bluuebunny/crossref_metadata_2025 huggingface dataset:
Survey for Picloram in North Dakota Groundwater
Authors: Lym Rodney G. , Messersmith Calvin G.
Published: March 2018

Wells and streams in 10 North Dakota counties were surveyed for picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), the major herbicide used to control leafy spurge (Euphorbia esulaL. # EPHES). Three rivers and 144 wells were sampled in 1985. Picloram concentration ranged from <0.1 to 12.4 ppb in the water from five wells in five counties and from <0.1 to 6 ppb in two rivers. An additional 44 wells were sampled in 1986; they were located within 2 km of the five wells where picloram was detected in 1985. Picloram concentrations in 1986 ranged from non-detectable to 6.7 ppb in the original contaminated wells and was 0.97 ppb in water from one of the additional 44 wells. Picloram concentration in the river water was lower in 1986 than in 1985 but was detected farther downstream. All contaminated wells were within 1.5 km of an area treated for leafy spurge, but picloram had been spilled accidentally or misapplied near all but one of the wells. The concentrations detected were at least 100 times below suggested tolerance levels for water.
New Technological Developments to Reduce Groundwater Contamination by Herbicides
Authors: Schweizer Edward E.
Published: March 2018

Strategies to prevent chemical contamination of groundwater will be more effective and cost less than cleaning up groundwater. Advances in weed control technologies have improved timing of herbicide applications, have reduced application rates from kg/ha to g/ha, and have distributed herbicides better within the weed-crop complex. These technologies include microbial pesticides, controlled-release formulations, herbicide chemistry, improved integrated weed management systems, and bioeconomic weed-crop models that reduce herbicide use. These new technologies should reduce the quantity of herbicides used by farmers and lessen the chances of groundwater contamination.
Influence of Tillage on Horseweed,Conyza canadensis
Authors: Brown Steven M. , Whitwell Ted
Published: March 2018

Conservation tillage systems for cotton production were monitored for their influence on horseweed populations. Without fall tillage, horseweed became established and was present the following spring. Disking in the fall or spring controlled horseweed for the subsequent cotton crop.
Wheat(Triticum aestivum)Response to Triallate Plus Chlorsulfuron
Authors: Gillespie Greg R. , Nalewaja John D.
Published: March 2018

Greenhouse experiments were conducted to determine ‘Len’ hard red spring wheat response to triallate and chlorsulfuron applied separately and together. Chlorsulfuron at 12 or 23 g/ha plus preplant incorporated (PPI) triallate at 1120 g/ha antagonized triallate toxicity to wheat. Chlorsulfuron reduced triallate injury to wheat less when applied preemergence (PRE) after PPI triallate compared to both herbicides applied PPI. Soaking wheat seeds in 21 and 31 ppbw chlorsulfuron solutions for 24 h before placing into triallate-treated soil did not reduce triallate injury to wheat. Applying chlorsulfuron to triallate did not reduce triallate toxicity to wild oats.
Fenoxaprop for Grass Control in Dry Seeded Rice (Oryza sativa)
Authors: Khodayari Khosro , Nastasi Paolo , Smith Roy J.
Published: March 2018

Barnyardgrass and bearded sprangletop are severe weed pests in rice in the southern United States. These weeds are controlled with standard herbicide programs of propanil alone or propanil combined with pendimethalin or thiobencarb. However, new herbicides, such as fenoxaprop, may be effective alternatives for grass weed control in rice. Fenoxaprop at 0.17 kg ai/ha applied postemergence in programs with propanil, thiobencarb, or pendimethalin controlled barnyardgrass and bearded sprangletop in rice and performed as well as or better than standard treatments of propanil with thiobencarb or pendimethalin. Rice yielded well, and grain was of high quality.
Giant Foxtail (Setaria faberi) Control in Full-Season No-Till Soybeans (Glycine max)
Authors: Ritter Ronald L. , Kaufman Lisa M.
Published: March 2018

Alachlor plus linuron tank mixed with paraquat and applied preemergence (PRE) did not control giant foxtail all season in full-season no-till soybeans. Alachlor applied early preplant (EPP) plus PRE was necessary to control (>70%) giant foxtail acceptably all season. Metolachlor applied PRE or EPP plus PRE were equally effective in controlling giant foxtail (71 to 74%). Oryzalin at 1.7 or 2.2 kg ai/ha applied fall or spring EPP controlled giant foxtail better than 70% through July. Oryzalin applied PRE did not control giant foxtail acceptably.
Comparative Persistence and Mobility of Pyridine and Phenoxy Herbicides in Soil
Authors: Jotcham James R. , Smith David W. , Stephenson Gerald R.
Published: March 2018

Bioassays with soybeans and lentils were used to compare the persistence of 2,4,5-T, triclopyr, and picloram in soil after applying 0.038, 0.38, and 3.8 kg ae/ha under field conditions. Soil samples were collected from 1 to 269 days after spraying and were kept frozen until growth room bioassays were conducted. Triclopyr was slightly less persistent than 2,4,5-T, but neither herbicide was biologically active during the next season. At least 90% of picloram disappeared within 7 months, but its biological activity was more persistent than that of either triclopyr or 2,4,5-T. Nine months after treatment, neither lentils nor soybeans could be grown in soil treated with picloram at 3.8 kg/ka. Triclopyr and 2,4-D had smiilar soil thin layer chromatographic mobilities in four different scils. Picloram was significantly more mobile than either triclopyr or 2,4,5-T, primarily due to its lower adsorption in the soils examined.
Response of Common Cocklebur (Xanthium strumarium) toAlternaria helianthi
Authors: Quimby P. Charles
Published: March 2018

