Abstract: Broadleaf weed control with postemergence applications of CGA-248757 and flumiclorac applied alone and in tank mixtures was evaluated in greenhouse and field studies. In greenhouse studies velvetleaf, common lambsquarters, redroot pigweed, common ragweed, common cocklebur, eastern black nightshade, and wild mustard shoot weight were reduced by 50% from 0.1, 2.9, 0.9, 1.1, 0.8, 0.4, and 1.2 g/ha of CGA-248757 and 0.7, 3.0, 2.4, 3.3, 3.0, 3.4, and 74.1 g/ha of flumiclorac, respectively. Under greenhouse conditions, tank mixtures of CGA-248757 or flumiclorac with atrazine, bentazon, bromoxynil, dicamba, halosulfuron, imazethapyr, lactofen, primisulfuron plus prosulfuron, or 2,4-D increased velvetleaf, common lambsquarters, redroot pigweed, or common ragweed control 14 d after treatment (DAT) when compared with the control provided by atrazine, bentazon, bromoxynil, dicamba, halosulfuron, imazethapyr, lactofen, primisulfuron plus prosulfuron, or 2,4-D applied alone. In field studies, adding CGA-248757 or flumiclorac to atrazine, bentazon, bromoxynil, dicamba, halosulfuron, imazethapyr, lactofen, CGA-277476, primisulfuron plus prosulfuron, or 2,4-D increased crop injury 3 DAT, but there was no reduction in corn or soybean yields as a result. In corn, tank mixtures of CGA-248757 or flumiclorac plus atrazine, dicamba, or 2,4-D increased velvetleaf control compared with treatments without CGA-248757 or flumiclorac. Tank mixtures of CGA-248757 or flumiclorac with primisulfuron plus prosulfuron increased common lambsquarters control compared with primisulfuron plus prosulfuron alone. Similarly, in soybean CGA-248757 or flumiclorac tank mixtures with bentazon or CGA-277476 increased control of redroot pigweed, and tank mixtures with lactofen increased common lambsquarters control. However, season-long broadleaf control in soybean with bentazon, lactofen, and CGA-277476 tank mixtures with CGA-248757 or flumiclorac did not provide acceptable weed control. Compared with imazethapyr alone the addition of CGA-248757 and flumiclorac improved soybean yield and provided season-long eastern black nightshade, common lambsquarters, redroot pigweed, and common ragweed control.

Nomenclature: Atrazine; bentazon; bromoxynil; CGA-248757 (proposed common name fluthiacet), methyl[[2-chloro-4-fluoro-5-[(tetrahydro-3-oxo-1H, 3H-[1,3,4]thiadiazolo[3,4-a]pyridazin-1-ylidene)amino]phenyl]thio]acetate; CGA-277476 (proposed common name oxasulfuron), 2-[[[[(4,6-dimethyl-2-pyrimidinyl)-amino]carbonyl]amino]sulfonyl] benzoic acid, 3-oxetanyl ester; dicamba; flumiclorac; halosulfuron; imazethapyr; lactofen; primisulfuron; prosulfuron; 2,4-D; common cocklebur, Xanthium strumarium L. #³ XANST; common lambsquarters, Chenopodium album L. # CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; corn, Zea mays L. Pioneer 3751, Dekalb 404SR, and Dekalb 493 SR # ZEAMA; eastern black nightshade, Solanum ptycanthum Dun. # SOLPT; redroot pigweed, Amaranthus retroflexus L. # AMARE; soybean, Glycine max (L.) Merr. Conrad # GLYMA; velvetleaf, Abutilon theophrasti Medik. # ABUTH; wild mustard, Brassica kaber (D.C.) L.C. Wheeler # SINAR.

Additional index words: Acifluorfen, antagonism, chlorimuron, Digitaria sanguinalis, glyphosate, herbicide interaction, nicosulfuron, protox, Setaria faberi, sethoxydim, Sorghum bicolor, thifensulfuron.

Abbreviations: COC, crop oil concentrate;

Abstract: A full-season field study was conducted near College Station, TX to determine the competitive interference of Palmer amaranth on cotton development, yield, and fiber properties and to measure Palmer amaranth development as influenced by intraspecific competition. Palmer amaranth densities ranged from 0 to 10 plants/9.1 m of row. Palmer amaranth decreased cotton canopy volume by 45% at 10 wk after cotton emergence (WAE) and cotton biomass by greater than 50% at 8 WAE at the highest density. Cotton yields decreased linearly from 13 to 54% for 1 to 10 Palmer amaranth plants/9.1 m of row. Cotton lint properties were not influenced by Palmer amaranth density. Palmer amaranth volume and individual biomass were not affected by intraspecific competition at any of the densities.

