bluuebunny/crossref_metadata_2025 huggingface dataset:
New Herbicides for Postemergence Application in Sugarbeet (Beta vulgaris)
Authors: Wilson Robert G.
Published: March 2018

Field experiments were conducted near Scottsbluff, NE, to evaluate the selectivity of sequential POST applications of ethofumesate and triflusulfuron for weed control in sugarbeet. When applied alone ethofumesate and triflusulfuron reduced common lambsquarters, hairy nightshade, and redroot pigweed density while triflusulfuron also reduced kochia density compared with an untreated control. Combining ethofumesate with desmedipham plus phenmedipham increased sugarbeet injury compared with desmedipham plus phenmedipham. Combining triflusulfuron with desmedipham plus phenmedipham increased kochia control but did not increase sugarbeet injury over that obtained with desmedipham plus phenmedipham. Weed control and sugarbeet injury from herbicides generally were unaffected by application in 97 or 182 L/ha of water carrier. However, herbicide control of hairy nightshade in 1993 was greater with 97 than 182 L/ha of water carrier.
Science and Policy in Regulating Pesticides: Will They Collide or Merge?
Authors: Andersen Janet L.
Published: March 2018

The Environmental Protection Agency (EPA) is required by law to assure that the use of pesticides does not cause unreasonable risks to humans or the environment when risks are compared with benefits. Weed scientists conduct hundreds of comparative efficacy tests each year, but the results are often of little use to the Agency in benefit assessments because the tests are unpublished or otherwise unavailable to the Agency, the tests are conducted in a manner unusable for regulatory purposes, or there are inconsistencies between tests conducted year to year or at different sites. Despite the lack of high quality data, the Agency is compelled to make the best regulatory decision possible with the information at hand, and it may appear to some that decisions are based more on policy than science. EPA is looking for experimental methods that will improve the quality of benefits data available to the Agency.
Common Pokeweed
Authors: Mitich Larry W.
Published: March 2018

Phytolaccaceae, virtually a tropical family, encompasses from 15 to 18 genera (11), usually herbs, but also a few tropical trees and shrubs (13). Of the 25 species in the genus Phytolacca (11), only one is represented in eastern North America (1).
Future Priorities in Weed Science
Authors: Riggleman James D.
Published: March 2018

Dr. James D. (Jim) Riggleman of Wilmington, DE, is Manager of Licensing for Du Pont's Agricultural Products Dep. He is responsible for identifying new herbicides, insecticides, fungicides, growth regulators and life science materials for Du Pont's development and marketing. Prior to this assignment, he was Manager, New Products Development.
Effect of Atrazine Residue on Soybean Growth Under Three Tillage Systems and Various Herbicides
Authors: Pawlak John A. , Kells James J. , Barrett Michael , Meggitt William F.
Published: March 2018

Field experiments were conducted to examine the effect of tillage on atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] persistence in the soil and soybean [Glycine max(L.) Merr.] injury. Tillage systems evaluated were no-tillage, chisel plowing, and moldboard plowing. Reduced tillage systems, such as no-tillage or chisel plowing, resulted in greater soybean injury from atrazine residue than did moldboard plowing. Regardless of atrazine residue level, metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] resulted in the greatest injury to soybeans. Metribuzin application in combination with atrazine residue increased soybean injury under the chisel plowed system.
Factors Affecting the Loss of EPTC Applied Through a Sprinkler
Authors: Ogg Alex G.
Published: March 2018

Increasing the air temperature from 20 to 32 C, the water temperature from 21 to 30 C, and the wind velocity from 0 to 8 km/h increased the loss of EPTC (S-ethyl dipropyl carbamothioate) from water applied through a sprinkler by 24 to 138%. Decreasing the water temperature from 21 to 10 C decreased the loss of EPTC by 35 to 50%. Decreasing the water pressure or nozzle size by 33% or doubling the herbicide concentration did not affect the percentage of EPTC lost.
Training Weed Scientists for Industry
Authors: Antognini Joe
Published: March 2018

The three major needs in training weed scientists for a career in the agricultural industry are an understanding and appreciation for the screening and evaluation process, a thorough knowledge of the Environmental Protection Agency (EPA) registration requirements and procedures, and a clear picture of the scientific job opportunities available in the total industry, not just in chemical companies. These needs should be fulfilled during the early part of undergraduate studies so the student can design a program to prepare him/her for industry positions after B.S., M.S., or Ph.D. studies.
Training Weed Scientists for Extension
Authors: Knake Ellery L.
Published: March 2018

Those preparing for a career in weed science extension are expected to take formal courses in weed science and related subject matter. They should gain experience in conducting and interpreting research. They also can benefit from formal courses and experience to develop communication skills for technology transfer. Such courses as psychology, journalism, photography, and public speaking should be considered. Along with research and teaching assistantships, educational institutions should establish extension assistantships to help those preparing for a career in weed science extension.
The Devil's Grass: Quackgrass
Authors: Mitich Larry W.
Published: March 2018

Quackgrass [Agropyron repens (L.) Beauv. #3 AGRRE] infests farms and gardens throughout the northern United States, southern Canada, almost all of Europe—its native home—and parts of Asia. It grows in Alaska, extends above the Arctic Circle in Norway, and plagues coffee plantations in New Guinea. While quackgrass occurs in every state in the United States, it is rarely a troublesome crop weed in the South.
Methods to Study Interactions Among Crops and Weeds
Authors: Radosevich Steven R.
Published: March 2018

