BAS 9052 {2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio)-propyl]-3-hydroxy-2-cyclohexene-1-one} and difenopenten {4-[4-[4-(trifluoromethyl)phenoxy]phenoxy]-2-pentenoic acid} concentrations less than 1% (w/w) did not normally inhibit apparent photosynthesis (AP) of corn (Zea mays L. ‘Mo 17 × B73′) leaves for at least 24 h. However, leaf growth was completely inhibited by BAS 9052 within 24 h. Leaf AP was initially more inhibited in soybean (Glycine max L. ‘Corsoy’) than in corn by each herbicide, but within 48 h soybean AP was usually recovering and plants grew normally. Because inhibition of corn leaf growth preceded that of AP, leaf photosynthesis could not be a primary mode of action for BAS 9052.

CGA-43089 [α-(cyanomethoximino)-benzacetonitrile], CGA-92194 {α-[(1,3-dioxolan-2-yl-methyl)imino] benzeneacetonitrile}, and MON-4606 [5-thiazolecarboxylic acid, benzyl ester, 2-chloro-4-(trifluoromethyl)], applied as seed treatments at 1.25 g/kg seed, prevented yield losses in grain sorghum [Sorghum bicolor (L.) Moench.] in the field due to metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], alachlor [2-chloro-2′, 6′-diethyl-N-(methoxymethyl)acetanilide] or acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide] applied at 1.7, 2.2 and 1.7 kg/ha, respectively. CGA-92194, applied at 0.8 g/kg seed, prevented yield reduction from metolachlor applied at 4.5 kg/ha. MON-4606 was more effective in protecting grain sorghum when applied as a seed treatment than when applied in the furrow with a clay or sand granule as carrier.

Over 9 yr, bandane (polychlorodicyclopentadiene isomers) at 67 kg/ha, bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] at 11 and 22 kg/ha, DCPA (dimethyl tetrachloroterephthalate) at 22 kg/ha, and terbutol (2,6-di-tert-butyl-p-tolyl methylcarbamate) at 22 kg/ha applied preemergence controlled 94 to 100% of large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSP] in a lawn of common bermudagrass [Cynodon dactylon (L.) Pers. # CYNDA]. Control from benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) at 5 kg/ha, DCPA at 11 kg/ha, simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] at 5 kg/ha, and terbutol at 11 kg/ha was 90 to 99%. Bandane and bensulide persisted in soil to control large crabgrass a year after treatment.

Laboratory, greenhouse, and field studies were conducted to determine the allelopathic potential of sunflower (Helianthus annuus L.) cultivars to suppress weed germination and growth. Germination of wild mustard [Brassica kaber (DC.) L.C. Wheeler var. pinnatifida (Stokes) L.C. Wheeler] seeds at 25 C in undiluted aqueous extracts of sunflower leaf tissue was inhibited 75%, but was stimulated by up to 150% at 10- and 100-fold dilutions. Stem-tissue extracts at all concentrations stimulated wild mustard seed germination. The germination response of other weed species varied with the sunflower cultivar and concentration of tissue extract. In sand culture, leachates of dried sunflower leaf and stem tissue inhibited broadleaf - weed seedling growth, but had little or no effect on the growth of grass weeds. Sunflower root exudates inhibited seedling growth, but were less effective than leaf and stem tissue leachates. Germination of weed seeds was unaffected by root exudates. Over a 5 -yr period, weed density and percent ground cover increased less in field plots of sunflower than in control plots.

Absorption, translocation, and distribution of 14C-glyphosate [N-(phosphonomethyl)glycine] were examined in quackgrass [Agropyron repens (L.) Beauv.] plants growing at 10/8, 15/12, and 21/18 C day/night temperatures at 300 μE·m-2·s-1. Absorption of 14C-glyphosate followed similar trends in all environments, apart from an initial delay at the highest temperature. Approximately 67% of the applied 14C-glyphosate was absorbed after 120 h. Glyphosate translocation to the rhizomes was initially slower in plants growing at 10/8 C than at the higher temperatures, but after 24 h continued at a rate similar to that observed at the higher temperatures. CO2 exchange rates (CER) were only slightly influenced by temperature between 5 and 25 C, which may explain the lack of temperature effect on the rate of glyphosate translocation. Approximately 47% of the applied 14C-glyphosate was recovered in the rhizomes and associated roots 120 h after application in all environments. Glyphosate accumulated predominantly in new rhizomes under all growing conditions.

