bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Rye Residues and Weed Control Strategies in Reduced Tillage Potatoes
Authors: Lanfranconi Luis E. , Bellinder Robin R. , Wallace Russell W.
Published: March 2018

Experiments were conducted to evaluate the effect of tillage, rye residue levels, and control strategies on weed suppression and potato yield. Reduced tillage (RT) yields in 1989 were lower than in conventional tillage (CT) due to high hairy galinsoga populations. However, in 1990, potato yields were greater in RT when early emerging weeds were suppressed. Increasing residue levels up to 2300 kg ha−1had no effect on weeds or yields in either year. In a separate study, preemergence herbicides (linuron plus metolachlor, 1.7 kg ai ha−1each) applied 10 d after planting (DAP) in reduced tillage controlled weeds for 6 wk, but efficacy decreased after hilling. Metribuzin applied postemergence (0.19 kg ai ha−1) 7 d after hilling controlled late germinating weeds. Potato yields were greatest when the preemergence herbicides were applied.
Hemp Dogbane (Apocynum cannabinum) and Wild Blackberry (Rubus allegheniensis) Control in No-tillage Corn (Zea mays)
Authors: Glenn Scott , Anderson Neil G.
Published: March 2018

Hemp dogbane and wild blackberry have become significant weed problems in no-tillage corn production in Maryland. Nicosulfuron (31 to 62 g ha−1) plus crop oil concentrate (COC) gave 67% or more hemp dogbane and wild blackberry control. There was no difference in hemp dogbane or wild blackberry control between 31 and 94 g ai ha−1nicosulfuron. Tank mixtures of 2,4-D or dicamba with nicosulfuron gave 72 to 100% hemp dogbane and wild blackberry control. Hemp dogbane control following applications of 560 g ha−12,4-D was 97% in 1989 and 63% in 1990. Wild blackberry control with 2,4-D was 40% both years. Dicamba at 280 g ha−1gave 70 and 55% control of hemp dogbane and 75 and 65% control of wild blackberry in 1989 and 1990, respectively. Triclopyr plus 2,4-D provided 72 to 98% hemp dogbane control and 92 to 98% wild blackberry control. However, triclopyr plus 2,4-D applied at 280 plus 560 g ha−1injured corn, and corn yields were reduced compared with weedy controls in 1990.
Weed Control in Corn (Zea mays) with Primisulfuron as Influenced by Rate, Timing, and Herbicide Combinations
Authors: Ngouajio Mathieu , Hagood Edward S.
Published: March 2018

Weed control and corn vigor were evaluated to determine the effects of application rate, timing, and other POST herbicides on primisulfuron activity. Corn injury caused by primisulfuron was very low. Weed control varied with species and stage of growth. Primisulfuron showed high activity on emerged johnsongrass, particularly with early postemergence (EP) and mid postemergence (MP) applications. However, these treatments did not provide full season control of this species due to regrowth from rhizomes and continuous germination of new seeds. Primisulfuron controlled giant foxtail with the EP timing (< 5 cm weed height), but not with MP and late postemergence (LP) applications. Common lambsquarters and redroot pigweed control was most effective with EP applications. Primisulfuron in combination with cyanazine, atrazine, cyanazine plus tridiphane, atrazine plus tridiphane, bentazon, 2,4-D, dicamba, or paraquat controlled common lambsquarters and redroot pigweed better than primisulfuron applied alone. Johnsongrass control decreased when primisulfuron was combined with paraquat or 2,4-D and giant foxtail control decreased when primisulfuron was combined with 2,4-D or dicamba.
Imazethapyr and Imazaquin Control Puncturevine (Tribulus terrestris) but Carry Over to Spinach (Spinacia oleracea)
Authors: Johnson David H. , Talbert Ronald E.
Published: March 2018

The control of puncturevine in southern peas with imazethapyr and imazaquin and the potential for carryover of these herbicides to spinach was evaluated in Arkansas. Imazethapyr (0.07 kg ai ha−1) and imazaquin (0.14 kg ha−1) applied to southern peas either PPI tank-mixed with trifluralin (0.84 kg ha−1) or PRE or POST following trifluralin controlled puncturevine at least 70%. Imazaquin and imazethapyr remaining in soil after use caused injury and yield reduction to spinach planted 3 to 4 mo after herbicide application in the fall after southern pea harvest. In spring spinach planted 8 to 9 mo after herbicide application, the only injury observed was from soil residues of imazethapyr applied POST in one of two years, with no yield reduction. In rate by timing experiments, imazethapyr at 0.07 kg ha−1applied PPI, PRE, and 3 and 6 d after puncturevine emergence controlled puncturevine at least 95% at the 2-wk rating. At the 4-wk rating, imazethapyr at 0.07 kg ha−1applied PRE provided this level of control. Imazaquin at 0.07 and 0.14 kg ha−1controlled puncturevine greater than 93% when applied up to 12 d after emergence. Puncturevine control was less with both herbicides at lower rates and as application timing increased.
Control of Yellow and Purple Nutsedges (Cyperus esculentusandC. rotundus) in Nursery Crops
Authors: Derr Jeffrey F. , Wilcut John W.
Published: March 2018

Experiments were conducted to evaluate selective herbicides for yellow and purple nutsedge control in nursery crops. Chlorimuron at 0.03 and 0.06 kg ai ha−1suppressed yellow and purple nutsedge shoot growth either PRE or POST and did not reduce growth of barberry, Burford holly, Compacta holly, azalea, juniper, or photinia, although shoot tip chlorosis was noted in all species except Burford holly and juniper. Imazaquin at 0.25 and 0.5 kg ha−1and imazethapyr at 0.06 and 0.21 kg ha−1reduced growth of azalea. Imazethapyr also reduced growth of barberry, juniper, and photinia. Chlorimuron, imazaquin, and imazethapyr inhibited liriope and daylily growth. Pyridate applied at 1.0 and 2.0 kg ha−1POST did not control purple nutsedge. Pyridate and flurtamone applied POST did not control yellow nutsedge as effectively as chlorimuron, imazaquin, or imazethapyr. Flurtamone at 0.5 and 1.0 kg ha−1applied PRE or POST controlled purple nutsedge. Both pyridate and flurtamone visibly injured most nursery crops tested, although plants generally outgrew the damage.
Cotton (Gossypium Hirsutum) Response to DPX-PE350 Applied Postemergence
Authors: Jordan David L. , Frans Robert E. , McClelland Marilyn R.
Published: March 2018