Studies of weed and crop competition can be used to predict yield losses from weed presence and to determine optimum levels or periods of weed control. However, competition is a complex phenomenon that is governed by various biological, environmental, and proximity factors. The factors of proximity include plant density, species proportion, and spatial arrangement among individuals. Several experimental methods have been developed that attach different levels of importance to proximity factors. These methods are described, and the advantages and disadvantages of each are discussed. Density, proportion, and arrangement of plants influence the outcome of competition experiments and should be incorporated into studies of crop-weed interference, since differing estimates for the effects of weeds on crop productivity can be obtained, depending upon the experimental method used.
Predicting Crop Yield Reductions from Weeds
Authors: Aldrich Richard J.
Published: March 2018

Predicting crop yield reductions from weeds continues to challenge weed science. Useful methods based upon weed densities and upon area weeds influence have been developed. Results vary greatly from year to year and location to location for several reasons which are reviewed: 1) the shift in crop yield from a weed density-dependent to a weed density-independent relationship; 2) the effect of density on essential growth factor competed for; 3) differences among weed species in relative competitiveness for essential growth factors; 4) the differential effect of environmental conditions on the competitiveness of weed species; and 5) the effect of time of emergence on competition. To reduce the variability in prediction methods will necessitate developing a method based upon the factor(s) responsible for yield reduction.
Image of Weed Science
Authors: Burnside Orvin C.
Published: March 2018

After 25 yr in research and teaching, I moved into administration about 2 yr ago. Thus I shall discuss with you the image of weed science as a recent outsider, which I consider myself. From this perspective, I want to point out both the positive and negative aspects of our weed science image. In other words, what are our strengths and weaknesses? Can we build on our strengths and overcome our weaknesses?
Turfgrass Species Response to Herbicides Applied Postemergence
Authors: Johnson Billy J.
Published: March 2018

Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one} at 0.34 kg ai/ha, fluazifop {(+)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} at 0.13 kg ai/ha, and SC-1084 {3-hydroxy-4-[4-[[5-trifluoromethyl)-2-pyridinyl] oxy] phenoxy] pentanoic acid} at 0.28 kg ai/ha controlled ‘Tifway’ bermudagrass [Cynodon transvaalensisBurtt-Davy #3CYNTR] x [Cynodon dactylon(L.) Pers. # CYNDA] nearly 100% when applied for 2 consecutive years. Tall fescue (Festuca arundinaceaSchreb. ‘Ky 31’ # FESAR) tolerated fluazifop at 0.13 kg/ha and SC-1084 at 0.07 to 0.28 kg/ha; however, centipedegrass [Eremochloa ophiuroides(Munro) Hack, ‘common’ #ERLOP] and zoysiagrass (Zoysia japonicaSteud. # ZOYJA xZoysia tenuifoliaWilld. ex trin. ‘Emerald’ #ZOYTE did not tolerate these treatments. Centipedegrass tolerated sethoxydim, zoysiagrass tolerance was intermediate, and tall fescue was injured severely. Sethoxydim at 0.22 kg/ha discolored leaves of zoysiagrass, but the turf recovered fully. Thus, bermudagrass, when mixed with either tall fescue, centipedegrass, or zoysiagrass, can be controlled selectively with herbicides applied postemergence.
Common Lambsquarters (Chenopodium album) Interference in Spring Barley
Authors: Conn Jeffery S. , Thomas Dana L.
Published: March 2018

The effect of common lambsquarters (Chenopodium albumL. #3CHEAL) density on spring barley (Hordeum vulgareL. ‘Lidal’) was studied in a 2-yr field experiment near Fairbanks, AK. The data were fit to a rectangular hyperbola model. Common lambsquarters densities explained 74 to 75% of the variability in barley yield. The maximum yield loss attributable to common lambsquarters was 23% in 1982 and 36% in 1983.
A Rotary Herbicide Wiper for Postemergence Weed Control in Perennial Horticultural Crops
Authors: Welker William V. , Peterson Donald L.
Published: March 2018

A rotary wiper was developed to apply herbicides selectively to weeds beneath horticultural crops such as fruit trees and ornamentals. Herbicide is delivered internally through a circular pipe manifold imbedded in a rotary polyurethane foam disk, thus avoiding herbicide drift. A free-wheeling bumper wheel, larger than the wiper disk, is mounted just above the disk causing it to move around a tree trunk or shrub on contact. The rotary wiper effectively applied herbicides to weeds within the row of fruit trees.
Enhanced Biodegradation of Herbicides in Soil and Effects on Weed Control
Authors: Harvey R. Gordon , Dekker J. H. , Fawcett Richard S. , Roeth Fred W. , Wilson Robert G.
Published: March 2018

Research conducted since 1979 in the north central United States and southern Canada demonstrated that after repeated annual applications of the same thiocarbamate herbicide to the same field, control of some difficult-to-control weed species was reduced. Laboratory studies of herbicide degradation in soils from these fields indicated that these performance failures were due to more rapid or “enhanced” biodegradation of the thiocarbamate herbicides after repeated use with a shorter period during which effective herbicide levels remained in the soils. Weeds such as wild proso millet [Panicum miliaceumL. spp.ruderale(Kitagawa) Tzevelev. #3PANMI] and shattercane [Sorghum bicolor(L.) Moench. # SORVU] which germinate over long time periods were most likely to escape these herbicides after repeated use. Adding dietholate (O,O-diethylO-phenyl phosphorothioate) to EPTC (S-ethyl dipropyl carbamothioate) reduced problems caused by enhanced EPTC biodegradation in soils treated previously with EPTC alone but not in soils previously treated with EPTC plus dietholate. While previous use of other thiocarbamate herbicides frequently enhanced biodegradation of EPTC or butylate [S-ethyl bis(2-methylpropyl)carbamothioate], previous use of other classes of herbicides or the insecticide carbofuran (2,3 -dihydro-2,2 -dimethyl-7-benzofuranyl methylcarbamate) did not. Enhanced biodegradation of herbicides other than the thiocarbamates was not observed.
Woollyleaf Bursage (Ambrosia grayi) and Texas Blueweed (Helianthus ciliaris) Control by Dicamba
Authors: Keeling J. Wayne , Abernathy John R.
Published: March 2018

