bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutsedge (Cyperusspp.) Control in Peanut (Arachis hypogaea) with AC 263,222 and Imazethapyr
Authors: Grichar W. James , Nester Paul R.
Published: March 2018

Experiments were conducted from 1991 through 1993 to evaluate AC 263,222 and imazethapyr for yellow and purple nutsedge control in peanut. AC 263,222 at 0.05 to 0.07 kg/ha controlled purple nutsedge (88 to 99% late season) whether applied preplant incorporated (PPI), preemergence (PRE), early postemergence (EPOST) at peanut emergence, or postemergence (POST). Yellow nutsedge control with AC 263,222 was inconsistent at the 0.04 kg/ha rate; however, the 0.05 and 0.07 rate gave 88% early season yellow nutsedge control, but late season control was variable. Yellow nutsedge control with soil-applied treatments of AC 263,222 and imazethapyr were similar but AC 263,222 provided better postemergence control than did imazethapyr. Purple nutsedge control was similar for both herbicides across all application methods.
Efficacy of Pyrithiobac and Bromoxynil Applied with Low-Volume Spray Systems
Authors: Tredaway Joyce A. , Patterson Michael G. , Wehtje Glen R.
Published: March 2018

Field experiments were conducted in 1994 and 1995 to determine if the sodium salt of pyrithiobac or bromoxynil applied in a low-volume, air-assist spray system controlled entireleaf morningglory, pitted morningglory, and smallflower morningglory as well as treatments applied with a conventional hydraulic fan spraying system, and to determine if herbicide rates could be reduced when using the low-volume spraying system. Pyrithiobac at 0.035 and 0.071 kg ai/ha and bromoxynil at 0.56 and 1.12 kg ai/ha were applied alone and in combination with DSMA at 1.7 kg ai/ha or MSMA at 1.7 kg ai/ha. Spraying systems were calibrated to deliver 26 L/ha and 140 L/ha for the low-volume and conventional systems, respectively. No significant differences in control were noted between low-volume and conventional spray systems when herbicides were applied at the suggested use rates of 0.071 and 1.12 kg ai/ha for pyrithiobac and bromoxynil, respectively. Morningglory control was reduced when pyrithiobac and bromoxynil were applied at one-half the suggested use rate regardless of the spraying systems. Bromoxynil alone generally controlled pitted and entireleaf morningglory better than pyrithiobac alone regardless of rate and application method. However, pyrithiobac generally provided better control of smallflower morningglory than bromoxynil. Adding MSMA or DSMA to bromoxynil and pyrithiobac increased control of both weed species.
Diets of Angora Goats Grazing Leafy Spurge (Euphorbia esula)-Infested Rangeland
Authors: Kirby Donald R. , Hanson Thomas P. , Sieg Carolyn Hull
Published: March 2018

Angora goats have been suggested as biological control agents for leafy spurge, especially in environmentally sensitive or limited access areas. Dietary preferences and dietary nutritive content of herded Angora goats were evaluated over a two-year period in North Dakota. Relative preferences of forages were evaluated by comparing botanical composition of diets as determined by microhistological analysis of fecal samples to forage availability in the field. Leafy spurge and shrubs comprised the largest percentage of goat diets throughout each grazing season. Goats preferred leafy spurge and shrubs at all times and avoided most cool-season grass species. The nutritional requirements of Angora goats nursing kids were met throughout the grazing season. Use of Angora goats is another tool available to land managers to manage leafy spurge infestations in the Northern Plains.
Accuracy of a Global Positioning System (GPS) for Weed Mapping
Authors: Webster Theodore M. , Cardina John
Published: March 2018

Experiments were conducted to test the accuracy of a global positioning system (GPS) in measuring the area of simulated weed patches of varying size and to determine the accuracy in navigating back to particular points in a field. Circular areas of 5, 50, and 500 m2 were established and measured using point and polygon features of a GPS. The GPS estimations of the area of those patches had errors ranging from 7 to 45%, 6 to 15%, and 3 to 6%, respectively, when compared to actual measurements. As patch size increased, errors decreased. A curve describing the relationship between GPS error and patch size had an excellent fit (r2 = 0.92). The error remained the same in all measurements across all patch sizes, but composed a smaller percentage of large patches. The GPS had submeter accuracy in navigation to the correct quadrat 73% of the time, located the correct quadrat 27% of the time, and invariably navigated to within 1.58 m of the correct quadrat. The relationship between patch size and measurement error was applied to natural infestations of hemp dogbane.
Acetolactate Synthase-Resistant and -Susceptible Corn (Zea mays) Response to Imazethapyr, Imazaquin, Chlorimuron, and CGA-152005
Authors: Krausz Ronald F. , Kapusta George , Matthews Joseph L.
Published: March 2018

Field experiments were conducted from 1993 to 1995 to evaluate the response of ALS-resistant and ALS-susceptible corn to imazethapyr, imazaquin, chlorimuron, and CGA-152005 at label and twice label rates applied preplant incorporated (PPI) and postemergence (POST). The susceptible hybrid (P3245) and the resistant hybrid (P3245IR) grain yield were not different where weeds were removed by hand-weeding alone. Alachlor plus atrazine alone plus hand-weeding reduced grain yield by 5% compared to hand-weeding only. Imazethapyr applied PPI and POST reduced height of the susceptible hybrid 11 and 6%, respectively, averaged across imazethapyr rates. Imazaquin reduced the final height of the susceptible hybrid by 30 to 75% and reduced corn density by 62 to 78%. Chlorimuron applied PPI reduced final corn height of the susceptible hybrid by 26 to 36% and density by 27%. Chlorimuron applied PPI and imazaquin applied PPI and POST reduced grain yield of the susceptible hybrid. Imazethapyr did not reduce grain yield of the susceptible hybrid, regardless of application timing or rate. Imazethapyr, imazaquin, and chlorimuron did not reduce height, density, or grain yield of the resistant hybrid, regardless of application timing or rate. CGA-152005 applied PPI reduced grain yield of the susceptible and resistant hybrid. CGA-152005 applied POST did not reduce grain yield, regardless of hybrid or rate.
Kyllinga, a Genus of Neglected Weeds in the Continental United States
Authors: Bryson Charles T. , Carter Richard , McCarty Lambert B. , Yelverton Fred H.
Published: March 2018