Field experiments were conducted from 1989 through 1991 to determine the effect of DPX-PE350 applied postemergence over-the-top on cotton yield and fiber quality. DPX-PE350, at rates ranging from 50 to 280 g ae ha−1applied to cotton in the VC to R6 growth stages, had no adverse effect on seed cotton yield, micronaire, fiber length, fiber length uniformity, or fiber strength. Cotton injury was 10% or less in all experiments.
Coupling Geographic Information Systems and Models for Weed Control and Groundwater Protection
Authors: Wilson John P. , Inskeep William P. , Rubright Paul R. , Cooksey Diana , Jacobsen Jeffrey S. , Snyder Robert D.
Published: March 2018

The Chemical Movement through Layered Soils (CMLS) model was modified and combined with the USDA-SCS State Soil Geographic Data Base (STATSGO) and Montana Agricultural Potentials System (MAPS) digital databases to assess the likelihood of groundwater contamination from selected herbicides in Teton County, MT. The STATSGO and MAPS databases were overlaid to produce polygons with unique soil and climate characteristics and attribute tables containing only those data needed by the CMLS model. The Weather Generator (WGEN) computer simulation model was modified and used to generate daily precipitation and evapotranspiration values. A new algorithm was developed to estimate soil carbon as a function of soil depth. The depth of movement of the applied chemicals at the end of the growing season was estimated with CMLS for each of the soil series in the STATSGO soil mapping units and the results were entered into ARC/INFO to produce the final hazard maps showing best, weighted average, and worst case results for every unique combination (polygon) of soil mapping unit and climate. County weed infestation maps for leafy spurge and spotted knapweed were digitized and overlaid in ARC/INFO with the CMLS model results for picloram to illustrate how the results might be used to evaluate the threat to groundwater posed by current herbicide applications.
An Index Model for Predicting Seed Germination and Emergence Rates
Authors: Alm David M. , Stoller Edward W. , Wax Loyd M.
Published: March 2018

We present a germination and emergence model that can be used as a sub-model in an individual-based model of population dynamics. Seed germination and seedling elongation rates were measured in petri dishes in the laboratory for ivyleaf morningglory, velvetleaf, corn, and soybean seeds, as functions of temperature and water potential. The analysis yielded a set of indices: the germination temperature index (GTI), the germination water index (GWI), the emergence temperature index (ETI), and the emergence water index (EWI). The seed populations were divided into 100 discrete cohorts, with each cohort (i), having its own germination rate (GR) as the product of a reference rate and the germination indices, or GRi= GRiREF× GTI × GWI. After germination, the emergence rate (ER) was the product of a reference rate and emergence indices, or ERi= ERREF× ETI × EWI. The model was tested against the timing of emergence in the field for seeds planted 1, 2, 4, and 8 cm deep in natural or rain-excluded environments. The predictions were more accurate for all depths combined than for any particular depth.
Carryover of DPX-PE350 to Grain Sorghum (Sorghum bicolor) and Soybean (Glycine max) on Two Arkansas Soils
Authors: Jordan David L. , Johnson David H. , Johnson William G. , Kendig J. Andrew , Frans Robert E. , Talbert Ronald E.
Published: March 2018

Field experiments were conducted to determine carryover potential to grain sorghum and soybean of DPX-PE350 applied POST at 0.05, 0.1, and 0.2 kg ai ha−1to cotton the previous year. DPX-PE350 did not injure soybean or affect yield adversely. Grain sorghum was injured and maturity delayed on a Sharkey silty clay but not on a Calloway silt loam. Grain sorghum yield was reduced on both soils 16 and 22%, respectively, by residues from the 0.1 and 0.2 kg ha−1rates of DPX-PE350. In an incubation study, dissipation of DPX-PE350 was greater at 35 C than at 5 C., and did not differ between the two soils.
Hogpotato (Hoffmanseggia glauca) Control with Herbicides and Rotational Crop Response
Authors: Westerman R. Brent , Murray Don S. , Castner Eric P.
Published: March 2018

Three field experiments were conducted in 1987 through 1989 to evaluate hogpotato control and rotational crop response resulting from applications of five herbicides. At the end of the first year, triclopyr and imazapyr controlled hogpotato late-season as high as 87 and 94%, respectively. Following a sequential application in 1988, triclopyr and imazapyr controlled 94 and 100% of hogpotato, respectively, during the 1989 growing season. Hogpotato biomass, collected at the termination of the experiments, was reduced by all treatments at all locations except at Altus where dicamba was applied in 1987 followed by a spot application of glyphosate in 1988. Soils from these experiments were bioassayed for residual herbicide activity using three potential rotational crop species. Tebuthiuron and imazapyr caused the greatest biomass reductions with cotton and wheat being the most sensitive species to these herbicides.
Johnsongrass (Sorghum halepense) Control in Sugarcane (Saccharumsp.) with Asulam Applied Alone and in Mixtures
Authors: Richard Edward P. , Griffin James L.
Published: March 2018

