bluuebunny/crossref_metadata_2025 huggingface dataset:
Influencing Agricultural Policy: Symposium Introduction
Authors: Gianessi Leonard P. , Bridges David C.
Published: March 2018

A major debate is going on in the United States regarding the proper methods for crop pest management. One issue in this debate is whether weed control should be based largely on nonchemical or chemical means. This isn't the only issue that should be of interest to weed scientists, but it is important, and it illustrates the need to extend weed science research to influence public policy.
Achieving Your Objectives in Washington, D.C.: The Challenge for WSSA
Authors: Emanuel Alyson A.
Published: March 2018

Given that the Weed Science Society of America's (WSSA's) long-term objectives may include increasing the level of public funding in weed science, WSSA needs to make its case successfully in the policy arena. A strategy to influence policy in Washington should include: identifying specific goals to be achieved in a reasonable time frame; building the case for increased funding, including supporting arguments and materials; identifying the key players that can affect the policy discussion; and knowing what positions those key players currently hold. The 1995 Farm Bill may be a potential window of opportunity to affect changes in agricultural policy with regard to weed science. The next two years are an appropriate time to implement whatever strategy is developed.
Science and Public Policy: Shotgun Wedding or Marriage Made in Heaven?
Authors: Doering Otto
Published: March 2018

Scientists, above all others, approach public policy believing it to be scientifically rational—as it has been portrayed by the Good Government Movement, the League of Women Voters, and Mark Twain. Today, the problem is that public policy does not appear rational to scientists. While there is great opportunity for scientific input, neither the policy process nor the most influential policy input is necessarily scientifically rational. To understand the relationship of science to policy, one has to look at how the public views science today, the style of policy, the style of science, and how the policy process may have been captured by “irrational” interests. Only then can a realistic marriage be made between science and policy.
Description of Purple and Yellow Nutsedge (Cyperus rotundusandC. esculentus)
Authors: Wills Gene D.
Published: March 2018

Both purple nutsedge (Cyperus rotundusL. # CYPRO) and yellow nutsedge (C. esculentusL. # CYPES) are problem weeds in crops in many parts of the world. Yellow nutsedge is found in all U.S. states. Purple nutsedge is confined to the southern region of the United States, ranging from North Carolina across southern Arkansas and into southern California.
Effects of Plant Growth Stage on Chlorsulfuron Suppression of Canada Thistle (Cirsium arvense) Shoots and Roots
Authors: Zuris Nancy K. , Wilson Robert G. , Nelson Lenis A.
Published: March 2018

Field research was conducted to evaluate the performance of chlorsulfuron {2-chloro-N-[[4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} applied to established Canada thistle plants [Cirsium arvenseL. scop. # CIRAR] in the spring or fall to young vegetative shoots, and in June to plants in the bud growth stage. Canada thistle shoot densities measured in the spring following chlorsulfuron applications the previous year were lower when chlorsulfuron was applied in the bud and fall growth stage as compared to applications made in the spring to young vegetative shoots. Suppression of Canada thistle shoots from chlorsulfuron application during the bud and fall growth stage increased with rate, and was greatest at 269 g ai/ha. Chlorsulfuron applied at 269 g/ha at the fall growth stage only partially controlled the root system of Canada thistle.
Effects of Application Variables on Glyphosate Phytotoxicity
Authors: Buhler Douglas D. , Burnside Orvin C.
Published: March 2018

Glyphosate [N-(phosphonomethyl)glycine] toxicity to volunteer wheat (Triticum aestivumL.) and large crabgrass [Digitaria sanguinalis(L.) Scop. # DIGSA] was influenced more by carrier volume than application method. Glyphosate phytotoxicity increased when carrier volume was reduced with both application methods. When compared at equal carrier volumes, there was little difference in volunteer wheat or large crabgrass control when glyphosate was applied with a controlled droplet applicator or flat fan nozzles. Volunteer wheat and large crabgrass control with controlled droplet applicators was influenced by application factors. At a given carrier volume, application factors which yielded larger droplets generally resulted in superior vegetation control.
Control of White Campion (Silene alba) in Birdsfoot Trefoil (Lotus corniculatus) with Dinitroaniline Herbicides
Authors: Wyse Donald L. , Mcgraw Robert L.
Published: March 2018

In 2 yr of field experiments, trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], profluralin [N-(cyclopropylmethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine], fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine], ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine], and benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine] controlled white campion [Silene alba (Mill.) E.H.L. Krause.# MELAL] during the establishment of birdsfoot trefoil (Lotus corniculatus L. ‘Leo’).
Plant Problem Diagnosis Field Days — An Approach to Extension Education
Authors: Kells James J. , Vitosh Maurice L. , Hesterman Oran B.
Published: March 2018

Field days on diagnosis of plant problems were conducted by Extension specialists at Michigan State University. The objective was to expose participants to a variety of plant growth problems. Techniques were developed to simulate crop injury from herbicide and fertilizer misapplication and environmental stress. Twenty demonstration plots each were established for corn (Zea maysL.) and soybeans [Glycine max(L.) Merr.]. A specific problem was demonstrated in each plot. Two field days were held in 1985. One field day was conducted for agribusiness personnel and the other for Extension field staff. Promotion of the field days was a cooperative effort among Michigan Cooperative Extension Service, Michigan Pesticide Association, and Michigan Plant Food Council. Resource people conducting tours of the plots and leading discussions of the problems included a weed scientist, a soil fertility specialist, and a crop production agronomist. An evaluation survey indicated that this event was useful in furthering the understanding of plant growth problems. Based on the survey responses, future plant problem diagnosis field days are being planned in Michigan.
Biological Control and Its Integration in Weed Management Systems for Purple and Yellow Nutsedge (Cyperus rotundusandC. esculentus)
Authors: Phatak Sharad C. , Callaway M. Brett , Vavrina Charles S.
Published: March 2018

