyphosate (14 vs. 8%) was translocated from upper rather than lower leaves of hemp dogbane, respectively. Higher temperatures (30 vs. 25 C) resulted in greater translocation of glyphosate (39 vs. 18%) but not 2,4-D (35 vs. 39%). Higher light intensities resulted in greater accumulations of 2,4-D into roots and of glyphosate into untreated areas of the treated leaf. Autoradiographs showed that both herbicides moved through hemp dogbane in a typical symplastic pattern and accumulated in roots and new leaves.

Combinations of MSMA (Monosodium methanearsonate) with either methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] or metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] were applied at various rates for postemergence control of fully developed goosegrass [Eleusine indica (L.) Gaertn.], a major weed grass in bermudagrass [Cynodon dactylon (L.) Pers.] turf. Two applications of MSMA at 2.24 kg/ha applied in combination with either methazole or metribuzin at 0.14 kg/ha controlled 96 to 98% of the goosegrass and it was as effective as methazole (1.12 kg/ha) or metribuzin (0.56 kg/ha) applied alone. Two applications of methazole (1.12 kg/ha) or metribuzin (0.56 kg/ha) had lower quality ratings (28 and 39, respectively) on bermudagrass putting green at 2 weeks after treatment than combinations of MSMA (2.24 kg/ha) with either methazole (0.14 kg/ha) or metribuzin (0.14 kg/ha) (54 and 59, respectively). The initial injury from combination treatments was not severe and turf recovered within 3 to 4 weeks.

Fosamine [ethyl hydrogen (aminocarbonyl)phosphonate] acted as a chemical inhibitor of shoot growth for periods of up to 3 yr following a single summer application to honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] trees. Anatomical study of field, greenhouse, and seedling mesquite indicated that the inhibition of primary and secondary growth caused by fosamine was due to a general cessation of nuclear activity in apical meristems and in the vascular and cork cambia of this species.

Nitrate reduction on a leaf fresh weight basis was measured in common lambsquarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.) in individual leaves as a function of the photosynthetic photon flux density (PPFD) under which the plants were grown. Common lambsquarters had greater rates of nitrate reduction than did redroot pigweed regardless of leaf age or PPFD and responded to a significantly greater degree when PPFD was increased, with a proportionately greater increase in nitrate reduction among younger leaves.

Three microcapsule formulations, two starch xanthate formulations, and one commercial formulation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) were evaluated in the greenhouse and field for their relative herbicidal efficacy and persistence. Biological assays with Italian ryegrass (Lolium multiflorum Lam.) revealed significant differences among the formulations in phytotoxicity and persistence. The commercial formulation of trifluralin was generally more phytotoxic than the others to Italian ryegrass sown the week of herbicide application. The two starch xanthate formulations and one microcapsule formulation of trifluralin were generally more phytotoxic and more persistent than the commercial formulation to Italian ryegrass sown from 1 through 19 weeks after herbicide application.

Twenty years after aerial application of 2.24 kg ae/ha of the butoxy ethanol ester of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] to release grass stage longleaf pine (Pinus palustris Mill.) seedlings, stocking was the same for each of three treated and control 4-ha plots. Treated plots, however, had significantly greater tree diameter (10%), taller trees (17%), and more merchantable tree volume/ha (40%). Merchantable tree volume differences 20 yr after treatment represent an 8 yr growth advantage for treated plots.

The patterns of buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2 imidazolidinone} uptake, translocation, and metabolism, and their potential contribution to crop selectivity, were studied in tolerant alfalfa (Medicago sativa L. ‘Vernal’) and susceptible quackgrass [Agropyron repens (L.) Beauv.]. 14C-Buthidazole was absorbed from a 5-μl droplet by leaves of both alfalfa and quackgrass plants, but did not move basipetally to the roots or nontreated leaves in 14 days. 14C-Buthidazole was absorbed very rapidly from Hoagland's solution by the roots of both species and translocated apoplastically to the leaves. Absorption and translocation of buthidazole did not differ between species, indicating that these processes did not contribute to crop selectivity. The herbicide and five metabolites were present in alfalfa leaf extracts 6 days after treatment. One unidentified metabolite accounted for 40% of the detected radioactivity 6 days after root application. Unmetabolized 14C-buthidazole accounted for 87% of the total radioactivity in quackgrass after 6 days. Metabolites having different chromatographic properties were recovered from the two species. Differential rate and type of metabolism appeared to contribute to buthidazole selectivity between the species.

