Repeated, foliar applications of monosodium methanearsonate (MSMA) controlled established, space-planted purple nutsedge (Cyperus rotundus L.) while three other herbicides were less effective. Four to eight applications of 5.6 to 16.8 kg/ha of MSMA in 1 year destroyed most plants. There was little difference in final control from applications made at 2, 3, or 4-week intervals or from 187 to 1496 L/ha of spray solution. Clones of purple nutsedge responded similarly to herbicide treatments.

Two methods of obtaining air samples were used over 4-month periods in 1976 and 1977 to quantitate trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) vapors arising from a silt loam. With the first method, only the air from an enclosure covering 0.37 m2 of soil was sampled. The second method used air probes to sample the air above the field. Rainfall and resultant soil moisture were related to trifluralin vaporization from field soil. Soon after trifluralin incorporation (0.84 kg/ha) and, while the soil was relatively dry, there was very little herbicide vaporization. Trifluralin vapors accumulated rapidly during a period in which several centimeters of rain fell, but with continued precipitation the vapor density declined. The influence of rainfall and resultant soil moisture upon vaporization became less apparent as the soil concentration of the herbicides declined. Less than 0.5% of the applied trifluralin was detected as vapors during each 4-month period.

Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} is used to control weedy grasses in red fescue (Festuca rubra L. # FESRU and F. rubra ssp. commutata), an important seed crop in Oregon. The sethoxydim rate required to reduce growth rate of 11 cultivars of red fescue and four cultivars of bentgrass (Agrostis tenuis Sibth. # AGSTE and A. stolonifera L. var. palustris # AGSST), a common contaminant in red fescue fields, by 50% (GR50) was determined in greenhouse and laboratory experiments. Field experiments compared only red fescue cv. ‘Pennlawn’ and bentgrass cv. ‘Penncross'. The GR50 values for Pennlawn red fescue in the field, the greenhouse, and the laboratory were 30 kg ai/ha, 15 kg/ha, and 5300 μM, respectively. Penncross bentgrass was approximately 400, 1400, and 12 900 times more susceptible than Pennlawn red fescue in the field, in the greenhouse, and in laboratory experiments, respectively. Plants were at different growth stages in the different experiments. The xylene and surfactant used as a solvent for the technical grade sethoxydim was as toxic to red fescue without sethoxydim as when sethoxydim was included. Cultivars of red fescue differed in their response to sethoxydim, but cultivars of bentgrass did not. The GR50's of other species tested in the greenhouse were >4 kg/ha for annual bluegrass (Poa annua L. # POAAN), 0.22 kg/ha for tall fescue (F. arundinacea Schreb. # FESAR), 0.37 kg/ha for downy brome (Bromus tectorum L. # BROTE), and 0.017 kg/ha for Italian ryegrass (Lolium multiflorum Lam. # LOLMU).

Greenhouse and laboratory studies were conducted to examine the activity and foliar absorption of foramsulfuron in giant foxtail and woolly cupgrass with various adjuvants. Adjuvant selection was important for giant foxtail control. Foramsulfuron provided 90% or greater giant foxtail control with the addition of methylated seed oil (MSO) or MSO plus 28% urea ammonium nitrate (UAN). When a crop oil concentrate (COC) or a nonionic surfactant (NIS) was added to foramsulfuron, giant foxtail control was only 20%. However, when 28% UAN was added to COC or NIS, control was increased to 90 and 85%, respectively. Foramsulfuron absorption and control were closely related in giant foxtail. Foliar absorption of 14C-foramsulfuron in giant foxtail ranged between 35 and 90% 24 h after treatment (HAT) depending on adjuvant selection. The rate of absorption was greatest when MSO plus 28% UAN was added to foramsulfuron and absorption was maximized 4 HAT. Foramsulfuron absorption in woolly cupgrass reached its maximum levels 2 HAT with all adjuvant combinations. Although the rate of foramsulfuron absorption was quicker in woolly cupgrass, absorption trends by adjuvants were similar to those in giant foxtail. Maximum absorption of 14C-foramsulfuron in woolly cupgrass was 84% with the addition of MSO plus 28% UAN. However, even with high levels of absorption, woolly cupgrass control with foramsulfuron was poor and may be related to rapid metabolism to nonphytotoxic compounds.