The sedge genus Kyllinga consists of 40 to 45 species distributed in tropical, subtropical, and warm temperate regions around the world (KUkenthal 1936; Tucker 1987). This genus of low rhizomatous perennials or cespitose annuals is classified in the large cosmopolitan family Cyperaceae. Many Kyllinga species are considered weedy (Holm et al. 1979; Tucker 1987), while Kyllinga nervosa Steudel is considered an important forage plant in Africa (McNaughton 1985).
Interference of Purple Nutsedge (Cyperus rotundus) Population Densities on Bell Pepper (Capsicum annuum) Yield as Influenced by Nitrogen
Authors: Morales-Payan Jose P. , Santos Bielinski M. , Stall William M. , Bewick Thomas A.
Published: March 2018

Additive series studies were conducted under greenhouse conditions to determine the effects of nitrogen (N) rate and purple nutsedge densities on the yield of ‘California Wonder’ bell pepper. Initial densities of purple nutsedge were 0, 100, 200, and 300 plants/m2. Nitrogen was applied at 70, 140, and 210 kg/ha. Plants were allowed to interfere for 10 wk. There were significant purple nutsedge population density by N rate interactions on bell pepper fruit yield. At 70 kg N/ha, no significant effect of weed population densities was found on fruit yield, whereas at the rates of 140 and 210 kg N/ha there were significant nutsedge density effects. As N rates and nutsedge densities increased, so did purple nutsedge biomass. Linear regression models described the interference. Bell pepper fruit yield reduction was 73% at 210 kg N/ha with an initial nutsedge population density of 300 plants/m2.
Metolachlor Efficacy as Influenced by Three Acetolactate Synthase-Inhibiting Herbicides
Authors: Novosel Karen M. , Renner Karen A. , Kells James J. , Spandl Eric
Published: March 2018

In preliminary field trials, a reduction in grass control was observed when flumetsulam or MON 12037 with and without the safener MON 13900 was applied with metolachlor compared to metolachlor alone. Greenhouse studies were initiated to study potential interactions between acetolactate synthase (ALS)-inhibiting herbicides and metolachlor. Metolachlor at 0.14, 0.28, and 0.56 kg ai/ha was applied alone and in combination with flumetsulam at 0.0073 and 0.015 kg ai/ha and MON 12037 with safener at 0.011 and 0.021 kg ai/ha. Flumetsulam and MON 12037 with safener alone provided 13 to 23% visible barnyardgrass control and metolachlor at 0.14 kg/ha provided 82% control. Combining flumetsulam and MON 12037 with metolachlor did not increase herbicide activity beyond that observed from metolachlor alone, regardless of the parameter evaluated. Combinations of 0.14 kg/ha of metolachlor with 0.011 and 0.021 kg/ha of MON 12037 with safener or 0.015 kg/ha of flumetsulam resulted in antagonism of barnyardgrass according to Colby's multiplicative interactive model. Visible control and plant dry weight were also antagonized when 0.28 kg/ha of metolachlor was applied with 0.021 kg/ha of MON 12037 with safener. Field studies were conducted in corn and soybean to evaluate giant foxtail control from metolachlor alone and in tank mixtures with flumetsulam, chlorimuron and MON 12037 with and without safener. Although isolated incidences of antagonism were noted, there was no consistent effect on grass control when these ALS-inhibiting herbicides were applied in combination with metolachlor in 3 years of field trials.
The Biology and Integrated Management of Leafy Spurge (Euphorbia esula) on North Dakota Rangeland
Authors: Lym Rodney G.
Published: March 2018

Leafy spurge, a long-lived perennial, grows in many habitats, from floodplains to grasslands and mountain slopes. The plant emerges in early spring and produces showy, yellow bracts that appear in late May. The true flowers emerge in mid-June. The plant spreads by both seeds and roots and contains a white sticky latex that deters grazing by many animals. Dicamba, 2,4-D, glyphosate, and picloram have commonly been used to control leafy spurge. Picloram plus 2,4-D is frequently used for leafy spurge control in North Dakota. Ten insect species for leafy spurge biocontrol have been released in North Dakota; the most successful have been the flea beetles,Aphthona nigriscutis, A. czwalinae, andA. lacertosa. The leafy spurge gall midge (Spurgia esulae) has been most successful near wooded areas. Herbicides combined with either the leafy spurge flea beetles or gall midge have controlled leafy spurge better than either method used alone. Grazing with sheep or goats is a cost-effective method for controlling leafy spurge top growth in large infestations. Grazing combined with fall-applied picloram plus 2,4-D reduced leafy spurge density more rapidly and maintained control longer than either method used alone. Several grass species are competitive with leafy spurge including ‘Rebound’ smooth brome, ‘Rodan’ western wheatgrass, ‘Pryor’ slender wheatgrass, and ‘Manska’ pubescent wheatgrass. Cultivating twice each fall after harvest for 3 yr in cropland completely controlled leafy spurge. A successful long-term management program should be designed for specific situations and should include combinations of herbicides, insects, grazing, and/or seeding competitive species.
Revegetating Leafy Spurge (Euphorbia esula)-Infested Rangeland with Native Tallgrasses
Authors: Masters Robert A. , Nissen Scott J.
Published: March 2018