Lanolin or lanolin + corn (Zea mays L.) starch rings are often used as barriers on leaves to prevent runoff of foliarly applied 14C-herbicide treatments. A preliminary experiment showed that 64 and 90% of the applied 2,4-D [(2,4-dichlorophenoxy)acetic acid] and 57 and 87% of the applied glyphosate [N-(phosphonomethyl)glycine] was adsorbed to or absorbed into a lanolin and lanolin + starch ring, respectively, during 6 days on a glass slide. Absorption and translocation of 2,4-D in hemp dogbane (Apocynum cannabinum L.) was decreased from 26% down to 16 or 17% of the total applied when a lanolin or lanolin + starch ring was used. Glyphosate absorption and translocation increased with the lanolin ring but not with the lanolin + starch ring. Distribution of the translocated 2,4-D and glyphosate was also altered by use of the ring barriers. Results indicate that one should avoid use of the lanolin ring in 14C-herbicide absorption studies to simulate field conditions.

Increased osmotic potential from 0 to −14 bars decreased the moisture uptake and germination of mechanically scarified hemp sesbania [Sesbania exaltata (Raf.) Cory] seed. Germination percentage for osmotic potential of 0, −2, −4, −6, and −8 bars was 86%, 86%, 70%, 19%, and 1%, respectively. This response to moisture stress was modified by imbibition, or hydration-dehydration, of the seed prior to the moisture stress. Imbibing the seed for as little as 2 h significantly increased its subsequent germination against moisture stress. One hydration-dehydration cycle had little or no effect on germination, but as the number of cycles increased, the germination percentage decreased. Prolonged hydration of 3 and 7 days followed by dehydration greatly reduced subsequent seed germination.

The competitive effects of pale smartweed (Polygonum lapathifolium L.) were studied on cabbage (Brassica oleracea L. ‘K-Y’) which was transplanted into rice (Oryza sativa L.) fields either 3 to 12 days before or 5 days after rice was harvested. Competitive effects were determined at weekly intervals from the time beds were formed around the cabbage at 5 days after rice harvest. Where cabbage was transplanted before rice harvest, at a time before pale smartweed germination, cabbage yields were reduced when weeds were allowed to grow for more than 4 weeks from the time the beds were formed. Where cabbage was transplanted at 5 days after the rice was harvested at a time when parts of pale smartweed had emerged, cabbage yields were reduced when weeds were allowed to grow for only 2 or more weeks after the beds were formed. Also, where weeds were removed at the beginning but allowed to grow at a later date, yield was reduced when cabbage was not kept weed-free for a minimum of 4 weeks.

In field plots, Japanese millet [Echinochloa crus-galli (L.) Beauv. var. frumentacea (Link) W. F. Wight] competed strongly with yellow nutsedge (Cyperus esculentus L.), reducing its dry weight and the number of plants and tubers with no loss of dry weight to the millet. Because Japanese millet did not shade the nutsedge for more than half the day, the main competition was thought to be ‘root’ competition (nutrient and water) with light competition as a minor factor. The greenhouse studies verified that roots were the primary area of competition. However, light competition between the two species was stronger in the greenhouse than in field plots. Also, when confined to limited light and soil volumes with a 1-month growing period, Japanese millet was reduced in dry weight by nutsedge competition.