Observations of the effects of living organisms on weeds dates from 1795 when an insect,Dactylopius ceylonicus, was introduced for drooping pricklypear (Opuntia vulgarisMiller) control over a vast area. Since that time, biological control of weeds employed mainly the classical strategy of introducing natural enemies from areas of co-evolution. Self-perpetuation and dissemination of these introduced enemies was essential to suppress successfully the weed below economic levels. This classical tactic is suited particularly for weeds that are distributed widely in less intensively cropped or noncropped areas. Guidelines to introduce foreign organisms for biological control of weeds in the United States have been established.
Smooth Crabgrass (Digitaria ischaemum) Control in Kentucky Bluegrass (Poa pratensis) Turf with Herbicides Applied Preemergence
Authors: Bhowmik Prasanta C.
Published: March 2018

In field experiments, preemergence applications of bensulide {O,O-bis(1-methylethyl)S-[2-[(phenylsulfonyl)amino] ethyl] phosphorodithioate} or DCPA (dimethyl-2,3,5,6-tetrachloro-1,4-benzenedicarboxylate) at 11.2 kg ai/ha controlled smooth crabgrass [Digitaria ischaemum(Schreb. ex Schweig.)Schreb. ex Muhl. #3DIGIS] selectively in turf. Granular and liquid formulations of bensulide performed similarly. Napropamide [N,N-diethyl-2-(1-naphthalenyloxy)propanamide] granules when applied alone at 1.1 to 3.4 kg ai/ha were partially effective, but when combined with 5.6 kg ai/ha bensulide, controlled smooth crabgrass for the entire season. Oxadiazon {3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one} controlled crabgrass but temporarily injured the turf. Residual control of crabgrass the year after treatment was unacceptable for all treatments.
The Weed Science Curriculum
Authors: Zimdahl Robert L.
Published: March 2018

A survey showed weed scientists agree that basic agronomy, crop production and plant-oriented courses are essential in weed science education. Although there was no consensus on the structure of a core curriculum or even on whether one was needed, they agreed that curricula must be constructed to fit student interests, goals, and abilities.
White Man's Foot: Broadleaf Plantain
Authors: Mitich Larry W.
Published: March 2018

Plantain, which weary toilers dig from their lawns, hoe from their gardens, or cultivate from their fields was brought to the United States to serve man. Originally considered a valuable medicinal herb and an edible green, it was grown in monastery gardens and was cultivated in botanic gardens. It still is raised as a crop for bird feed.
Future Directions for Allelopathy Research
Authors: Lind Mary E.
Published: March 2018

If classical hierarchy were based on survival rather than riches, then weeds would rank just behind cockroaches. It is known all too well that weeds are the most tenacious of plants, and that they interfere very successfully with the productivity of crops valuable to man for food and fiber.
Influence of Inorganic Salts and Imazapyr on Control of Pitted Morningglory (Ipomoea lacunosa) with Imazaquin and Imazethapyr
Authors: Wills Gene D. , McWhorter Chester G.
Published: March 2018

Effects of 0.1 M ammonium sulfate, 0.1 M potassium phosphate, and 7 g/ha of the isopropylamine salt of imazapyr {(+)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid} were evaluated on the phytotoxicity of the ammonium salt of imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} and the ammonium salt of imazethapyr {(+)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid} applied postemergence to pitted morningglory (Ipomoea lacunosaL. #3IPOLA). While each of these salts and imazapyr applied alone had no effect, combining them with imazaquin or imazethapyr significantly increased control of pitted morningglory.
Accelerated Biodegradation of Herbicides: Proceedings of a Symposium of the Weed Science Society of America February 6, 1986, Houston, Texas
Authors: Kaufman Donald D. , Harvey R. Gordon , Skipper Horace D.
Published: March 2018

Since the late 1970s, the reason(s) for the performance of certain pesticides to fail after several years of continuous use has been studied. These pesticides include representatives from the herbicide, insecticide, and fungicide groups, encompassing several classes of chemistry–carbamates, carbamothioates (thiocarbamates), and organophosphates.
Methodology in Accelerated Biodegradation of Herbicides
Authors: Subba-Rao Ravva V. , Cromartie Thomas H. , Gray Reed A.
Published: March 2018

Accelerated biodegradation of herbicides in soils can be demonstrated in the laboratory either by treating soil samples with a herbicide under conditions favorable for microbial growth or by sampling field soils soon after herbicidal treatment. Quantitative measurement of accelerated degradation of thiocarbamates in field soils is complicated by the difficulty both of obtaining a proper untreated soil and of obtaining a representative sample by proper mixing of treated soil. Both bacteria and fungi degrade thiocarbamate herbicides, and examples of either class of organisms can be isolated by suitable selection and enrichment conditions. The enzymes involved in the initial steps of thiocarbamate biodegradation seem labile and have not been characterized. Studies of accelerated biodegradation of pesticides should measure the disappearance of the parent or active herbicide using chemical analyses or bioassays. Measuring accelerated biodegradation by determining metabolites (including CO2) is complicated by potential formation of other products, by incorporation of radioactivity into soil microflora, and by complex kinetics partly due to co-metabolism of the herbicide. Additional index words: EPTC, butylate.
Cockleburs
Authors: Mitich Larry W.
Published: March 2018