Asulam applied POST alone and in mixtures with residual herbicides and with DSMA and MSMA was evaluated for johnsongrass control. Johnsongrass control following treatment with asulam at 3.7 kg ai ha−1was not improved by tank mixtures with the residual herbicides atrazine, metribuzin, pendimethalin, and terbacil compared with asulam applied alone. Johnsongrass injury symptoms appeared sooner when asulam was applied in mixtures with either DSMA or MSMA, but johnsongrass control 4 wk after treatment was similar to asulam applied alone. As a result of the johnsongrass control obtained with early POST treatments of asulam applied alone, cane and sugar yields were increased by 56 and 58%, respectively, when compared with the weedy check. Additional cane and sugar yield increases were not obtained by any of the asulam mixtures because johnsongrass control was not improved. Asulam applied again in May to johnsongrass regrowth improved late-season control in two of the three studies over a single early POST application, but cane and sugar yields were not increased.
Evaluation of Epicuticular Wax Removal from Whole Leaves with Chloroform
Authors: Bewick Thomas A. , Shilling Donn G. , Querns Robert
Published: March 2018

Leaves of torpedograss and American black nightshade were extracted with chloroform at room temperature. A 2-s dip was sufficient to remove most of the epicuticular wax from torpedograss. However, epicuticular hydrocarbon weight represented only 6.4% of the total extract weight and 6.94μg g−1fresh weight of chlorophyll were found in the 2-s extract. This represented 25% of the chlorophyll detected in the 232-h extract. In American black nightshade, epicuticular hydrocarbons continued to be removed from the leaf surface up to 6 h of extraction. Epicuticular hydrocarbons represented 0.6% of total extract weight. In the 6-h extract, 4.02μg g−1fresh weight of chlorophyll were found. This represented 17% of the chlorophyll detected in the 232-h extract. Evaluation of leaf surfaces using scanning electron microscopy indicated that epicuticular wax was being removed from torpedograss leaves up to 1 h. However, there was little visible evidence for wax extraction from the surface of American black nightshade leaves.
Growth Regulation of Common Bermudagrass (Cynodon dactylon) with Imazaquin and AC 263,222
Authors: Goatley J. Michael , Maddox Victor L. , Watkins Robert M.
Published: March 2018

Research was conducted in 1990 through 1992 to examine the vegetative and reproductive growth regulating activity of imazaquin and AC 263,222 on common bermudagrass. AC 263,222 at 0.06 kg ha−1, alone and in combination with imazaquin (0.21 kg ai ha−1), significantly reduced seedhead number, seedhead height, and vegetative canopy height for a 4-wk period after both May and July treatment. Imazaquin (0.42 kg ai ha−1) applied alone resulted in less turfgrass discoloration, but suppressed vegetative and reproductive growth of common bermudagrass less as compared with treatments containing AC 263,222.
Weed Science Challenges
Authors: Antognini Joe
Published: March 2018

Weed Science is facing two critical challenges. They are funding and interdisciplinary research, which to some extent are intertwined, but I will attempt to discuss them separately. Although some of my remarks may be critical of weed scientists let me say at the outset that the main reason we have these two challenges is because we have been highly successful, thanks to our visionary and dedicated scientists over the years. We have stayed ahead of the curve and have done too good a job. I would like to point out here that contrary to the beliefs of many outside our profession, we do more than spray and pray. We are ahead of the curve because we have conducted extensive and intensive research on application technology, formulations, environmental impacts, metabolism, mode of action, tillage practices, and many other areas.
Postemergence Shattercane (Sorghum bicolor) Control in Corn (Zea mays) in Northern Tamaulipas, Mexico
Authors: Rosales-Robles Enrique
Published: March 2018

Field studies were conducted in northern Tamaulipas, Mexico in 1991 and 1992 to determine the effectiveness of POST applications of primisulfuron and nicosulfuron on shattercane control in corn. Primisulfuron at 15 g/ha and nicosulfuron at 30 g/ha were the minimal doses required for shattercane control. Both herbicides applied on 5- to 9-leaf shattercane provided excellent (> 90%) control 35 d after application. No corn injury was evident with any herbicide and rates evaluated. Untreated check plots sustained 30 to 56% of yield reduction as compared to herbicide treatment plots.
Sweet Corn (Zea mays) Cultivar Tolerance to Application Timing of Nicosulfuron
Authors: Robinson Darren K. , Monks David W. , Schultheis Jonathan R. , Worsham A. Douglas
Published: March 2018

'Silver Xtra Sweet’, ‘How Sweet It Is', ‘Zenith’ and 'Sweetie 76’ were evaluated for response to 0, 35, and 70 g/ha nicosulfuron applied POST at the 5- to 6- or 7- to 8-leaf stages of growth. Nicosulfuron (35 g/ha) caused 60 to 80% visible injury to Silver Xtra Sweet. How Sweet It Is and Zenith were moderately tolerant (< 20% visible injury) and Sweetie 76 was the most tolerant (10% visible injury). All cultivars were less tolerant when nicosulfuron was applied at the 7- to 8-leaf than the 5- to 6-leaf stage. Plant height of Silver Xtra Sweet was reduced 51% by 35 g/ha nicosulfuron applied at the 5- to 6-leaf stage and injury increased when nicosulfuron was applied at the 7- to 8-leaf stage. Yield losses of Silver Xtra Sweet occurred as a result of the nicosulfuron treatments.
Effects of Thiazopyr and Trifluralin on Dodder (Cuscuta indecora) in Alfalfa (Medicago sativa)
Authors: Cudney David W. , Orloff Steve B. , Demason Darleen A.
Published: March 2018

Trifluralin selectively controls dodder in alfalfa. However, its soil activity dissipates allowing some late season dodder germination. Thiazopyr applied PRE was also found to control dodder selectively in alfalfa. Thiazopyr was more effective when applied in February than in November. Thiazopyr did not control dodder longer into the season than trifluralin in field tests, however it was more effective in greenhouse experiments. The effect of thiazopyr on dodder shoot tips was similar to that of trifluralin, in that both herbicides produced bulbous cells with thickened, globular nuclei, typical of cells treated with herbicides affecting microtubules.
MON 13200 Early Preplant Controls Giant Foxtail (Setaria Faberi) Season-Long in No-Till Soybean (Glycine Max)
Authors: Kapusta George , Krausz Ronald F. , Matthews Joseph L.
Published: March 2018

