We constructed an injector-planter which simultaneously plants seed and injects herbicides. It effectively placed volatile herbicides under the soil surface in precise spatial relationship to crop seed. Rolling coulters, placed in front of the herbicide delivery system, enabled the unit to cut through trash better than previously-described equipment and, therefore, perform effectively under a wider range of soil conditions.

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] was applied to newly sprigged centipedegrass [Eremochloa ophiuroides (Munro) Hack.] in field and greenhouse experiments at 0.56, 0.84, 1.68, and 3.36 kg/ha at various time intervals from 0 to 10 weeks after sprigging. Sequential pronamide treatments of 0.84 kg/ha applied at sprigging followed with 1.68 kg/ha at 3 weeks after sprigging did not affect plant survival and controlled large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.] sufficiently to allow optimum growth of the turfgrass. Plots treated with one pronamide application did not control weeds satisfactorily, while more than two applications either caused turf injury or generally offered no advantage in weed control when compared with sequential 0.84 and 1.68 kg/ha treatments. In field plots treated with 0.84 kg/ha at sprigging and 1.68 kg/ha at 3 weeks after sprigging, the turf ground cover was 66% after the first growing season. Plant and root growth were not adversely affected in greenhouse-grown turf receiving similar treatments.

We compared foliage sprays of (2,4-dichlorophenoxy)acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram) for control of Macartney rose (Rosa bracteata Wendl.) applied with ground equipment and airplane. Picloram at 0.5 lb/A was more effective than 2,4-D at 2 lb/A at all dates of application on mowed roses; however, time of application was important. Picloram was most effective in late April and early May, but 2,4-D was most effective in late May and early June. Combinations of picloram and 2,4-D were effective from late April to late June. If mowing is followed by foliage treatment of 2,4-D, the interval between mowing and spraying should be at least 1 year if mowing is done in the spring. The interval between mowing and spraying was not critical when picloram was applied not later than early May. Mowing in the summer reduced the effectiveness of subsequent 2,4-D and picloram treatments applied the following year. Aerial applications of 2,4-D and picloram on undisturbed Macartney rose plants in the fall were not as effective as spring applications; however, two successive fall applications of picloram at 1 lb/A resulted in control equivalent to that obtained with a single 2 lb/A application in spring.

In a location with cypress spurge (Euphorbia cyparissias L. ♯ EPHCY) and naturally occurring Uromyces scutellatus (Pers.) Lév. s.str., the percent of shoots deformed by this systemic rust increased from 6% in 1981 to 48% in 1982, followed by a decrease in both deformed and normal shoots in 1983 and 1984. After inoculation in 1981 of two cypress spurge crowns at a location near Zürich by teliospores of Uromyces alpestris Tranzsch., more than 80% deformed shoots were obtained in 1983 and 1984. Inoculations of cypress spurge root segments by U. scutellatus s.str. or U. alpestris in experimental plots in 1982 gave 50 to 100% infected plants, and in most cases more than 50% deformed shoots in 1984. The collection of U. alpestris studied (E-52) could be a promising candidate for mycocontrol of cypress spurge because of its pathogenicity and specificity.

A greenhouse experiment was conducted to determine the efficacy of glyphosate and acetyl-CoA carboxylase (ACCase)–inhibiting herbicides sethoxydim, clethodim, and quizalofop on prairie cupgrass and windmillgrass. Herbicides were applied at seedling, tillering, and heading growth stages. In addition, a study to determine glyphosate absorption and translocation in both species was conducted. Herbicide treatments were glyphosate at 541, 841, and 1121 g ha−1 and sethoxydim, clethodim, and quizalofop at 350, 210, and 70 g ha−1, respectively. In general, control of prairie cupgrass and windmillgrass increased as the rate of glyphosate increased. In addition, windmillgrass was less susceptible to glyphosate at heading and seedling stages than was prairie cupgrass. Efficacy of all ACCase-inhibiting herbicides applied at any growth stage was equal to or greater than efficacy of the highest rate of glyphosate applied at the same stage. Furthermore, all herbicide treatments were more phytotoxic to prairie cupgrass and windmillgrass at seedling stage than at tillering or heading. Differential response of prairie cupgrass and windmillgrass to glyphosate was attributed to differences in glyphosate translocation. Separate field experiments were conducted to evaluate preemergence (PRE) and postemergence (POST) herbicide treatments for prairie cupgrass and windmillgrass in no-till corn at Hays, KS, in 2001 and 2002. All PRE treatments provided at least 90% control of windmillgrass in both years 6 wk after treatment (WAT). Prairie cupgrass was controlled effectively by acetochlor plus atrazine, alachlor plus atrazine, and S-metolachlor plus atrazine in 2001. In 2002, the only PRE treatments that gave 90% control or greater of prairie cupgrass 6 WAT were alachlor plus atrazine and pendimethalin plus atrazine. Glyphosate sequential treatment was the only POST treatment that provided 100% control of prairie cupgrass and windmillgrass in both years.