A common sunflower isolate ofAlternaria helianthicollected near Stoneville, MS, was pathogenic to cultivated sunflower and common cocklebur. Soybean, cotton, rice, grain sorghum, corn, wheat, and 22 other weed and crop species/varieties in nine botanical families showed no response or only minor symptoms. Therefore, further research is warranted to determine the potential ofA. helianthias a biocontrol agent against common cocklebur in geographic areas where sunflower is not a crop.
Teaching Weed Identification at Twenty U.S. Universities
Authors: Lindquist John L. , Fay Peter K. , Nelson James E.
Published: March 2018

The methods used to teach weed identification at 20 U.S. universities were obtained for comparison through a telephone survey in December, 1986, and January, 1987. Weed identification is taught as a portion (30%) of the laboratory section in introductory weed science courses. Only five have a separate weed identification course. Field trips frequently are used to teach weed identification. Students must learn from 50 to 125 weed species with some seedling identification. Pressed plant collections of approximately 50 weed species normally are required. Most instructors strongly suggest using live plants and repetition for long-term learning.
Bermudagrass (Cynodon dactylon) Control with Postemergence Herbicides in Peanut (Arachis hypogaea)
Authors: Grichar W. James , Boswell Thurman E.
Published: March 2018

Field experiments were conducted from 1983 through 1987 to evaluate various postemergence grass herbicides on bermudagrass in peanuts. Fluazifop, haloxyfop, and SC-1084 applied once effectively controlled common bermudagrass when less than 8 cm tall, but resulted in variable control when applied to bermudagrass 15 cm or taller. Sethoxydim effectively controlled common bermudagrass one of 2 yr. ‘Coastal’ bermudagrass required two applications of BAS 517, fluazifop-P at 0.21 or 0.28 kg ai/ha, and haloxyfop for control of better than 88%. Clethodim and sethoxydim provided poor to fair control, respectively.
Assessment of Bentazon Tolerance in Pepper (Capsicumsp.)
Authors: Harrison Howard F. , Fery Richard L.
Published: March 2018

Preliminary evaluation of 11 pepper genotypes indicated a high degree of variability in bentazon tolerance. ‘Bohemian Chile’ and ‘Santanka’ hot pepper tolerated bentazon similarly in subsequent greenhouse and field experiments. Yields or shoot fresh weights of these two cultivars were not reduced by up to 9.0 kg ai/ha bentazon in the field. ‘Keystone Resistant Giant’ sweet pepper was more susceptible to bentazon compared to the tolerant cultivars, but it was more tolerant than the highly susceptible cultivar, ‘Sweet Banana’. An F1hybrid of Keystone Resistant Giant and Santanka tolerated bentazon better than Keystone Resistant Giant but slightly less than Santanka. Thus, bentazon tolerance in this genotype is genetically transferrable, and increasing bentazon tolerance through conventional plant breeding techniques may be possible.
Honeyvine Milkweed (Ampelamus albidus) Control in a Winter Wheat (Triticum aestivum) – Grain Sorghum (Sorghum bicolor) Rotation
Authors: Claassen Mark M. , Moshier Loren J.
Published: March 2018

Two 5-yr experiments in a winter wheat-grain sorghum rotation were conducted near Hesston, KS, to evaluate selected foliage-applied herbicides to control honeyvine milkweed in the fall after wheat harvest. Herbicides that suppressed honeyvine milkweed stem populations 9 months after treatment included glyphosate, glyphosate plus dicamba, glyphosate plus 2,4-D, picloram, and four combinations of picloram plus 2,4-D. Honeyvine milkweed had regrown sufficiently by 24 months after herbicide application to require retreatment. Stem populations were suppressed following repeat treatments. Herbicide treatments increased yields of grain sorghum planted 9 months later but did not increase yields of winter wheat planted 13 months or longer after herbicide application.
Response of Sugarcane (Saccharumsp.) Cultivars to Preemergence Herbicides
Authors: Richard Edward P.
Published: March 2018

The potential diversity in tolerance of eight commercial sugarcane cultivars to metribuzin, terbacil, and hexazinone was investigated. Herbicides were applied preemergence in the fall after planting and postemergence to the crop in the spring each year over the 3-yr crop cycle. Reductions in shoot counts and heights were not observed with any of the herbicide treatments in the fall following planting. Cultivar differences in growth and yield responses were obtained, particularly in the plant cane year of the 3-yr crop cycle. Metribuzin was the least phytotoxic and hexazinone the most phytotoxic. Reductions in sugar yields (kg/ha) were attributed to reductions in stalk populations and, to a lesser extent, to reductions in stalk height and sugar (sucrose) content. Cultivars sensitive to hexazinone either were equally sensitive to terbacil or were less sensitive to terbacil. Terminal fluorescence (FT)3measurements indicated that photosynthesis following postemergence applications of terbacil and hexazinone was no longer inhibited 5 weeks after treatment in the tolerant cultivars, CP 70–321 and CP 74–383, but continued to be reduced in the cultivars showing sensitivity, CP 65–357 and CP 48–103. The order of cultivar tolerance to hexazinone and terbacil from least tolerant to most tolerant is CP 48–103 < CP 65–357 ≤ CP 72–370 < CP 70–321 = CP 70–330 < CP 72–356 = CP 73–351 = CP 74–383.
Volunteer Wheat (Triticum aestivum) in Newly Seeded Alfalfa (Medicago sativaL.)
Authors: Ott Pablo M. , Dawson Jean H. , Appleby Arnold P.
Published: March 2018

Wheat that emerged with alfalfa seeded in the field in late August grew for 20 days after planting without suppressing the alfalfa but reduced yields if allowed to grow with alfalfa for 30 or more days. Uncontrolled wheat reduced the first cutting yield of alfalfa by 80% or more. Sethoxydim at 0.4 kg ai/ha, fluazifop at 0.2 kg ai/ha, and haloxyfop at 0.2 kg ai/ha controlled wheat selectively in alfalfa. Herbicides applied 20 days after seeding protected alfalfa from suppression by wheat. Control of wheat was equal when herbicides were applied 30 days after seeding, but in 1 of 2 yr, the wheat had suppressed the alfalfa enough to reduce yields the following May.
Moisture Stress Effects on Absorption and Translocation of Four Foliar-Applied Herbicides
Authors: Reynolds Daniel B. , Wheless Trina G. , Basler E. , Murray Don S.
Published: March 2018