Woollyleaf bursage [Ambrosia grayi(A. Nels.) Shinners # AMBGR] and Texas blueweed (Helianthus ciliarisDC. # HELCI) increasingly are weed problems on the Texas High Plains. Field experiments were established to evaluate dimethylamine, potassium, sodium, calcium, and aluminum salts of dicamba (3,6-dichloro-2-methoxybenzoic acid) applied at 1.1, 2.2, and 4.4 kg ai/ha to infestations of each species. Initial woollyleaf bursage control was better than initial Texas blueweed control. Dimethylamine and potassium salts provided highest control levels, and increasing rates improved control. One-year control was higher for Texas blueweed than woollyleaf bursage, and 1-yr control of both species improved with increased rates.
Effects of Bentazon, Imazaquin, or Chlorimuron on Haloxyfop or Fluazifop-P Efficacy
Authors: Croon Kent A. , Merkle Morris G.
Published: March 2018

Field studies were conducted to measure the response of sorghum [Sorghum bicolor(L.) Moench. ‘Conlee's Top Hand’] to foliar applications of haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} or fluazifop-P {(R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} plus either bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] at 0.84 kg ai/ha imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} at 0.21 kg ae/ha, or chlorimuron {2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl) amino] carbonyl] amino] sulfonyl] benzoic acid} at 12 g ae/ha. Tank-mixing imazaquin or chlorimuron with haloxyfop or fluazifop-P reduced phytotoxicity to sorghum 12 days after treatment (DAT) by 14 to 64% compared to applications of haloxyfop or fluazifop-P alone. Much of this antagonism was reduced 24 DAT as imazaquin and chlorimuron apparently delayed the activity of haloxyfop and fluazifop-P when losses in activity ranged from 13 to 21%. Increases in haloxyfop and fluazifop-P rates tended to reduce the severity of the antagonism. Tank-mixing bentazon with haloxyfop or fluazifop-P did not reduce phytotoxicity to sorghum compared to applications of haloxyfop and fluazifop-P alone.
Johnsongrass (Sorghum halepense) Management Systems
Authors: Bendixen Leo E.
Published: March 2018

Crop-herbicide systems for johnsongrass [Sorghum halepense(L.) Pers. # SORHA] control were compared in a 5-yr study at two locations in central Ohio. Monocultures of corn (Zea maysL.) and soybeans [Glycine max(L.) Merr.] were compared with a 3-yr rotation of corn, soybeans, and winter wheat (Triticum aestivumL.). Johnsongrass was controlled most effectively (over 95%) when glyphosate [N-(phosphonomethyl) glycine] was applied to emerged johnsongrass, followed by moldboard plowing, preplant incorporated (PPI) application of trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], then soybean planting (MS-G-T). The second best control was in corn (over 90%) treated PPI with EPTC (S-ethyl dipropylcarbamothioate) in the rotation (RC-E). Johnsongrass control was least in monocultured corn treated PPI with EPTC (MC-E) and in monocultured soybeans treated PPI with trifluralin (MS-T).
Establishing a Weed Nursery with Low Construction Costs and Maintenance Requirements
Authors: Moshier Loren J. , Swallow Clarence W.
Published: March 2018

A nursery of economically important weeds in Kansas field crops, representing 15 families, was designed to include 32 species from the Magnoliopsida (dicotyledons) class and 16 species from the Liliopsida (monocotyledons) class. Using hydraulically operated equipment, 48 facricated metal cylinders 60 cm in both diameter and length were inserted in 4 h. Cylinders were inserted 40 cm deep on an established turf site and were filled with Muir silt loam collected near Manhattan, KS. Thirty summer annual species, nine perennial species, and one biennial species were transplanted in the spring; and eight winter annual species either were seeded or were transplanted in the fall. All species except tall waterhemp (Amaranthus tuberculatus (Moq.) J.D. Sauer # AMATU), a dioecious species, Russian thistle (Salsola iberica Sennen & Pau # SASKR), and unicorn-plant [Proboscidea louisianica (Mill.) Thellung # PROLO] successfully propagated themselves from either seed or buds. Labor requirements for healthy plant growth and overall nursery attractiveness were estimated at 50 h/yr. Installation costs prorated over a 10-yr period plus annual labor costs totaled $300/yr.
Population Modeling Approach for Evaluating Leafy Spurge (Euphorbia esula) Development and Control
Authors: Maxwell Bruce D. , Wilson Mark V. , Radosevich Steven R.
Published: March 2018

Weed population models can serve as a framework to organize weed biology information and to develop weed control strategies. Models help to identify information gaps, to set research priorities, to develop hypotheses pertinent to weed population regulation, and to suggest control strategies. A population simulation model of leafy spurge (Euphorbia esulaL. # EPHES) was used to demonstrate the applicability of population models to weed science. Sensitivity analysis of an existing leafy spurge model indicated that transition from basal buds to vegetative shoots, survival of vegetative shoots, and survival of basal buds over winter were important transition parameters influencing population growth of this weed species. Possible mechanisms (intraspecific competition and environmental factors) that influence the transition from basal buds to vegetative shoots were shown. Intraspecific density effects on basal bud transition and production were included to show model refinement and second-generation model development. Four control strategies were simulated and were compared to field studies to show the predictive and management potential of the modeling approach. Simulations of population response to foliage feeding herbivores was highly correlated (r = 0.98) with field data for sheep grazing on leafy spurge. Simulation of picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) applied to leafy spurge also was correlated (r = 0.97) with field results.
Postattachment Control of Swamp Dodder (Cuscuta gronovii) in Cranberry (Vaccinium macrocarpon) and Carrot (Daucus carota)
Authors: Bewick Thomas A. , Binning Larry K. , Dana Malcolm N.
Published: March 2018