Degradation of Great Plains rangelands can be linked to past management practices that reduced native species diversity and accelerated establishment and expansion of exotic weeds and less desirable native species. Leafy spurge is an exotic perennial weed that infests more than 1 million ha in the northern Great Plains and reduces rangeland carrying capacity by competing with desirable forages and causing infested areas to be undesirable to cattle and wildlife. Research was conducted to determine the feasibility of using herbicides to suppress leafy spurge and other resident vegetation, which facilitated planting and establishment of native tallgrasses. Four experiments were conducted where 0.28, 0.56, and 0.84 kg ai/ha imazapyr and 0.1 kg ai/ha sulfometuron were applied alone and in combination and 0.84 kg ai/ha glyphosate was applied to leafy spurge-infested range sites in fall 1991 near Ainsworth, NE, and in fall 1991, 1992, and 1993 near Ansley, NE. Research areas were burned about 200 d after herbicide application to reduce plant residue. Monoculture stands of big bluestem and switchgrass were then no-till planted in each experiment and indiangrass was no-till planted in experiments initiated at Ansley in 1992 and 1993. Yields of the planted grasses, leafy spurge, and other vegetation were measured in August at each location starting the year after planting. Imazapyr was an essential component of treatments applied before planting to facilitate establishment of highly productive stands of the tallgrasses. Generally, yields were maximized by fall treatments of 0.28 kg/ha imazapyr + 0.1 kg/ha sulfometuron for big bluestem, 0.84 kg/ha imazapyr for indiangrass, and 0.84 kg/ha imazapyr + 0.1 kg/ha sulfometuron for switchgrass. Yields of the planted grasses were frequently four times greater where these herbicides were applied compared to where glyphosate or no herbicide were applied. Leafy spurge yields were usually reduced in areas where tallgrass yields were greatest. The sequential combination of suppressing vegetation with fall-applied herbicides, burning standing dead plant residue, then no-till planting desirable native tallgrasses in the spring increased productivity of these leafy spurge-infested range sites.
Annual Bluegrass (Poa annua L.)
Authors: Mitich Larry W.
Published: March 2018

The grasses or Poaceae (Gramineae) comprise some 9,000 species grouped into about 650 taxa. Although not the largest, the family is ecologically the most dominant and economically the most important in the world (Heywood 1993).
Biocontrol of Common St. Johnswort (Hypericum perforatum) withChrysolina hypericiand a Host-SpecificColletotrichum gloeosporioides
Authors: Morrison Kimberly D. , Reekie Edward G. , Jensen Klaus I. N.
Published: March 2018

Common St. Johnswort is widespread in eastern Canada but it seldom constitutes a serious weed problem. A demographic study conducted in 1993 and 1994 at four typical undisturbed sites indicated that 36 to 96% of established St. Johnswort shoots died during the growing season. Mortality was always associated with infection by a host-specificColletotrichum gloeosporioides. The leaf-feeding beetleChrysolina hypericioccurred at all sites and caused maximum midsummer defoliation of 27% in 1993 and 51% in 1994. Healthy plants readily recovered from defoliation during pupation of the fourth instar of the insect in June and following adult estivation in August. Although widespread,C. hypericipopulations appear transient and alone do not cause sustained feeding pressure resulting in weed control. WhenChrysolinalarvae and adults were collected at six field sites and placed on healthy seedlings under controlled conditions, up to 36% of the plants became infected withC. gloeosporioides. Scanning electron micrographs commonly showedColletotrichumconidia among the setae on legs, tarsal pads, and antennae of adults and larvae. In a series of three experiments conducted under controlled conditions in whichChrysolinalarvae and adults were placed on healthy plants after feeding on diseased ones, the incidence of infection ranged from 63 to 100%. Hence, under favorable conditionsChrysolinaadults may selectively transmit the pathogen in the field. This study demonstrated the potential of enhancing biological control of weeds by insects with the integration of an effective, host-specific pathogen.
Weed Management in Transplanted Bell Pepper (Capsicum frutescens) with Clomazone and Rimsulfuron
Authors: Ackley John A. , Wilson Henry P. , Hines Thomas E.
Published: March 2018

In field studies, in 1993, 1994, and 1995, clomazone at 390 g ai/ha and rimsulfuron at 35 g ai/ha were evaluated preplant incorporated (PPI) and postemergence (POST), respectively, for weed control and crop response in transplanted ‘Keystone RG3’ bell pepper. Clomazone did not injure bell pepper. Common lambsquarters and jimsonweed control was 77 to 95% by clomazone treatments but was variable by rimsulfuron treatments at 41 to 93% common lambsquarters control and 42 to 68% jimsonweed control; common ragweed control by both herbicides was unacceptable. Injury by rimsulfuron to bell pepper in the field was 19 to 47% at 21 DAT. In the greenhouse, injury to Keystone RG3 and three additional bell pepper varieties, ‘Camelot,’ ‘Jupiter,’ and ‘Memphis’ was similar at 44 to 62% by rimsulfuron at 17 to 35 g/ha POST, and bell pepper had lower height and dry weight than untreated controls. In the greenhouse, jimsonweed control was below 49% and black nightshade control was below 23% by 17 to 35 g/ha rimsulfuron. In these studies, clomazone controlled common lambsquarters and jimsonweed without injury to bell pepper. The solanaceous weeds treated in this study were not well controlled by rimsulfuron, and bell pepper was not sufficiently tolerant to rimsulfuron to permit its use in this crop.
Spray Adjuvant, Formulation, and Environmental Effects on Synergism from Post-Applied Tank Mixtures of SAN 582H with Fluazifop-P, Imazethapyr, and Sethoxydim
Authors: Scott Robert C. , Shaw David R. , O'neal William B. , Klingaman Troy D.
Published: March 2018