Laboratory experiments with14C-herbicides were conducted with grain sorghum as an indicator species to determine the effects of imposed moisture stress on absorption, precent recovery, and acropetal and basipetal translocation of the butyl ester of fluazifop, the methyl ester of haloxyfop, the ethyl ester of quizalofop, and sethoxydim. Haloxyfop was the only herbicide where recovery decreased between the 3-and 48-h interval. All plants absorbed more of the herbicide at the 48-h interval than at the 3- or 6-h interval under both stressed and non-stressed conditions. Increased drought stress caused more acropetal movement with fluazifop and sethoxydim and less acropetal movement with quizalofop at the 3-h interval. Basipetal transloation, although different among herbicides, responded similarly to imposed moisture stress, which decreased basipetal translocation approximately 19%.
Perspectives on Discovery of Microbial Phytotoxins with Herbicidal Activity
Authors: Cutler Horace G.
Published: March 2018

Biologically active natural products of microbial origin are attractive candidates for possible use in agriculture. They may be obtained by fermentation, used in their natural state, or subjected to synthetic modification for specific uses. These natural products are characterized by high specific activity and high selectivity, and they are biodegradable. The structures are extremely diverse and represent many classes of compounds ranging from very complex to simple. Cyclocarbamide A and B, fromStreptoverticilliumsp., have marked preemergence herbicidal activity. Nigerazine A and B, fromAspergillus nigervan Tieghem, also inhibit root growth in certain plants. Citreoviridin, fromPenicillium charlesiiSmith, preferentially controls the growth of monocotyledonous plants, as does a synthetic derivative of cladosporin, fromAspergillus repensDeBary, which bleaches chloroplasts. The 12-membered fungal macrolides (macrocyclic lactones) also inhibit root growth in many test plants and offer templates for further synthetic work. Herbicidins, fromStreptomyces saganonensis, are particularly effective against barnyardgrass, goosegrass, tufted mannagrass, and green panicum.Alternaria eichorniaeNag Raj et Ponnappa produces a toxin that is active against waterhyacinth and represents one of the more exotic structures. The macrocyclic trichothecenes are a significant class of natural products that tend to concentrate against a gradient in seeds of certain plants, which resist these microbially derived metabolites thereby producing seed with “built-in” natural herbicides.
Photodynamic Herbicides
Authors: Towers G.H.N. , Arnason J. T.
Published: March 2018

Many natural and synthetic plant compounds become toxic when irradiated by ultraviolet or visible light. These compounds may be considered for use as herbicides, remembering the requirement for light. Concurrently, methods for blocking metabolic pathways so that phototoxic intermediates accumulate and thus kill the plant also have been studied. The mechanisms of action of potentially useful plant phototoxins are described.
Postemergence Weed Control in Onions (Allium cepa) with Air-assisted, Flat Fan, and Rotary Nozzles
Authors: Zandstra Bernard H. , Wallace Thomas F.
Published: March 2018

Field studies were conducted in 1984, 1985, and 1986 to compare standard flat fan nozzles, low-volume flat fan nozzles, rotary controlled droplet applicators, and air-assisted nozzles for postemergence weed control in onions with oxyfluorfen and fluazifop-P. Herbicides applied with flat fan nozzles at 47 or 190 L/ha controlled broadleaf and grass weeds as good or better than with the other nozzles. Oxyfluorfen applied with flat fan nozzles controlled common lambsquarters and ladysthumb best. None of the nozzles improved control of the difficult marsh yellowcress. Carrier volume had minimal effect on weed control. Nozzle and carrier volume did not affect onion yield.
Response of Yellow Starthistle (Centaurea solstitialis) and Grass Biomass to Grass, Picloram, and Fertilizer Combinations
Authors: Larson Larry L. , McInnis Michael L.
Published: March 2018

A 2-yr study was conducted to evaluate the response of yellow starthistle density and grass biomass to combinations of newly seeded grass, picloram, and fertilizer. A combination of ‘Tualatin’ tall oatgrass or ‘Paiute’ orchardgrass with 0.14 or 0.28 kg ae/ha of picloram effectively controlled yellow starthistle and improved forage production. Grass seeded alone or combined with fertilizer neither controlled yellow starthistle nor improved forage production. Three-way combinations of grass, picloram, and fertilizer did not affect yellow starthistle density in either year but resulted in more ‘Tualatin’ tall oatgrass biomass in 1987.
Cotton (Gossypium hirsutum) Development and Yield Following Fluometuron Postemergence Applied
Authors: Guthrie David S. , York Alan C.
Published: March 2018

Fluometuron at 1.1 kg ai/ha was applied postemergence (over-the-top) to cotton in the V3 to V4 stage to determine effects on flower and boll production, yield, and fiber quality. Treated plants produced more bolls but boll weight was reduced. Lint yield was not affected. Flower and boll production during the first 2 weeks of flowering were reduced, but treated plants produced more flowers and bolls during mid- and late bloom. A delay in sympodia development delayed development of fruiting structures. Fluometuron treatment promoted sympodia development on monopodia at nodes three and four. Fiber micronaire was reduced in 1 of 2 yr. Fiber strength, length, and length uniformity were not affected.
Differential Tolerance of Peppers (Capsicum annuum) to Bentazon
Authors: Wolff David W. , Monaco Thomas J. , Collins Wanda W.
Published: March 2018