Field studies were conducted in 1991 and 1992 to evaluate the duration of giant foxtail control in no-till soybean with MON 13200 alone and with imazaquin applied up to 2 mo prior to planting. MON 13200 at rates ranging from 224 to 448 g ai/ha applied up to 57 d before planting controlled 97 to 99% of giant foxtail averaged over years. MON 13200 plus imazaquin applied approximately 45 or 30 d before planting controlled 92 to 99% of giant foxtail compared with 53, 64, and 65% and 61, 69, and 78% in plots treated with alachlor, metolachlor, or pendimethalin plus imazaquin, respectively. Differences in control of giant foxtail among the herbicides evaluated were minimal when applied 15 or 0 d before planting. Little or no soybean injury was observed in 1991; up to 30% was observed in 1992 but final soybean height was not affected.
Slow-Release Delivery System for Herbicides in Container-Grown Stock
Authors: Gorski Stanley F.
Published: March 2018

Metolachlor, applied to the surface of leaching columns as dicalcium phosphate tablets, was recovered over a period of 25 d compared with 2 and 3 d for emulsifiable concentrate and granular formulations, respectively. In similar studies, approximately 27% of napropamide was recovered from tablets during the same period. Adding an adjuvant to the napropamide tablet mixture increased the recovery rate to 55%. Tablet hardness and size had little effect on the release rate of napropamide. Tablets containing 4% ai napropamide released greater amounts of herbicide at a single collection period than did tablets containing 1% ai. Adding an adjuvant to the napropamide tablet mixture significantly improved Italian ryegrass control in the area adjacent to herbicide placement.
Soybean (Glycine max) Tolerance to 2,4-D Ester Applied Preplant
Authors: Krausz Ronald F. , Kapusta George , Matthews Joseph L.
Published: March 2018

Field studies were conducted in 1991 and 1992 to determine potential soybean injury due to 2,4-D ester at 560, 1120, and 1680 g ai/ha applied 0, 7, and 14 d before planting (DBP). Delayed emergence and increased injury of soybean were observed as 2,4-D rate increased and interval between application and planting decreased. Delay in emergence ranged from 0 to 67% and 0 to 50% in 1991 and 1992, respectively. Injury at 15 days after planting (DAP) combined over years ranged from 0 to 61%. Minimal (0 to 8%) delay in emergence and minimal (0 to 5%) injury at 15, 30, 45, and 60 DAP occurred when 2,4-D at 560 or 1120 g/ha was applied 7 or 14 DBP. No significant yield reduction occurred due to 2,4-D rate, application timing, or their interaction.
Soybean (Glycine Max) Cultivar Response to AC 263,222 as Influenced by Supplemental Irrigation
Authors: Miller Donnie K. , Griffin James L.
Published: March 2018

In field studies conducted over two years, soybean cultivars ‘Deltapine 415’, ‘Forrest’, ‘Asgrow 6785’, ‘Centennial’, 'Sharkey’, ‘Terra Vig 616’, ‘Hartz 6686’, and ‘Pioneer 9791’ responded similarly to POST application of AC 263,222. With supplemental overhead irrigation of 5.1 cm weekly for 4 wk initiated 21 d after herbicide applications, mature soybean height for the cultivars averaged 18% less than that of the untreated check for 27 g/ha AC 263,222, but only 8% less when not irrigated. Although nonirrigated soybean seed yield following AC 263,222 application the first year was not reduced compared with the untreated check, with irrigation seed yield reductions of 12 and 32% were noted for 13 and 27 g/ha AC 263,222, respectively. Seed yield the second year was not negatively affected with herbicide application whether soybean was irrigated or not irrigated. For individual years, seed yield for the untreated irrigated and nonirrigated checks was similar. In the first year soybean yield following AC 263,222 at 13 and 27 g/ha with irrigation was 16 and 30% lower, respectively, than when soybean was not irrigated. Decreases in soybean 100-seed weight accompanied the yield reductions.
Control of Rush Skeletonweed (Chondrilla juncea) with Herbicides
Authors: Heap John W.
Published: March 2018

A range of herbicide treatments was evaluated for long-term control of rush skeletonweed, a perennial weed of crops and pastures in North and South America, the Mediterranean region, central Europe, and Australia. Clopyralid (75 to 300 g ai/ha) and clopyralid mixtures with 2,4-D, MCPA, or dicamba were effective, resulting in survival rates of 0 to 4% for the most successful treatments applied for three consecutive seasons. Metsulfuron (9 g ai/ha) and 2,4-D (850 g ai/ha) significantly reduced survival when applied at high rates for three years. Barley yield in the season following control was increased by up to 195 to 199% of yield from untreated plots. Evidence was found for differences in herbicide susceptibility between narrowleaf and broadleaf forms of rush skeletonweed.
Postemergence Horsenettle (Solanum carolinense) Control in Field Corn (Zea mays)
Authors: Prostko Eric P. , Ingerson-Mahar Joseph , Majek Brad A.
Published: March 2018

Field trials were conducted in New Jersey during 1991 and 1992 to evaluate the efficacy of nicosulfuron, primisulfuron, dicamba, and clopyralid on horsenettle control in field corn. Horsenettle biomass was reduced 74%, 68%, 64%, 61%, 48%, and 40% by primisulfuron + dicamba, primisulfuron, nicosulfuron + dicamba, dicamba, clopyralid, and nicosulfuron, respectively. No treatment was statistically more effective than dicamba. Corn yields were not influenced by the herbicide treatments. Horsenettle populations were not reduced by any treatment.
Kenaf (Hibiscus cannabinus L.) Response to Four Grass Control Herbicides Broadcast Postemergence
Authors: Webber Charles L.
Published: March 2018