The effect of adding a spray adjuvant to SAN 582H tank mixtures with fluazifop-P, imazethapyr, and sethoxydim was evaluated. SAN 582H synergistically increased broadleaf signalgrass control with reduced rates of all three postemergence (POST) herbicides when no spray adjuvant was used and when crop oil concentrate was added. For example, broadleaf signalgrass control increased from 50% to 83% when SAN 582H was tank-mixed with 52 g ai/ha sethoxydim and crop oil concentrate. In another experiment, several formulations of SAN 582H, including blank solvent-only formulations (no SAN 582H), were evaluated in combination with a reduced rate of sethoxydim to determine the source of synergism from tank mixtures. The SAN 582H molecule, not the carrier solvents in formulated product, was determined to be the source of synergism. The synergistic properties of SAN 582H were compared to other chloroacetamides. Synergism from acetochlor was similar to SAN 582H when applied POST with a reduced rate of either fluazifop-P, imazethapyr, or sethoxydim for grass control. Metolachlor also synergistically increased the control of grasses with the POST herbicides; however, metolachlor caused considerable phytotoxicity when applied alone and synergistic interactions were detected less frequently. The efficacy of sethoxydim mixed with SAN 582H was evaluated under different soil moisture conditions. Broadleaf signalgrass control increased from 81% to 93% under dry, moisture-stressed conditions when 210 g/ha sethoxydim was tank- mixed with SAN 582H.
Differential Tolerance of Corn (Zea mays) Inbreds to Four Sulfonylurea Herbicides and Bentazon
Authors: Green Jerry M.
Published: March 2018

Nine corn inbreds were selected from a test on 250 inbreds based on distinctly different response to herbicides. These inbreds showed up to 50,000-fold differences, which varied by inbred and herbicide. Only the inbred GA209 was sensitive to bentazon and the four sulfonylurea herbicides. GA209 and B90 were the most sensitive inbreds to the sulfonylurea herbicides. F2R was generally the most tolerant inbred. The pattern of herbicide tolerance varied greatly. For example, the relative tolerance of F2 to thifensulfuron was 12-fold more than to rimsulfuron while Mo17 was 56-fold more tolerant to rimsulfuron than thifensulfuron. F2 was fivefold more tolerant of chlorsulfuron than chlorimuron, whereas B80 was 100-fold the reverse. These inbreds provide a small subset of varieties to evaluate the large and inherent differences in herbicide tolerance of corn.
Contribution of Nitrogen Fertilizer Placement to Weed Management in Spring Wheat (Triticum aestivum)
Authors: Kirkland Kenneth J. , Beckie Hugh J.
Published: March 2018

The contribution of nitrogen (N) fertilizer placement to management of annual weeds in spring wheat grown under two tillage systems was examined at sites located in three ecoregions of the northern Great Plains from 1994 to 1996. The effect of three different fertilizer placements on narrowleaf and broadleaf weed emergence, growth, and N uptake were determined in a no-till and a conventional tillage system. Fertilizer was broadcast, subsurface-banded in the spring prior to seeding, or side-banded at the time of seeding. Tillage system generally did not influence weed and crop response to fertilizer placement. Broadcast-applied fertilizer was more effective than banded fertilizer in promoting wild oat and broadleaf weed emergence and growth over the growing season. Weed densities, biomass, and N uptake measured early in the growing season averaged 20 to 40% less, and grain yield of wheat at maturity averaged 12% higher where fertilizer was side-banded compared to broadcast. In contrast, the addition of fertilizer, regardless of placement, was detrimental to green foxtail because of enhanced crop competitiveness. Banding fertilizer at recommended rates can be an effective cultural practice for managing weeds in no-till and conventional tillage wheat-cropping systems in semiarid to subhumid regions of the northern Great Plains, but it is not reliable when used as the sole method of weed management.
The Influence of Weed Management in Wheat (Triticum aestivum) Stubble on Weed Control in Corn (Zea mays)
Authors: Webster Theodore M. , Cardina John , Loux Mark M.
Published: March 2018

The objectives of this study were to determine how the timing of weed management treatments in winter wheat stubble affects weed control the following season and to determine if spring herbicide rates in corn can be reduced with appropriately timed stubble management practices. Field studies were conducted at two sites in Ohio between 1993 and 1995. Wheat stubble treatments consisted of glyphosate (0.84 kg ae/ha) plus 2,4-D (0.48 kg ae/ha) applied in July, August, or September, or at all three timings, and a nontreated control. In the following season, spring herbicide treatments consisted of a full rate of atrazine (1.7 kg ai/ha) plus alachlor (2.8 kg ai/ha) preemergence, a half rate of these herbicides, or no spring herbicide treatment. Across all locations, a postharvest treatment of glyphosate plus 2,4-D followed by alachlor plus atrazine at half or full rates in the spring controlled all broadleaf weeds, except giant ragweed, at least 88%. Giant foxtail control at three locations was at least 83% when a postharvest glyphosate plus 2,4-D treatment was followed by spring applications of alachlor plus atrazine at half or full rates. Weed control in treatments without alachlor plus atrazine was variable, although broadleaf control from July and August glyphosate plus 2,4-D applications was greater than from September applications. Where alachlor and atrazine were not applied, August was generally the best timing of herbicide applications to wheat stubble for reducing weed populations the following season.
Duration of Broadleaf Weed Control with Isoxaben Using Soil Bioassays
Authors: Chandran Rakesh S. , Derr Jeffrey F.
Published: March 2018