Construction and use of a portable electronic metronome as an aid in maintaining the desired speed while spraying with an operator-propelled sprayer is described. Use of such a metronome should minimize fluctuations in spray application caused by variations in walking speed during spraying.

Growth dynamics, water relations, and photosynthesis of soybean [Glycine max (L.) Merr. ‘Ransom’], common cocklebur (Xanthium pensylvanicum Wallr.), jimsonweed (Datura stramonium L.), prickly sida (Sida spinosa L.), sicklepod (Cassia obtusifolia L.), smooth pigweed (Amaranthus hybridus L.), spurred anoda [Anoda cristata (L.) Schlect.], and velvetleaf (Abutilon theophrasti Medic.) were compared in a controlled-environment greenhouse programmed for 32C day and 23C night temperatures. Net photosynthetic rates, net assimilation rates, and water-use efficiency on a whole-plant or single-leaf basis were greatest in the C4-plant, smooth pigweed. Total dry-matter production at 29 days after planting was greatest in common cocklebur and least in jimsonweed. Interspecific differences in dry-matter production were highly positively correlated with leaf area duration and negatively correlated with net assimilation rate. Threshold leaf water-potential levels causing stomatal closure varied among species. The stomata of jimsonweed were the most sensitive to water stress and those of prickly sida were the least sensitive.

The performance of BAS 9052 {2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio)-propyl]-3-hydroxy-2-cyclohexen-1-one} was evaluated when applied postemergence to rhizome and seedling johnsongrass [Sorghum halepense (L.) Pers. # SORHA] in soybeans [Glycine max (L.) Merr. ‘Bragg’ and ‘Centennial’] when the soybeans had four or five trifoliate leaves (V3 to V4 stages) or when they had six to eight trifoliate leaves (V5 to V7 growth stages). The degree of weed control was more strongly associated with rainfall conditions than with the size of the johnsongrass. An exponential equation was used to describe the relationship of soybean seed yield to BAS 9052 rate. BAS 9052 applications of 0.28 kg ai/ha provided an estimated 98% of the potential soybean yield increase when rainfall was adequate but, 0.41 kg ai/ha was required when the plants were grown under moisture stress. Soybean yields were increased by 260 kg/ha when BAS 9052 was applied at the V3 to V4 compared to the V5 to V7 growth stage.

When glyphosate [N-(phosphonomethyl)glycine] at 0.075 kg/ha, DCPA (dimethyl tetrachloroterephthalate) at 10 kg/ha, and H 26905 [O-ethyl-O-(3-methyl-6-nitrophenyl)-N-sec-butyl phosphorothioamidate] at 0.25 and 0.5 kg/ha were sprayed on foliage of alfalfa (Medicago sativa L. ‘Vernal’) on which field dodder (Cuscuta campestris Yunck.) and largeseed dodder (Cuscuta indecora Choisy) were attached and growing vigorously, almost all visible dodder tissue was killed and alfalfa was not injured noticeably. Some dodder recovered from haustoria within the alfalfa stems and from remnants of twined tendrils, but devastation of the alfalfa by uncontrolled dodder was prevented. PP 009 (butyl 2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy] propionate), BAS 9052 (2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) and RO 13-8895 (acetone-O-[D-2-[p-[(α,α,α-trifluoro-p-tolyl)-oxy] phenoxy] propionyl] oxime) at 0.25, 0.50, or 1.0 kg/ha did not control dodder.

Tall ironweed (Vernonia altissima Nutt.) is a perennial with underground, axillary vegetative buds from which new shoots are produced. In a 2-yr study, tall ironweed plants averaged 6115 seeds/plant. Germination of buried seeds increased with increased time of burial. Foliar herbicide applications were evaluated for control of tall ironweed plants in the pre- to early-bud stages of growth. The triethylamine salt or ethylene glycol butyl ether ester of triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} was the most effective, providing 93 to 90% control of top growth and regrowth of tall ironweed. The butoxyethanol and propylene glycol butyl ether esters of 2,4-D [(2,4-dichlorophenoxy) acetic acid] alone and in combination with the amine salt of triclopyr also provided excellent control.