The effects of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] were studied on electron transport and phosphorylation in isolated spinach (Spinacia oleracea L.) chloroplasts and on the response of green bean (Phaseolus vulgaris L. ‘Spartan Arrow’) to applications of oxyfluorfen alone or in combination with other herbicides. Coupled non-cyclic electron transfer and phosphorylation through photosystems I and II (H2 O å methyl viologen) were inhibited about 30% and 55%, respectively, by 10−4 M oxyfluorfen. Photosystem II-linked phosphorylation with dimethylbenzoquinone (2,5-dimethyl-p-benzoquinone) as the electron acceptor (H2 O å DMQ) was completely inhibited by 10−4 M oxyfluorfen. Photosystem II electron transport with dimethylbenzoquinone as the electron acceptor was inhibited 60% by 10−4 M oxyfluorfen, whereas photosystem I electron transport with 2,6-dichlorophenol indophenol as electron donor (DCIPH2 å MV) was not susceptible to oxyfluorfen inhibition. Photosystem I-linked phosphorylation and the accompanying electron transport supported by durohydroquinone electron donation (DQH2 å MV) were inhibited about 50% by 10−4 M oxyfluorfen, whereas cyclic phosphorylation was not inhibited at that concentration. Increased conductivity of a solution that contained leaf discs taken from green beans treated with various combinations of foliar-applied herbicides was a measure of membrane damage caused by the herbicides, and revealed that oxyfluorfen has a different site of action than do photosynthesis inhibitor and bipyridilium herbicides. Oxyfluorfen plus dinoseb (2-sec-butyl-4,6-dinitrophenol) injury to green beans was additive, but the two herbicides did not have the same site of action. Oxyfluorfen did not appear to inhibit electron transport in chloroplasts at herbicidal rates, nor was it dependent on electron transport for activation.

Cotton (Gossypium hirsutum L. ‘Stoneville 213’) was grown with densities of sicklepod (Cassia obtusifolia L.) or redroot pigweed (Amaranthus retroflexus L.) ranging from 0 to 32 weeds/15 m of row. Regression of seed cotton yields on weed density revealed a linear decrease in yield with increasing weed densities. In the 3 yr these studies were conducted, losses in hand harvested yields of seed cotton ranged from 34 to 43 kg/ha for each sickledpod plant/15 m of row and 21 to 38 kg/ha for each redroot pigweed plant per 15 m of row. Under comparable weed densities, yields of seed cotton differed only slightly when hand harvested or mechanically harvested. Mechanical harvesting efficiencies of cotton were reduced only at higher densities of weeds. The percentage of trash in cotton generally increased with increasing density of weeds. Neither sicklepod nor redroot pigweed affected cotton grade or micronaire.

In field studies, postemergence applications of HOE 29152 {2-[4-(trifluoromethyl phenoxy)phenoxy] propanoate} at rates of 1.68 to 3.36 kg/ha effectively controlled quackgrass [Agropyron repens (L.) Beauv.] when applied to plants in the one- to three-leaf stage. Control was still effective the following year. The addition of a surfactant to HOE 29152 did not increase quackgrass control, but it did increase soybean [Glycine max (L.) Merr.] injury. Cultivation 1 or 7 days after herbicide application increased the efficacy of HOE 29152 on quackgrass. Due to abundant moisture in 1977, untreated quackgrass-infested plots yielded as much as the weed-free plots. However, in 1976, a very dry year, the control of quackgrass with HOE 29152 resulted in greatly increased soybean yields. In greenhouse studies, postemergence applications of HOE 29152 at rates of 0.56 to 3.36 kg/ha effectively killed rhizome buds and reduced shoot dry weights of quackgrass. The phytotoxicity of HOE 29152 at 0.56 kg/ha was less at a postspray temperature of 36 C than at 17 or 27 C; however, the phytotoxicity of HOE 29152 at rates of 1.68 and 3.36 kg/ha was similar at all three temperatures. HOE 29152 can volatilize from soybean leaves, with volatility greater at 38 C than at 21 C. Postemergence applications injured soybeans similarly in field and growth chamber studies. Injury was observed only on leaves that were expanded at time of treatment, was short-term, and was most prevalent at 3.36 kg/ha.