Two field studies were conducted to compare bentazon tolerance in “Bohemian Chili” (BCH) and “Keystone Resistant Giant” (KRG) with other pepper cultivars and plant introductions (PIs). In the first study, BCH, KRG, “Santaka” (SA), and “Sweet Banana” (SB) were treated with five rates of bentazon from 1.1 to 9.0 kg ai/ha. Based on foliar injury, the cultivars ranked BCH = SA < KRG < SB; based on yield tolerance to bentazon, they ranked KRG ≤ SB < SA ≤ BCH. In the second study, the response of BCH, KRG, SA, SB, and five PIs to 4.5 kg/ha bentazon showed that 3 PIs (127445, 163187, 246123) tolerated bentazon similarly to BCH and SA.
Adjuvant and pH Effects on Sethoxydim and Clethodim Activity on Rhizome Johnsongrass (Sorghum halepense)
Authors: Bridges David C.
Published: March 2018

Rhizome johnsongrass control with sethoxydim and clethodim was evaluated with the addition of three adjuvants: Agrioil3, BAS8153, and Li7003. Johnsongrass control was similar with the three adjuvants when either sethoxydim or clethodim was applied alone, but when bentazon was added, johnsongrass control declined with both sethoxydim and clethodim. Control generally declined less with BAS815 than with Agrioil or Li700, but the addition of BAS815 did not completely reverse the effects of adding bentazon to sethoxydim or clethodim. Johnsongrass control was not affected by adjusting pH when sethoxydim or clethodim was applied with bentazon and Agrioil. Johnsongrass control over a pH range of 3.5 to 6.5 via the addition of glacial acetic acid and calcium hydroxide or ammonium hydroxide indicated a lack of pH dependence for these herbicides. The addition of ammonium hydroxide resulted in slight, but inconsistent increases in johnsongrass control.
Influence of Spotted Knapweed (Centaurea maculosa) on Surface Runoff and Sediment Yield
Authors: Lacey John R. , Marlow Clayton B. , Lane John R.
Published: March 2018

The influence of spotted knapweed on surface runoff and sediment yield was determined under simulated rainfall conditions near Garrison, MT. Comparisons were made in 12 paired plots: one of each pair dominated by bunchgrass and the other dominated by spotted knapweed. Runoff and sediment yield were 56% and 192% higher, respectively, for the spotted knapweed, rather than the bunchgrass vegetation types. Spotted knapweed invasion onto bunchgrass range of western Montana is thus detrimental to the protection of soil and water resources.
Bermudagrass (Cynodonspp.) Cultivar Response to Diclofop, MSMA and Metribuzin
Authors: McCarty Lambert B. , Miller Landon C. , Colvin Daniel L.
Published: March 2018

Postemergence grass weed control in turf-type bermudagrass is currently available only with repeated applications of organic arsenicals and/or with combinations of metribuzin which decrease turf quality. Research was conducted to determine tolerance of the turf-type bermudagrass cultivars, Tifway, Ormond, and common, to diclofop rates ranging from 0.54 to 4.48 kg ai ha-1with and without MSMA (2.2 kg ai ha-1) and metribuzin (0.2 kg ai ha-1). Bermudagrass cultivars tolerated diclofop well. When injury was evident, a rate response was noted, with higher rates (3.4 and 4.5 kg ha-1) resulting in increased phytotoxicity. However, this level of phytotoxicity was acceptable and the turf soon recovered (3 to 14 d). The addition of crop oil concentrate (1.25% v/v) did not affect turf quality. Addition of MSMA resulted in slightly lower turf quality than diclofop alone. However, these responses were acceptable and usually the turf recovered by 14 d after treatment. Metribuzin applied alone or in combination with diclofop damaged turf to unacceptable levels and up to 21 d were required for turf recovery.
Velvetleaf (Abutilon theophrasti) Control in Sugarbeet (Beta vulgaris)
Authors: Renner Karen A. , Powell Gary E.
Published: March 2018

Velvetleaf control in sugarbeet by clomazone and commercially available sugarbeet herbicides was investigated in greenhouse and field studies. In greenhouse studies, clomazone at 0.07 and 0.04 kg ai ha-1controlled 97 and 69% of velvetleaf, respectively, with little visible sugarbeet injury. Adding clomazone to pyrazon, TCA, ethofumesate, pyrazon plus TCA, or TCA plus ethofumesate increased velvetleaf control but increased visible sugarbeet injury. In field studies, clomazone at 0.07 kg ha-1did not enhance sugarbeet injury. However, velvetleaf was not controlled by clomazone alone or clomazone plus pyrazon, ethofumesate, combinations of pyrazon plus TCA, pyrazon plus ethofumesate, or pyrazon plus TCA plus ethofumesate. Cycloate preplant incorporated plus pyrazon preemergence followed by postemergence herbicides controlled velvetleaf in all 3 yr of research. Postemergence herbicides increased velvetleaf control from soil-applied herbicides in 1987 and 1988.
Herbicide Inputs for a New Agronomic Crop, Annual Wormwood (Artemisia annua)
Authors: Bryson Charles T. , Croom Edward M.
Published: March 2018

Annual wormwood has been cultivated on a small scale for production of the artemisinin class of antimalarial drugs in sufficient quantities for preclinical and clinical trials. Large scale cultivation will require a reliable, efficient crop production system. Production systems using 32 herbicides alone or in combinations were evaluated in growth chamber, greenhouse, and field experiments at Stoneville, MS from 1985 through 1988. The herbicide treatments that provided the best weed control were (A) metolachlor at 2.2 kg ai ha-1preemergence (PRE), (B) chloramben at 2.2 kg ai ha-1(PRE), or (C) trifluralin at 0.6 kg ai ha-1preplant soil incorporated (PPI) followed by fluazifop at 0.2 + 0.2 kg ai ha-1postemergence broadcast (POST) and acifluorfen at 0.6 kg ai ha-1(POST). These herbicide production systems provided excellent weed control (≥85%) and minimal crop injury (≤10%) with no effect on crop height or weight at harvest. Production of artemisinin was not reduced by herbicide treatments A, B, and C in 1987 and treatments B and C in 1988 when compared with the hand-weeded plots.
Mutant Weeds of Iowa:S-Triazine Resistant Pennsylvania Smartweed (Polygonum pensylvanicum)
Authors: Dekker Jack , Burmester Ronald , Wendel Jonathan
Published: March 2018