Injection of undiluted dimethylamine salt of (2,4-dichlorophenoxy)acetic acid (2,4-D) containing 479 g/L killed several species of bottom-land hardwoods when applied in 1 or 2-ml dosages in injections spaced from edge-to-edge to 23 cm apart. Most hardwoods were easier to kill in June than in September or December. For greatest economy, treatments should be varied by species and seasons. A 4:1 mixture of triisopropanolamine salts of 2,4-D and 4-amino-3,5,6-trichloropicolinic acid (picloram) containing 305 g/L was effective on some species resistant to 2,4-D, including eastern persimmon (Diospyros virginiana L.), swamp privet (Forestiera acuminata (Michx.)Poir.), and bitter pecan (Carya x lecontei Little).

Leafy spurge seeds are responsive to alternating temperature rather than constant temperature for germination. Transcriptome changes of dry leafy spurge seeds and seeds imbibed for 1 and 3 d at 20 C constant (C) and 20 : 30 C alternating (A) temperature were determined by microarray analysis to examine temperature responsiveness. Principal component analysis revealed differences in the transcriptome of imbibed seeds based on the temperature regime. Computational methods in bioinformatics parsed the data into overrepresented AraCyc pathways and gene regulation subnetworks providing biological context to temperature responses. After 1 d of imbibition, the degradation of starch and sucrose leading to anaerobic respiration were common pathways at both temperature regimes. Several overrepresented pathways unique to 1 d A were associated with generation of energy, reducing power, and carbon substrates; several of these pathways remained overrepresented and up-regulated at 3 d A. At 1 d C, pathways for the phytohormones jasmonic acid and brassinosteroids were uniquely overrepresented. There was little similarity in overrepresented pathways at 1 d C between leafy spurge and arabidopsis seeds, indicating species-specific effects upon imbibition of dry seeds. Overrepresented gene subnetworks at 1 d and 3 d at both temperature regimes related to signaling processes and stress responses. A major overrepresented subnetwork unique to 1 d C related to photomorphogenesis via the E3 ubiquitin ligase COP1. At 1 d A, major overrepresented subnetworks involved circadian rhythm via LHY and TOC1 proteins and expression of stress-related genes such as DREB1A, which is subject to circadian regulation. Collectively, substantial differences were observed in the transcriptome of leafy spurge seeds imbibed under conditions that affect the capacity to germinate.

This research compared effects of the weed control practice, soil cultivation, and the conventional practice, glyphosate application on weed seedbank, in a vineyard system. The experiment was conducted in a commercial wine-grape vineyard in the Napa Valley of northern California from 2003 to 2005. The annual treatments were “winter–spring glyphosate,” “spring cultivation,” “fall–spring cultivation,” and “fall cultivation–spring glyphosate,” and were applied “in-row,” under the vine. Composition of the weed seedbank collected in 2002 before treatment establishment did not differ among treatments. After 3 yr of weed treatments, detrended correspondence analysis indicated that the composition of spring cultivation and winter–spring glyphosate tended to differ from each other, but the remaining two treatments showed little differentiation. As determined by linear discriminant analysis, the specific weed species were associated with seedbanks of certain treatments. These were Carolina geranium, annual bluegrass, brome grasses, California burclover, and scarlet pimpernel, which do not pose problems with regard to physical aspects of grape production. Although ‘Zorro’ rattail fescue was ubiquitous among treatments, its distribution between depths in the cultivated treatments indicated that tillage provided some homogenization of seedbank along the vertical soil profile. The seedlings from the seedbank study were not congruent with those measured aboveground in the field, suggesting that both treatment and microclimatic effects in the field may have influenced germination, and thus, aboveground composition.