The availability of postemergence grass control herbicides can prevent dependence on potentially unnecessary preemergence herbicides. No postemergence grass control herbicides have federal registration for kenaf in the United States. This research was conducted to collect data to support such registration. Clethodim, fluazifop, quizalofop, and sethoxydim applied at three rates did not injure established kenaf, reduce plant populations, reduce plant heights, or reduce stalk yields.
Chlormequat Chloride (CCC) Pretreatments May Enhance Quackgrass (Elytrigia repens) Control with Sethoxydim
Authors: Harker K. Neil , Taylor John S.
Published: March 2018

Laboratory, greenhouse, and field experiments were conducted at the Lacombe Research Station to determine if CCC, ethephon, or CCC/ethephon had direct activity on quackgrass rhizome buds, and to determine if foliar applications of CCC/ethephon could predispose quackgrass to more effective control with sethoxydim. CCC, ethephon, and CCC/ethephon had growth regulating effects on the axillary buds and the apex of detached quackgrass rhizomes. CCC increased rhizome bud sprouting on rhizomes with the apex excised, but not on rhizomes with an intact apex. Ethephon or CCC/ethephon inhibited bud sprouting on rhizomes with an intact or excised apex. CCC/ethephon, but not CCC or ethephon alone, increased rhizome elongation on rhizomes with intact apices. In the greenhouse, pretreatments of CCC/ethephon increased sethoxydim activity on quackgrass rhizome buds and caused lower shoot emergence from one-bud rhizome segments. Results of field experiments were less consistent than those in the greenhouse. However, sometimes CCC or CCC/ethephon pretreatments resulted in increased quackgrass control in the field with sethoxydim.
Surfactant-Induced Phytotoxicity
Authors: Falk Richard H. , Guggenheim Richard , Schulke Gerhard
Published: March 2018

The leaves of tall morningglory, giant duckweed, and common purslane were treated with nine surfactants at a concentration of 0.1% and examined after 24 hr using cryo-scanning electron microscopy for phytotoxicity as evidenced by tissue damage and epicuticular wax morphology changes. In some instances, tissue damage could be discerned; however, the effects of a particular surfactant were not uniform across the three species. Morphological alteration of epicuticular waxes was not observed. Gas chromatographic analyses of the epicuticular waxes of the species used in the study reveal component differences and may, in part, explain the lack of uniform response across species for a particular surfactant.
Giant Ragweed (Ambrosia trifida) Canopy Architecture and Interference Studies in Soybean (Glycine max)
Authors: Webster Theodore M. , Loux Mark M. , Regnier Emilie E. , Harrison S. Kent
Published: March 2018

Field experiments were established at Columbus and near South Charleston, OH to determine the effects of giant ragweed population density on soybean yield and to characterize the development of giant ragweed grown in 76-cm soybean rows. An economic threshold was calculated for Ohio using a common treatment for giant ragweed control in soybean. A cost of $41/ha was estimated for a farmer to apply 0.56 kg/ha bentazon plus 0.28 kg/ha fomesafen plus COC (1.25% v/v). Assuming a soybean value of $0.22/kg, the cost of control was equivalent to 5.4 and 7.1% of the soybean yield in 1991 and 1992, respectively, which corresponded to the yield loss caused by 0.08 and 0.03 giant ragweed plants/m2. The competitiveness of giant ragweed can be at least partly attributed to its ability to initiate and maintain axillary leaves and branches within the shaded confines of the soybean canopy.
Effect of Sodium Bicarbonate on Clethodim or Quizalofop Efficacy and the Role of Ultraviolet Light
Authors: McMullan P. M.
Published: March 2018

Research was conducted at two sites during 1991 and 1993 at Brandon, MB to determine if sodium bicarbonate antagonizes clethodim or quizalofop efficacy and if ultraviolet light is a factor in any antagonism. Sodium bicarbonate in the spray solution reduced the efficacy of clethodim. However, removal of ultraviolet light partially reversed sodium bicarbonate antagonism of clethodim activity with all adjuvants except crop oil concentrate with or without ammonium sulfate. Amigo, crop oil concentrate plus ammonium sulfate, and Merge were the most effective adjuvants for clethodim with distilled water. However, only the adjuvant crop oil concentrate plus ammonium sulfate overcame sodium bicarbonate antagonism of clethodim. Enhance increased the activity of clethodim when sodium bicarbonate was present in the spray solution but overall was not as effective an adjuvant as crop oil concentrate plus ammonium sulfate. Sodium bicarbonate in the spray solution did not reduce quizalofop efficacy.
Efficacy of Fall Incorporated and Non-incorporated Granular Triallate on Wild Oat (Avena fatua) and Wheat (Triticum aestivum)
Authors: Kirkland Kenneth J.
Published: March 2018

The influence of incorporation vs no incorporation on the efficacy of granular triallate applied in mid-October at 1400 and 1700 g ai/ha to control wild oat was evaluated in spring wheat in west central Saskatchewan over a 7-yr period. All fall-applied triallate reduced wild oat panicles and fresh weight, and increased yield compared to untreated checks. With applications in standing wheat stubble there was no difference in wild oat control from incorporation versus no incorporation. All triallate treatments reduced wild oat panicles and fresh weight by over 95%, and resulted in wheat yield increases ranging from 29 to 67%. In tilled fallow, incorporated granules provided better wild oat control than when there was no incorporation. Wheat yield increases ranged from 50 to 85% for triallate treatments with yield for incorporated triallate approximately 15% greater than non-incorporated. The rate of triallate did not affect the level of wild oat control achieved with either incorporation method. In separate tolerance studies triallate incorporation method did not affect spring wheat emergence or subsequent development.
Effects of Celery (Apium graveolens) Root Residue on Growth of Various Crops and Weeds
Authors: Bewick Thomas A. , Shilling Donn G. , Dusky Joan A. , Williams Deborah
Published: March 2018