Nomenclature: Cotton, Gossypium hirsutum L. Delta and Pineland 50; Palmer amaranth, Amaranthus palmeri S. Wats #³ AMAPA.

Additional index words: Cotton biomass, interspecific competition, intraspecific competition, weed density.

Abbreviations: POST, postemergence; WAE, weeks after emergence.

Abstract: Management of corn (Zea mays) row spacings and populations has been used for many years to increase corn productivity. In 1998 and 1999, nonirrigated corn was grown in 38-, 56-, and 76-cm row spacings at populations averaging 59,300, 72,900, and 83,900 plants/ha in Michigan. Glufosinate at 0.29 kg/ha was applied to common lambsquarters (Chenopodium album L.) averaging 5 cm in height in each plot. Corn population and row spacing did not influence weed emergence following application of glufosinate. Common lambsquarters biomass and seed production were reduced when grown under canopies of corn planted in populations exceeding 72,900 plants/ha. Common lambsquarters biomass was reduced as corn row spacings were reduced from 76 to 38 cm. Early-season interception of photosynthetic active radiation (PAR) by corn canopies increased as row spacings decreased, but differences were not apparent later in the season. Interception of PAR was similar throughout the season when corn populations exceeded 72,900 plants/ha. Corn yields were not affected by row spacing, but they were increased with corn populations of 72,900 plants/ha or higher.

Nomenclature: Glufosinate; common lambsquarters, Chenopodium album L,. #³ CHEAL; corn, Zea mays L. ‘DK 493GR’.

Additional index words: Crop density, herbicide-tolerant crops, narrow-row corn.

Abbreviation: PAR, photosynthetic active radiation.

Abstract: Field studies were conducted near Archer, FL, and Vienna, GA, in 1995 and 1996 to investigate the effects of pyridate formulation and adjuvants on broadleaf weed control in peanut (Arachis hypogaea). Pyridate formulations SAN 319H 450EC 361LZ, SAN 319H 450EC 216LZ, and SAN 319H 600EC 418LZ were evaluated at two rates, 1.07 and 2.14 kg/ha. Pyridate at 1.07 kg/ha plus 2,4-DB at 0.23 kg/ha were evaluated alone and with five adjuvants. The adjuvants included a crop oil concentrate, a nonionic surfactant, a nonionic surfactant with organosilicone blend, urea ammonium nitrate plus a nonionic surfactant, and chlorothalonil (a fungicide) plus a nonionic surfactant. No pyridate treatment injured peanut. Pyridate formulation did not affect broadleaf weed control. Increasing pyridate rate increased weed control and yield. Mixing 2,4-DB with pyridate generally enhanced sicklepod (Senna obtusifolia) and common cocklebur (Xanthium strumarium) control. Florida beggarweed (Desmodium tortuosum), smallflower morningglory (Jacquemontia tamnifolia), hairy indigo (Indigofera hirsuta), sicklepod, and common cocklebur control with pyridate was not enhanced by adjuvants. Adding chlorothalonil to pyridate plus 2,4-DB did not affect weed control or peanut injury.

Nomenclature: 2,4-DB; chlorothalonil; tetrachloroisophthalonitrile; pyridate; common cocklebur, Xanthium strumarium #³ XANST; Florida beggarweed, Desmodium tortuosum # DEDTO; hairy indigo, Indigofera hirsuta # INDHI; peanut, Arachis hypogaea ‘Sunrunner’ and ‘GK-7’; sicklepod, Senna obtusifolia # CASOB; smallflower morningglory, Jacquemontia tamnifolia # IAQTA.

Additional index words: SAN 319H 450EC 361LZ, SAN 319H 450EC 216LZ, SAN 319H 600EC 418LZ, crop oil concentrate, nonionic surfactant, organosilicone-nonionic surfactant blend, urea ammonium nitrate.

Abbreviations: COC, crop oil concentrate; NIS, nonionic surfactant; NIS/OS, nonionic surfactant with organosilicone; POST, postemergence; WAT, weeks after treatment.