Although the word “xanthium” may conjure up visions of the exotic Far East, it is the generic name of spiny cocklebur (Xanthium spinosum L. #3 XANSP) and common cocklebur (X. strumarium L. # XANST). A familiar weed of fields and roadsides, cocklebur may have originated in the Mediterranean region and has plagued farmers and shepherds since Biblical times. Common cocklebur was considered a beneficient herb in ancient times. Its roots, seeds, and leaves were used as a diuretic and as a tonic to purify the blood. North American Indians used the leaves of spiny cocklebur to counteract hydrophobia.
Barley (Hordeum vulgare) Response to Herbicides Applied at Three Growth Stages
Authors: Martin Duane A. , Miller Stephen D. , Alley Harold P.
Published: March 2018

The response of irrigated spring barley (Hordeum vulgare L. ‘Steptoe’) to broadleaf herbicides applied at three growth stages was studied at Torrington, WY, in 1984 and 1985. Dicamba (3,6-dichloro-2-methoxybenzoic acid), dicamba plus 2,4-D [(2,4-dichlorophenoxy)acetic acid], and dicamba plus MCPA [(4-chloro-2-methylphenoxy)acetic acid] visibly injured barley when applied at all growth stages. These same treatments reduced barley height when applied at the 2- to 4-leaf and fully tillered stages. Yield differences among treatments were not significant. However, kernels/spike and kernel weight were reduced by dicamba or dicamba plus MCPA when applied at the fully tillered or boot stages, and test weight was reduced when dicamba was applied at all growth stages. Seed protein content did not differ in 1984. However, several herbicide treatments increased seed protein in 1985, especially when applied at the boot stage. Proline or lysine content did not differ among treatments.
Thioproline Protection of Crops Against Herbicide Toxicity
Authors: Hilton James L. , Pillai Parthasarathy
Published: March 2018

Thioproline (L-thiazolidine-4-carboxylic acid) partially protects sorghum [Sorghum bicolor(L.) Moench. ‘DK 42Y’] seedlings against the herbicides tridiphane [2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane] and alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] in controlled environment chambers. Thioproline alone inhibits plant growth at concentrations above 10−5M. Its phytotoxicity is intermediate between the two herbicide antidotes OTC (L-2-oxothiazolidine-4-carboxylic acid) and flurazole [phenylmethyl 2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylate]. The two thiazolidine antidotes increased thiol content of excised corn (Zea maysL. ‘DK T 1100’) seedling roots whereas thiol content was decreased by the two herbicides. While thioproline or OTC partially offset tridiphane-induced decreases in thiol content, none of the antidotes effectively circumvented the reduced thiol content resulting from alachlor treatment.
Drop Formation and Impaction on the Plant
Authors: Reichard Donald L.
Published: March 2018

The effect of variables that influence the retention of spray droplets impacting on leaf surfaces was studied, using a uniform-size droplet generator to produce drops ranging from 63 to 545 μm diam. To observe the impaction of spray droplets more easily and to measure their velocity before and after impaction, high-speed motion photography (6000 frames/sec) was used. Rebound of spray droplets depends on the micro-structure of the target surface. Leaf surfaces of several crops and weeds reflected 63 to 545 μm diam water drops traveling at velocities less than velocities of drops delivered by popular nozzles at commonly used spray pressures. If the concentration is high enough, some surfactants can reduce the rebound of drops. With one surfactant, its concentration had to be much greater than the critical micelle concentration to reduce reflection of spray drops.
Air-Assist, Air-Foil, and Air-Curtain Sprayers
Authors: Bode Loren E.
Published: March 2018

Air-assist nozzles that use pneumatic energy to help atomize the spray liquid were reviewed. These nozzles use larger orifices than conventional hydraulic nozzles for low-volume applications. By changing the air pressure, various droplet sizes can be produced without changing nozzle tips. Several systems use air to transport the atomized spray to specific target sites. Various air volumes and velocities have been evaluated in these systems. Preliminary research indicated that air can improve canopy penetration and can cover the entire plant more uniformly. Undersides of leaves can be treated easier with air-assist systems compared to conventional applications with hydraulic nozzles.
Rotary Disk Atomization
Authors: Gebhardt Maurice R.
Published: March 2018

In the late 1930s, European engineers discovered that, for very low flow rates, rotary disk atomizers produced a more definable range of droplet sizes than hydraulic atomizers. In the late 1970s, a cup-like spinning atomizer was developed to apply herbicides at low and ultra-low volumes. Rotary atomizers distribute droplets in a pattern similar to hollow cone nozzles. The droplet trajectory could affect deposits adversely since droplets released horizontally are exposed to wind and other environmental effects longer than hydraulic spray nozzles. Propellers and fans were used to enhance downward movement of droplets without considering that droplet impingement velocity was critical for efficient deposition. In the early 1980s, rotary atomizers were promoted to reduce herbicide rates, but the claims were products of unconfirmed testing. Herbicide efficacy in confirmed research was not influenced by application with the rotary atomizer, but lower carrier rates reduced the amount of water handled during the spraying operation. The cost of the atomizer, more maintenance, and greater care during operation with no decrease in herbicide rates discourage continued use.
Quackgrass (Agropyron Repens) Control with SC-0224 and Glyphosate
Authors: Kivlin Paul T. , Doll Jerry D.
Published: March 2018