The potential dispersal of Benghal dayflower seeds by mourning doves was studied in southern Georgia, U.S.A. The gut contents (both crop and gizzard) of mourning doves harvested in the autumn months were investigated to determine if mourning doves fed on Benghal dayflower and whether seeds can survive conditions in the bird gut. Research indicated that mourning doves fed selectively on Benghal dayflower with some harvested birds containing hundreds of Benghal dayflower seeds and capsules in their guts. Further, some seeds recovered remained highly viable. Germination rates in seeds taken from bird crops were similar to controls over the first 4 wk of germination and enhanced over control treatments during the latter 16 wk of a 20-wk germination study. Ultimately, seeds extracted from dove crops had 92% germination as compared to 80% for control seeds. Seeds extracted from dove gizzards had 45% germination, about half that of controls. Benghal dayflower seeds have a structurally reinforced seed coat that probably aids in survival of mechanical damage through bird intestinal tracts. Benghal dayflower seeds exposed to 1.0 M HCl treatment for 2 h had little loss in viability, successfully germinating after such treatment. When evaluating mechanisms for the eradication of Benghal dayflower from agricultural crops, consideration needs to be given to the large number of mourning doves and other bird species that visit cropland and potentially aid in its dispersal.

A mobile, metal cabinet sprayer is described, in which an electrically-powered, chain-driven carriage with spray assembly travels back and forth over the pots or flats to be sprayed.

Dandelion is a cosmopolitan weed of economic and environmental significance because of its negative effects on crop yield and the large amount of herbicides used for its control in agricultural, residential, and recreational areas in North America. Asexual dandelion plants, which are apomictic and produce genetically identical seeds, provide a great experimental model for biological studies, such as examination of its reproductive responses to global environmental changes. In a growth chamber experiment, we investigated how elevated CO2 affected reproduction and seed dispersal properties in dandelion. Dandelion plants were grown at ambient (370 µmol mol−1) or elevated (730 µmol mol−1) CO2 until reproductive maturity. Results showed that dandelion plants examined in our study produced 83% more inflorescences and 32% more achenes, i.e., single-seed fruits, per plant at elevated than at ambient CO2. Seeds from elevated CO2-grown plants were significantly heavier and had a higher germination percentage, leading to larger seedlings and earlier establishment in the subsequent generation. Furthermore, achenes from plants grown at elevated CO2 had characteristics, such as higher stalks at seed maturity, longer beaks, and larger pappi, which would increase the distance of seed dispersal by wind. In addition to these elevated CO2-induced changes in reproductive properties, dandelion has a number of inherent characteristics, e.g., high competitiveness and adaptations to disturbance, that would increase its vegetative and reproductive success in a higher CO2 environment. Consequently, dandelion can potentially become more widespread and noxious as atmospheric CO2 continues to rise because of human activities.

Decision-making processes must indicate if, how, and when weed control should be practiced. So far, Decision Support Systems (DSSs) for weed control to prevent crop yield losses can guide decisions on “if” and “how.” Experience shows that farmers need a DSS that can also guide when to treat, but this can only be done if the actual weed density observed in the field is known during the crop cycle. Emergence models allow the prediction of daily density, but precision depends on the survey date. This study focuses on the estimation of the date of the survey for the best prediction of the daily density throughout the crop cycle. The predicted daily density of each species can be used by DSSs without any further survey, saving time and money and improving the use of the DSSs. Results showed that the best date is when the actual density of each weed reaches or exceeds 50% emergence, and this is earlier than the critical point date, supporting the validity of the date estimation method. The possibility to provide specific advice for farmers considering a proper mortality rate of weed seedlings is then discussed. The ability to optimize the date of sampling can improve the reliability of decision-making tools for integrated weed management, in agreement with the European Union goal of sustainable use of pesticides and more environmentally sustainable cropping systems through the use of integrated pest management.

Four modes of competition were studied in relation to early development of common milkweed (Asclepias syriaca L.) alone and in competition with green foxtail [Setaria viridis (L.) Beauv], redroot pigweed (Amaranthus retroflexus L.), and sorghum [Sorghum bicolor (L.) Moench ‘RS-626’]. The three species were used to study the effect of no competition, light competition, soil competition, and light and soil (full) competition on common milkweed. Common milkweed height was significantly reduced by soil and full competition with the three species, while only green foxtail caused a significant reduction in height due to light competition. Shoot weight of common milkweed was significantly reduced by light, soil, and full competition by the three species. Reproduction percentage of common milkweed roots was most severely reduced by light and full competition from green foxtail and redroot pigweed. An environment conducive to the establishment of the perennial common milkweed from seed exists when annual weeds are removed by herbicides.

Experiments were conducted to determine the effect of 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron) and 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) on oxygen consumption by mitochondria isolated from the hypocotyls of soybean (Glycine max L., var. Lee) seedlings. Prometryne caused a decrease in second state 3 oxidation of both malate and succinate, but the decrease was overcome by 2,4-dinitrophenol (hereinafter referred to as DNP), indicating a response similar to that of oligomycin. Fluometuron caused an increase in second state 4 oxidation of both malate and succinate and overcame the inhibition of oxidative phosphorylation caused by oligomycin, indicating an uncoupling response similar to DNP. Fluometuron was also shown to reverse the inhibition of oxidative phosphorylation caused by prometryne. Concentrations of prometryne causing the 50% inhibitory response were somewhat higher than those reported for s-triazines on other tissues, while those for fluometuron were well within the inhibitory range reported for other substituted ureas.