The relative sensitivity of various crops and weeds to celery root residue incorporated into soil was determined in greenhouse experiments. A range of concentrations was used to determine the percentage of celery residue needed to cause a 50% reduction in plant growth (I50). The most sensitive weed was spiny amaranth and the least sensitive was common purslane. The most sensitive crop was radish and the least sensitive was celery. Selectivity was calculated as crop I50/weed I50and varied from a maximum of 13 for celery and spiny amaranth to a low of 0.4 for radish and common purslane. Selective weed suppression might be obtained when celery residue is present.
Postemergence Control of Annual Grasses and Corn (Zea mays) Tolerance Using DPX-79406
Authors: Swanton Clarence J. , Chandler Kevin , Elmes Monica J. , Murphy Stephen D. , Anderson Glenn W.
Published: March 2018

DPX-79406 was evaluated for POST annual grass weed control in both controlled environment and field experiments. In controlled environment experiments, green foxtail was most susceptible to DPX-79406; whereas yellow foxtail was least susceptible of the species evaluated. DPX-79406 at 12 g/ha completely controlled six leaf black-seeded proso millet, yellow foxtail, green foxtail, and barnyardgrass. In the field, DPX-79406 at 3.0 to 25.0 g/ha effectively controlled annual grass weeds without injury to three- to six-leaf corn. There was more variation in the effectiveness of DPX-79406 applied in the field. Early POST applications provided less weed control than the late application, especially for barnyardgrass, because of weeds emerging after application. As a result, higher doses were sometimes needed for effective control. In weed-free field trials at two sites in 1990 and 1991, corn tolerated doses up to 75 g/ha of DPX-79406 applied at the three- to six-leaf growth stage. However, doses as low as 18.8 g/ha applied at the six- to nine-leaf growth stage reduced grain yield. In 1991, corn tillering increases and height and yield reductions were related linearly to the dose of DPX-79406 applied during later growth stages. DPX-79406 should be applied early POST in order to avoid crop injury while providing effective weed control.
Soil pH Effect on Imazaquin Persistence in Soil
Authors: Marsh Brian H. , Lloyd Randy W.
Published: March 2018

Field studies were conducted to determine the effect of soil pH ranging from 5.1 to 7.1 on imazaquin persistence on a Grundy silty clay loam (2.8% OM). Imazaquin residues were equivalent at pH 5.5 or higher but persisted longer at pH 5.1. Corn shoot growth was not different at any soil pH. Corn grain yields in 1993 were lower in imazaquin-treated plots than in the check plots at the lowest pH (5.1), where initial imazaquin soil concentrations were between 10 and 13 μg/kg across all pH levels. Corn grain yields were not affected by herbicide carryover in 1994 where soil imazaquin residues were well below critical levels at planting. Yields were lower where soil pH was less than 5.5.
Influence of Cover Crop and Herbicide Treatment on Weed Control and Yield in No-Till Sweet Corn (Zea maysL.) and Pumpkin (Cucurbita maximaDuch.)
Authors: Galloway Bethany A. , Weston Leslie A.
Published: March 2018

Sweet corn and pumpkin were planted no-tillage (NT) into cover crop residue treatments of vetch, rye, crimson clover, and ladino clover controlled with glyphosate, and a bare ground conventional tillage (CT) control. Objectives included evaluation of crop growth, yield, and weed suppression in NT versus CT treatments. Herbicide application was also investigated, with a plus and minus herbicide treatment (alachlor plus cyanazine for sweet corn, or ethalfluralin for pumpkin) as the main factor in the factorial experiment, and cover crops the subfactors. Weed control 4 wk after planting was dependent upon cover crop. The fewest weed numbers and least biomass were found in the ladino clover plots, but clover regrowth and subsequent competition with the cash crop were severe. Herbicides also affected weed biomass at 4 wk after vegetable planting, with least biomass in herbicide-treated plots. Neither cover crop nor herbicide treatment significantly affected weed weight by 8 wk after planting or pumpkin fruit weight at harvest. Pumpkin yield was not influenced by herbicide application. The vetch cover, although harboring greatest weed biomass, produced the greatest total yield (ear weight) in sweet corn. When averaged over cover crop, sweet corn yields were higher in herbicide-treated plots than in untreated ones. Both sweet corn and pumpkin maturity were generally delayed in the absence of herbicide treatments or in the presence of cover crop residues, especially clover and rye residues.
Weed Management Programs in Potato (Solanum tuberosum) with Rimsulfuron
Authors: Ackley John A. , Wilson Henry P. , Hines Thomas E.
Published: March 2018

Weed management programs in ‘Superior’ potato with PRE and POST rimsulfuron treatments were investigated during 1992, 1993, and 1994 in Virginia on a State sandy loam soil. Common ragweed control by PRE combinations of metolachlor with linuron or metribuzin was higher when treatments included PRE or POST rimsulfuron. Common lambsquarters control was 93 to 96% by treatments that included POST rimsulfuron. In the absence of PRE herbicides, POST applications of 35 g ai/ha rimsulfuron plus 280 g ai/ha metribuzin controlled weeds comparable to sequential applications of this combination. Potato recovered from occasional terminal leaf chlorosis caused by rimsulfuron, rimsulfuron plus metribuzin, and organophosphate insecticides combined POST with rimsulfuron plus metribuzin. These studies demonstrate that rimsulfuron can be a useful component of weed management programs that include metolachlor, linuron, and metribuzin.
Strategies to Manage Conflicts Among Multiple Users
Authors: Rasmussen G. Allen , Brunson Mark W.
Published: March 2018