A soil bioassay experiment was conducted in Blacksburg, VA, to determine the effect of isoxaben application timings and rates on duration of weed control. Flats containing soil were imbedded into the field. Isoxaben was applied in the spring, fall, and spring followed by fall (double application) at 0.56, 0.84, and 1.12 kg ai/ha. Flats were moved to a greenhouse at 0, 1, 3, 6, and 9 months after treatment (MAT) and seeded with yellow rocket, buckhorn plantain, and spotted spurge for the bioassays. Weed counts from treated flats were compared to those in untreated flats to determine percent control. Fall and spring followed by fall applications provided approximately 20% greater control of yellow rocket 3 MAT and 30% greater control 6 MAT, compared to a single spring application of isoxaben. Isoxaben at all rates controlled yellow rocket > 70% at 6 mo after fall application. At 3 MAT, fall and spring plus fall-applied isoxaben provided about 15 and 20% greater buckhorn plantain control, respectively, compared to spring application. The two highest rates of isoxaben controlled buckhorn plantain > 70% at 3 mo after fall application, but provided poor control at 6 MAT. Control of spotted spurge was similar among the three application timings for isoxaben and was unacceptable at most evaluation dates. Overall, isoxaben applied at 1.12 kg/ha provided better control of all three weed species for a longer time than the reference herbicide, oxadiazon, applied at 3.36 kg/ha.
Effect of Isoxaben Application Rate and Timing on Residual Broadleaf Weed Control in Turf
Authors: Chandran Rakesh S. , Derr Jeffrey F. , Bingham S. Wayne
Published: March 2018

Duration and spectrum of preemergence (PRE) weed control following isoxaben application at 0.56, 0.84, and 1.12 kg ai/ha in spring, fall, or spring plus fall (double) application were evaluated by field experiments. Residual activity of isoxaben was assessed by monitoring weed counts at two locations for 12 mo after treatment (MAT). Buckhorn plantain and dandelion control from spring-applied isoxaben at 1.12 kg/ha was > 90% at 4 MAT in Blacksburg but dropped to < 51% at 12 MAT. Isoxaben at 1.12 kg/ha applied in fall provided ≥ 90% control of buckhorn plantain for 8–9 MAT, with control ranging from 69 to 91% at approximately 12 MAT. Dandelion control with fall-applied isoxaben at 1.12 kg/ha ranged from 60 to 75%, 8–9 MAT. Fall application of 1.12 kg/ ha isoxaben at Virginia Beach controlled henbit and cornspeedwell for 2–3 MAT. Multiple applications of isoxaben improved weed control at Virginia Beach, but results were inconclusive at Blacksburg. In comparison, oxadiazon controlled white sweet clover and dandelion for 1 MAT following spring application in Blacksburg, but < 65% broadleaf control was observed at 4 MAT. Broadleaf weed control following single application of oxadiazon at 3.36 kg/ha was < 60% at 9 MAT Poor weed control resulted from spring applications of isoxaben and oxadiazon when a 25-cm precipitation occurred within 2 wk after application in one study.
Cucumber (Cucumis sativus) Response to Selected Foliar- and Soil-Applied Sulfonylurea Herbicides
Authors: Schroeder Jill
Published: March 2018

Field experiments were conducted at six locations across the U.S. in 1995 and at two locations in 1996 to determine the yield and grade of slicer type cucumber after treatment with sulfonylurea herbicides. In 1995, thifensulfuron, bensulfuron, or 2,4-D amine was applied postemergence (POST) to cucumber at the initiation of vines. Thifensulfuron and bensulfuron were applied at concentrations between 0 and 2.24 g ai/ha, and 2,4-D amine was applied at 0 to 28 g/ha. Only thifensulfuron applied at 2.24 g/ha (51% of the maximum use rate in soybean) reduced yield of No. 1 cucumber. In 1996, chlorimuron and metsulfuron were applied preplant incorporated (PPI) at rates between 0 and 2.24 g/ha, and atrazine was applied at 0 to 1,120 g/ha. The herbicides were incorporated to a depth of 7.6 cm prior to planting cucumber. Only atrazine applied at ≥ 560 g/ha reduced yield of No. 1 and No. 2 grades of cucumber. The results led us to conclude that these sulfonylurea herbicides, at the low rates used in this research, do not adversely affect yield or grade of field-grown cucumber.
Johnsongrass (Sorghum halepense) Control Systems for Field Corn (Zea mays) Utilizing Crop Rotation and Herbicides
Authors: Ghosheh Hani Z. , Chandler James M.
Published: March 2018

Johnsongrass control systems that included commercially available corn herbicides applied to crop sequences of continuous corn or corn–cotton–corn rotation were evaluated over a 3-yr period at the Texas Agricultural Experiment Station in Burleson County. Herbicide treatments evaluated were EPTC + R-25788 applied preplant incorporated (PPI); metolachlor applied preemergence (PRE); nicosulfuron applied postemergence (POST); and the combination of metolachlor PRE and glyphosate POST applied after corn harvest. Weed control practices applied to plots planted to cotton in the second growing season provided excellent johnsongrass control (≈ 95%). Visual control ratings indicated that nicosulfuron provided the best johnsongrass control (> 80%) among the herbicides evaluated all three years. Metolachlor and glyphosate combinations provided acceptable johnsongrass control the third year of the experiment in both cropping sequences. Corn grain yield and johnsongrass control were best in cotton-rotated plots. The highest returns observed in continuous corn were from either nicosulfuron or the combination of metolachlor and glyphosate. Net returns for all control systems in corn–cotton–corn rotated plots were greater than the weedy check and were equivalent to the lead systems in continuous corn.
Red Rice (Oryza sativa) andEchinochloaspp. Control in Texas Gulf Coast Soybean (Glycine max)
Authors: Noldin José A. , Chandler James M. , McCauley Garry N. , Sij John W.
Published: March 2018