Suspected triazine resistant Pennsylvania smartweed plants were discovered near Holy Cross, Dubuque County, IA. Subsequent variable chlorophyllafluorescence assays confirmed these selections to be triazine resistant. This is the first reported evidence ofs-triazine resistance in Pennsylvania smartweed.
Response of Seedling Alfalfa (Medicago sativa) to Four Postemergence Herbicides
Authors: Tonks Dennis , Jeffery Larry S. , Webb Bruce L.
Published: March 2018

Response of seedling alfalfa to four herbicides applied at the 2nd, 4th, and 8th trifoliate leaf stages was evaluated in 1988 and 1989. There was no interaction between the herbicides and alfalfa growth stages at the time of herbicide application in either year. Bentazon did not reduce alfalfa height or yield of the first cutting in either year. The dimethylamine salt of 2,4-DB and bromoxynil reduced first-cutting alfalfa yield in 1988 and 1989, respectively, and the butoxyethanol ester of 2,4-DB reduced first-cutting alfalfa yield both years. Each herbicide affected one or more measurements of alfalfa quality in at least one year.
Differential Response of Hemp Dogbane (Apocynum cannabinum) to Clopyralid, Dowco 433, and 2,4-D
Authors: Orfanedes Michael S. , Wax Loyd M.
Published: March 2018

Field studies were conducted to compare the short- and long-term control of hemp dogbane by POST applications of Dowco 433, clopyralid, and 2,4-D amine. Dowco 433 at 140 g ae ha–1controlled 81 to 93% of weeds at 8 wk after treatment. Good control (79 to 89%) was also achieved with 560 g ae ha–12,4-D amine at 8 wk after treatment. Twelve months after treatment, control of hemp dogbane averaged 65 to 75% where Dowco 433 was applied at rates of 140 g ha–1or higher. Similar results were obtained with 2,4-D amine at 560 g ha–1. Control with clopyralid was minimal. Weed height and dry weight were reduced with all treatments except clopyralid. The effect of early versus late application was also evaluated in two studies. In certain situations, control 8 wk after treatment was greater when application was made during the early reproductive growth stage as opposed to the vegetative growth stage.
Epidemiology and Toxicology of 2,4-D
Authors: Mullison Wendell R. , Bond Gregory G.
Published: March 2018

The herbicide 2,4-D has been in commerce and a subject for research since 1944. It is undoubtedly among the most thoroughly researched pesticides in the world. In our society, 2,4-D has played an indispensable role. It is most important in the production of our food and fiber; in the control of noxious weeds causing public health problems such as common ragweed (Ambrosia artemisiifoliaL.) and poison-ivy [Toxicodendron radicans(L.) Ktze.] in the maintenance of our utility supply lines and highway and railroad systems; and as a useful tool for creating desirable wildlife habitats and beautifying our parks, golf courses, and the grounds about our homes.

Recently completed toxicological studies support the conclusions of earlier studies that 2,4-D may be used without undue risk to man, wildlife, or the environment. This does not mean, of course, that we should lessen our precautions to avoid exposure to applicators, prevent spray drift from getting on bystanders, or on pets such as dogs and cats, and following general good sanitation practices in its use.

There have been some reports of an association between the use of 2,4-D and NHL. However, in our opinion after considering all the toxicological and epidemiological evidence, it has not been established that the use of 2,4-D causes NHL or any other type of cancer including soft tissue sarcomas and Hodgkin's disease. As cited in this review, most scientific experts who have carefully examined all the data share this opinion.
Foliar Absorption and Translocation of Dicamba from Aqueous Solution and Dicamba-Treated Soil Deposits
Authors: Al-Khatib Kassim , Parker Robert , Fuerst E. Patrick
Published: March 2018

This study was conducted to compare foliar absorption and translocation of dicamba applied to plants as an aqueous solution or as dicamba-treated soil deposits. When applied as an aqueous solution, 65 to 95% of14C-dicamba was absorbed by pea, alfalfa, and grape; whereas, limited absorption (0.4 to 4.7%) occurred from dicamba-treated soil. Based on dose-response evaluation, the low levels absorbed from treated soil are unlikely to cause crop damage.14C-dicamba translocation was more than 80% of absorbed14C in pea, alfalfa, and grape. Acropetal translocation exceeded basipetal translocation.
Response of Centipedegrass (Eremochloa ophiuroides) to Plant Growth Regulators
Authors: Johnson B. Jack
Published: March 2018

CGA 163935, paclobutrazol, and paclobutrazol plus mefluidide were evaluated for their growth regulating effect on centipedegrass over 3 yr. Paclobutrazol did not effectively suppress seedhead production or vegetative growth. Paclobutrazol plus mefluidide at 1.1 + 0.3 kg ai ha–1in each of two applications at a 2-wk interval suppressed seedhead development 77% (average of 3 yr) at 10 wk after the initial treatment without severe injury or loss of stand, but duration of vegetative growth suppression was variable (0 to 6 wk). CGA 163935 applied at 0.4 kg ai ha–1and followed by 0.2 kg ai ha–12 wk later suppressed vegetative growth of mowed and nonmowed centipedegrass for 10 wk, while suppressing seedhead production for 3 to 5 wk. CGA 163935 caused severe injury and stand loss of centipedegrass.
Integrated Wild Oat (Avena fatua) Management Affects Spring Barley (Hordeum vulgare) Yield and Economics
Authors: Barton David L. , Thill Donald C. , Shafii Bahman
Published: March 2018

