Two, 4-dichloro-6-fluorophenyl-p-nitrophenyl ether (CFNP) is similar in herbicidal property and chemical structure to nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether). CFNP inhibits the growth of the hypocotyl and young buds of germinating weeds. Henry Crabgrass (Digitaria adscendens H.B.K. Henr.) was controlled by CFNP at 0.5 kg/ha, however sunflower (Helianthus annuus L.) was tolerant to 16 kg/ha of CFNP. CFNP also effectively controlled largeseed dodder (Cuscuta indecora Choisy) which is a serious problem in sunflower. Although trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) did not control common dodder at 8 kg/ha, CFNP gave control at 0.5 kg/ha.

Freshly harvested Florida pusley (Richardia scabra L.) seeds do not germinate in continuous dark, but do germinate if exposed to more than 2 hr of light each day. Increasing periods of illumination up to 16 hr per day increases the germination percentages. Scarification increases the rate of germination in the presence of light. Scarification also causes germination of seeds stored for 8 months or longer in total darkness. The seeds fail to germinate at constant temperatures of 15 C or less and at 40 C. Almost complete germination occurs at a constant temperature of 30 C, or at alternating temperatures of 20 and 30 C. The seeds germinate equally well in the pH range of 3 to 8. Increasing depths of planting reduces percent emergence, and none of the seedlings emerge from a depth of 1.5 cm or more. Air-dried seeds can be stored either at 5 or at 25 C without losing viability, at least up to a period of 1 year after harvest. Moist storage of seeds at 5 C reduces germinability.

Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], and benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) were applied at two rates for five consecutive years (1966 through 1970) as soil-incorporated treatments to cotton (Gossypium hirsutum L. ‘Acala SJ-1’) before the preplanting irrigation. Repeated applications did not significantly affect stand or yield of cotton. Soil samples taken to depth of 120 cm showed that herbicide residues were confined to the tilled zone of soil (upper 30 cm), and about 80% of the residue was in the upper 15 cm of soil. The amount of herbicide residue found annually in the upper 15 cm of soil varied with herbicide and with season. Residues 15 months after final application had been reduced markedly, but were still sufficient to injure sensitive crops. Residues at 30 months had been reduced to innocuous amounts.

The effectiveness of postemergence applications of triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate] for wild oat (Avena fatua L.) control in spring wheat (Triticum aestivum L. ‘Waldron’) was evaluated in the field and greenhouse. The stage of the wild oat plants at the time of treatment did not appear to influence wild oat control with postemergence applications of triallate in the field; however, in the greenhouse, wild oat plants became more resistant with increased maturation. Granular triallate was more effective than the emulsifiable concentrate for postemergence wild oat control. Fair season-long postemergence wild oat control was obtained with the granular formulation of triallate at rates of 2.24 kg/ha or greater. However, some wheat injury was observed in the field with the 2.80 and 3.36 kg/ha rates of granular triallate. Moisture and temperature influenced postemergence wild oat control with triallate.

A dense bloom of the blue-green alga, Anabaena variabilis Kuetzing suddenly died in a pond heavily stocked with channel catfish (Ictalurus punctatus L.). Low light intensity caused the formation of gas vacuoles in A. variabilis. The buoyant filaments accumulated at the surface in large numbers during a period of calm, warm weather. Light injury to cells in the surface scum apparently triggered the mass mortality of phytoplankton. Decomposition of dead algae quickly resulted in depletion of dissolved oxygen. Concentrations of CO2 and ammonia increased to high levels and the pH declined following the phytoplankton die-off. A period of 7 days was required for re-establishment of a phytoplankton community and little improvement in water quality occurred until high densities of healthy phytoplankters were present. Massive mortality of fish was prevented by pumping oxygenated water into the pond at two sites and by mechanically agitating surface water in a limited area.

Single and repeated applications of MSMA (monosodium methanearsonate) with and without 2,4-D [(2,4-dichlorophenoxy)acetic acid], metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one], and methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-di-one] were evaluated for control of large crabgrass (Digitaria sanguinalis L. Scop.) and goosegrass (Eleusine indica L. Gaertn.). Large crabgrass was controlled satisfactorily at Griffin in 1972 and 1973 with a single application of 1.7 kg/ha of MSMA, however, repeated applications were required for similar control at Griffin in 1974 and at Blairsville in 1973 and 1974. Repeated treatments at 0.6 kg/ha resulted in satisfactory large crabgrass control in only 2 of 3 years at Griffin and 1 of 3 experiments at Blairsville. The optimum time interval between the first and second MSMA treatments (average 1973 and 1974) was 12 days for the 1.1 kg/ha rate and anytime between 12 and 19 days for the 1.7 and 2.2 kg/ha rates. There was no advantage in large crabgrass control from treatments of methazole, metribuzin, or combinations of MSMA + 2,4-D when compared with MSMA. Single applications of 1.1 kg/ha of metribuzin or 2.2 kg/ha of methazole resulted in excellent goosegrass control without causing any permanent injury to common bermudagrass [Cynodon dactylon (L.) Pers.]. Repeated treatments of 3.3 kg/ha of MSMA were required to obtain satisfactory goosegrass control.