Field studies were conducted from 1982 to 1984 to evaluate the effectiveness of SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] for quackgrass [Agropyron repens(L.) Beauv. # AGRRE] control. The herbicides were compared 1) in different rates and carrier volumes, 2) on several spring and fall application dates, and 3) with varying time intervals between application and moldboard plowing. Glyphosate and SC-0224 controlled quackgrass equally well at carrier volumes of 25 to 400 L/ha. Both herbicides generally provided similar control as fall and spring applications and with time intervals of 12 to 96 h between application and plowing. Occasionally the low rate of SC-0024 gave less quackgrass control the next season than the same rate of glyphosate. Adding nonionic surfactant at 0.5% (v/v) did not influence the phytotoxicity of these herbicides at the rates and carrier volumes tested. These herbicides controlled quackgrass comparably and greater than 85% when applied under appropriate environmental conditions.
Thistles I: Cirsium and Carduus
Authors: Mitich Larry W.
Published: March 2018

When Scotland was under an imminent Viking invasion, the Scots piled the beaches with thistles and waited. During the night of the invasion, the sandal-clad Norsemen leaped onto the thistle-strewn beach and let out cries of pain and curses. Warned of their approach, the Scots drove the Norsemen back to their ships. Small wonder that the thistle became Scotland's heraldic emblem and the source of her motto, “Touch Me Who Dares”. Since 1687, induction into Scotland's Order of the Thistle has been a great honor. Linnaeus named Scotch thistle, Onopordum acanthium L. # ONRAC, from the Greek onos, or donkey, and perdo, to consume; the species name is from the Latin acanthus, meaning spiny. Thus it is a spiny plant eaten by donkeys.
Weed Control in Direct-Seeded Tomato,Lycopersicon esculentum, for Transplants
Authors: Glaze Norman C.
Published: March 2018

Herbicides were evaluated alone, in combinations, or as sequential treatments on direct-seeded tomato each year from 1982 through 1984. Diphenamid at 4.5 kg ai/ha or napropamide at 1.1 to 2.2 kg ai/ha alone are registered but frequently do not control weeds adequately, particularly when yellow nutsedge and/or Florida pusley is common. Combinations or sequential treatments are necessary to overcome these weed problems in cropping systems. Metolachlor at 0.8 to 3.4 kg ai/ha injured direct-seeded tomato in proportion to the rate applied. Pendimethalin at 0.6 kg ai/ha also injured tomatoes. Fluazifop at 0.3 to 0.6 kg ae/ha and sethoxydim at 0.2 to 0.5 kg ai/ha effectively controlled annual grasses without injuring tomato seedlings. These herbicides would reduce competition and would increase harvesting efficiency where grass weeds are a problem.
Thidiazuron Effects on Malvaceae, Corn,Zea mays; and Soybean,Glycine max
Authors: Hodgson Richard H. , Snyder Robert H.
Published: March 2018

The growth of two mallow family weeds, velvetleaf and prickly sida, was inhibited 50% when seedlings were treated with less than 200 g ai/ha of thidiazuron. Spurred anoda was unaffected by treatment with up to 1120 g/ha of thidiazuron. Cotton, okra, and hibiscus, all in the mallow family, also were susceptible to thidiazuron treatment. Leaf development in 2-week-old cotton seedlings was inhibited 20% by less than 35 g/ha thidiazuron as were seedling okra and hibiscus. Plants of all these susceptible species were more resistant when grown for 2 months before treatment. Seedlings of soybean displayed localized injury after treatment, but plant height, biomass, and seed production were not significantly affected 10 weeks after treatment with up to 1120 g/ha thidiazuron. Seedlings of corn appeared unaffected by treatment with up to 1120 g/ha thidiazuron.
Herbicide-Oil-Water Emulsions
Authors: Manthey Frank A. , Nalewaja John D. , Szelezniak Edward F.
Published: March 2018

Oil-water emulsion stability was determined for crop origin and refinement of seed oils and their methyl esterified fatty acids (methylated seed oil) as influenced by emulsifiers and herbicides. Oil-in-water emulsion stability of one-refined, degummed, and crude seed oils was affected by the emulsifier. However, emulsion stability of methylated seed oil was not affected by the refinement of the seed oil used to produce the methylated seed oil or by the emulsifier. Oils without emulsifiers or emulsifiers alone added to formulated herbicide-water emulsions reduced emulsion stability depending upon the herbicide and emulsifier. Further, emulsion stability of formulated herbicides plus oil adjuvants was influenced by the oil type, the emulsifier in the oil adjuvant, and the herbicide. Oil-in-water emulsions improved or were not affected by increasing concentration of the emulsifier in the oil. However, T-Mulz-VO at a concentration greater than 10% with soybean oil or 5% with methylated soybean oil reduced emulsion stability with sethoxydim. Emulsion stability of herbicides with adjuvants depends upon the herbicide, the emulsifier, emulsifier concentration, and the crop origin, type, and refinement of oil.
Winter Wheat (Triticum aestivum) Response to Herbicides Applied at Three Growth Stages
Authors: Martin Duane A. , Miller Stephen D. , Alley Harold P.
Published: March 2018

Several labeled herbicide treatments reduced winter wheat height and grain yield when applied at different growth stages in 1984 and 1985. Yield reductions were related to reduced spike production. Wheat height and yield generally were greatest when herbicides were applied at Zadoks' Stage 29 and lowest at Stage 13. Herbicide treatments did not affect wheat kernels per spike, kernel weight, volume weight, or germination either year. However, most herbicide treatments either increased or decreased seed protein content, depending on the year.
Effect of Adjuvant Concentration and Carrier Volume on Large Crabgrass (Digitaria sanguinalis) Control with Fluazifop
Authors: Smeda Reid J. , Putnam Alan R.
Published: March 2018