In this work, we evaluated the short time-induced oxidative stress–mediated rapid metabolic and physiological responses of resistant and susceptible Sumatran fleabane [Conyza sumatrensis (Retz.) E. Walker; syn.: Erigeron sumatrensis Retz.] to 2,4-D herbicide. Under fixed conditions (25 C and 65 ± 5% relative humidity), we assayed injury symptoms, chlorophyll a fluorescence, and antioxidative systems of biotypes both resistant and susceptible to 2,4-D (1,005 g ae ha−1). Under 15 versus 25 C temperatures and light and dark conditions, oxidative stress–mediated damage was assayed on plants that received 2,4-D herbicide applications. The injury symptoms observed in the 2,4-D–resistant biotype were rapid necrosis in leaves within 30 min, with the reestablishment of normal growth within 1 to 2 wk after 2,4-D treatment. The basal antioxidant enzyme activities of superoxide dismutase, catalase, and ascorbate peroxidase were greater in the resistant than in the susceptible biotype, although the activities of all enzymes generally did not differ between untreated and treated in the resistant biotype. The resistant biotype showed great reduction (at 1 and 4 h after application) in the photosynthetic electron transport chain performance index, while these metabolic changes were only detected after 4 h in the susceptible biotype. The resistant biotype recovered from the foliar damage 1 to 2 wk after 2,4-D application, while the susceptible biotype was controlled. The production of H2O2 was responsive to temperature and increased more rapidly in the 2,4-D–resistant biotype than in the susceptible one at both 15 and 25 C; however, there was a greater increase at 25 C in the resistant biotype. H2O2 production was not light dependent in 2,4-D–resistant C. sumatrensis, with increases even under dark conditions. The 2,4-D–resistant biotype showed rapid photosynthetic damage, possibly due to the rapid necrosis and leaf disruption, and increased H2O2 content compared with the susceptible biotype.

The control of glyphosate-resistant (GR) horseweed (Conyza canadensis) in soybean has been variable with glyphosate plus saflufenacil. The objective of this research was to determine the biologically effective rate (BER) of saflufenacil, saflufenacil mixed with glyphosate, and metribuzin mixed with saflufenacil and glyphosate applied preplant (PP) for the control of GR horseweed in no-till soybean; a study was conducted to determine each of the three treatments. For each study, seven field sites infested with GR horseweed were used over a 2-yr period (2014, 2015). Saflufenacil alone at 25 and 36 g ai ha–1 provided 90 and 95% control of GR Horseweed 8 wk after application, while the BER to achieve 98% control was outside of the treatment range tested. The saflufenacil plus glyphosate (900 g ai ha–1) BER experiment found less saflufenacil was required as 25, 34, and 47 g ha–1 provided 90, 95, and 98% control of GR horseweed respectively. The metribuzin BER experiment found 61, 261, and 572 g ha–1 was required to provide 90, 95 and 98% control of GR horseweed, respectively, mixed with saflufenacil (25 g ha–1) and glyphosate (900 g ha–1). The addition of metribuzin with the recommended rate of saflufenacil (25 g ha–1) plus glyphosate improved control and a second effective herbicide mode of action for the control of GR horseweed. The use of a threeway herbicide mixture can be an effective weed management strategy to control GR horseweed in soybean.