In the pea straight growth bioassay, both benazolin and indole-3-acetic acid (auxin) solutions promoted the elongation of etiolated pea (Pisum sativum L. ‘Alaska’) epicotyls. Maximal elongation occurred at auxin concentrations ranging from 10-6 to 10-4 M; comparable elongation occurred at a benazolin concentration of 10-4 M. Results of this bioassay indicate that benazolin functions as an auxin, but is much less active than naturally occurring indole-3-acetic acid.

Napropamide [2 - (α - naphthoxy) -N,N- diethylpropionamide] influx was studied using excised root segments of corn (Zea mays L.). An initial rapid influx was followed by a slower, steady influx rate. Total influx was separated into a component that eluted from the tissue (exchangeable fraction) and a nonexchangeable fraction (residual fraction). After 5 min the residual fraction was responsible for the continued influx. In further studies with root segments this fraction was nonsaturating, increased with increased temperature, and was reduced by anaerobic conditions. The exchangeable fraction was controlled by diffusional processes. The overall influx process was attributed to an initial passive diffusion supplemented with time by a binding of napropamide into the residual fraction.

An increased rate of butylate (S-ethyl diisobutylthiocarbamate) degradation occurred on a Kennebec silt loam (sil) exhibiting rapid EPTC (S-ethyl dipropylthiocarbamate) breakdown in the field. Butylate degradation was not as rapid as EPTC degradation on field soils previously treated with EPTC. Addition of R-33865 (O, O-diethyl-O-phenol phosphorothioate) to butylate extended its persistence in field soils with and without prior EPTC application. Although microbial degradation of butylate, EPTC, and vernolate (S-propyl dipropylthiocarbamate) was increased on EPTC-pretreated soils, EPTC and vernolate degradation was much more rapid than butylate degradation. Addition of R-33865 to butylate, EPTC, or vernolate extended their soil persistence on soils pretreated with EPTC. In a laboratory experiment, a maximum rate of EPTC degradation resulted from one prior application. The rate of butylate degradation increased with each successive butylate application, but the degradation rate was not as high as those observed for EPTC on EPTC-pretreated soil.

Greenhouse and on-farm tests were conducted in North Carolina in 1979 and 1980 to evaluate sicklepod (Cassia obtusifolia L. # CASOB) management in soybeans [Glycine max (L.) Merr.]. All postemergence herbicide applications gave better sicklepod control when applied following vernolate [S-dipropylthiocarbamate) preplant incorporated than when applied following alachlor [2-chloro-2,6-diethyl-N-(methoxymethyl)acetanilide] preemergence. This resulted from decreased fatty alcohols and hydrocarbons in the epicuticle of vernolate-treated sicklepod. When applied sequentially to vernolate, toxaphene (chlorinated camphene, 67 to 69% chlorine) plus an oil concentrate and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} applied postemergence to the first true-leaf stage of sicklepod resulted in 95 and 90% control, respectively. Linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] applied alone or as tank mixes with 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] provided greater than 90% sicklepod control when applied postemergence-directed to soybeans. Metribuzin was more injurious to soybeans than linuron.

Equipment is described that assists experimental work on controlled-drop application techniques. An electronic tachometer measures centrifugal nozzle rotational speeds in the range 0 to 5000 rpm. Speed control is achieved with a simple regulator incorporated in the tractor electrical system. Both devices are also suggested as worthwhile additions to commercial spray rigs.

Effects of temperature and interference were examined in a replacement series experiment with soybean [Glycine max (L.) Merr. ‘Ransom’], common cocklebur (Xanthium pensylvanicum Wallr.), and smooth pigweed (Amaranthus hybridus L.). Plants were grown in controlled-environment greenhouses at day/night temperatures of 32/23, 29/20, or 26/17C and harvested 14 and 34 days after planting. In all species, height, dry weight, and leaf area at both harvests, and dry matter and leaf area duration for the harvest interval, increased significantly with temperature. Net assimilation rate in all species peaked at 29/20C. Dry weight and leaf area at day 34, and dry matter production and leaf area duration for the harvest interval, were reduced in plants subjected to interference. Temperature modified the effects of interference upon growth in smooth pigweed, but not in the other species. Common cocklebur and soybean were roughly equivalent as competitors at all temperatures and were superior to smooth pigweed.