Foliar activity of the butyl ester of fluazifop on large crabgrass was determined by varying the concentration of a petroleum-based oil concentrate and the carrier volume. Increasing the concentration of petroleum oil or reducing the carrier volume improved large crabgrass control. Under greenhouse conditions, both visible injury and plant dry weight reflected greater control with adjuvant concentrations increasing from 0.62 to 5.0% v/v. Similarly, reducing carrier volumes from 374 to 47 L/ha increased grass control. No significant interaction between carrier volume and adjuvant concentration suggests the effects of these two variables are independent of one another. For both variables, effects were greater with sublethal rates of fluazifop.
Rotational Crop Response to Repeated Applications of Norflurazon
Authors: Keeling J. Wayne , Lloyd Randy W. , Abernathy John R.
Published: March 2018

A long-term study was established to determine the effects of rate, application method, and repeated applications of norflurazon on soil persistence and plant injury for sorghum, corn, and wheat. Preplant incorporated (PPI) and preemergence (PE) applications of norflurazon at 1.1 (1X) and 2.2 kg ai/ha (2X) initially were applied in 1981. Subplots were retreated in 1982 and 1983. Rotational crops were planted each year from 1982 to 1987. Evaluations taken in 1982 (14 months after initial treatment) showed slight injury to wheat, sorghum, and corn from 1X applications and significant injury from 2X applications. Evaluations 1 to 3 yr after final application indicated that repeated applications, even at the 1X rate, increased norflurazon residues and rotational crop injury. At both 1X and 2X rates, PPI treatments increased norflurazon persistence compared to PE applications.
Herbicide Antagonism at the Whole Plant Level
Authors: Green Jerome M.
Published: March 2018

Antagonistic interactions between herbicides or between herbicides and nonherbicides are common and prevent the use of certain mixtures. Although antagonism is detrimental when it reduces weed control, the degree of antagonism is critical to determine whether a mixture is agronomically useful. If antagonsim is not severe, herbicides with different weed spectrums can be used together to complete the weed spectrum. Antagonism can be beneficial when it increases crop safety. In cases where antagonism significantly reduces control, key factors must be identified and managed to decrease antagonism and increase efficacy. These factors, which include the herbicide rate(s), mode of action, plant species, formulation, adjuvants, timing, stage of growth, and environment, often are complex and poorly understood at the whole plant level. The growing dependence on herbicide mixtures has increased the practical importance of understanding herbicide antagonism.
Weed Control Strategies for Forage Legumes
Authors: Malik Najib , Waddington John
Published: March 2018

Tolerance and subsequent yield response of established alfalfa, red clover, alsike clover, sainfoin, birdsfoot trefoil, and cicer milkvetch to sethoxydim and fluazifop spring applied and to hexazinone, metribuzin, and terbacil fall applied were determined in a field study. All legumes tolerated sethoxydim. Fluazifop was safe on all legumes except sainfoin. Alfalfa and cicer milkvetch tolerated hexazinone, metribuzin, and terbacil. Alfalfa dry matter yield was not affected by any of the herbicide treatments, but cumulative cicer milkvetch yield increased 9% over a 3-yr period with hexazinone applications. Sainfoin yield increased 20% with hexazinone and terbacil treatment. Hexazinone injured red clover and reduced yield. Alsike clover was the most susceptible legume to the residual herbicides. Weed dry matter yield associated with the legumes indicated that alfalfa and sainfoin were the most and the least competitive species, respectively. Plots treated with hexazinone contained the least amount of weeds, regardless of the legume species. Field peas seeded in rotation was not affected by herbicide residues; however, residues from terbacil applied at 1.0 kg/ha reduced seed yield of lentils.
Postemergence Grass and Broadleaf Herbicide Interactions for Red Rice (Oryza sativa) Control in Soybeans (Glycine max)
Authors: Minton Bradford W. , Shaw David R. , Kurtz Mark E.
Published: March 2018

Quizalofop controlled 2- to 3-leaf and 5- to 6-leaf red rice better than fluazifop-P, haloxyfop, or sethoxydim applied alone. Red rice control increased when acifluorfen was tank mixed with haloxyfop, fluazifop-P, or sethoxydim. Antagonism was most severe when imazaquin was tank mixed with any of the grass herbicides. The efficacy of sethoxydim, fluazifop-P, and haloxyfop was reduced when applied with chlorimuron or bentazon. In greenhouse experiments, all of the grass herbicides, except for fenoxaprop, reduced fresh weight of red rice 71% or more. Based on fresh weight reduction, acifluorfen, fomesafen, and lactofen only reduced the activity of fluazifop-P, while imazaquin decreased the activity of all grass herbicides.
Influence of Chemical Treatment andFusarium oxysporumon Velvetleaf (Abutilon theophrasti)
Authors: Kremer Robert J. , Schulte Lisa K.
Published: March 2018