Hairy galinsoga [Galinsoga ciliata (Raf.) Blake] and smallflower galinsoga [G. parviflora Cav.] are widespread weeds in New York State. Freshly harvested achenes (seed) are not dormant and germinate in the field from early May until frost. Rate of germination but not final total percentage was stimulated by alternating temperature, with the fastest rate being at 30 C day and 20 C night and with a 16-hr photoperiod and 11,000 lux of light. Some seed in each seed-lot required light for germination. Both species were day-neutral with respect to flowering. Smallflower galinsoga produced its first flower after node seven and hairy galinsoga after node six on the main axis 6 to 8 weeks after germination. Decreasing light intensity 83% decreased fresh weight.

This study provides the first phytochemical characterization of the morphologically identified natural hybrid Solidago×niederederi Khek compared with the native Solidago virgaurea and two invasive species, Canada goldenrod (Solidago canadensis L.) and giant goldenrod (Solidago gigantea Aiton). The phenolic compounds, namely, chlorogenic acid, rutin, isoquercitrin, hyperoside, and quercitrin, were detected in leaves and inflorescences by the high-performance liquid chromatography–photodiode array detector/ultraviolet (PAD/UV) method. All analyzed Solidago species contained all of the phenolic compounds investigated. The quantitative phytochemical differentiation among Solidago taxa was shown by principal component analysis. The results indicated that S. gigantea plants were characterized by significantly different quantities of phenolic compounds compared with three other Solidago taxa, which formed a separate cluster in the space of the principal component model, indicating the high similarity of their profiles. An additional multivariate analysis of the three species studied revealed a chemical gradient from S. canadensis to S. virgaurea with a slightly overlapping zone on the score plots presented by S.×niederederi and S. virgaurea accessions. The results showed that S.×niederederi was closely related to S. virgaurea. This result is suggestive of a hybrid origin with significant contributions from the native species. However, S.×niederederi was significantly different from its parental species with respect to chlorogenic acid and quercitrin in leaves and rutin with isoquercitrin in inflorescences. Conversely, samples indicating intermediate chemical composition between native S. virgaurea and invasive S. gigantea were not distinguished. The comparison of phenolic compound accumulation in Solidago plants supported the additional identification of the origin of S.×niederederi.

Soybean [Glycine max (L.) Merr. ‘Hark’] plants responded similarly to a sublethal application of metribuzin [2-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] or to low light intensities. Both treatments increased soluble amino acid, ATP, nitrate reductase, and nitrate levels (up to 67, 140, 190, and 10,000%, respectively) and decreased soluble reducing sugars (33%), malate levels (86%), and the chlorophyll a/b ratio (24%). The similar response of light-limited and of chemically photosynthesis-inhibited plants is thought to be induced by a carbohydrate stress or another parameter related to a decreased rate of photosynthetic electron flow. However, during the induction process in shaded plants, light quality might play an important role in some cases. The results obtained with metribuzin and soybean plants are compared to and discussed together with (a) the results obtained by other authors working with s-triazine herbicides and (b) results obtained with methabenzthiazuron [N-(benzothiazol-2-yl)-N,N′-dimethylurea] in earlier experiments.

Populations of the waterhyacinth mite (Orthogalumna terebrantis Wallwork) of ca 200,000 galleries/m2 (or 10,000 per plant) caused serious damage to waterhyacinth [Eichhornia crassipes (Mart.) Solms.] in the field, but such damage was sporadic and confined to small areas of plants in midsummer. Two or three generations a year occurred in the field. Adults emerged in late December, March, and May and adults were found on waterlettuce (Pistia stratiotes L.) throughout the winter. Development, appearance of the different stages, behavior of immatures and adults, and manner of attacking waterhyacinth is described. Only small differences were found between the biology of the mites studied in Argentina and of that reported in Uruguay and the United States.

Sulfometuron, when applied as a foliar and/or soil application, prevented regrowth of bahiagrass. Sulfometuron application did not reduce regrowth of centipedegrass regardless of method of application. Sulfometuron was absorbed by the roots and foliage of centipedegrass and bahiagrass. Symplasmic translocation of the herbicide was evident in both species. Translocation of foliar-applied sulfometuron increased from approximately 1% at 48 h after application to 23% at 72 h in bahiagrass. Metabolism of sulfometuron was greater in centipedegrass (69% of foliar-applied, 10% of root-applied) at 72 h after application than in bahiagrass (30% of foliar-applied and 4% of root-applied). Tolerance of centipedegrass to sulfometuron appeared to be related to a high degree of herbicide metabolism in this species.