Twelve sequential herbicide treatments were compared to cycloate (S-ethyl N-ethylthiocyclohexanecarbamate), a standard treatment, for control of annual weeds in sugarbeets (Beta vulgaris L.) in three field experiments conducted from 1971 through 1977. At harvest, seven sequential treatments had less than 10 annual broadleaf weeds per 30 m of row, whereas there were 40 broadleaf weeds per 30 m of row for the cycloate treatment. Four of these sequential treatments had significantly higher root yields and net returns than the cycloate treatment. Dependent on the sequential treatment and year, tonnage was increased 7.3 to 20.3 t/ha, and net returns $150 to $515/ha above those with cycloate. The most effective sequential treatment for control of weeds was a preplanting mixture of 2.2 kg/ha of ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] plus 1.7 kg/ha of diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} followed by a postemergence mixture of 0,6 kg/ha each of desmedipham [ethyl m-hydroxycarbanilate carbanilate (ester)] plus phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate). This sequential herbicide treatment increased root yields by an average of 20.3 t/ha and net returns by $515/ha above those with cycloate.

Several herbicides were applied in January, February, and March with a comparison of the intervals of treatment of 2 and 4 weeks after the initial treatment each month for postemergence control of winter annual weeds in bermudagrass [Cynodon dactylon (L.) Pers.] turf. Glyphosphate [N-(phosphonomethyl)glycine] treatments applied at 2-week intervals with the initial treatment made in January or February controlled a higher percentage of annual bluegrass (Poa annua L.) than when applied in March. Hop clover (Trifolium agrarium L.) control was also higher when glyphosate was initially applied in January or February than when applied in March regardless of time interval between first and second treatment. Combination treatments of (a) 2,4-D [(2,4-dichlorophenoxy)acetic acid] + dicamba (3,6-dichloro-o-anisic acid) and (b) 2,4-D + mecoprop {2-[(4-chloro-o-tolyl)oxy] propionic acid} + dicamba applied at 2-week intervals with the initial treatment made in January or February controlled more corn speedwell (Veronica arvensis L.) and hop clover than when applied in March. Highest henbit (Lamium amplexicaule L.) control was obtained from the combination 2,4-D treatments made at 4-week intervals when initial treatment was made in February and March. Weed control was not influenced by dates and interval of repeated treatments with either paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) or atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] treatments. Germination and regrowth of weeds were greater in plots treated with glyphosate and paraquat initially in January or February than other herbicide-treated plots. Weeds were not reestablished in any of the atrazine-treated plots. Paraquat and combinations of 2,4-D + dicamba or 2,4-D + mecoprop + dicamba injured bermudagrass when applied initially in January and February even though they were applied to turf that appeared dormant. All herbicides injured bermudagrass more when applied to semi-dormant turf in March than to dormant turf in January or February. Atrazine affected bermudagrass less than any of the other herbicides tested when initial treatment was applied in March to semi-dormant turf.

Dwarf spikerush [Eleocharis coloradoensis (Britt.) Gilly], a perennial aquatic plant, is composed of many individual rosettes connected by rhizomes. Each rosette has needlelike culms attached to a stalk, a crown with an apical meristem, and many fibrous roots. It reproduces by achenes, subterranean tubers, and crown tubers. Dwarf spikerush achenes were harvested three times in 1 yr after the water level had been manipulated to promote flowering. The annual yield of achenes following this treatment was 79 kg per ha. Subterranean tubers began to form in September and formation was maximum in October. Individual plants grown for 1 yr developed an average of 351 tubers. Maximum density of tubers formed in hydrosoil was 7 per cm2. Longevity studies showed that the percentage germination of achenes and tubers decreased, respectively, from 48 to 32% and from 100 to 46% when stored wet at 4 C for 4 yr. Plants grown for 6 months from a single subterranean tuber, rosette, or achene spanned 150, 127, and 99 cm, respectively. The species thrived in a wide range of water qualities and on soft hydrosoils largely made up of silt, clay, and organic matter. On plants immersed in 0 to 100% sea water for 1 month, culms were injured in 30% sea water and killed in 40% sea water. Surviving plants showed some new growth after transfer to fresh water. Some tubers were incubated in diluted sea water. They germinated in solutions up to 80% sea water. Plants grown in water under different light intensities grew best at the maximum of 3,900 lux. More rosettes, culms, and inflorescences were produced with a 14-h photoperiod than 11- or 17-h photoperiod. Dwarf spikerush displaced other species by invading them when growth of the other plants was suppressed. The erect crowded culms of dwarf spikerush mechanically resisted incursion of other aquatic plants.