In a 3-y field study, the isopropylamine salt of glyphosate [N-(phosphonomethyl)glycine] at 1.7 kg ai/ha and sulphosate [trimethyl sulfonium salt of N-(phosphonomethyl)glycine] at three rates, a split application of 0.6 + 0.6 or single applications of 1.1 or 1.7 kg ai/ha satisfactorily controlled swamp dodder (Cuscuta gronoviiWilld. ex R. & S. # CVCGR) in cranberry (Vaccinium macrocarponAit.). While none of these treatments decreased cranberry yield, sulphosate at 1.1 or 1.7 kg/ha did increase yield. Glyphosate at 0.4 kg/ha applied late in the life cycle of carrot (Daucus carotaL.) when swamp dodder was in full flower satisfactorily controlled swamp dodder while increasing yield of carrot roots. Glyphosate applied early in the life cycle of carrot and dodder controlled swamp dodder but lowered yield of carrot roots.
Identification of Grass and Morningglory Species with Simple Dichotomous Keys
Authors: Murdock Edward C. , Guice J. Bradley , Toler Joe E.
Published: March 2018

Agriprofessionals and technical college students took an examination without and with simple dichotomous keys. Without keys, only 15% and 30% of the agriprofessionals identified 71% or more of the grass and morningglory species (Ipomoeaspp. # IPOZZ), respectively; 97% scored in this range for both weed groups with keys. Without keys, no student scored higher than 40% or 30% on grass and morningglory species, respectively. With keys, all students identified more than 60% and 50% of the grasses and morningglories, respectively. For grasses, only 3% of the agriprofessionals and none of the students achieved an excellent (>90%) score without keys, while 56% and 8% did with keys. Twelve percent and 65% of the agriprofessionals achieved an excellent score on the morningglory species without and with keys, respectively; 42% of the students scored higher than 80% with keys.
Seed Wasp on Multiflora Rose, Rosa multiflora, in Virginia
Authors: Mays Warren T. , Kok Loke-Tuck
Published: March 2018

Multiflora rose is a major weed in pastures, highway embankments, and recreational areas. A chalcid wasp, Megastigmus aculeatus (Swederus) (Hymenoptera: Torymidae), which feeds on the multiflora rose seeds, is a potential biological control agent for this weed. Distribution of multiflora rose and the seed wasp was studied from 1983 to 1986 in Virginia. Multiflora achenes collected from 58 sites in 51 counties showed that M. aculeatus was present in all but one of the counties surveyed; female:male sex ratio was high (94:1), indicating parthenogenesis. Infestation rates of the achenes averaged 26.5% in 1985 and 23.9% in 1986. Severe winter temperatures appear to affect the wasp population adversely.
Control of Texas Gourd,Cucurbita texana, withFusarium solanif. sp.cucurbitae
Authors: Weidemann Gregory J. , Templeton George E.
Published: March 2018

The soil-borne fungus,Fusarium solani(Mart.) App. & Wr. f. sp.cucurbitae, has shown potential as a mycoherbicide to control Texas gourd. Formulations and times of application that effectively controlled Texas gourd were determined in field studies. Aqueous conidial suspensions (1 × 108microconidia/ml) were applied preplant incorporated, postemergence, or both at 280 L/ha alone or combined with trifluralin at 1 kg ai/ha. Alginate granules containing fungal spores and hyphae and amended with 2% (w/v) soyflour were applied pre- or postemergence at 220 kg/ha alone or sequentially with conidial applications. Mortality of 70% or greater was achieved with eight of nine fungal treatments. The fungus applied as conidia combined with trifluralin, as well as trifluralin alone, significantly reduced Texas gourd emergence.
Bentazon Reduces Rust-Induced Disease in Yellow Nutsedge,Cyperus esculentus
Authors: Bruckart William L. , Johnson Dennis R. , Frank J. Ray
Published: March 2018

Puccinia canaliculata(Schw.) Lagerh. from Salisbury, MD, identified in greenhouse tests as specific to yellow nutsedge, was field evaluated for biological control of yellow nutsedge over a 2-yr period. Treatments included all combinations ofP. canaliculataand 0.3 or 0.6 kg ai/ha benzaton. Disease development was reduced 50% by treatment with bentazon, compared withP. canaliculataalone.P. canaliculatareduced tuber recovery by 44%. Phytotoxicity was significantly higher from the rust treatments than controls. Treatment with P.canaliculatadid not affect the number of shoots/m2.
Common Waterplantain,Alisma plantago-aquatica, Control in Wild Rice,Zizania palustris, with MCPA and 2,4-D
Authors: Ransom Joel K. , Oelke Ervin A.
Published: March 2018