Field studies were conducted from 1992 to 1994 to evaluate herbicides applied preplant incorporated (PPI), preemergence (PRE), and postemergence (POST) for red rice andEchinochloaspp. control in soybean. Metolachlor PPI at 3.4 kg ai/ha controlled red rice late season 90 to 92%. Alachlor at 4.5 kg ai/ha and SAN 582H at 2.2 or 3.4 kg ai/ha, PPI or PRE, metolachlor plus imazaquin at 2.8 + 0.14 kg ai/ha PRE, and quizalofop-P POST at 0.07 kg ai/ha provided 83 to 95% red rice control in at least 2 of 3 yr. The addition of imazaquin to metolachlor or pendimethalin did not improve red rice control. Early-seasonEchinochloaspp. control with trifluralin, pendimethalin, and pendimethalin + imazaquin applied PPI; metolachlor, SAN 582H at 2.2 or 3.4 kg/ha, and metolachlor + imazaquin applied PPI or PRE; alachlor, AC 263,222 + imazaquin, and AC 263,222 + imazethapyr applied PRE; and sethoxydim and quizalofop-P applied POST was 90 to 100% in at least 2 of 3 yr. However,Echinochloaspp. control decreased for all treatments later in the season. Pendimethalin applied PPI at 2.2 kg ai/ha or in mixture with imazaquin at 1.7 + 0.14 kg ai/ha injured soybean 14 to 34% in 2 yr. Trifluralin PPI, SAN 582H at 2.2 or 3.4 kg/ha PPI or PRE, imazaquin PPI, metolachlor + imazaquin PPI or PRE, and AC 263,222 + imazethapyr injured soybean 12 to 41% in at least 1 of 3 yr.
Glucosinolate Production by Five Field-GrownBrassica napusCultivars Used as Green Manures
Authors: Eberlein Charlotte V. , Morra Matthew J. , Guttieri Mary J. , Brown Paul D. , Brown Jack
Published: March 2018

Winter rape (Brassica napusL.) green manures have shown potential for erosion control and suppression of weeds and other pests in potato cropping systems. However, little information on residue cover, biomass production, glucosinolate concentration, and glucosinolate production with winter rape grown as a green manure is available. In field trials in southern Idaho, ‘Aspen,’ ‘Bridger,’ ‘Cascade,’ ‘Dwarf Essex,’ and ‘Humus’ winter rape were planted in mid-August and incorporated the following spring in late April or early May. All five cultivars provided > 80% fall, winter, and early spring residue cover. Winter rape dry weight just before incorporation was 2,880 to 4,462 kg/ha in 1994 and 5,438 to 7,837 kg/ha in 1995. The major glucosinolate in roots of all five cultivars was phenylethyl glucosinolate; the major glucosinolates in shoots were 4-pentenyl, 2-hydroxybutenyl, 3-butenyl, and 2-hydroxypentenyl glucosinolate. Glucosinolate concentrations varied between years, but concentrations were higher in Dwarf Essex and Humus than in Aspen both years. Glucosinolate production per hectare also was highest in Dwarf Essex and Humus and lowest in Aspen. Dwarf Essex and Humus produced higher amounts of isothiocyanate (ITC) and oxazolidinethione (OZT)-producing glucosinolates than Aspen, Bridger, or Cascade, and therefore may be better biofumigants.
Weeds From Other Places: The Florida Beachhead Is Established
Authors: Hall David W. , Currey Wayne L. , Orsenigo Joseph R.
Published: March 2018

Florida has more non-native species of plants established in the state than has any other state in the continental U.S.; the vast majority of these species are harmless. As settlement and population increased and additional exotic species were introduced at increasing rates, some non-native species were able to obtain the edge needed for exponential growth. Among the weeds discussed are those that demonstrate different types of entry, ecological systems, and control. Weeds representing the potential of a small population, a major escaped ornamental, rapid expansion in vegetables, major pests in tree crops, utilization of a biocontrol, distribution in turf, major invaders along roadsides and into open lands and pastures, and exotic aquatic weeds are discussed.
Where Do We Go From Here? The Challenges of Risk Assessment for Invasive Plants
Authors: White Peter S. , Schwarz Allison E.
Published: March 2018

Exotic species invasions in natural areas are one of the most significant threats to biological diversity globally. Pest plants pose a significant problem because they often go undetected until widespread ecological damage has already occurred. Effective control is both uncertain and expensive. However, not all introduced species become invasive, leading to the hope that we can develop risk assessment criteria for new plant introductions. Two recently proposed assessment programs are reviewed, one based on North American woody plants and the other based on Australian pest species, and the challenges in their application are discussed. Among the significant issues are spatial and temporal variation in plant performance that affect the documentation of invasive behavior and the tendency for horticulturists to value traits that produce invasive behavior (rapid growth, early and consistent flowering, lack of pests and diseases, and vegetative persistence). Two policy alternatives are suggested for botanical gardens as examples of models for plant introduction policies that could be adapted to other institutions: the Conservation Aware Garden and the Strict Conservation Garden. The former is based on risk assessment, whereas the latter prohibits movement of species across barriers to their dispersal. Information needs, the importance of international communication, and adaptive management are discussed as elements of a program to reduce the spread of pest invaders.
Red Rice (Oryza sativa) Biology. I. Characterization of Red Rice Ecotypes
Authors: Noldin José A. , Chandler James M. , McCauley Garry N.
Published: March 2018

Plant characteristics of red rice ecotypes obtained from Arkansas, Louisiana, Mississippi, and Texas, including 11 strawhulled, five blackhulled, two goldhulled, and one brownhulled type, were evaluated under field conditions. Most ecotypes were uniform and stable but manifested considerable genetic variability. Red rice plants had pubescent leaves, were taller with lighter green color, and produced more tillers and panicles per plant than rice cultivars ‘Lemont,’ ‘Mars,’ and ‘Maybelle.’ Most ecotypes were highly susceptible to seed shattering starting about 14 d after anthesis when seed moisture was more than 25%. Seeds of most ecotypes were highly dormant at harvest. Rice cultivars had a larger flag leaf and more total leaf area per plant at anthesis and produced more seeds per panicle than red rice. Some red rice ecotypes had plant characteristics closely related to cultivated rice suggesting natural hybridization with rice.
Identifying Acetolactate Synthase Inhibitors for Potential Control of Quackgrass (Elytrigia repens) and Canada Thistle (Cirsium arvense) in Corn (Zea mays)
Authors: Sprague Christy L. , Frasier Amy L. , Penner Donald
Published: March 2018