The production of new shoots of American pondweed (Potamogeton nodosus Poir.) and sago pondweed (P. pectinatus L.) was reduced significantly when winterbuds and tubers of these species were planted in dwarf spikerush [Eleocharis coloradoensis (Britt.) Gilly] sod. In most instances, the number of shoots produced was several times greater when winterbuds and tubers were planted in bare soil than when planted in spikerush sod. Similar results were obtained when the pondweeds were grown in separate aquaria, each aquarium being exposed to 500 ml of leachate per day from spikerush sod. The differences in reproduction of pondweeds could not be attributed to altered water quality nor to reduced levels of nutrients. No appreciable allelopathic response was elicited by the pondweed plants originating from planted tubers or winterbuds. The principal response appeared to be reduction in numbers of new shoots produced from the original propagules, although the reduction in biomass of the pondweeds exposed to the effects of spikerush was obvious. Of the two pondweeds investigated, sago pondweed was most sensitive to the influence of spikerush.

The influence of acetamide herbicide applications on efficacy of CGA-43089 [α-(cyanomethoximino)-benzacetonitrile] in grain sorghum [Sorghum bicolor (L.) Moench] was studied under field conditions. Acetamide herbicides applied preplant and incorporated on a Haynie very fine sandy loam caused more grain sorghum injury in 1979 than in 1978. Reductions in plant population, plant height and yield, along with delay in maturity, were severe for acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-O-acetotoluidide], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide]; moderate for diethatyl [N-(chloroacetyl)-N-(2,6-diethylphenyl)glycine], xylachlor [2-chloro-N-(2,3-dimethylphenyl)-N-(1-methylethyl)acetamide], and butam [2,2-dimethyl-N-(1-methylethyl)-N-(phenylmethyl)propanamide]; and did not occur for propachlor (2-chloro-N-isopropylacetanilide) treatments. Acetamide herbicides caused less grain sorghum injury on a Reading silt loam than on a Haynie very fine sandy loam in 1979. CGA-43089 applied as a seed treatment protected grain sorghum grown on soils treated with metolachlor, alachlor, diethatyl, or xylachlor. Metolachlor-triazine combinations at five locations in Kansas reduced yields at two locations. CGA-43089 provided protection from metolachlor injury at those two locations.

The growth regulator, glyphosine [N,N-bis(phosphonomethyl)glycine], and other possible metabolites of glyphosine and glyphosate [N-(phosphonomethyl)glycine] [glycine, sarcosine, and aminomethylphosphonic acid (AMPA)] were tested individually (0.5 mM) or as a mixture (each at 0.5 mM) for their effects on growth, extractable phenylalanine ammonia-lyase (PAL) activity, hydroxyphenolic-compound production, chlorophyll and anthocyanin contents, and on soluble-protein levels in soybean [Glycine max (L.) Merr. ‘Hill’] seedlings. Most chemical treatments caused some inhibition of growth either on fresh weight accumulation or on root elongation in the light and dark over 72 h. Glyphosine was generally the most inhibitory and caused the greatest inhibition on axis dry-weight accumulation. Glyphosine significantly increased extractable PAL activity in axes of light- and dark-grown soybeans to a lesser extent than did glyphosate. AMPA had some inhibitory effects on extractable PAL activity whereas other compounds had little influence on the enzyme. These compounds had little effect on total soluble protein in axes or on soluble protein in PAL preparations from 12 to 72 h in light-or dark-grown seedlings. No in vitro effect of the chemicals on PAL activity was found at concentrations up to 0.5 mM. Hydroxyphenolic compound levels increased within 24 to 72 h (per gram fresh weight basis) in light- or dark-grown soybean axes treated with glyphosine, AMPA, or a metabolite mixture (AMPA, sarcosine, and glycine). Anthocyanin content was decreased by glyphosate and to a lesser extent by glyphosine, but was increased by AMPA and the mixture. Glyphosate significantly increased the chlorophyll a/b ratio and decreased total chlorophyll, but glyphosine decreased the chlorophyll content to a lesser degree.