Storage of intact Texas gourd [Cucurbita texana (A.) Gray] pepos for 21 days after harvest increased germination of seeds from pepos collected 15 to 47 days after flowering. Germination increased as day length decreased and as osmotic potential of germination media increased. Temperatures of 20, 25, and 30C resulted in 72, 93, and 99% germination, respectively. No seeds germinated at 10 or 40C. Seedling emergence decreased as planting depth increased, with no emergence from 12.5 cm. Control of Texas gourd in soybeans [Glycine max (L.) Merr.] was achieved with preemergence applications of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], metribuzin plus alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)-acetanilide], and oxadiazon [2-tert-butyl-4 (2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one], with successful control partially dependent on soil and climatological conditions. Postemergence treatments that resulted in adequate control included applications of acifluorfen {5-[2-chloro-4-(trifluoromethyl)-phenoxy]-2-nitrobenzoic acid}, oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene], and metribuzin plus 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] applied at an early soybean growth stage and repeated.

We previously reported that napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] was highly toxic to achlorophyllous callus of tomato (Lycopersicon esculentum Mill. ‘San Marzano’), whereas foliar application to seedlings was almost without effect. Experiments were performed to ascertain the effects of napropamide on green and achlorophyllous calli of tomato and broadleaf dock (Rumex obtusifolius L.). The growth of achlorophyllous tissues was more severely inhibited. Foliar applications were not as inhibitory in both species. Napropamide was applied to tomato seedlings via roots and cut shoots and root growth was more inhibited than shoot growth. Thus napropamide is toxic to achlorophyllous tissue and is either less toxic to, or detoxified by green tissue.

Prediction of the developmental stages of wheat and wild oats would be useful in order to: 1) correctly time the application of herbicides, and 2) accurately schedule research and cultural operations. The Haun developmental scale which numbers leaf development and describes floral development on the main stem of grasses was found to be suitable for describing the development of semidwarf wheat and wild oats in California. Haun developmental rates of wheat and wild oats were similar. Interference by wheat or wild oats in mixed cultures did not change the developmental rate of either species when grown with added nutrients and water. Degree days gave better correlations with development than calendar days when different planting dates, years, and locations were compared. A degree day model with a 5 C base temperature and a second-order polynomial expression gave accurate predictions of developmental stage, which correlated well with field data.

Experiments were conducted to determine the effect of triglycerides, free fatty acids (FFA), and fatty acid methyl esters (FAME) on the foliar absorption, translocation, and phytotoxicity of quizalofop. Absorption, translocation, and phytotoxicity of quizalofop in oats were greater when quizalofop was applied with FFA or FAME than with their respective triglycerides. Triglycerides and FFA generally enhanced quizalofop absorption and translocation more when they contained unsaturated than saturated fatty acids. Methylation of the fatty acids reduced differences among fatty acids, but methyl stearate and methyl linolenate enhanced absorption of quizalofop less than the other FAME for oats and yellow foxtail. Quizalofop absorption and phytotoxicity to oats were greater when applied with sunflower oil, sunflower oil FFA, and sunflower oil FAME than with the corresponding linseed oil derivatives. Emulsifier generally reduced differences between linseed oil and sunflower oil derivatives in their enhancement of absorption, translocation, and phytotoxicity of quizalofop.

Herbicide treatments containing the butoxyethanol ester of 2,4-D [(2,4-dichlorophenoxy)acetic acid], the dimethylamine salt of dicamba (3,6-dichloro-o-anisic acid), the potassium salt of picloram (4-amino-3,5,6-trichloropicolinic acid), and the isopropylamine salt of glyphosate [N-(phosphonomethyl)glycine] were applied for 6 yr to a pasture in east-central South Dakota containing leafy spurge (Euphorbia esula L. ♯ EPHES). Several treatments resulted in leafy spurge control exceeding 90%. Mean herbage dry-weight yield in treated plots was 2340 kg/ha, a 67% increase over untreated plots. Forage yields did not significantly differ among treatments controlling 90% or more leafy spurge. Marginal net return over marginal cost from herbicide treatments ranged from $35 to –$63/ha. Treatments providing satisfactory leafy spurge control with minimum economic risk were annual spring applications of 2,4-D at 1.7 kg ae/ha or dicamba + 2,4-D at 0.6 + 1.1 kg ae/ha and the biannual application of 2,4-D at 0.8 kg ae/ha.