N-1-naphthylthalamic acid (NPA), 3-amino-2,5-dichlorobenzoic acid (amiben), and the dimethyl ester of 2,3,5,6-tetrachloroterephthalic acid (DCPA), in granular and liquid or wettable powder formulations, were applied to the soil and then activated by either overhead or sub-irrigation.

Granular formulations of the herbicides were as effective as liquid formulations for weed control, providing there was ample moisture for activation. High temperatures and dry soils were conducive to losses by volatilization of NPA. DCPA underwent less loss by volatilization at high temperatures. Both overhead and sub-irrigation were effective in activating these herbicides, but overhead generally was more effective. Under sub-irrigation, use of a granular carrier was more effective with a volatile herbicide. Formulation differences decreased in importance under overhead irrigation. Under conditions of high temperatures and soil moisture, soil persistence of the herbicides varied inversely with their volatility.

Uptake and translocation of 14C label from S-2,3-dichloroallyl N,N-diisopropylthiolcarbamate (diallate) by roots and coleoptiles of wild oat (Avena fatua L.), wheat (Triticum aestivum L., var. Selkirk), barley (Hordeum vulgare L., var. Traill), and flax (Linum usitatissimum L., var. Bolley) were compared. The pattern of 14C label uptake and movement was similar in wild oat, barley, and wheat. However, translocation of the 14C label to the roots of wild oat was less than for barley. Although differential uptake and translocation per se did not appear to account for the selectivity of diallate for wild oat, some differences in translocation may have beep the result of metabolic breakdown products.

Glyphosate transport was studied using the 14C-labeled herbicide. Because glyphosate appears to undergo little metabolism in plants, detected 14C was assumed to indicate the presence of glyphosate. Leaf-girdling experiments demonstrated that 14C-glyphosate [N-(phosphonomethyl)glycine] transport in treated quackgrass [Agropyron repens (L.) Beauv. ♯3 AGRRE] leaves occurred in both leaf symplast and apoplast. Symplastic transport was toward the leaf tip and the leaf base. Apoplastic transport was toward the leaf tip only. Rhizome-girdling experiments showed that translocation of glyphosate from a treated shoot to another shoot on the same rhizome occurs primarily in the rhizome symplast. Girdling the base of quackgrass culms showed that acropetal transport of glyphosate from the rhizome into quackgrass shoots is in the apoplast and the symplast of the culms of quackgrass shoots. Excision of rhizome buds and rhizome apices indicated that the rhizome is a sink for glyphosate independent of rhizome buds or rhizome apices. The concentration of 14C-glyphosate in rhizome buds was less in plants with rhizome apices removed than in those with apices intact. The concentration of C-glyphosate in rhizome apices did not differ between plants with buds removed and those with buds intact. 14C-glyphosate applied to a girdled rhizome apex remained primarily in the apex. Some transport of glyphosate past the girdle occurred, indicating apoplastic transport of glyphosate in the rhizome. Apoplastic transport of 14C-glyphosate in the rhizome was greatest in water-stressed plants.

Whole plant studies were conducted to examine the effects of glyphosate on components of carbon balance, transpiration, and biomass partitioning of wheat plants grown in Olton sandy clay loam soil and in a well-aerated fritted clay medium under controlled environmental conditions. Well-irrigated plants were transferred from a nursery room into a test chamber about 48 d after planting. Two to five days later, 12 to 42 ml of a glyphosate solution with a concentration of 480 mg ai L–1 were sprayed until full coverage of the foliage. Environmental conditions in the chamber were air temperature 25 C, dew point 18 C, windspeed 1.1 m s–1, and PPFD 1500 mmol m–2 s–1 (at the top of the foliage) for 12 h daily. Glyphosate treatment resulted in destruction of the root system, as determined at the end of the tests, and at the start of tests using companion plants. Plants grown in soil lost 0.53 kg kg–1 of the initial root mass, while this loss was 0.38 kg kg–1 in plants grown in fritted clay. Glyphosate treatment rapidly inhibited daily rates of gross carbon uptake and transpiration of wheat plants grown in both media. Effects occurred more than twice as rapidly in plants grown in soil as in fritted day. Similarity in the patterns of inhibition of gross carbon uptake and transpiration suggests that glyphosate may also affect leaf stomata. After applying glyphosate, daily rates of carbon loss increased for 3 d in soil-grown plants but remained almost constant for 10 d in plants grown in fritted clay; thereafter, the rates of carbon loss declined. The early increase or the constancy of carbon loss observed after applying glyphosate was related to catabolic processes occurring in roots.