The effect of barley seeding rate and row spacing, and triallate, diclofop, and difenzoquat herbicide rate on barley grain yield and quality, and wild oat control were evaluated in field experiments near Bonners Ferry, Idaho, in 1989 and 1990. The purpose of the study was to develop integrated control strategies for wild oat in spring barley. Barley row spacing (9 and 18 cm) did not affect barley grain yield. Barley grain yield was greatest when barley was seeded at 134 or 201 kg ha–1compared to 67 kg ha–1. Wild oat control increased as wild oat herbicide rate increased and barley grain yield was greatest when wild oat herbicides were applied. However, barley grain yield was similar when wild oat biomass was reduced by either 65 or 85% by applications of half and full herbicide rates, respectively. Net return was greatest when the half rate of herbicide was applied to 100 wild oat plants per m2and was greatest when half or full herbicide rates were applied to 290 wild oat plants per m2. Net return increased when the seeding rate was increased to 134 or 201 kg ha–1when no herbicide was applied and when 290 wild oat plants per m2were present.
Influence of Herbicides on Sweetpotato (Ipomoea batatas) Plant Production
Authors: Monks David W. , Kalmowitz Kathie E. , Monaco Thomas J.
Published: March 2018

Studies were conducted to determine the response of ‘Jewel’ sweetpotato in propagation beds to DCPA and napropamide. Napropamide at 2.2 and 4.4 kg ha–1caused slight injury, and reduced plant number and weight when compared with the untreated control. Napropamide at 1.1 kg ha–1combined with chloramben at 3.3 kg ha–1was not injurious; plant production was equal to the untreated control, diphenamid at 4.4 kg ha–1, and chloramben at 3.3 kg ha–1. DCPA at 8.3 and 10.0 kg ha–1caused unacceptable injury and reduced plant number and weight.
Weed Science Extension in Transition
Authors: Elmore Clyde L.
Published: March 2018

Weed Science Extension is in a period of change. Though there is decreased funding for extension in the United States and Europe, the number of programs including extension activities is increasing in developing countries as shown by World Bank funding. There is a perception problem with the name weed science; we need a strong, recognizable science name. Decreases in one-on-one contact method for teaching, fewer extension weed specialists, and the increased need for interdisciplinary projects to support Integrated Pest Management and Sustainable Agriculture will increase stresses on our positions. These factors also increase the challenge for weed specialists and extension advisors (agents) to become leaders in current programs, initiate new multidisciplinary programs, and choose those programs that will benefit our discipline. Our clientele and the method of communicating with them will change, presenting yet another challenge.
Postemergence Grass Control with Herbicides Applied at ULV in Paraffinic Oil
Authors: McWhorter Chester G. , Barrentine William L. , Hanks James E.
Published: March 2018

Variables affecting ultra-low-volume (ULV) application of herbicides for postemergence grass control in soybeans were evaluated in field experiments from 1988 to 1990. Air-assist applications of clethodim at 2.3 and 4.7 L ha–1were compared with 94 and 187 L ha–1applications with a conventional hydraulic sprayer. Rate of herbicide, volume of diluent, type of diluent, air pressure, and four other herbicides were evaluated. Clethodim at 28, 56, and 112 g ha–1applied in paraffinic oil at 2.3 L ha–1controlled johnsongrass better 10 wk after treatment than equivalent rates applied at 2.3 or 187 L ha–1in water. At 2.3 L ha–1, barnyardgrass control was improved by applying clethodim in paraffinic oil rather than water. Johnsongrass control 10 wk after treatment was better with clethodim at 28 g ha–1applied in paraffinic oil than when applied in soybean oil, cottonseed oil, No. 2 diesel fuel, kerosene, or jet A fuel. Low air pressures of 14 or 28 kPa resulted in better control of johnsongrass and barnyardgrass than higher pressures of 56 and 112 kPa. Clethodim, fluazifop-P, haloxyfop, quizalofop, or sethoxydim were more effective on johnsongrass and barnyardgrass when applied in paraffinic oil than in water at 2.3 and 4.7 L ha–1with an air-assist sprayer.
Response of Sweet Corn (Zea mays) to Nicosulfuron and Primisulfuron
Authors: Monks David W. , Mullins Charles A. , Johnson Kenneth E.
Published: March 2018

Eight sweet corn cultivars differed in response to 35 g ai ha–1 nicosulfuron or 42 g ai ha–1 primisulfuron. ‘Merit’ sweet corn was killed 4 wk after nicosulfuron or primisulfuron application. Nicosulfuron and primisulfuron reduced height of Merit, 'Silver Queen’, 'Silverado’ and ‘How Sweet It Is'. Ear number of How Sweet It Is, ‘Pinnacle’ and Silverado was reduced by primisulfuron. ‘Landmark’, Silver Queen, and 'Sweetie 76’ were the most tolerant cultivars to nicosulfuron and primisulfuron with yield similar to that of the control.
Tolerance of Putting Green Turfgrasses to Simazine in Irrigation Water
Authors: Murphy Tim R. , Johnson B. Jack
Published: March 2018

Field experiments were conducted in 1989 and 1990 to evaluate the tolerance of ‘Penncross' creeping bentgrass and ‘Tifway’ bermudagrass fall-overseeded with perennial ryegrass to irrigation water containing simazine. Creeping bentgrass was more sensitive to simazine than the bermudagrass/ryegrass mixture. The predicted critical simazine concentration necessary to reduce creeping bentgrass quality ≤ 60% was 0.22 mg L–1which corresponded to a cumulative simazine rate of 98 g ha–1. For bermudagrass/ryegrass, the predicted critical simazine concentration and cumulative simazine rate that reduced quality ≤ 60% was 0.68 mg L–1and 306 g ha–1, respectively.
Tolerance of Asparagus (Asparagus officinalis) to Clopyralid
Authors: Boydston Rick A.
Published: March 2018