Germination stimulants were tested for effectiveness on velvetleaf seed imbibition and germination and concurrent microbial attack of seed to deplete weed seed in soil. Several chemicals increased in vitro seed germination and decreased the numbers of hard, viable seed. The proportion of nonviable seed, 5% withFusarium oxysporum(Schlech.), was enhanced to 40% by adding ethephon at 100 μg/ml. Fungal density on seedling roots and imbibed (nonviable seed) was increased by chemical treatment. Seedling emergence was reduced 15% when ethephon or carbofuran was applied to soil with the fungus. Shoot dry weight decreased and root infection increased with all treatments regardless of fungal inoculation. Butylate and carbofuran increased infection of imbibed seed in soil byF. oxysporumwhile ethephon and AC94377 increased infection by other soil fungi.
Alkaloid Response to Defoliation of Velvet Lupine (Lupinus leucophyllus)
Authors: Ralphs Michael H. , Williams Coburn
Published: March 2018

Velvet lupine planst were defoliated (50% of upper foliage) in 1983 and 1984 to determine total alkaloid concentration (TAC), percent crude protein (CP), and fiber in regrowth foliage. TAC in regrowth leaves was 15% lower than in the original leaves removed at the beginning of the study. Percent CP of regrowth leaves was 22% lower than in original defoliated leaves. Alkaloids and CP did not increase in response to defoliation stress from simulated herbivory as plant defense theories predicted.
Allelochemicals from Plants as Herbicides
Authors: Putnam Alan R.
Published: March 2018

Allelochemicals representing numerous chemical groups have been isolated from over 30 families of terrestrial and aquatic plants. Some of the compounds also have been isolated from soil in quantities sufficient to reduce plant growth. Although selected allelochemicals are believed to influence plant densities and distributions, none isolated from higher plants have been considered active enough for development as commercial herbicidal products. Almost all herbicidal allelochemicals exist in plants in nontoxic, conjugated forms. The toxic moiety may be released upon exposure to stress or upon death of the tissue. The most successful use of allelochemicals in weed control has been management of selectively toxic plant residues. For example, rye residues have controlled weeds effectively in a variety of cropping systems. Several weed species may interfere with crop growth through chemicals released from their residues. A number of noxious perennial species appear to exploit allelochemicals in their interference processes. This review focuses on the more recent chemical discoveries and how they might be exploited for weed control.
Potential New Herbicides – Phytotoxins from Plant Pathogens
Authors: Kenfield Doug , Bunkers Greg , Strobel Gary A. , Sugawara Fumio
Published: March 2018

A rationale for the study of phytotoxins from fungal pathogens of plants is presented. Structural chemistries and biological data are given for numerous, recently discovered phytotoxins in such diverse chemical classes as polyketides, terpenoids, diketopiperazines, and isocoumarins. The biological activities of these compounds range from broadly toxic (curvulin) to host specific (maculosin-1). Phytotoxicology offers a viable supplement to organic synthesis as a means of developing and implementing new, biorational, and economical herbicides.
A Surface-Roller Herbicide Applicator for Weed Control in Turf
Authors: Welker William V. , Peterson Donald L.
Published: March 2018

A surface-roller wiper that rotates by direct contact with the ground was developed to apply herbicides to broadleaf weeds in turf. The free-wheeling roller 1.8 m wide consists of a 30-cm diam PVC pipe covered with a 1.3-cm thick carpet The herbicide is delivered by gravity to the carpet through a pipe manifold. Broadleaf weeds in turf were effectively controlled with 2,4-D roller applied once as a2%solution (2.2 kg ae/ha) or twice as a 1% solution (1.1 kg/ha). Herbicide drift was avoided with the roller applicator as indicated by lack of injury to tomato plants downwind from 2,4-D roller applied as a5%(5.6 kg/ha) solution.
Broomrapes (Orobanchespp.): A Potential Threat to U.S. Broadleaf Crops
Authors: Jain Rakesh , Foy Chester L.
Published: March 2018

Five broadleaf crops, alfalfa, peanut, soybean, tobacco, and tomato, were tested for their susceptibility to three broomrape species, branched, Egyptian and crenate, in the greenhouse. All five crop species were parasitized by one or more broomrape species. Peanut plants were most susceptible and soybean plants were least susceptible to parasitism by broomrape. Egyptian and branched broomrapes had a wider host range affecting plants in both the Solanaceae and Fabaceae. Crenate broomrape mainly infected plants belonging to Fabaceae, except for the few attachments to tomato and tobacco. Apparently, this is the first report on parasitism of peanut plants by branched broomrape and that of peanut and alfalfa plants by crenate broomrape. Parasitism of soybean plants by any of the broomrape species also was observed for the first time in these experiments. These results indicate that broomrapes, although not a major problem on any of the crops in the United States, could parasitize several major broadleaf crops should the parasite become established.
Wild Oat (Avena fatua) and Spring Barley (Hordeum vulgare) Density Affect Spring Barley Grain Yield
Authors: Evans Richard M. , Thill Donald C. , Tapia Lawrence , Shafii Bahman , Lish Joan M.
Published: March 2018

Addition series field experiments were conducted near Moscow, ID, in 1987 and 1988 to determine the relative aggressiveness of spring barley and wild oat and to determine the effect of barley and wild oat density and proportion on barley grain yield and wild oat seed rain. Regression analysis was used to describe the relationship of the aboveground biomass and grain yield to species density. Barley was more aggressive than wild oat. Barley biomass was affected most by intraspecific competition, while wild oat biomass was affected most by interspecific competition. Barley aggressiveness changed little throughout the growing season. Wild oat aggressiveness varied but was always less than barley aggressiveness. Increasing wild oat density had a negative, asymptotic-type effect on barley grain yield at all barley densities. However, the effect of wild oat was greatest at the lower density of barley. Increasing barley density decreased wild oat seed rain.
Soybean (Glycine max) Response to Postemergence Herbicide Mixtures Containing 2,4-DB
Authors: York Alan C. , Wilcut John W. , Keene Mark M. , Walls Frank R.
Published: March 2018