Field experiments were conducted to evaluate the effect of application time on common waterplantain control in wild rice with MCPA and 2,4-D. Common waterplantain control was greatest when MCPA or 2,4-D were applied at 1.1 or 1.7 kg ai/ha at the two-aerial leaf stage. The best late-season control was MCPA applied at the scape elongation growth stage. Common waterplantain was controlled adequately when 0.6 to 0.8 kg/ha of MCPA were applied at the scape elongation or early flowering stage. However, because of common water plantain interference and sensitivity of wild rice to late herbicide applications, the best treatment stage for wild rice yield was when MCPA was applied at 0.6 kg/ha to common waterplantain at the two-aerial leaf stage. Wild rice at this time is at the more tolerant one-aerial leaf growth stage.
Evaluation of Acetanilide Injury and Its Potential for Yield Reduction in Cabbage,Brassica oleraceaL.
Authors: Bellinder Robin R. , Warholic Donald T.
Published: March 2018

Field studies were conducted from 1984 to 1986 to assess cabbage injury and yield response to several acetanilide herbicides. When incorporated, metolachlor significantly injured cabbage and reduced yields while post-transplant applications caused foliar flecking but did not reduce yields. Crop injury from pretransplant applications of 4.4 kg ai/ha was significant for all herbicides in both 1985 and 1986. Although total yields in 1985 and 1986 were comparable, maturity was delayed in 1986. With few exceptions, the acetanilides did not differ in either injury or yield-reducing potential. However, compared to trifluralin, metolachlor reduced yields in both years and at both rates.
Established Foxtail Barley,Hordeum jubatum, Control with Glyphosate Plus Ammonium Sulfate
Authors: Donald William W.
Published: March 2018

The spread of perennial weeds, such as foxtail barley, is a prime deterrent to adoption of no-till cereal production in the Northern Great Plains. In a 3-yr study, the isopropylamine salt of glyphosate at 0.56 kg ai/ha plus nonionic surfactant at 0.25% (v/v) did not control established perennial foxtail barley in early spring. However, adding ammonium sulfate at 2.8 kg/ha to glyphosate plus surfactant improved the effectiveness and year-to-year consistency of glyphosate for killing this weed. This spring treatment fits into no-till farm practice in the Northern Great Plains, providing no-till farmers with a defined strategy to manage this perennial bunch-grass weed.
Thistles II: Sonchus and Centaurea
Authors: Mitich Larry W.
Published: March 2018

The thistle invasion in the United States which began over 3 centuries ago included plumed thistles, pasture thistles, swamp thistles, and lance thistles, comprising more than 120 species.
Presidential Address: Cooperation, Contribution, Communication, and Commitment
Authors: Dawson J. H.
Published: March 2018

Weed Science is knowledge about unwanted plants and about methods to control such plants. The concept “weeds” probably was born when man first learned that desirable plants would grow better if surrounding plants were killed. Knowledge of elementary weed control began when man learned that unwanted plants died if they were separated from the soil. Thus rudimentary Weed Science is as old as man's efforts to grow crop plants.
Honorary Member Address: Weed Science in Germany
Authors: Koch Werner
Published: March 2018

Plants are components of ecosystems (Figure 1). The primary or sole target of an agro-ecosystem is still production. Production systems are centered around two points: the ecosystem and the socio-economic system (Figure 2). Weeds, except parasitic weeds, are primary producers and compete with the crop plants. They may have beneficial effects besides their detrimental ones. Weeds are, therefore, plants which are more harmful than beneficial.
Control of Seedling Grasses with Postemergence Grass Herbicides
Authors: Brewster Bill D. , Spinney Robert L.
Published: March 2018

Field experiments were conducted in 1982 through 1986 to evaluate the effect of six postemergence grass herbicides, clethodim, the methyl ester of diclofop, the butyl ester of fluazifop-P, the methyl ester of haloxyfop, the methyl ester of quizalofop, and sethoxydim, on 31 seedling grass species. All herbicides except diclofop controlled most of the species tested. None of the herbicides controlled rattail fescue or red fescue. Only clethodim and haloxyfop controlled annual bluegrass.
Relative Susceptibility of Oats (Avena sativa) and Wheat (Triticum aestivum) to Fluazifop, Haloxyfop, and Sethoxydim
Authors: Beardmore Richard A. , Linscott Dean L.
Published: March 2018

The purpose of the research was to determine the effect of several postemergence herbicides on transpiration and growth of seedling oats and wheat. Fluazifop, haloxyfop, and sethoxydim were applied postemergence at various rates to oats and wheat in the 1- to 2-leaf stage in controlled environment rooms and the field. In all cases where transpiration was reduced significantly, oats were affected more than wheat. Generally, haloxyfop and sethoxydim in both controlled environments and the field suppressed oat growth more than wheat. Fluazifop controlled both small grain species equally in the field, but oats were suppressed more under controlled environment conditions. Effects of the three herbicides were always greater in the controlled environments than in the field.
Control of Wasatch Milkvetch (Astragalus miservar.oblongifolius) and Associated Species on Mountain Rangeland
Authors: Williams M. C. , Ralphs M. H.
Published: March 2018

Eight herbicides or herbicide combinations were evaluated for control of Wasatch milkvetch and other broadleaf plants. Triclopyr at 2.2 kg ae/ha controlled Wasatch milkvetch and associated mountain big sagebrush and mulesears 100%. A combination of triclopyr plus dicamba at 1.1 plus 1.1 kg ae/ha also controlled these species. When compared to untreated plots, grass production increased over 400% on plots treated with triclopyr at 1.7 and 2.2 kg/ha and more than 300% on plots treated with triclopyr plus dicamba at 1.1 plus 1.1 kg/ha.
A Statistical Analysis for Area-of-Influence Experiments
Authors: Jordan Nicholas
Published: March 2018