Plants that release molecules affecting other plants are a source of potential bioherbicides. Silver wattle (Acacia dealbata Link), considered invasive worldwide, was found to be phytotoxic to various other plant species. Combining the search for alternative bioherbicides while reducing the spread of this invader by preventing seed formation is a good potential strategy to solve both agricultural and environmental problems. This study aimed to identify nonvolatile compounds from A. dealbata flowers and explore their phytotoxicity on the germination process and seedling and plant growth of lettuce (Lactuca sativa L.), wheat (Triticum aestivum L.), and rigid ryegrass (Lolium rigidum Gaudin). We identified methyl cinnamate and methyl anisate as potential phytotoxins in the extracts, but we used pure commercial molecules to conduct bioassays. Methyl cinnamate showed higher phytotoxicity than methyl anisate and was selected for further bioassays. Methyl cinnamate reduced guaiacol peroxidase activity by 57% and 85% in L. rigidum and lettuce, respectively, and α-amylase by 6% in L. rigidum. This compound also inhibited early stem and radicle growth of dicotyledonous lettuce (60% and 89%, respectively) and monocotyledonous L. rigidum (76% and 87%, respectively), both species having small seeds. However, wheat with a larger seed size was not affected by the phytotoxin. The results obtained indicate a potential bioherbicidal effect for methyl cinnamate, and its application might be useful in wheat crops infested by L. rigidum. We suggest that collecting A. dealbata flowers would prevent Acacia seed formation and thus play a role in invasive pest management, as well as serving as a source of potential herbicides to other species.

Rhizome sections of ironweed from which the fleshy roots had been pruned made less than half as much growth in the greenhouse as sections which had three inches of fleshy roots attached. Rhizome sections at least two inches long with portions of the fleshy roots intact should be used for asexual reproduction of ironweed. Ironweed plants in the field after 8 and 9 years of mowing treatments at 2 dates were approximately ⅔ as tall as untreated plants. No significant reduction in stand was obtained by 9 successive years of mowing.

Lanolin or lanolin + corn (Zea mays L.) starch rings are often used as barriers on leaves to prevent runoff of foliarly applied 14C-herbicide treatments. A preliminary experiment showed that 64 and 90% of the applied 2,4-D [(2,4-dichlorophenoxy)acetic acid] and 57 and 87% of the applied glyphosate [N-(phosphonomethyl)glycine] was adsorbed to or absorbed into a lanolin and lanolin + starch ring, respectively, during 6 days on a glass slide. Absorption and translocation of 2,4-D in hemp dogbane (Apocynum cannabinum L.) was decreased from 26% down to 16 or 17% of the total applied when a lanolin or lanolin + starch ring was used. Glyphosate absorption and translocation increased with the lanolin ring but not with the lanolin + starch ring. Distribution of the translocated 2,4-D and glyphosate was also altered by use of the ring barriers. Results indicate that one should avoid use of the lanolin ring in 14C-herbicide absorption studies to simulate field conditions.

Germination of wild carrot (Daucus carota L.) was not confined to any season but was correlated with abundant soil moisture in field studies. In laboratory studies, germination percentage for any seed lot increased with time as dormancy was overcome. Further, the germination was not clearly correlated with seed weight, light, or pH, but temperature and the availability of water were clearly significant. Dormancy was due to the endosperm which surrounds the embryo. When part of the endosperm covering the tip of the radicle was digested or broken off, germination was increased nearly to the potential for a given lot of seed

Internal dormancy was shown to occur in western ironweed (Vernonia baldwinni Torr.) and leafy spurge (Euphorbia esula L.) in late summer and fall. Time required for emergence and extent of growth were important indicators of dormancy. Dormancy is apparently broken naturally in the field by low soil temperatures.

The robustness of competitive attributes of cereals such as rapid and uniform seedling emergence, tillering, early biomass accumulation and canopy closure, and height advantage over weeds have not yet been tested under environmental conditions typical of no-till (NT) cropping systems. Our objective was to evaluate the effects or NT practices on growth and productivity of Avena sativa, Triticum aestivum, Hordeum vulgare, and associated weeds. The experiment was conducted on a Kamouraska clay at La Pocatière, QC, in 1994, 1995, and 1996. Avena sativa, T. aestivum, and H. vulgare were grown under tilled and NT practices. Cereal growth parameters were measured six (1994) or seven (1995) times between planting and the 11th week after planting but only once in 1996. Grain yields and yield components were determined at crop maturity. Avena sativa and H. vulgare populations were little affected by tillage, whereas T. aestivum populations were reduced by 16 to 20% in NT systems. Growth in height in NT systems was either similar or greater than in tilled systems in all three cereals. Cereal leaf area index (LAI) and biomass accumulation was also comparable between tillage systems, except for T. aestivum LAI in 1994, which was greater in tilled plots on two sampling dates. Response of annual dicots to tillage was inconsistent in all crops. Annual monocots dominated in some but not all NT systems. Perennial dicots dominated in NT systems, whereas perennial monocots were more abundant in tilled systems in all three cereals. Avena sativa and T. aestivum yields in NT plots were comparable or greater than in tilled plots, in spite of having either lower test weights (A. sativa) or lower 1,000-grain weights (T. aestivum). NT T. aestivum productivity was maintained in spite of reduced plant establishment. Hordeum vulgare yields were also similar across tillage systems, except in 1995, when yields in tilled plots were greater than in NT plots. The height advantage observed for NT H. vulgare did not result in improved yields. All three cereals, and particularly A. sativa, appeared well suited to NT systems, despite the pressure provided by different weed groups, compared to tilled systems. However, results suggest that NT production of cereals could benefit from improved attention to perennial dicot control and crop seedling establishment, particularly for T. aestivum.