Herbicide effects on chromate leakage from liposomes prepared from crude soybean [Glycine max (L.) Merr.] phosphatidylcholine were determined over a concentration range of 2.5 × 10-5 to 5.0 × 10-3 M. Dye levels in the dialysate were measured spectrophotometrically (370 nm) after 1 h. Barban (4-chloro-2-butynyl-m-chlorocarbanilate) at 2.5 to 5.0 × 10-4 M and PCP (pentachlorophenol) at 0.5 to 1.0 × 10-3 M induced significant leakage. MCPB {4-[(4-chloro-o-tolyl)oxy] butyric acid}, 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and ioxynil (4-hydroxy-3,5-diiodobenzonitrile), all at 2.5 × 10-3 M, also caused dye leakage, but metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] induced dye leakage only at 3.0 to 5.0 × 10-3M. Nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] were least effective over the concentration range tested.

Field and greenhouse experiments were conducted to evaluate factors affecting johnsongrass [Sorghum halepense (L.) Pers. # SORHA] control in soybeans [Glycine max (L.) Merr. ‘Essex’] with three foliarly-applied herbicides. In 1980, johnsongrass height at treatment time had little effect on control due to inadequate soil moisture. In 1981, a wet year, best control was achieved on 15- or 40-cm-tall johnsongrass. BAS-9052 {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} at 0.6 kg/ha gave good to excellent control at all growth stages. Two applications of 0.3 kg/ha of BAS-9052 in both years and PP-009 butyl {2-[4-[5-(trifluoromethyl-2-pyridinyloxy)] phenoxy] propanoate} in 1981 increased johnsongrass control compared to only one treatment. Mixing BAS-9052 with other herbicides significantly reduced johnsongrass control. Greenhouse studies to determine the effect of soil water on herbicide response indicated that drier soils decreased johnsongrass regrowth with PP-009 and increased regrowth with BAS-9052.

Yellow nutsedge (Cyperus esculentus L. # CYPES) was hoed in two cotton (Gossypium hirsutum L. ‘Acala SJ-2′) fields each year (1979 to 1981) for 2 to 12 weeks after crop emergence to evaluate the influence of several nutsedge-free periods on the growth and reproduction of nutsedge and yields of seed cotton. Compared to the control (plots cultivated but not hoed), a 2-week nutsedge-free period reduced the average number of nutsedge shoots at harvest by 52% (61 vs 29 shoots/m2). Additional hoeings for 4 to 12 weeks further reduced populations by 67 to 87%. Compared to tubers counted in the spring, populations of tubers in control plots increased 3- to 12-fold by harvest. However, compared to control plots, two weekly hoeings reduced tuber populations at harvest by 70 to 90% (treatment average of 884 vs 221 tubers/m2), and additional hoeings tended to reduce, or reduced, tuber populations further (75 to 98% reduction). When cotton yields were reduced in control plots in 1979 and 1980, a 2- to 6-week nutsedge-free period substantially decreased yield losses. Averaged over six locations, yields in plots with a 4- to 12-week nutsedge-free period were greater than yields of control plots.

Four days after treatment of corn (Zea mays L. 'SX111′) seedlings with BAS 9052 OH {2 - [1-(ethoxyimino) butyl] - 5 - [2 - (ethylthio) - propyl] - 3 - hydroxy - 2 - cyclohexene-1 - one} growth was inhibited and a purple color developed in the leaves. Low dosages (0.02 and 0.04 kg/ha) caused bleaching of the newly expanding leaves. Dosages higher than 0.04 kg/ha caused significant reductions in length and fresh and dry weights of both shoots and roots. Anthocyanin and total - sugar content increased, whereas chlorophyll accumulation and respiratory activity were reduced by herbicide treatment. BAS 9052 OH did not alter the mitotic index of corn root tips, but induced binucleate cells by preventing cell-plate and -wall formation. In some cells, the daughter nuclei were reoriented with respect to the longitudinal axis of the cells, and in others, the nuclei failed to migrate to the poles. These physiological and cytological effects of BAS 9052 OH on corn seedlings may be responsible for the phytotoxic action of the herbicide on grasses.