Land management practices have been developed primarily by focusing on resource objectives. Public perceptions of these practices are seldom considered until after they have been introduced and conflicts have developed among different user groups. This paper reviews attitudes about conflicts and approaches to managing conflicts. The causes of conflict (misunderstanding, lack of information, differing interests, and/or personal values) will determine how successfully a conflict can be managed. Collaborative methods have become very popular, and can effectively address conflicts originating from misunderstandings or differing interests. However, for collaborative processes to be successful when dealing with value-based conflicts, considerable time and a skilled third party facilitator has generally been required.
Yellow Nutsedge (Cyperus esculentus) Control POST With Acetolactate Synthase-Inhibiting Herbicides
Authors: Ackley John A. , Wilson Henry P. , Hines Thomas E.
Published: March 2018

Efficacy of several acetolactate synthase (ALS)-inhibiting herbicides was evaluated for yellow nutsedge control over a 3-yr period on a State sandy loam and in the greenhouse. Herbicides were applied POST to yellow nutsedge at actual or anticipated commercial rates. Yellow nutsedge control was above 77% from MON 12000 and chlorimuron. Control ranged from 41 to 89% from primisulfuron, pyrithiobac, and rimsulfuron. Control from nicosulfuron and imazethapyr was 58% or less while thifensulfuron and CGA-152005 had almost no activity on yellow nutsedge. In greenhouse studies, MON 12000 controlled yellow nutsedge better than did chlorimuron, and imazethapyr gave better control than in the field.
Velvetleaf (Abutilon theophrasti) Population Dynamics Following a Single Year's Seed Rain
Authors: Hartzler Robert G.
Published: March 2018

At a northern Iowa location, populations of 145, 203, 62, and 37 velvetleaf plants/m2emerged in the four years following seed production by 0.4 velvetleaf plants/m2growing in soybean. Annual velvetleaf densities in areas with no seed input averaged less than 6 plants/m2. At a central Iowa location, verticillium wilt reduced velvetleaf seed production, resulting in an average increase of 9 plants/m2in the two years following seed production compared to the control treatment. This type of information is necessary to develop economic optimum thresholds, but the variability between locations demonstrates the difficulty in predicting crop and weed responses to management strategies implemented early in the growing season.
Controlling Weeds with Phytopathogenic Bacteria
Authors: Johnson David R. , Wyse Donald L. , Jones Keith J.
Published: March 2018

Until recently, phytopathogenic bacteria have not been considered potential biological weed control candidates because they lack the ability to penetrate intact plants. This deficiency can be overcome by providing entry wounds or using surfactants. Spray application ofPseudomonas syringaepv.tagetis(5 × 108cells/ml) in aqueous buffer with a surfactant produced severe disease in Canada thistle, common ragweed, Jerusalem artichoke, sunflower, and certain other members of the Compositae under field conditions. Spray application of the bacterium without surfactant was ineffective on all reported hosts.Xanthomonas campestrispv.poannuacontrolled annual bluegrass in bermudagrass golf greens when applied by spray during mowing. The bacterium entered through mowing injuries, causing lethal, systemic wilt. Application of the bacterium to annual bluegrass in the absence of fresh mowing injuries failed to produce symptoms. Under field conditions, this previously unknown pathovar's host range was limited to a single subspecies of annual bluegrass, but inundative application to freshly mowed turf resulted in infection of diverse annual bluegrass biotypes. In field trials, six monthly applications resulted in greater than 70% control. The preceding examples are among the first attempts to use foliar phytopathogenic bacteria for biological weed control. Efficacy of these bacterial bioherbicides and of future biocontrol strategies employing bacteria is dependent on facilitated host penetration.
Adjuvants, Formulations, and Spraying Systems for Improvement of Mycoherbicides
Authors: Boyette C. Douglas , Quimby P. C. , Caesar A. J. , Birdsall J. L. , Connick W. J. , Daigle D. J. , Jackson M. A. , Egley G. H. , Abbas H. K.
Published: March 2018

Herbicides are used in the production of almost 100% of agronomic crops in the United States and in most horticultural row crops. By volume, herbicides represent nearly two-thirds of all pesticides used in crop production. However, public pressure is mounting to force industry to develop safer, more environmentally responsible approaches for controlling weeds. Biological weed control with plant pathogenic fungi used as mycoherbicides offers such an approach. But there are several biological and environmental limitations which are inherent to nearly all mycoherbicides which must be overcome before they will be widely acceptable for practical use. Recent advances in adjuvant formulation and delivery systems have been used to overcome some of these limitations, such as lengthy dew requirements, inconsistent efficacy, and limited host ranges. Examples of current research to overcome these limitations will be presented in this review.
Tulip (Tulipaspp.), Daffodil (Narcissusspp.), and Iris (Irisspp.) Response to Preemergence Herbicides
Authors: Al-Khatib Kassim A
Published: March 2018

Broadleaf weed control and tulip, daffodil, and iris response to alachlor, dithiopyr, diuron, isoxaben, napropamide, oryzalin, oxadiazon, oxyfluorfen, pendimethalin, pronamide, and thiazopyr applied preemergence were evaluated. All herbicides controlled broadleaf weeds for five months after application, but control with oxyfluorfen, pendimethalin, alachlor, pronamide, and napropamide decreased six months after application. The greatest weed control was with oxadiazon, isoxaben, thiazopyr, dithiopyr, and diuron, whereas the least weed control was with napropamide and alachlor. In general, tulip was more sensitive to herbicides than daffodil and iris. All herbicides injured tulips at early growth stages but bulb yield of tulip was reduced only by oxadiazon, oxyfluorfen at 0.28 kg ai/ha, pronamide, and dithiopyr. Tulip flower quality was reduced only by oxadiazon, oxyfluorfen at 0.28 lb/ha, and pronamide. Daffodil and iris were tolerant to thiazopyr, isoxaben, pronamide, alachlor, oryzalin, napropamide, and diuron.
Tank-Mixed Postemergence Herbicides for Large Crabgrass (Digitaria sanguinalis) and Goosegrass (Eleusine indica) Control in Bermudagrass (Cynodon dactylon) Turf
Authors: Johnson B. Jack
Published: March 2018