Control of two perennial weeds, quackgrass and Canada thistle, and the differential sensitivities of three imidazolinone-resistant (IMI) corn hybrids and their sensitive isolines to various acetolactate synthase (ALS)-inhibiting herbicides were evaluated in greenhouse studies. The postemergence sulfonylurea herbicides nicosulfuron and primisulfuron controlled quackgrass > 80%. The imidazolinone herbicides imazapyr and imazamox applied postemergence controlled quackgrass 70 and 74%, respectively. Canada thistle control was 89% with the sulfonylurea herbicide metsulfuron. Primisulfuron, chlorsulfuron, and tribenuron controlled Canada thistle > 70%. The imidazolinonesensitive corn hybrids did not tolerate the imidazolinone herbicides imazethapyr, imazaquin, imazapyr, AC 263,222, and imazamox; the sulfonylurea herbicides chlorimuron, chlorsulfuron, metsulfuron, tribenuron, and triflusulfuron; and the pyrimidinylthiobenzoate herbicide pyrithiobac applied postemergence. The ‘Ciba 4393 IMR’ corn hybrid, homozygous for an unknown allele, was resistant to all of the various ALS-inhibiting herbicides that injured its sensitive isoline. The magnitude of resistance for this hybrid was greater than the other IR corn hybrids. The ‘Pioneer 3751 IR’ corn hybrid, homozygous for theXA-17ALS allele, was also resistant to a number of ALS-inhibiting herbicides. The ‘ICI 8692 IT’ corn hybrid, heterozygous for theMut2allele, was only resistant to the imidazolinone herbicides.
Field Evaluation of a Native Fungus for Control of Melaleuca (Melaleuca quinquenervia) in Southern Florida
Authors: Rayachhetry Min B. , Elliott Monica L. , Center Ted D. , Laroche Francois
Published: March 2018

A native fungus,Botryosphaeria ribis, was evaluated under field conditions to determine its potential to control melaleuca. Applications consisted of either wound inoculations of trees withB. ribisor fresh stump treatments withB. ribisalone or mixed with imazapyr herbicide. There was no mortality among nondefoliated trees inoculated withB. ribis. Mortality ofB. ribis-inoculated trees was increased by three complete defoliation cycles. Defoliated trees inoculated with isolate BR-5 exhibited 100% mortality compared to 17% for defoliated but noninoculated trees. Wounds inoculated withB. ribisduring winter produced longer cankers than did noninoculated wounds. Stump regrowth reduction by treatment withB. ribisalone was less effective than treatment with imazapyr alone. Mixtures ofB. ribiswith imazapyr or imazapyr alone at comparable concentrations did not differ in stump regrowth control.
Selective Control of Jointed Goatgrass (Aegilops cylindrica) with Imazamox in Herbicide-Resistant Wheat
Authors: Ball Daniel A. , Young Frank L. , Ogg Alex G.
Published: March 2018

Jointed goatgrass (Aegilops cylindrica) is a serious problem for winter wheat producers throughout the western U.S. Interference from this weed can severely reduce grain yield and contaminate harvested grain, resulting in dockage losses. There are currently no selective herbicides registered for controlling jointed goatgrass in wheat. Imazamox, an imidazolinone herbicide, was applied to an imidazolinone herbicide-resistant (IMI) wheat mutant of the winter wheat cultivar ‘Fidel.’ Jointed goatgrass control from spring postemergence application of imazamox ranged from 61 to 97% when applied at 36 g/ha. Negligible crop injury from imazamox treatment was observed at 36 g/ha at several locations under dryland environments in the U.S. Pacific Northwest. Wheat yield was increased 19 to 41% by imazamox treatment in three of four experiments. Percent dockage resulting from jointed goatgrass spikelet contamination of harvested wheat grain was eliminated by imazamox treatment. Introduction of the IMI trait into commercial wheat cultivars could provide an effective method for selective control of jointed goatgrass in winter wheat.
Mowing as a Weed Control Supplement to Herbicides and Cultivation in Peanut (Arachis hypogaeaL.)
Authors: Wehtje Glenn , Wells Larry W. , Choate James H. , Martin Neil R. , Curtis John M.
Published: March 2018

A 3-yr field study was conducted in peanut in which weed control systems with varying levels of herbicides, cultivation inputs, or both were supplemented with mowing to remove weeds extending above the crop canopy. Highest yield and net returns were consistently obtained with the highest level of herbicide/cultivation inputs, and mowing was of no value. However, mowing was consistently beneficial to yield and net return when the only other weed control inputs were paraquat and 2,4-DB applied at 4 wk after planting (WAP) and cultivation at 10 WAP. In the absence of any other weed control inputs, mowing was detrimental in a drought stress year, but beneficial in years with near-normal growing conditions. Although disease incidence was aggravated by the lack of weed control inputs, it was generally independent of mowing.
Degradation of Acetanilide Herbicides in History and Nonhistory Soils from Eastern Virginia
Authors: Kotoula-Syka Eleni , Hatzios Kriton K. , Berry Duane F. , Wilson Henry P.
Published: March 2018