In 1965 and 1966, alfalfa (Medicago sativa L., var. Cayuga) and birdsfoot trefoil (Lotus corniculatus L., var. Viking) were seeded in soil treated just before planting with ethyl N,N-dipropylthiocarbamate (EPTC). To determine herbicidal interaction on a field scale, 4,6-dinitro-o-Sec-butylphenol (DNBP) was applied as a postemergence treatment. No significant interaction of EPTC and DNBP was evident on legume or weedy grass stands on yield. Interaction of EPTC and DNBP on control of annual broadleaf weeds was noted 1 year but not the second. DNBP but not EPTC significantly reduced birdsfoot trefoil stands during both years and reduced alfalfa stands 1 year but not the other. EPTC controlled annual and perennial weed grasses and DNBP controlled annual broadleaf weeds successfully. The incorporation of EPTC in soil before planting alfalfa and birdsfoot trefoil followed by a postemergence DNBP treatment was considered to be a practical weed control method.

The temporal dynamics of spatial heterogeneity was studied for the weed communities in a seashore paspalum turf with the use of a power-law model. Surveys were conducted in January, March, May, July, September, and November in 2007. In every survey, we set 100 quadrats (50 by 50 cm) referred to as L quadrats on a 50-m line transect at the same position in the turf. Each L quadrat was then divided into four S quadrats (25 by 25 cm) and all plant species occurring in each of these S quadrats were identified and recorded. These data were summarized into frequency distributions and the percentage of S quadrats containing a given species, and the variance of each species was estimated. The power law was used to evaluate the spatial heterogeneity (δ) and frequency of occurrence (p) for each species in the weed communities in six survey months. The results showed that weeds emerged more frequently in the summer–spring season than in winter–autumn, and the spatial heterogeneity was much higher in summer–spring than winter–autumn, especially in summer. The Shannon–Wiener diversity indexes (H') from large to small were July (5.9202) > May (5.6775) > September (5.6631) > March (5.5727) > January (5.1742) > November (4.9668). Likewise, the spatial heterogeneity index (δc ) of the whole community was also different in different months. The biggest δc (0.2790) was in July, and the smallest (0.1811) in November. Meanwhile, manilagrass had a high p (= 1.0), indicating that it occurred in all S quadrats in every weed community of every month. However, the turfgrass, seashore paspalum, only emerged in March, May, July, and November, and possessed a low p, indicating the seashore paspalum turf has been naturally replaced by manilagrass.

Foliar-applied 3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea (chloroxuron), chloroxuron with dodecyl ether polyethylene glycol surfactant, and dimethylamine salt of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) effectively controlled cocklbur (Xanthium sp.) in soybeans (Glycine max (L.) Merr. ‘Hampton’ or ‘Lee’). While treatments caused crop injury, treated soybeans produced higher seed yields than untreated soybeans infested with cocklebur plants. Seed yields from soybeans growing free of cocklebur were not reduced by treatment with chloroxuron or chloroxuron with surfactant but in some cases were reduced by 2,4-DB treatment.