A two-year experiment was conducted to determine if tank-mixes of postemergence (POST) herbicides would consistently control large crabgrass and goosegrass in common bermudagrass turf compared to herbicide alone treatments. Tank-mixes of MSMA plus quinclorac at 2.2 + 0.6 kg/ha effectively controlled large crabgrass (≥ 81%) for 10 to 11 weeks during 1993 and 1994. The control from MSMA plus dithiopyr at 2.2 + 0.3 kg/ha was higher during this period than when each herbicide was applied alone at the same rate. There was no increase in large crabgrass control from tank-mixes of MSMA and diclofop applied in a single application, when compared with two applications of MSMA applied at 2.2 kg/ha. Goosegrass control at 9 wk after tank-mixed treatments of MSMA (2.2 kg/ha) and diclofop (≥ 0.3 kg/ha) in 1994 was lower (12 to 28%) than when diclofop at 1.1 kg/ha was applied alone (85%). Tank-mixes of MSMA with quinclorac or dithiopyr did not control goosegrass. In general, common bermudagrass injury was no higher from herbicide combinations than when each was applied alone. An exception occurred at 1 wk after treatment in 1993 when common bermudagrass injury was higher from tank-mixes of MSMA plus diclofop at 2.2 + 1.1 kg/ha, than when either herbicide was applied alone.
Flax (Linum usitatissimum) Response to Thifensulfuron Mixtures with Sethoxydim Plus Broadleaf Weed Herbicides
Authors: Derksen Douglas A. , Wall David A.
Published: March 2018

Recently, roundleaved mallow, redroot pigweed, and annual smartweed species have become problems for flax producers in the Canadian prairies. The use of thifensulfuron to enhance weed control with commonly used herbicide mixtures was tested at Indian Head, SK and Morden, MB. Visible crop injury and reduced height, yield, and quality occurred at rates as low as 0.5–1.0 g/ha. Improved control of broadleaf weeds was not consistent and antagonism of grassy weed control with sethoxydim occurred.
Evaluation of Registered Herbicides for Cheat (Bromus secalinus) Control in Winter Wheat (Triticum aestivum)
Authors: Koscelny Jeffrey A. , Peeper Thomas F.
Published: March 2018

Seven field experiments were conducted in Oklahoma to compare efficacy and wheat response to currently registered cheat suppression or control herbicide treatments. Chlorsulfuron + metsulfuron premix (5:1 w/w) at 26 g ai/ha applied PRE controlled cheat 20 to 61%, increased wheat grain yields at two of seven locations, and decreased dockage due to cheat at five of seven locations. Chlorsulfuron + metsulfuron at 21 g/ha tank-mixed with metribuzin at 210 g/ha, applied early fall POST, controlled cheat 36 to 98% and increased wheat yield at four of seven locations. Metribuzin applied POST in the fall at 420 g/ha controlled cheat 56 to 98% and increased wheat yields at five of seven locations. Both POST treatments decreased dockage at all locations.
English Pea (Pisum sativum) Tolerance to Paraquat and Paraquat Plus Bentazon
Authors: Bellinder Robin R. , Wallace Russell W. , Jordan Grant L.
Published: March 2018

Field studies were conducted between 1990 and 1992 to determine tolerance of English pea at different growth stages to bentazon (0.56 kg ai/ha) and paraquat (0.14 kg ai/ha), applied alone and in combination. Initial crop injury with paraquat and paraquat plus bentazon averaged 37 and 21%, respectively. Crop injury dissipated by 21 d after treatment. Foliar injury at the different growth stages was equivalent but yields of peas treated at the six-node stage were reduced in two of four trials. Applying paraquat plus bentazon at the earlier growth stages consistently resulted in pea yields equivalent to those of plots receiving trifluralin plus handweeding or bentazon alone. Greenhouse studies were conducted to determine the effect of paraquat plus bentazon on control of selected weeds common to pea production fields. Redroot pigweed, common purslane, and common lambsquarters mortalities were 100, 100, and 90%, respectively, with the bentazon plus paraquat combination. However, barnyardgrass and large crabgrass mortalities decreased 88 and 91%, respectively, when bentazon was added, compared to paraquat alone.
Sicklepod (Senna obtusifolia) Management in an ALS-Modified Soybean (Glycine max)
Authors: Culpepper A. Stanley , York Alan C. , Batts Roger B. , Jennings Katherine M.
Published: March 2018

Herbicide systems consisting of PRE, early POST, and late POST options arranged factorially were compared for control of sicklepod in narrow-row soybean with modified acetolactate synthase (ALS) (E.C.4.1.3.18). Other weeds present included common cocklebur and mixed infestations of entireleaf, ivyleaf, pitted, and tall morningglories. PRE options were alachlor or alachlor plus metribuzin plus chlorimuron. Early POST options included chlorimuron, chlorimuron plus thifensulfuron, and no herbicide applied 3 wk after planting. Late POST options were chlorimuron and no herbicide applied 5 wk after planting. POST herbicides were more effective than PRE herbicides on all weeds. Chlorimuron and chlorimuron plus thifensulfuron applied early POST were equally effective on these weeds and usually more effective than chlorimuron applied late POST. There was no advantage of two POST applications compared with a single early POST application. Greatest net returns were obtained in systems using only early POST herbicides. There was no economic advantage from using metribuzin plus chlorimuron PRE in systems that included an early POST herbicide.