Studies were conducted to examine over time the effects of propachlor (2-chloro-N-isopropylacetanilide) on the growth of cucumber (Cucumus sativus L. ‘Straight Eight’) roots and associated biosynthetic reactions. Complete inhibition of root elongation occurred within 16 hr after exposure to propachlor. Inhibition of growth was not found to be a result of an effect on ATP formation or respiration. Protein biosynthesis was reduced several hours before the observed inhibition of growth therefore implicating it as the causal factor. Inhibition of protein synthesis occurred prior to an observed reduction in RNA synthesis suggesting that the primary effect of propachlor is on protein biosynthesis and that its effect on nucleic acid synthesis is secondary. It is concluded that the primary mechanism of action of propachlor is its effect on nascent protein biosynthesis.

Herbicide mobility in soils was compared by three laboratory methods. The Rf values calculated from soil thin-layer chromatography correlated closely with those obtained from soil thick-layer chromatography (r = 0.96). Herbicides leached slightly further in slotted column chromatography as compared with the other methods. The working hours required to conduct a study with each method were in the increasing order of thin-layer, thick-layer, and column chromatography. However, the thin-layer method required the longest waiting times, followed by the column and thick-layer chromatography. If radioactive herbicides are not available or obtainable, the thick-layer chromatography is simplest and quickest. The relative mobility of herbicides studied was fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] > napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] > terbutryn [2-(tert-butyl-amino)-4-(ethylamino)-6-(methylthio)-s-triazine] > trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). Less herbicide mobility was observed in heavier soil than in sandy soil.

Laboratory, greenhouse, and field experiments were conducted in 1972 and 1973 on the efficacy of controlling yellow nutsedge (Cyperus esculentus L.) in soybeans [Glycine max (L.) Merr.] with bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide], glyphosate [N-(phosphonomethyl)glycine], and perfluidone [1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide]. Young nutsedge plants (four- to six-leaf stage) were more susceptible to foliar sprays of the three herbicides than were older (six- to eight-leaf stage) plants. Foliar application of bentazon resulted in slow acropetal translocation of the herbicide, but killed the parent tubers. Good coverage of the foliage by bentazon sprays is essential, because the bentazon frequently kills only the foliage contacted by the spray. Applied as a postemergence broadcast spray, glyphosate injured soybeans severely at rates higher than 0.3 kg/ha, but did not satisfactorily control yellow nutsedge at rates less than 2.2 kg/ha. Perfluidone was active on yellow nutsedge when applied to either soil or foliage; yellow nutsedge was controlled best with preplant incorporated treatments at 4.5 kg/ha. Applications of 4.5 kg/ha perfluidone in the field significantly injured soybeans and reduced yields.

The effect of surface corn (Zea mays L.) plant residue on weed control with atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] or alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] was studied in the field and greenhouse. Plant residue did not significantly affect weed control when herbicides were applied at recommended rates but had an increased influence on control as herbicide rates were reduced. In the greenhouse, simulated rain improved the control of velvetleaf (Abutilon theophrasti Medic.) and foxtail millet [Setaria italica (L.) Beauv.].

MSMA (monosodium methanearsonate) and DSMA (disodium methanearsonate) killed 27 to 90% of the broomsedge (Andropogon virginicus L.) plants when applied at 1.1 to 6.7 kg/ha in July. These rates did not reduce yields of smooth bromegrass (Bromus inermis Leyss.) or affect the density of Kentucky bluegrass (Poa pratensis L.) growing in association with the broomsedge.

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] was most phytotoxic to oat (Avena sativa L.) when placed in the seed zone and to quackgrass (Agropyron repens (L.) Beauv.), when placed in the rhizome zone. Inhibition of part of the buds by pronamide on detached quackgrass rhizome sections did not influence other buds. Foliar applications of pronamide were not phytotoxic to established oat or quackgrass. Foliar-applied 14C-pronamide showed little uptake by quackgrass. Application to the roots of established plants showed rapid root uptake and movement to the foliage. 14C-pronamide was rapidly absorbed by oat seedlings for the first 0.5 hr and subsequently at a much slower rate. Over 60% of the pronamide taken up after 1 hr was exchangeable. Pronamide was adsorbed to the cell walls of treated roots, but little was associated with nuclear, mitochondrial, microsomal, or soluble protein fractions. Pronamide was adsorbed to varying degrees depending on soil type. Adsorption was more highly correlated with soil organic matter content than with cation exchange capacity, clay content, or pH.