Substances having anesthetic-like properties were examined for stimulation of redroot pigweed and witchgrass seed germination. Chemicals included the n-alcohols through C-5, 2-propanol, benzyl alcohol, diethyl ether, chloroform, and 2-bromo-2-chloro-1,1,1-trifluoroethanol. Redroot pigweed seeds required the far-red absorbing form of phytochrome (Pfr) for an anesthetic substance to increase germination, but in witchgrass seeds the active anesthetic substances stimulated germination without added Pfr. The correlation coefficient comparing relative activity (RA) versus the membrane/buffer partition coefficient (M/B) of the active substances was very poor (−0.37) for pigweed seeds but was −0.91 for witchgrass. Leakage of cellular materials, including electrolytes, substances absorbing at 280 nm, and amino acids from seeds treated with either active or inactive anesthetics, was not particularly indicative of effects on germination in both species. Application of increased pressure (0.965 MPa) during anesthetic treatment, which in animals prevents anesthesia, was found to act oppositely and increase seed response to ethanol in redroot pigweed seeds, but in witchgrass seeds pressure suppressed the stimulatory action of ethanol. In both species, pressure appeared to have an action of its own, but for this action to be expressed the presence of a stimulatory anesthetic was also required. The results do not appear to support a good relationship of anesthetic activity with seed membrane lipophilic components in redroot pigweed seeds, but the relationship seems likely for witchgrass seeds.

In greenhouse experiments, sago pondweed plants were grown from three different size classes of tubers and treated with four levels of fluridone. Results indicate that although fluridone significantly reduced mean plant weight, the extent of the reduction in weight depended on the size of tuber from which the plant was grown. Mean plant weight was greater for plants exposed to fluridone (up to 0.5 mg/L) for 7 days, if the plants were initially from larger tubers (51 to 60 or 101 to 200 vs. 11 to 20 mg fresh weight). Mean plant length and the number of ramets/plant were affected in a similar manner. The results underscore the importance of specifying the size of tubers used in growth studies and contribute to understanding of the roles that biological factors play in regulating aquatic plant response to herbicide treatment.

The selectivity of 4-chloro-2-oxobenzothiazolin-3-ylacetic acid (benazolin) in wild mustard [Brassica kaber (DC.) L. C. Wheeler var. pinnatifida (Stokes) L. C. Wheeler], turnip rape (Brassica campestris L. ‘Echo’), and rape (Brassica napus L. ‘Target’) was studied. On an ED50 basis wild mustard was 19 and 32 times more susceptible to foliar-applied benazolin than was turnip rape and rape, respectively. The addition of surfactant increased the toxicity of benazolin to the Brassica species. Benazolin was less selective when applied via roots. Selectivity was further studied on the bases of differential spray retention and foliar penetration. Rape retained less spray than did wild mustard and turnip rape. The inclusion of surfactants in formulations increased spray retention by rape. Less 14C-benazolin penetrated leaves of the rape species as compared to wild mustard. Surfactant enhanced penetration of 14C-benazolin into leaves of the three species. Leaf surface features which resulted in high spray retention and rapid penetration of benazolin partly explained the susceptibility of wild mustard. The variation in tolerance between the two rape species was attributed to differential spray retention.

The herbicide 3-amino-2,5-dichlorobenzoic acid (chloramben) was applied preemergence to soybeans [Glycine max (L.) Merr.] in 1969, 1970, and 1971. Herbicide band widths were 18, 36, and 53 cm, and there was a broadcast treatment. Cultivation and rotary hoeing were also imposed on the herbicide band widths as variables. A 36-cm band of chloramben was the minimum band width used which consistently maintained soybean yield when supplemented with mechanical tillage. Broadcast treated soybeans without mechanical tillage yielded as well as handweeded soybeans in 2 of 3 years. Each 4 kg/ha of weed growth reduced soybean yield 1 kg/ha. Average weed yield reduction due to cultivation was 100, 76, and 54% in 1969, 1970, and 1971, respectively, when average weed yields were 360, 1650, and 4720 kg/ha in successive years. Rotary hoeing reduced weed growth 48% and increased soybean yield 20% in 1970 but did not significantly affect weed or soybean yields in 1969 and 1971.

Phenolic content, germination percentage, and host preference were compared among 11 seed populations of witchweed (Striga hermonthica (Del.) Benth. # STRHE). Significant differences in germination percentage occurred among the seed populations after preconditioning by their exposure to different durations of warm-moist conditions. Greatest percentage of seed germinated after 8 days of preconditioning. Preconditioning for more than 16 days reduced percentage germination. The host specificity range of witchweed seed populations that parasitized pearl millet [Pennisetum americanum (L.) K. Schum] was broader than were those seed populations that attacked sorghum [Sorghum bicolor (L.) Moench.]. Results of thin-layer chromatography indicated large variations in phenolic content among the witchweed seed populations.

