The controlled release of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] and alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] from pine kraft lignin was studied using 14C-labeled herbicides and 3H-labeled lignin with soil thin-layer chromatography. NB-5203-58 series and PC940 series kraft lignins adsorbed and desorbed metribuzin as soil plates were developed with water. PC671, a formulated kraft lignin control release product, did not provide controlled release with metribuzin. NB-5203-58B and PC940C were the most effective of their respective series of kraft lignins. PC940C also provided controlled release of alachlor.

Control of monoecious and dioecious hydrilla [Hydrilla verticillata (L.f.) Royle # HYLLI] biotypes required a minimum 2 days of exposure to diquat (6,7-dihydrodipyrido [1,2-α:2′,1′-c] pyrazinediium ion) at a concentration of 0.25 mg/L under laboratory conditions. When treatment concentration was increased to 2.0 mg/L diquat, the minimum required contact time was reduced to 6 or 12 h depending on plant growth stage. Early growth emerging from sprouting tubers appeared to be more susceptible to diquat treatments. Herbicide uptake was linear during a 4-day exposure to 14C-diquat up to 1.0 mg/L, and the amounts of radioactivity in plant tissue varied proportionally with ambient levels of 14C-diquat in water. The lethal concentration of diquat in hydrilla tissue was estimated to be 81 μg/g plant dry weight when hydrilla was exposed to diquat at 0.25 mg/L for 2 days.

The addition of surfactant (trimethylnonylpolyethoxyethanol) at 0.5% (v/v) of the spray solution caused a twofold increase in the deposit of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) applied at 0.14 or 0.28 kg ae/ha on greenhouse-grown honey mesquite (Prosopis glandulosa Torr. # PRCJG) and increased transport into the plants compared to clopyralid applied alone. Application of equal rates of benazolin [4-chloro-2-oxo-3(2H)-benzothiazoleacetic acid] with clopyralid at 0.28 + 0.28 kg/ha enhanced transport of clopyralid into honey mesquite. Spray deposit, absorption, and translocation of clopyralid was unaffected by addition of 0.5% (v/v) of d'limonene (4-isopropenyl-1-methyl-cyclohexane). Greater spray deposit of clopyralid on plant surfaces after addition of surfactant was associated with reduced liquid surface tension and greater percentage of spray volume in small droplets (<204-μm diam).

Twenty-five winter wheat (Triticum aestivum L.) cultivars were sprayed with herbicides when in the tillering stage in April at North Platte, NE. In 1978, ‘Lindon’ and ‘Vona’ stands were reduced and grain yields of ‘Larned′, Lindon, ‘Roughrider′, 'Sage′, 'Scout 66′, 'Sentinel′, ‘Turkey′, and Vona cultivars were reduced by metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] plus pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] at 0.3 plus 2.8 kg ai/ha. There were no differences among cultivars in response to herbicides in 1979, 1981, and 1982. During 1980, wheat was more tolerant to a mixture of pendimethalin and 2,4-D [(2,4-dichlorophenoxy)acetic acid] than metribuzin plus pendimethalin. In 1981 and 1982, combinations of 2,4-D with pendimethalin or metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] did not reduce wheat yields. The mixture of pendimethalin plus 2,4-D performed satisfactorily in 4 yr of use.

Copper content and growth of excised hydrilla [Dioecious Hydrilla verticillata (L.f.) Royle # HYLLI] apical shoot segments were determined following exposure to copper sulfate (CuSO4), copper-triethanolamine (Cu-TEA), and copper-ethylenediamine (Cu-EDA). For all copper formulations, inhibition of growth was related to the amount of copper associated with the excised shoots. At equal copper exposure, the Cu-EDA formulation produced the greatest inhibition of growth and generally the highest copper levels in the plants. The Cu-EDA formulation inhibited dry weight gain by more than 80% 3 weeks after a 2-h exposure to 2.0 or 4.0 ppmw copper. Under similar conditions, CuSO4 or Cu-TEA produced 60% inhibition. The presence or absence of light during a 2-h exposure had no effect on the efficacy of uptake of copper from any of the formulations. Formulation-dependent differences in the mechanism of copper uptake is suggested because rinsing of exposed shoots with dilute acid (0.01N HNO3) removed copper from shoots treated with CuSO4 or Cu-TEA but not from those treated with Cu-EDA.