Early postemergence application of atrazine [2-chloro-4- (ethylamino)-6-(isopropylamino)-s-triazine] at 0.28 kg/ha in combination with alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 0.42 kg/ha plus a non-toxic oil-surfactant blend gave season-long weed control in sweet corn (Zea mays L. var. rugosa ‘Seneca Chief’). Bioassay with oats (Avena sativa L.) showed no detectable atrazine residue in the soil 3 months after herbicide application. In greenhouse studies, the response of Japanese millet (Echinochloa crus-galli L. Beauv. var. frumentacea) to early postemergence application of atrazine and alachlor combinations plus an oil-surfactant blend was synergistic. Soil uptake played a major role in the activity of the herbicides. Formulants used in commercial alachlor when added to atrazine spray, enhanced atrazine activity in a way similar to that of the non-toxic oil-surfactant.

Tolerance of sugarbeets (Beta vulgaris L. ‘Mono-Hy A1’) to ethofumesate (2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulphonate) was associated with rate of application and soil type. Yield of roots was significantly reduced by preplant-incorporated applications of 3.4, 4.5, or 9.0 kg/ha of ethofumesate to a sandy loam soil, but only the 9.0 kg/ha rate reduced the yield on a loam soil. Pinto beans (Phaseolus vulgaris L. ‘Idaho #111’) yielded normally when planted on a sandy loam soil within 4 to 6 weeks after ethofumesate was incorporated at rates of 2.2 to 9.0 kg/ha. Corn [Zea mays L. ‘Pioneer brand 3773 MFS(N) hybrid’] yields were reduced in proportion to the rate of herbicide applied 3 weeks before planting. In greenhouse studies, barley (Hordeum vulgare L. ‘Moravian’) and wheat (Triticum aestivum L. ‘Scout’) were about 10 times more susceptible to soil residues of ethofumesate than corn. Concentrations of ethofumesate in the soil as low as 0.1, 0.2, and 1.5 ppmw reduced the height of wheat, barley, and corn, respectively.

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] inhibited root and shoot growth, but had little effect on the germination of oat (Avena sativa L.) or cucumber (Cucumis sativus L.), and sprouting of quackgrass [Agropyron repens (L.) Beauv.] buds. Root growth was more sensitive than shoot growth. Pronamide decreased the longitudinal growth rate and caused radial enlargement in the elongation region of the roots of oat seedlings within 4 hr. Dry weights of the swollen root tips increased 6% over the controls after 4 hr. Pronamide stopped the growth of established oat plants within 24 hr when added to nutrient culture medium. It caused a slight increase in 86Rb uptake by excised oat roots. Pronamide stopped normal mitosis in treated oat roots within 0.5 hr. Examination of treated root tips under a microscope showed numerous cells in arrested metaphase, c-pairs, multinucleate cells, polyploidy and swollen and misshapen nuclei. Incorporation of 14C-glucose into oat root cell walls and 14C-leucine into protein were increased by 26 and 20% respectively, following 4-hr incubations in pronamide. The primary mode of action of pronamide is mitotic poisoning.

Studies of the differential responses of soybean [Glycine max (L.) Merr.] cultivars to bentazon [3-isopropyl-1H-2,1,3,-benzothiadiazin-(4)3H-one 2,2-dioxide] revealed slightly greater translocation and about a twofold greater foliar absorption in the sensitive cultivar ‘PI 229.342 (Nookishirohana),’ than in the tolerant cultivar, ‘Clark 63.’ Clark 63 metabolized bentazon faster than did PI 229.342. Bentazon was metabolized to unidentified polar metabolites I and II in Clark 63, and only to metabolite II in PI 229.342. The differential absorption and metabolism resulted in a tenfold greater concentration of bentazon in the treated leaflet of PI 229.342 than in that of Clark 63 at 8 days after foliar treatment. Leaflets contained similar amounts of 14C in petiole uptake studies, but no bentazon was detected in Clark 63 leaflets 24 hr after pulse treatment, whereas about 20% of the methanol-extractable 14C from PI 229.342 leaflets cochromatographed with bentazon. Metabolite I was labile to selected enzymes with β-glycosidic activity, whereas metabolite II was unaffected. Bentazon concentrations of 30 to 50 μM inhibited O2 evolution about 50% in isolated chloroplasts from the two cultivars. Differential bentazon metabolism appears to be the main cause of the differential responses of these soybean cultivars to bentazon.

Soil enrichment studies were conducted with trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) with and without exogenous carbon and nitrogen. From 72 bacterial isolates obtained, eight representative ones were tentatively identified as members of the genus Pseudomonas based on size, shape, Gram reaction, and reaction on fluorescent and motility agar. Two of these eight isolates exhibited a significant increase in numbers of viable cells when grown in a medium with trifluralin as the only exogenous carbon and nitrogen source. Chromatographic analysis of culture medium extracts revealed the presence of a degradation product which was not present in the herbicide control. The concentration of this unknown was greatest at the 50 mg/L level of trifluralin which also supported the greatest bacterial growth.