The objective of this study was to determine the effect of fertilizer placement on the growth of eclipta [Eclipta prostrata (L.) L.] and evaluate its interference with container-grown ornamental plants, including Japanese boxwood (Buxus microphylla Siebold & Zucc.) and ligustrum (Ligustrum lucidum W.T. Aiton). Results indicated that subdressing reduced E. prostrata shoot weight by 28%, 42%, and 46% at depths of 2.5, 5.0, and 7.5 cm, respectively, in comparison with a topdressed fertilizer treatment (a standard industry practice). Presence of E. prostrata reduced the growth of both ornamental species. Ligustrum shoot weight decreased as subdressing depth increased, while boxwood growth was most notably reduced at the 7.5-cm depth in comparison with topdressed containers. Overall, results indicated that subdressing may be an effective weed management strategy, but subdressing depth needs to be based on initial liner size to prevent possibly delays in production time.

Apocynum cannabinum is a native creeping perennial distributed throughout the U.S., with increasing importance in reduced tillage systems throughout the Midwest. Apocynum cannabinum has been shown to be a difficult species to control in field crops. Effective weed management is often a function of the timing of control practice. Knowledge of weed emergence patterns may be useful in predicting the optimum time of weed management. The objectives of these studies were to describe how temperature and moisture affect A. cannabinum seed germination and to describe the relationship between growing degree units (GDU) and A. cannabinum vegetative shoot emergence. At constant temperatures, seed germination was described as a sigmoidal function of temperature (r 2 = 0.83), with maximum germination (32%) from 26 to 34 C. Under alternating temperatures, seed germination increased in a linear relationship between mean temperatures of 15 and 34 C (r 2 = 0.85). Maximum seed germination (88%) occurred at a mean temperature of 34 C under alternating temperatures. The relationship between seed germination and osmotic potential between −1.0 and 0 MPa was described by a gompertz function (r 2 = 0.98). Germination at −1.0 MPa was 4% and increased in a near linear manner to the nontreated control (0 MPa), which had 80% germination. Vegetative shoot emergence in 1997 and 1998 had a sigmoidal relationship to GDU using a base temperature of 6 C (r 2 = 0.96). However, initial shoot appearance was not consistent over years, with first emergence recorded on May 21, 1997 (132 GDU), and May 5, 1998 (73 GDU). Approximately 50% of the shoots emerged before June 7, 1997 (282 GDU), and May 21, 1998 (285 GDU); therefore, optimal weed management programs will need to be initiated following this GDU accumulation.

Pretreatment of potato (Solanum tuberosum L., var. Russet) tuber discs in pH 5.5 buffer significantly reduced uptake of picloram (10−3M). Tissue pretreated in buffer at 7 C subsequently absorbed more picloram than tissue pretreated at 25 C. Inclusion of cetyl trimethyl ammonium bromide (hereinafter referred to as CTAB) (2 × 10−4M) in the treating solution caused a significant increase in picloram uptake in tissues that were not pretreated in buffer. The reduction in uptake caused by buffer pretreatment was effectively reversed when CTAB was included in the treating solution. The results suggest that picloram uptake by potato tissue is related to the availability of the quaternary ammonium binding sites provided by membrane phosphatides.

Metabolites from 906 microbial isolates were evaluated for herbicidal properties. These included 266 isolates of Streptomyces, 502 isolates of non-Streptomyces actinomycetes representing 18 genera, 28 unidentified aerobic actinomycetes, 70 fungi, and 40 isolates of eubacteria. Metabolites from 72 isolates significantly inhibited germination of cress seeds. In terms of generic specificity and frequency, about 18% of all the Streptomyces and Nocardiopsis isolates and 13% of Actinoplanes isolates were toxic to cress (Lepidium sativum L.) seeds. Among other inhibitors were three isolates of Actinomadura and one isolate each of Micromonospora, Micropolyspora, Strep to sporangium, Streptoverticillium, and Bacillus, and two isolates of unidentified actinomycetes. The toxigenic fungi included two isolates of Penicillium and one isolate each of Aspergillus, Scopulariopsis, and Paecilomyces species. About half the isolates toxic to cress were toxic to barnyardgrass (Echinochloa crus-galli L. Beauv. # ECHCG) seeds. of the isolates found effective in the secondary screening on the potted weeds, eight belonged to the genus Streptomyces and one was identified as Scopulariopsis brumptii. None of the examined isolates of Rhodococcus, Nocardia, Oerskovia, Thermoactinomyces, Thermomonospora, and six other genera of actinomycetes showed any appreciable toxicity to the seeds of either species.