Several environmental and edaphic factors were monitored to determine their association with tolerance of seeded tomatoes (Lycopersicon esculentum Mill.) to diphenamid (N,N-dimethyl-2,2-diphenylacetamide). Injury increased with increasing soil pH and reduced temperature within 7 days of seeding in both field and growth chamber tests. The application of soluble fertilizer and diphenamid at planting acted synergistically to increase tomato injury. Prior to emergence of the tomato seedlings, 14C-diphenamid uptake was slight but increased with higher temperatures, while growth was inhibited at both low and high temperatures. Uptake and metabolism of 14C-diphenamid by plants in the cotyledon stage was not greatly affected by temperature or pH; however, translocation from the root to the shoot was reduced under low temperatures and high pH. These differences in translocation paralleled reported differences between tolerant and susceptible species, and may account for the increased diphenamid injury to tomatoes grown under stress conditions.

The growth regulator NAA was investigated to determine whether it would control creeping woodsorrel (Oxalis corniculata L. # CYPES) with no phytotoxicity to container ornamental species. Dosage, carrier volume, number of applications, and plant age and growth stage were examined as factors in the phytotoxicity of NAA. Creeping woodsorrel response to the ethyl ester formulation of NAA was linear for dosages up to 5.6 kg/ha; this rate resulted in about 80% injury in all experiments. NAA applied at 8.4 and 11.2 kg/ha achieved 99 and 100% control, respectively. Neither carrier volume nor split applications had any effect on phytotoxicity of NAA. In all experiments, phytotoxicity appeared to increase until around 2 to 3 weeks from application. Phytotoxicity to creeping woodsorrel was related to plant age; as plant age at the time of treatment increased, the level of injury decreased. When plants treated with NAA at rates up to 2.8 kg/ha were cut back to soil level, some regrowth occurred in all cases. Rates of NAA that controlled creeping woodsorrel (5.6 and 11.2 kg/ha) were not phytotoxic to several ornamental species.

Early postemergence applications of 2,6-dichlorobenzonitrile (dichlobenil) granules at 15 lb/A controlled 97 to 99% of dwarf waterlily (Nymphaea tetragona Georgi) in a shallow lake for 3 years. Dichlobenil alone was superior to a combination of dichlobenil and (2,4-dichlorophenoxy)acetic acid (2,4-D) for the control of dwarf waterlily and western yellow waterlily (Nuphar polysepalum Engelm). Reinfestation was more rapid on plots 25 by 25 ft in size than on plots 50 by 50 ft in size. When a high degree of control was maintained for 2 or 3 years, rhizomes of dwarf waterlily and a 1 to 2-ft layer of hydrosoil floated to the lake surface 17 months after dichlobenil was applied.

The rates of foliar dark respiration and net photosynthesis in attached leaves of 25 C3, C4, and C3-C4 intermediate dicotyledonous weed species were determined using the infrared gas analyzer. The ratio of dark respiration to photosynthesis per unit leaf area in attached leaves of each species was inversely proportional to leaf age. Highly significant, positive linear correlation was observed between the rates of foliar dark respiration and net photosynthetic CO2 uptake in dicot weeds irrespective of the photosynthetic type. The higher foliar dark respiration rate found in some of the weed species can be attributed in part to the higher carbohydrate levels as generated by a rapid photosynthetic CO2 assimilation. The significance of higher dark respiration rate in relation to carbon and energy economy of weeds is discussed.