Area-of-influence (AOI3) experiments measure the effect of a single weed on crop growth at intervals away from the weed plant. Effects of treatment variables, e.g., weed species or control measures, on the AOI of a single weed can be estimated. AOI experiments can be analyzed by regression of crop growth on distance from the weed plant, but this analysis violates an important regression assumption: independece of observations. Statistical dependence can occur among successive observations along the row because uncontrolled sources of variation are likely to act in similar ways on adjacent individuals. Multivariate analysis of variance (MANOVA) is a statistical technique that accounts for dependencies among crop growth measurements along the row. The technique tests three hypotheses: first, that different treatments cause weed AOI to differ in spatial distribution of competitive effects; second, that different treatments cause weed AOI to differ in size; and third, that the weed has an effect, i.e., crop growth near the weed differs from growth away from weed. MANOVA can be applied to most common experimental designs, e.g., randomized blocks or split plots, and can be implemented on various mainframe and microcomputer statistical packages.
Minimum Effective Rate of Chlorimuron and Imazaquin Applied to Common Cocklebur (Xanthium strumarium)
Authors: Barrentine William L.
Published: March 2018

A field experiment was conducted in 1986 and 1987 to determine the minimum effective rate (MER)3of imazaquin and chlorimuron applied postemergence to common cocklebur. MER is defined as the quantity required to provide at least 90% control. Based on probit regression analyses, the mean calculated MERs of imazaquin and chlorimuron for 2-leaf common cocklebur were 27.5 and 4.5 g ai/ha, respectively. Under optimum growing conditions, the calculated MERs of imazaquin and chlorimuron for 6-leaf common cocklebur were 34 and 4.6 g/ha, respectively. When applied to 6-leaf plants under slight moisture stress, the calculated MERs for imazaquin and chlorimuron were 54 and 17.4 g/ha, respectively.
Weed Control in Corn (Zea mays) as Affected by Till-Plant Systems and Herbicides
Authors: Schweizer Edward E. , Zimdahl Robert L. , Mickelson Rome H.
Published: March 2018

The impact of three till-plant and two weed management systems on weed seed reserves of soil, yearly weed problems, and corn production was assessed under center-pivot irrigation for 3 consecutive years. Annual weeds were controlled in disced, bedded, and strip rotary till-plant systems with a moderate or intensive level of herbicides. Weed seed of seven annual weed species were identified, with common lambsquarters and stinkgrass, comprising 45 and 41%, respectively, of the initial 305 million seed/ha in the upper 25 cm of the soil profile. After the third cropping year, overall decline in total seed number in soil was 45% when averaged over till-plant and weed management systems. Grain yields did not differ between weed management systems, but the disced till-plant system produced 16% less grain than the bedded and strip rotary till-plant systems over 2 yr.
Seed Bank Longevity of Common Crupina (Crupina vulgaris) in Natural Populations
Authors: Zamora David L. , Thill Donald C.
Published: March 2018

Seedling emergence and seed bank longevity were followed in field experiments with natural populations of common crupina for 4 yr. Emergence the first fall after dissemination was 90 to 98% of all seedlings eventually to emerge from the seedbank. Seedling emergence over time did not differ between plots which either were treated with the potassium salt of picloram or were hand weeded. No viable seed remained in the soil 25 to 26 months after seed production stopped. Five locations in a common crupina infestation undergoing eradication were sampled for seed in the soil. No viable seeds were found during the first year of the eradication, and no intact seeds were found after 4 yr.
Loss of Metribuzin and Ethyl-metribuzin from Glass and Soil Surfaces
Authors: Peek Daniel C. , Appleby Arnold P.
Published: March 2018

The loss of metribuzin and ethyl-metribuzin from soil and glass surfaces was studied to determine if volatilization and/or photodegradation could explain inconsistent weed control with these herbicides. In growth chamber experiments, phytotoxicity of ethyl-metribuzin decreased as the time between surface application and initial watering increased. Approximately 50% of the applied metribuzin and ethyl-metribuzin volatilized from soil within 24 h, with an additional 15 to 20% lost during the next 11 days, except about 5% additional ethyl-metribuzin was lost from Chehalis sandy loam. Both herbicides volatilized more rapidly from glass than from soil, with 75 to 90% of the loss occurring within 24 h and as great as 99% loss after 12 days. Loss by photodecomposition from soil or glass surfaces was minimal.
Role of Humified Organic Matter in Herbicide Adsorption
Authors: Shea Patrick J.
Published: March 2018

Organic matter is the soil constituent most often associated with herbicide adsorption. Structural diversity makes humified organic material an ideal substrate for the adsorption of many pesticides, but variability in composition and distribution in situ complicates interpretation of its quantitative effect on adsorption. Variability in the adsorption distribution coefficient (KD) of a herbicide among soils often is due to differences in organic matter content and can be reduced by adjusting KDfor soil organic carbon content and computing the organic carbon partition coefficient (Koc). Koccan be estimated from the octanol-water partition coefficient (Kow) of organic compounds, but the correlation weakens as compound polarity increases. Kocalso can be correlated with aqueous solubility if a correction is made for the melting point of compounds that are solids at 25 C. Relative adsorption can be estimated from parachor and molecular connectivity indices; but corrections are needed for polar compounds, and correlations with KDor Kochave been variable. Such predictive methods may be useful for broad classification purposes, but accurate extrapolation generally requires site-specific adsorption measurements. Empirical models which accommodate the multiple regression of organic matter content and other soil properties such as clay content, pH, and cation exchange capacity on herbicide adsorption can increase accuracy, but interpretation may be restricted to a small number of sites.
Behavior of Dinitroaniline Herbicides in Plants
Authors: Appleby Arnold P. , Valverde Bernal E.
Published: March 2018