Experiments were conducted at 12 locations in North Carolina and Virginia to determine soybean response to postemergence application of 2,4-DB in combination with 420 g ae ha-1of sodium salt of acifluorfen, 13 g ae ha-1of ethyl ester of chlorimuron, and 70 g ae ha-1of ammonium salt of imazethapyr. Adding dimethylamine salt of 2,4-DB at 35 or 70 g ae ha-1to acifluorfen, chlorimuron, or imazethapyr increased soybean injury 2 to 14% 7 d after application. Soybean quickly recovered and no injury was observed 21 d after application. Acifluorfen, chlorimuron, or imazethapyr alone or in combination with 2,4-DB at 35 g ha-1did not reduce soybean yield. Adding 2,4-DB at 70 g ha-1reduced yield at four of the 12 locations.
Factors Affecting Winter Survival of Johnsongrass (Sorghum halepense) Rhizomes
Authors: Hartzler Robert G. , Gover Art , Stellingwerf Joanne
Published: March 2018

There were no differences in johnsongrass rhizome winter survival at central and southeastern locations in Pennsylvania in 1988 or 1989. At a 6-cm depth of burial, survival rates of 5 and 25% were found for rhizome segments 7.5 and 15.0 cm in length, respectively. Survival rates for rhizomes buried 25 cm averaged 86%, with no difference in survival between rhizome lengths. The majority of rhizome biomass produced by the biotype used in these studies was found at soil depths allowing a high percentage of survival.
Tebuthiuron Effects on Elemental Nutrients in Blue Grama (Bouteloua gracilis) Forage
Authors: Johnsen Thomas N.
Published: March 2018

Tebuthiuron has been found in soils and plants a decade after application to rangelands in semi-arid areas. Forage production, length of growing season, and preference by grazing animals are greater on treated than on untreated areas. It is not understood how these differences occur. Blue grama forage was assayed for concentrations of N, P, K, Ca, Cu, Fe, Mg, Mn, and Zn in treated and untreated plants on adjacent paired plots in the field, 6 to 11 yr after tebuthiuron applications at three locations in Arizona. Only Fe and Mn concentration differed among treatments, being significantly higher (P = 0.05) in blue grama from treated plots.
Effect of Ammonium Sulfate, Imazapyr, and Environment on the Phytotoxicity of Imazethapyr
Authors: Kent Lisa M. , Wills Gene D. , Shaw David R.
Published: March 2018

The effects of 1.24 kg ha-1ammonium sulfate, 5 g ae ha-1of the isopropylamine salt of imazapyr, and air temperature of 18, 27, and 35 C at 40 and 100% relative humidity on the phytotoxicity of 35 g ae ha-1of the ammonium salt of imazethapyr applied postemergence to pitted morningglory were evaluated. Both ammonium sulfate and imazapyr increased imazethapyr phytotoxicity to pitted morningglory. Ammonium sulfate enhanced imazethapyr phytotoxicity the most at 40% whereas imazapyr was most effective at 100% relative humidity. Imazethapyr phytotoxicity was enhanced more by the combination of ammonium sulfate and imazapyr than with either alone regardless of relative humidity. Variations in temperature had little effect on phytotoxicity.
Format of a Weed Control Database
Authors: Mueller-Warrant George W.
Published: March 2018

Access to detailed descriptions of the effects of applying specific rates of herbicides to crops and weeds in various growth stages is hampered by the format in which the relevant information is stored. Compared to traditional formats of journal articles and herbicide registration labels, computer database systems could easily cross-reference data from large numbers of experiments and answer specific questions concerning herbicide performance under particular conditions. Availability of this type of information could have far-reaching consequences for herbicide users, consultants, researchers, and regulators. A preliminary format for storing weed control information in IBM-PC compatible computers was developed, including procedures to enter data and retrieve information. Weed control efficacy or crop injury data for all rates of a herbicide or tank-mixture applied at a specific growth stage in a single test are used to generate dose/response equations by means of regression analysis routines. The best fitting of these equations is then used to estimate herbicide rates that would provide ten categories of control, ranging from a “no observable effect level” (NOEL) up to complete control. Rates are estimated only for those categories either within or bordering the range of the observed data, the remaining categories are empty. The estimated rates are stored in the database, along with the original data and other qualifying information. Access to information is organized around searches for a single herbicide, plant species, or pair of species. Search output is presented in a tabular format listing species, growth stage, herbicide name, and herbicide rates for the ten categories: NOEL, 10, 30, 50, 70, 83, 90, 95, 98, and 100% control or injury.
Effect of Adjuvants on Weed Control and Soybean (Glycine max) Tolerance with AC 263,222
Authors: Wixson Marshall B. , Shaw David R.
Published: March 2018

Field experiments were established to observe the effects of adjuvants and time of application on weed control and ‘Terra-Vig 515’ soybean tolerance with POST applications of AC 263,222. A nonionic surfactant or a crop oil concentrate increased sicklepod control with AC 263,222 applied at either V2 or V6 soybean growth stages. Sicklepod control increased as AC 263,222 was increased from 35 to 70 g ai ha–1only when applied without an adjuvant. Late in the season, there was no difference in sicklepod control between V2 and V6 applications. Adjuvants and application timing within herbicide treatments had no effect on pitted morningglory control, and, though adjuvants increased common cocklebur control, all treatments controlled more than 85% of both species. AC 263,222 with adjuvants at all rates and timings injured and stunted soybean more 2 wk after treatment compared to AC 263,222 alone. AC 263,222 at 35 or 70 g ha–1with crop oil concentrate reduced yields more than AC 263,222, with either a surfactant or no adjuvant when applied to V2 soybeans.
Effects of Topsoil Thickness On Winter Annual Weed Biomass Production and Nutrient Flux
Authors: Pettry David E. , Switzer Richard E. , Cole A. Wayne
Published: March 2018