Field experiments were conducted to determine the effects of tank-mixing fluometuron {N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl] urea} or MSMA (monosodium salt of methylarsonic acid) with sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} or the butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanic acid} on cotton (Gossypium hirsutum L.) tolerance and large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] control. Postemergence (over-the-top) application of 1.7 kg ai/ha of fluometuron reduced cotton lint yield 17 to 23% in three of four tests. No yield reduction resulted from postemergence application of 1.1 kg ae/ha of MSMA. Tank-mixing 0.1 or 0.2 kg ai/ha of sethoxydim or 0.1 or 0.2 kg ae/ha of fluazifop with fluometuron or MSMA did not alter the effect of fluometuron or MSMA on cotton yield. Tank mixtures of 1.1 to 2.2 kg/ha of fluometuron plus sethoxydim or fluazifop were antagonistic. No antagonism was observed when fluometuron was applied 3 days before or 6 h following sethoxydim or fluazifop application. Tank-mixing 1.1 or 2.2 kg/ha of MSMA with sethoxydim or fluazifop initially reduced control of large crabgrass. Antagonism was not observed at 4 weeks after tank-mix application of MSMA plus sethoxydim, and was observed in only one of three experiments 4 weeks following tank-mix application of MSMA plus fluazifop. When antagonism was observed with tank mixtures of fluazifop plus MSMA, sequential application of MSMA 1 to 7 days before application of fluazifop did not overcome the antagonism. No antagonism occurred when MSMA was applied 6 or more hours after fluazifop application.

Ethyl ester of DPX-Y6202 {2-[4-[(6-chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid} and butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} applied during the reproductive phase of development at 0.07 and 0.28 kg ai/ha prevented seed formation in downy brome (Bromus tectorum L. # BROTE). Fluazifop prevented seed formation over a wider range of application rates and growth stages than did DPX-Y6202. Seed production was prevented most readily by herbicide applications made early in the reproductive phase. Environmental factors during reproduction affected herbicide performance. Foliar absorption and translocation of 14C-fluazifop into the developing spikelets was greater than that of 14C-DPX-Y6202 in downy brome.

Soil factors that may affect activity of the propynyl ester of CGA-82725 {2-[(3,5-dichloro-2-pyridinyl) oxy] phenoxy] propanic acid}, methyl ester of haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, and butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} were examined. Adsorption of the three herbicides on three Illinois soils was similar but very low. Linear partion coefficients (Kd) ranged from 0 to 1.75 for CGA-82725 and haloxyfop, while no adsorption was detected for fluazifop on Drummer silty clay loam, Cisne silt loam, or Bloomfield sand. Conversion to the parent acid (active form) following application to the soil was rapid. The acid form was predominant for 2 months. Two metabolites were recovered; one was common to all three herbicides and intermediate in polarity to the acid and ester forms, and the other, unique to CGA-82725, was slightly more polar than the acid form. Extractability of the herbicides decreased dramatically over time. Haloxyfop and CGA-82725 leached to similar depths in soil column studies. Fluazifop tended to move more readily in the silty clay loam but less rapidly in the sand. Adsorption studies with 15 additional soil or sediment samples with widely varying physiochemical properties yielded adsorption (Kd) values of 0.79, 1.09, and 1.15 for fluazifop, haloxyfop, and CGA-82725, respectively, when averaged over all samples studied. Adsorption did not appear to be significantly influenced by organic carbon content, clay content, or pH.

Field and laboratory experiments were conducted in 1983 and 1984 to compare the degradation of dichlormid (2,2-dichloro-N,N-di-2-prophenylacetamide), dietholate (O,O-diethyl O-phenylphosphorothioate), EPTC (S-ethyl dipropyl carbamothioate), and butylate [S-ethyl bis(2-methylpropyl) carbamothioate] in soils that had or had not been previously treated with each chemical. EPTC + dichlormid, butylate + dichlormid, EPTC + dichlormid + dietholate, or butylate + dichlormid + dietholate were applied annually for 4 yr to field plots to establish treatment histories. Butylate and EPTC degradation was enhanced in soils with previous histories of butylate and EPTC, respectively. Degradation rates of dietholate were equivalent in untreated soils or soils previously treated with EPTC + dietholate or butylate + dietholate.

Field spectroradiometric plant canopy measurements showed that broom snakeweed [Gutierrezia sarothrae (Pursh.) Britt. and Rusby # GUESA] and spiny aster (Aster spinosus Benth. # ASTSN) had lower near-infrared (0.85-μm) reflectance than did other associated rangeland shrubs and herbaceous vegetation. The low near-infrared reflectances of both species were attributed to their erectophile (erect leaf/stem) canopy structures. These low near-infrared reflectance values caused broom snakeweed to have a dark-brown to black image on color-infrared aerial photos (0.50- to 0.90-μm), whereas spiny aster had a dark reddish-brown to black image. Other rangeland plant species had light-brown, red, or magenta images. Computer-based image analyses of color-infrared film positive transparencies showed that broom snakeweed and spiny aster infestations could be quantitatively differentiated from associated rangeland species. Computer analyses can permit “percent land area infested” estimates of broom snakeweed and spiny aster infestations on rangelands.