Dinitroaniline herbicides are absorbed readily by roots and emerging shoots, but shoot exposure is more phytotoxic. Translocation within the plant varies by specific herbicide but commonly is minor. Dinitroaniline herbicides injure plants by binding to tubulin, a dimer protein in the ceil that polymerizes to form microtubules (MTs). MTs form the major part of the mitotic apparatus, including spindle fibers, which enable chromosomes to separate during cell division. Dinitroaniline herbicides prevent tubulin from polymerizing into MTs, thus arresting mitosis. This leads to abnormal cells with more than the normal complement of chromosomes and, frequently, lobed nuclei. MTs also are responsible for orienting cell wall microfibrils in such a way that they prevent lateral enlargement of cells. Treatment with dinitroaniline herbicides leads to disorientation of the microfibrils, leading to one of the common symptoms—spherical cells instead of rectangular ones. Studies on the metabolism of trifluralin in plants have shown that amination, dealkylation, and cyclization all can occur. However, metabolites often amount to a small percentage of the original herbicide. In general, trifluralin seems quite stable within the plant.
The Impact of Adjuvants on Herbicide Antagonism
Authors: Penner Donald
Published: March 2018

Adjuvants are used to improve spray delivery, to increase spray retention on weed foliage, and to enhance foliar penetration by postemergence herbicides for increased herbicide efficacy. Numerous factors govern adjuvant efficacy, including the specific herbicide, plant species, and environmental conditions. Adding superior surfactants as adjuvants to a sethoxydim tank mix with Na-bentazon may overcome the Na-bentazon antagonsim of sethoxydim activity by facilitating increased sethoxydim absorption and by masking the antagonism similar to increasing the sethoxydim rate. Herbicides such as Na-bentazon contribute alkaline or alkaline earth cations that can form salts of a weakly acidic herbicide such as sethoxydim that are not absorbed readily by the plant. Adding abundant ammonium from ammonium sulfate or other sources may prevent and/or may overcome this antagonism.
Control and Seedhead Suppression of Red Rice (Oryza sativa) in Soybeans (Glycine max)
Authors: Salzman Frederick P. , Smith Roy J. , Talbert Ronald E.
Published: March 2018

Experiments were conducted in 1985 and 1986 at three locations in eastern Arkansas to evaluate red rice control in soybeans with postemergence grass herbicides and plant growth regulators applied singly or sequentially at early to late-tillering growth stages of red rice. Haloxyfop at 0.21 kg ai/ha and quizalofop at 0.14 kg ai/ha applied singly or sequentially and fluazifop at 0.21 kg ai/ha applied sequentially consistently controlled red rice and suppressed seedhead production in soybeans. Mid-season treatments were not beneficial when high soil moisture stress conditions existed. Mefluidide or sethoxydim applied singly or sequentially or amidochlor applied singly provided erratic control and seedhead suppression of red rice in soybeans.
Corn (Zea mays) Tolerance and Weed Control with Thiameturon
Authors: Eberlein Charlotte V. , Miller Timothy L.
Published: March 2018

Weed control with thiameturon applied postemergence at 8 to 32 g ai/ha varied with species, growth stage, addition of surfactant, and environmental conditions. Pennsylvania smartweed control was excellent, velvetleaf control ranged from poor to excellent, and common lambsquarters control was poor with thiameturon applied without surfactant. When surfactant was added to the thiameturon spray mixture, velvetleaf and common lambsquarters control was >85% at 8 g/ha when weeds were growing actively and at 16 g/ha when weeds were under moisture stress. However, in weed-free studies, corn yields were reduced by 35 kg/ha for each 1 g/ha thiameturon applied in 1986 and by 10 kg/ha for each 1 g/ha thiameturon applied in 1987 when surfactant was added to the spray mixture. When no surfactant was added, yields were reduced 12 kg/ha for each 1 g/ha thiameturon applied in 1986 but were not reduced in 1987.
Adsorption and Deactivation of Norflurazon by Activated Charcoal
Authors: Lamoreaux Robert J. , Corbin Virginia L. , Johl Balraj S.
Published: March 2018

Laboratory and greenhouse experiments were conducted to determine if activated charcoal can remove norflurazon from water and from a sand matrix, thereby reducing its availability for plant uptake. A ratio of approximately 10:1 activated charcoal:norflurazon completely inactivated norflurazon in water. In a sand matrix, activated charcoal: norflurazon ratios of approximately 100:1 and 200 to 300:1 completely reduced norflurazon injury to cotton and to soybean and corn, respectively. The amount of activated charcoal required to remove norflurazon from soil was estimated from bioassay and regression analyses. The accuracy of this method to eliminate injury to cotton without reducing control of prickly sida and seedling johnsongrass was confirmed by bioassay using a sandy loam soil.
Application Timing of Metribuzin, Chlorimuron, and Imazaquin for Common Cocklebur (Xanthium strumarium) Control
Authors: Wesley Richard A. , Shaw David R. , Barrentine William L.
Published: March 2018

Field experiments were conducted in 1986 and 1987 to evaluate the effect of herbicide rate (two-thirds and maximum labeled rate) and timing of application before soybean planting on common cocklebur control. In 1986, chlorimuron plus metribuzin at 50 plus 320 and 80 plus 480 g ai/ha and imazaquin at 90 g ai/ha applied at planting controlled common cocklebur better than when applied 4 weeks before planting (WBP). Imazaquin at 140 g/ha applied at planting controlled common cocklebur better than when applied 6 WBP. All treatments at two-thirds of the labeled rate applied at planting controlled common cocklebur comparable to the full labeled rate applied 2, 4, or 6 WBP. In 1987, all treatments applied 2 WBP controlled common cocklebur better than when applied 4, 6, or 8 WPB.
HOE-39866 use in Chemical Fallow Systems
Authors: Blackshaw Robert E.
Published: March 2018