The effects of topsoil thickness on winter annual weed growth and nutrient concentration were assessed for three consecutive years in soybean plots. The topsoil treatments had high fertility levels, uniform textures, and no herbicides were used in the study. Common chickweed composed 75% of the winter annual weed species. Weed biomass production decreased as topsoil thickness decreased from 22.5 cm to 0. Topsoil thickness of 22.5 cm produced 800 kg ha–1 more weed growth than 0 cm topsoil. The weed biomass grown in thicker topsoil had higher total amounts of N, K, Mg, and Ca.
Weed Control and Tobacco (Nicotiana tabacum) Tolerance with Fomesafen
Authors: Bridges David C. , Stephenson Michael G.
Published: March 2018

Research was conducted to determine the tolerance of flue-cured tobacco to fomesafen and the potential for weed control in tobacco with fomesafen. Treatments consisted of fomesafen at 0.4 or 0.6 kg ai ha–1applied pretransplant incorporated (PTI), pretransplant (PRE-T), post-transplant (POS-T), postemergence-over-top (POT), or post-directed (PD). Tobacco injury within 30 d of application was as high as 30%, but tobacco recovered and few significant differences in tobacco yield, grade index, or price were observed except where fomesafen was applied PTI at 0.6 kg ha–1. Tobacco tolerance relative to time of application was generally PRE-T = POT > POS-T = PTI. Florida pusley and large crabgrass control was > 80% for all fomesafen treatments. Yellow and purple nutsedge control was approximately 30% before cultivation.
WEEDING: A

W

eed

E

cology and

E

conomic

D

ecision Making

IN

structional

G

ame
Authors: Wiles Lori J. , Wilkerson Gail G. , Coble Harold D.
Published: March 2018

Process-level simulation models can be a unique and effective medium for teaching concepts of crop biology and management which can usually only be studied in the field. WEEDING was developed from several research models to demonstrate concepts of weed ecology, herbicide efficacy and selectivity, and economic thresholds for weed control decisions. Users of WEEDING interactively grow a soybean crop, making management decisions throughout the seaason. The program includes real weather data and a realistic assortment of soybean varieties, soil types, weed species, and weed control options. Production costs and profit are calculated at the end of a simulated season. The structure of a process-level model driven by real weather data simulates the risk involved in management decisions.
Hairy Nightshade (Solanum sarrachoides) Control in Potatoes (Solanum tuberosum) with Bentazon Plus Additives
Authors: Eberlein Charlotte V. , Guttieri Mary J. , Schaffers William C.
Published: March 2018

Field studies were conducted to examine hairy nightshade control with, and potato tolerance to, bentazon or bentazon plus nonionic surfactant (NIS), petroleum oil concentrate (POC), methylated seed oil (MSO), BCH-815, or urea-ammonium nitrate (UAN). Bentazon treatments were applied early or late POST. Hairy nightshade control with bentazon at 0.56 kg ha–1plus POC, MSO, BCH-815, or UAN was equal to or better than bentazon alone at 1.12 kg ha–1regardless of time of application. Potato injury with bentazon plus additives applied late POST was sometimes greater than with bentazon alone, but use of additives did not reduce potato yield or quality. Yield of US ♯1 tubers was lower when bentazon was applied late POST than when applied early POST in one of two years.
Tolerance of Chinese Milkvetch (Astragalus sinicus) to Herbicides
Authors: Cai Zhongling , Brauen Stanton E. , Gealy David R. , Johnston William J. , Lumpkin Thomas A.
Published: March 2018

Chinese milkvetch is the most important green manure crop in the rice producing regions of China. The tolerance of Chinese milkvetch to 29 herbicides approved for other legume crops was determined in the greenhouse. Chinese milkvetch was tolerant to bentazon, diclofop-methyl, and EPTC at 2.0, 1.6, and 6.0 kg ai ha–1, respectively. Barban, bromoxynil, 2,4-DB, dinoseb, fluazifop, quizalofop, sethoxydim, and triallate at 0.5, 0.6, 1.0, 1.5, 0.3, 0.3, 0.5, and 1.0 kg ai ha–1, respectively, slightly injured Chinese milkvetch but did not substantially reduce biomass. Trifluralin, propham, DCPA, acifluorfen, and MCPA were moderately phytotoxic to Chinese milkvetch at 0.5, 3.0, 5.0, 0.5, and 0.5 kg ai ha–1, respectively.
Tolerance of Kenaf to Selected Postemergence Herbicides
Authors: Kurtz Mark E. , Neill Samuel W.
Published: March 2018

In field trials conducted in 1989 and 1990, fifteen postemergence herbicides were tested for phytotoxicity to kenaf. Clethodim (110 g ai ha–1), fluazifop (220 g ai ha–1), quizalofop (70 g ai ha–1), and sethoxydim (210 g ai ha–1) were not phytotoxic to kenaf in the cotyledonary stage. MSMA (2.2 kg ha–1) was not phytotoxic to kenaf at the cotyledonary or 35-cm stage. All other herbicides applied postemergence to kenaf caused significant injury.