Application of the ethylene-releasing agent ethephon (2-chloroethylphosphonic acid) as a lanolin paste to stems of honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockrell] caused the development of abnormal periderm, cortical, and xylem tissues in a localized portion of the stem within 1 cm of the treatment site. Ethephon inhibited secondary wall deposition in xylem parenchyma cells, whereas normal vessel element differentiation was unaffected. Similar changes in xylem formation occur in ethephon-treated huisache [Acacia farnesiana (L.) Willd.]. Ethephon and 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] applied separately to honey mesquite and huisache stems have similar inhibitory effects on parenchyma cell differentiation but differ markedly in their effects on vessel element formation.

The influence of various additives on CGA-82725 [2-propanyl-2,4-(3,5-dichloro-2-pyridyloxy)phenoxy propanoate] absorption and translocation was determined in oats (Avena sativa L. ‘Lyon’). The absorption and translocation of 14C was greater when 14C-CGA-82725 was applied with petroleum oil compared to soybean [Glycine max (L.) Merr.] oil. The translocation of 14C was greater at 96 than 48 h after 14C-CGA-82725 application. The absorption of 14C was greater at 48 than 24 h but was similar at 48 and 96 h after 14C-CGA-82725 application with no additive, petroleum oil, or soybean oil. The absorbed and translocated 14C was greater when 14C-CGA-82725 was applied with oil at 1.2 compared to 0.6 L/ha. No additional increase in 14C absorption and translocation was obtained if the oil volume was increased to 2.3 L/ha. The addition of petroleum oil to 14C-CGA-82725 increased 14C absorption and translocation more than the addition of palm (Eleais quineeneis Jalq.), safflower (Carthamus tinctorius L.), linseed (Linum usitatissimum L.), or soybean oil. The four seed oils and the emulsifier At Plus 300F caused similar increases in 14C absorption and translocation over 14C-CGA-82725 applied alone. Ethylene glycol did not increase 14C absorption and translocation compared to 14C-CGA-82725 applied alone.

Single and sequential applications of mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl] amino] phenyl] acetamide} and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} were evaluated in the field for velvetleaf (Abutilon theophrasti Medic. ♯ ABUTH) and common cocklebur (Xanthium pensylvanicum Wallr. ♯ XANPE) control in soybeans [Glycine max (L.) Merr. ‘Williams’]. Acifluorfen was applied at 0.4 or 0.6 kg ai/ha alone or 3, 5, or 7 days following application of 0.1 or 0.3 kg ai/ha mefluidide. Acifluorfen applied alone provided acceptable control of velvetleaf and common cocklebur in the two- and three-leaf stage of growth, but acifluorfen was not as effective when applied to weeds with five to eight true leaves. Sequential applications of mefluidide and acifluorfen often increased velvetleaf and common cocklebur control, compared to either herbicide applied alone.

Sprayed aqueous emulsions of long chain amine salts of (2,4-dichlorophenoxy)acetic acid (2,4-D) penetrated faster into sunflower (Helianthus annuus L. ‘Peredovik’) leaves than did sprayed dimethylamine salt aqueous emulsions at 21 C and 5% relative humidity (RH). The initial absorption (65 to 70% in 13 hr) was independent of light, but the following much slower absorption was strongly light dependent. The long-chain amine salts sprayed in diesel oil as carrier were 90% absorbed in 4 hr. It was concluded that long chain amine salts should be sprayed in this carrier to facilitate penetration into leaves and to reduce possible environmental contamination.