Studies were conducted to determine the usefulness of HOE-39866 (HOE-00661) in chemical fallow systems on the Canadian prairies. HOE-39866 at 0.5 to 1.0 kg ai/ha controlled Russian thistle, kochia, green foxtail, wild oats, and wheat comparable to paraquat, glyphosate, and glyphosate plus the isopropylamine salt of 2,4-D. However, control of barley with HOE-39866 was unacceptable. HOE-39866 was compatible in tank mixtures with ammonium sulfate, paraquat, chlorsulfuron, and metsulfuron. Ammonium sulfate improved weed control when HOE-39866 was applied at 0.25 kg/ha but not at 0.75 kg/ha. Adding paraquat at 0.07 to 0.21 kg ai/ha to HOE-39866 improved control of grass species over HOE-39866 alone. Adding chlorsulfuron and metsulfuron to HOE-39866 provided greater initial control of certain species as well as residual control of many weeds. HOE-39866 alone or in conjunction with other herbicides is an alternative to the herbicides used in chemical fallow systems.
Survival of Leafy Spurge Hawk Moths (Hyles euphorbiae) When Larvae Are Exposed to 2,4-D or Picloram
Authors: Rees Norman E. , Fay Peter K.
Published: March 2018

Larvae of the leafy spurge hawk moth were sprayed with and/or were fed leafy spurge plants sprayed with 2,4-D or picloram. Larval survival was not affected from contact with the chemicals, from feeding on contaminated foliage, or from a combination of both. Viable second-generation adult moths were produced in all treatments. Thus, leafy spurge infested with the leafy spurge hawk moth can be sprayed with 2,4-D or picloram without injury to larvae that have reached the fourth or fifth instar stages.
The Toxicity of Tansy Ragwort
Authors: Howatt Stephen
Published: March 2018

Tansy ragwort (Senecio jacobaea L.), commonly called stinking willie and sometimes incorrectly called ragweed, is an abundant weed in many parts of Prince Edward Island and Nova Scotia. It is found in pastures, hayfields, waste areas, clearings in woodland and along roadsides. This species is extremely poisonous to cattle and horses and thus is a problem in pastures.
Biocontrol of Three Leguminous Weed Species withAlternaria cassiae
Authors: Boyette C. Douglas
Published: March 2018

Alternaria cassiaeJurair and Khan applied as conidia at 1 × 105spores/ml controlled 100% of sicklepod, and 1 × 106spores/ml controlled coffee senna in the greenhouse. In the field, sicklepod control did not differ between one or two fungal applications, but coffee senna control increased following two applications. Although showy crotalaria resistedA. cassiaeinfection more than the other two weeds, total biomass was reduced significantly in both greenhouse and field tests.
Downy Brome (Bromus tectorum) Control in Winter Wheat
Authors: Swan Dean G. , Whitesides Ralph E.
Published: March 2018

Metribuzin at 0.42 kg ai/ha and metribuzin plus terbutryn at 0.28 plus 0.67 kg/ha were applied in the fall and spring to control downy brome in winter wheat from 1981 through 1985. Downy brome control averaged 88% from the fall-applied treatments and 63% from the spring-applied treatments. Yields from the fall- and spring-applied treatments averaged 136% and 132% of the check, respectively. Metribuzin plus terbutryn fall-applied controlled downy brome best (93%), and wheat yields were significantly higher than the checks in all experiments. Moreover, as downy brome density among locations increased, wheat yields decreased.
Combine Harvesting Affects Weed Seed Germination
Authors: Currie Randall S. , Peeper Thomas F.
Published: March 2018

Seed of three weed species collected from the grain bins of combines while standing hard red winter wheat was harvested germinated better than hand-harvested seed. Combine-harvested curly dock seed germinated from 4 to 24% more than hand-harvested seed. Curly dock seed harvested with a commercial-type combine germinated better than those harvested with a small-plot combine. Harvesting slimleaf lambsquarters and Venice mallow seed with a commercial-type combine also enhanced germination compared to hand-harvested seed.
Mitotic Disrupters from Higher Plants and Their potential uses as Herbicides
Authors: Vaughan Martin A. , Vaughn Kevin C.
Published: March 2018

Mitotic disrupters from higher plants have been studied for their effects on animal cells, but their effects on plant cells have been studied less. The plant-derived compounds have counterparts among herbicides with respect to cellular effects and, in some cases, mode of action. Cellular effects in common are arrested prometaphases (colchicine, dinitroanilines), multipolar divisions (Vincaalkaloids, carbamates), and production of binucleate cells (caffeine, dichlobenil). The potential of these natural compounds, either directly or as the basis of new chemistries for herbicides, has remained largely untapped.
Tentoxin, a Chlorosis-Inducing Toxin fromAlternariaas a Potential Herbicide
Authors: Lax Alan R. , Shepherd Hurley S. , Edwards Judson V.
Published: March 2018

The potential for use of compounds isolated from diverse sources, ranging from microbial to higher plants, has received increasing attention. These natural products represent a vast array of chemistries and mechanisms of action often having the requisite specificities to be ideal herbicides. Tentoxin, a cyclic tetrapeptide, has potent chlorosis activity on a variety of weeds of soybean and corn while not affecting these crops. Investigations into this toxin's mechanism suggest several enzyme target sites for the development of herbicidal analogues, each having the inherent specificity of the parent compound. Structure/activity relationships determined so far may permit a directed synthesis of efficacious analogues. New insights into biosynthesis of the toxin suggest possible means of increasing production to allow economical exploitation of the toxin itself as a herbicide.