Clopyralid at 0.3 or 0.6 kg ae ha–1applied once or twice during the asparagus harvest season for two consecutive years did not significantly reduce the number of spears or total weight of asparagus harvested. In a second study, clopyralid applied at 0.3 kg ha–1twice during the harvest season and once at layby for two consecutive years did not reduce asparagus yield in the first year of treatment. In the second year, the number and weight of asparagus spears was reduced. Clopyralid applied during the harvest season caused some epinastic growth of asparagus after layby. Clopyralid applied to emerged asparagus spears slightly increased the number of cull spears harvested, but was less damaging than 2,4-D or dicamba.
Soybean (Glycine max) Cultivar Tolerance to Chlorimuron and Imazaquin with Varying Hydroponic Solution pH
Authors: Newsom Larry J. , Shaw David R.
Published: March 2018

Twenty determinate soybean cultivars were grown in hydroponic solutions to determine differential tolerance to chlorimuron and imazaquin at pH 6, 7, or 8. ‘Epps' exhibited tolerance to chlorimuron at each pH, and to imazaquin except at pH 8. ‘9641 Pioneer’ was highly sensitive to both herbicides at each pH, and ‘Asgrow 5979’ was sensitive to chlorimuron, and to imazaquin except at pH 7. ‘Hutcheson’ was sensitive to chlorimuron at each pH, and imazaquin at pH 6. ‘Asgrow 6785’ was sensitive to chlorimuron at pH 6 and 8, with shoot weight reductions of 31 and 28%, respectively, and ‘Coker 686’ was similarly sensitive at pH 6 and 7. ‘Hartz 6200’ was tolerant to imazaquin at pH 6 and 7, ‘Hartz 6686’ was tolerant at pH 6 and 8, and Coker 686 was tolerant at pH 7 and 8. Coker 686 and 'Sharkey’ were tolerant to chlorimuron at some pH levels, though highly sensitive at other pH levels. ‘Asgrow 5403’ and Coker 686 also had varying tolerance and sensitivity to imazaquin across pH levels. Shoot length and shoot weight were the best indicators of differential cultivar sensitivity when compared with previous field studies.
Reduced and Standard Herbicide Rates for Grass Control in Rice (Oryza sativa)
Authors: Carey Victor F. , Smith Roy J. , Talbert Ronald E.
Published: March 2018

Field research was conducted in 1988 and 1989 to compare effects of clethodim, fenoxaprop, haloxyfop, and sethoxydim each applied singly and sequentially at full (1X) and reduced (0.5X) rates on barnyardgrass, bearded sprangletop, and rice. A tank-mixture of propanil plus thiobencarb (2.2 + 2.2 kg ha–1) applied sequentially was included as a standard treatment. Control of barnyardgrass and bearded sprangletop was equal to that of the standard treatment both years with 1X rates of clethodim and fenoxaprop, and with 0.5X rates of clethodim, fenoxaprop, and sethoxydim each applied after propanil; rice so treated produced high grain yields. In 1988, severe rice injury occurred after the second application of clethodim at the 0.5X rate, but rice recovered. Grass control costs were reduced 57% with a single application of fenoxaprop at the 1X rate compared with the standard treatment, but net returns were not different.
Systems Inquiry, Scientific Creativity, and Disciplinary Fringes
Authors: William Ray D.
Published: March 2018

Basic, applied, operational, and human activity research systems represent an array of inquiry methodologies. Techniques or methods within each methodology exhibit similar functions, although purposes and results of each inquiry process differ. Appreciation and possible use of the entire inquiry process focuses attention on scale questions within a hierarchy, and encourages use of all methodologies to enhance resolution of diverse situations. Systems inquiry recognizes the need for weed scientists and agriculturists to participate in activities ranging between reductionist science and human action research.
Resistance of Palmer Amaranth (Amaranthus palmeri) to the Dinitroaniline Herbicides
Authors: Gossett Billy J. , Murdock Edward C. , Toler Joe E.
Published: March 2018

Trifluralin-resistant Palmer amaranth populations were confirmed at eight locations within two of the ten-county cotton growing region of South Carolina. Different levels of resistance to six dinitroaniline herbicides were observed, but no resistance was observed to herbicides from nine other chemical groups. Five to six times more trifluralin was required to control a resistant than a susceptible biotype under field conditions.
Developing Herbicide-Tolerant Crop Cultivars: Introduction
Authors: Harrison Howard F.
Published: March 2018

In recent years considerable research in the private and public sectors has been directed toward introducing herbicide tolerance into normally susceptible crop species (9). Interest in developing herbicide-tolerant crop cultivars, clones, or hybrids (HTCs)3has been spurred by the reduction in the rate of discovery of new herbicidal compounds, the rising expense of developing new herbicides, and new tools of biotechnology that greatly increased our ability to develop HTC genotypes. Potential benefits of developing HTCs include: a) an increased margin of safety with which herbicides can be used with subsequent reduced crop losses due to herbicide injury, b) reduced risk of crop damage from residual herbicides from rotational crops, and c) introduction of new herbicides for use on normally susceptible crops. The last objective can be considered to be similar to breeding for resistance to diseases or insects. The most serious weed problems for a crop can be solved by developing crop tolerance to herbicides that control the weeds. This approach is particularly promising for minor crops for which new herbicide development is essentially lacking. However, the reluctance of herbicide manufacturers to register their products for minor crops may impede this approach. By developing tolerance to nontoxic, nonpolluting herbicides that are suitable for conservation tillage, the negative environmental effects of weed control can be reduced.
Introduction to the Symposium
Authors: Wauchope R. Don , Duffy Michael J.
Published: March 2018