The degradation of14C-labeled metolachlor, acetochlor, and pretilachlor in control and soils with 10-yr metolachlor- history or 3-yr butylate history was studied by monitoring the evolution of14CO2in soil biometer flasks. The degradation rate of14C-phenyl-labeled metolachlor was similar in soils with 0- and 10-yr metolachlor history over 52 d.14C was released from carbonyl-labeled metolachlor about 40% faster than from phenyl-labeled metolachlor in both soils. Soil sterilization by autoclaving reduced significantly the metolachlor degradation rate in both soils. Degradation of14C-labeled EPTC in soils with 3-yr butylate history was much faster than in soils with no history. Soil sterilization reduced the EPTC degradation rate, confirming microbial degradation. The degradation rates of acetochlor, metolachlor, and pretilachlor were similar in soils with and without butylate history. Most of the14C that remained in history and nonhistory soils was extractable with ethyl acetate or sodium hydroxide. Three major metabolites of metolachlor and EPTC were detected by thin-layer chromatography (TLC) of extracts from both soils. In contrast to the situation with carbamothioate herbicides, soils exposed repeatedly to metolachlor or other acetanilides are not prone to become adapted to these herbicides. Soils with carbamothioate history did not exhibit any apparent cross-adaptation toward acetanilide herbicides.
Wild Carrot (Daucus carota) Control in No-Tillage Cropping Systems
Authors: Stachler Jeff M. , Kells James J.
Published: March 2018

Wild carrot is becoming a serious weed problem in Michigan continuous no-tillage crop production. Greenhouse and field research was conducted to identify effective management strategies for wild carrot control in no-tillage cropping systems. In the greenhouse, PRE applications of acetochlor plus dichlormid (5.8:1 w:w), cyanazine, linuron plus chlorimuron (18:1), and metribuzin plus chlorimuron (10:1) and POST applications of bentazon, CGA-152005, clopyralid, cyanazine, and MON 12000 provided the greatest control of wild carrot seedlings. In the field, PRE and POST treatments containing chlorimuron consistently controlled overwintered wild carrot greater than 71% at 30 d after the POST application in no-tillage soybean. Atrazine, MON 12000, nicosulfuron, and primisulfuron applied POST consistently controlled overwintered wild carrot greater than 78% at 30 DAT in no-tillage corn. Glyphosate at 0.84 or 1.68 kg ae/ha applied in October to established wild carrot provided greater than 74% control the following spring. Early preplant (EPP) applications of glyphosate at 0.84 kg/ha in no-tillage soybean gave 95 and 24% control of overwintered wild carrot in St. Clair and Lenawee Counties, MI, respectively, at 70 DAT. PRE applications of glyphosate at 0.84 kg/ha controlled overwintered wild carrot less than 69% at 58 DAT in no-tillage corn and soybean. Fall applications of 2,4-D ester at 1.12 kg ae/ha provided 18 and 88% control of wild carrot the following spring in Clinton and Lenawee Counties, respectively. EPP applications of 2,4-D ester at 1.12 kg/ha provided 7 and 72% control of overwintered wild carrot in St. Clair and Lenawee Counties, respectively.
Initial Weed Densities Affect No-Tillage Weed Management with a Rye (Secale cereale) Cover Crop
Authors: Zasada Inga A. , Linker H. Michael , Coble Harold D.
Published: March 2018

The objective of this research was to evaluate the influence of different initial weed densities on weed control effectiveness in no-tillage corn at two locations in North Carolina during 1994 and 1995. Different weed densities were established over a 4-year period (1989–1992) by using various weed management strategies. Resultant density levels were estimated and used to establish high and low weed density plots. Treatments applied were PRE, POST, at-planting, and an untreated control. Weed density estimates were made 37 and 57 DAP. Common lambsquarters at low densities (20 to 40 weeds/m2) was controlled with the cover crop alone, but common lambsquarters at high densities (150 to 170 weeds/m2) and redroot pigweed at any density were not controlled. POST herbicides reduced weed densities as well as the PRE herbicides, regardless of initial weed densities.
Sicklepod (Senna obtusifolia) Interference with Soybean (Glycine max) Cultivars Following Herbicide Treatments
Authors: Shaw David R. , Rankins Alfred , Ruscoe Jon T.
Published: March 2018

Three Group V soybean cultivars were grown in the greenhouse to quantify interference when planted at various intervals with sicklepod, and the effects of chlorimuron and imazaquin POST on this interspecific interference. Soybean shoot height or fresh weight was not affected by sicklepod interference when sicklepod was planted 10 d after soybean in most cases. ‘Asgrow 5979’ soybean shoot height was not reduced when planted with sicklepod, but was reduced when planted 10 d after sicklepod and no herbicide treatment was added. When sicklepod was planted 10 d before Asgrow 5979 and ‘9592 Pioneer’ soybean, shoot height was reduced more than ‘Hutcheson,’ regardless of herbicide treatment. The cultivar 9592 Pioneer was more effective in reducing sicklepod shoot height than Asgrow 5979 when no herbicide treatment was used. Chlorimuron or imazaquin had little or no effect on sicklepod interference with soybean under these conditions.
Purple Nutsedge (Cyperus rotundus) Management in Corn (Zea mays) and Cotton (Gossypium hirsutum) Rotations
Authors: Webster Theodore M. , Coble Harold D.
Published: March 2018

A field study was conducted in 1994 and 1995 to determine the effect of MON 12037, linuron, and ametryn on purple nutsedge density in field corn in a 2-yr rotation with cotton. Each corn treatment included cultivation and noncultivation. A standard treatment for purple nutsedge control was applied to all cotton plots in the second season of the corn–cotton rotation. Purple nutsedge shoot densities were reduced in cultivated MON 12037, noncultivated MON 12037, and cultivated ametryn in the corn–corn and corn–cotton rotations. Purple nutsedge tuber population was reduced in the corn–corn rotation by MON 12037 with and without cultivation, cultivated linuron, and cultivated ametryn treatments relative to the noncultivated check. In the corn–cotton rotation, purple nutsedge tuber population was reduced only by the cultivated MON 12037 and cultivated ametryn treatments relative to the noncultivated check.