At the 1990 meeting of the Weed Science Society of America (WSSA) in Montreal a Symposium titled “Pesticide Transport to Groundwater: Perspectives and Field Methodology” was Chaired by Thanh H. Dao. That symposium made it clear that simulation modeling is being used more and more to integrate the field test data generated by pesticide companies as part of the environmental impact assessment required for pesticide registration with the Environmental Protection Agency (EPA). At the Soil Aspects Section Business Meeting it was decided that a Symposium on the state of the art of this technology would be timely and the authors agreed to organize it.
Pesticide Runoff Simulations: Long-Term Annual Means vs. Event Extremes?
Authors: Leonard Ralph A. , Truman Clint C. , Knisel Walt G. , Davis Frank M.
Published: March 2018

The GLEAMS model (Groundwater Loading Effects of Agricultural Management Systems) is used to illustrate model application in evaluating potential pesticide runoff of two similar pesticides from one soil. This limited application was chosen for simplicity in illustrating relationships between annual means and single events. When using annual totals of simulated pesticide runoff for comparing two pesticides or assessing risks, long-term 50-yr simulations are preferable to short 10-yr simulations. When short-term simulations are performed, care must be exercised in selecting representative climatic periods. For short half-life pesticides, as demonstrated in this study, initial rainfall events on or near the day of application will often contribute most to annual pesticide lost. In these cases, single event analysis may be required. Procedures are demonstrated for expressing annual total pesticide losses and single rainfall event losses probabilistically in terms of expected recurrence intervals.
Cost Effective Vegetation Management on a Recently Cleared Electric Transmission Line Right-of-way
Authors: Nowak Christopher A. , Abrahamson Lawrence P. , Neuhauser Edward F. , Foreback Curtis G. , Freed H. Dale , Shaheen Scott B. , Stevens Craig H.
Published: March 2018

Several application modes and methods (schemes) of using herbicides are available to control undesirable vegetation on electric transmission line rights-of-way (ROW). Preferential use of a management scheme can be based on its cost effectiveness, i.e., degree of vegetation control and treatment cost. A treatment that increases/maintains desirable plants, decreases/maintains undesirable plants, and has relatively low cost, can be considered cost effective. Three common herbicides, 2,4-D, picloram and triclopyr, were applied in the field to test treatment mode (selective and nonselective) and method (cut stump, basal, and stem-foliar) effects on cost effectiveness during initial clearing and first and second conversion cycles on one electric transmission line ROW in Upstate New York. Clear or selective cutting with no herbicide was most cost effective during initial clearing. Nonselective and selective stem-foliar schemes were most cost effective during the first and second conversion cycles, respectively.
Yellow Nutsedge (Cyperus esculentus) Control in Tomato withPuccinia canaliculataand Pebulate
Authors: Beste C. Edward , Frank J. Ray , Bruckart William L. , Johnson Dennis R. , Potts William E.
Published: March 2018

Yellow nutsedge control with rust (Puccinia canaliculata(Schw.) Lagerh.) collected in Salisbury, MD., was evaluated alone or in combination with pebulate at 1.7 or 3.3 kg ai ha-1in transplanted tomato. Foliar applications of urediniospores in mid-June did not affect the yellow nutsedge population; however, tuber biomass was reduced 32%. In July, yellow nutsedge infection was manifest as an increase of phytotoxicity from 2.3 to 4.1 (0 to 10) and of disease incidence increase from 3 to 37%. Pebulate, 3.3 kg ha-1reduced the yellow nutsedge population and ground cover by 79 and 90%, respectively, in June, with a 48% reduction of both tuber population and biomass in September. Tomato yields were not increased by rust or pebulate treatments. Marketable tomato yield was increased 46% by handweeding. Yellow nutsedge control was not enhanced by the combination treatments of pebulate followed by rust inoculation.
Cost-Efficient Weed Control in Soybean (Glycine max) with Cultivation and Banded Herbicide Applications
Authors: Poston Daniel H. , Murdock Edward C. , Toler Joe E.
Published: March 2018

Field studies were conducted in 1988 and 1989 to examine the interrelations of cultivation and herbicide band width in controlling pitted morningglory and sicklepod in soybean. Alachlor + imazaquin PRE followed by imazaquin + surfactant POST were not applied or were applied on bands 15, 30, 45, 60, 75 cm wide or were broadcast. Plots were cultivated zero, one, two, or three times. Without cultivation, at least a 60-cm wide band was needed to achieve maximum soybean seed yields. A slight linear increase in soybean seed yield in response to increasing band width was observed with one cultivation. With two cultivations, soybean seed yields were similar with and without herbicides, but a 15-cm wide herbicide band was needed to achieve maximum production with three cultivations. Greatest gross returns exclusive of weed management costs were realized with two or three cultivations and a 15-cm wide band.
Survey of Beginning Weed Science Courses
Authors: Pearce R. Brent , Appleby Arnold P.
Published: March 2018

A mail survey was undertaken in 1991 to obtain information on beginning weed science courses being taught in the United States and Canada. Out of 74 questionnaires sent to 44 states and 7 provinces, there were 54 responses of which 49 institutions had a beginning weed science course. The responses showed that these courses are taught primarily once a year (88%) in the fall term (77%). Most schools are under the semester system (82%) with the credits arranged so that there are about 30 hours of lecture per term with a one-credit laboratory. The students in beginning weed science courses are mostly seniors (47%) and juniors (34%) and are primarily from Agronomy, Plant Science, or Crop Science departments (46%) and Horticulture (23%). The average time spent on different topics agreed well with the priorities and are listed in the text. The survey also gathered data on weed identification requirements, special requirements of individual courses, evaluation of students, additional comments by instructors, and special teaching guides or techniques that instructors are willing to share with others.