Abstract: Field experiments were conducted during 1998, 1999, and 2000 in Santa Fe, Argentina, to evaluate chlorimuron, clethodim, flumetsulam, 2,4-DB, glyphosate, and haloxyfop for control of broadleaf and grass weeds in established alfalfa. Herbicides were applied to alfalfa, 6 to 10 cm in height, after first or second cuttings. Clethodim and haloxyfop were highly effective against bermudagrass, barnyardgrass, and knotroot foxtail, and alfalfa yields were increased. 2,4-DB was effective against Scotch thistle, swinecress, turnipweed, and birdsrape mustard, but no effects were observed on alfalfa yields. Chlorimuron, flumetsulam, and glyphosate were effective against burning nettle, common chickweed, common lambsquarters, spiny cocklebur, and Persian speedwell, but they injured alfalfa and decreased yields.

Nomenclature: Chlorimuron; clethodim; 2,4-DB; flumetsulam; glyphosate; haloxyfop; alfalfa, Medicago sativa (L.); barnyardgrass, Echinochloa crus-galli (L.) Beauv. #³ ECHGA; bermudagrass, Cynodon dactylon (L.) Pers. # CYNDA; birdsrape mustard, Brassica rapa (L.) # BRACA; burning nettle, Urtica urens (L.) # URTUR; common chickweed, Stellaria media (L.) Villars # STEME; common lambsquarters, Chenopodium album (L.) # CHEAL; knotroot foxtail, Setaria geniculata (Lam.) Beauv. # SETGE; Persian speedwell, Veronica persica Poir. # VERPE; Scotch thistle, Onopordum acanthium (L.); spiny cocklebur, Xanthium spinosum (L.) # XANSP; swinecress, Coronopus didymus Sm. # COPDI; turnipweed, Rapistrum rugosum (L.) All. # RASRU.

Abbreviation: DAT, days after treatment.

Abstract: Field experiments were conducted in 1996 and 1997 to evaluate weed control and dry bean response to mechanical tillage and herbicide treatments. Herbicide treatments were EPTC plus ethalfluralin, dimethenamid, and imazethapyr plus bentazon. Herbicides were applied alone or combined with rotary hoeing and in-row cultivation. Differences in dry bean yields between years were due to differences in weed density. Weed species included redroot pigweed, common lambsquarters, hairy nightshade, wild proso millet, and green foxtail. Weed density in the untreated check plots at the end of the growing season was 35 plants/m² in 1996 and 134 plants/m² in 1997. Dry bean stands were not reduced by rotary hoeing, in-row cultivation, and herbicides in 1996, but in-row cultivation reduced dry bean populations 27% compared to the hand-weeded check in 1997. In-row cultivation and rotary hoeing provided similar weed control in both years. At low weed densities, either mechanical tillage or herbicides alone were effective in suppressing weeds, whereas at higher densities, herbicides combined with mechanical tillage were required for effective control.

Nomenclature: Bentazon; dimethenamid; EPTC; ethalfluralin; imazethapyr; common lambsquarters, Chenopodium album L. #³ CHEAL; dry bean, Phaseolus vulgaris, Great Northern ‘Beryl’; green foxtail, Setaria viridis L. Beauv. # SETVI; hairy nightshade, Solanum sarrachoides Sendt. # SOLSA; redroot pigweed, Amaranthus retroflexus L. # AMARE; wild proso millet, Panicum miliaceum L. # PANMI.

Additional index words: Combinations, herbicides and mechanical tillage, postemergence herbicides, preemergence herbicides, preplant-incorporated herbicides.

Abbreviations: DAP, days after planting; IR, in-row cultivation; POST, postemergence; PRE, preemergence; RH, rotary hoeing.

Abstract: The potential of Colletotrichum dematium f.sp. epilobii (ATCC 20981) to control fireweed (Epilobium angustifolium) was investigated. Under controlled environment conditions, plant age, inoculum density, length of the dew period, and temperature during the dew period affected the efficacy of C. dematium f.sp. epilobii. Seedlings sprayed with 1 × 10⁹ conidia/m² sustained the most damage. Susceptibility decreased with increasing plant age, and 10-wk-old plants were slightly affected by the fungus. Satisfactory levels of control were achieved when the dew period was >20 h and temperature during the dew period was 30 C. Control of fireweed increased when the C. dematium f.sp. epilobii conidia were suspended in a 25% v/v canola oil/water emulsion. Using this formulation, control of 4-wk-old seedlings was obtained with a 10-fold reduction in inoculum concentration (1 × 10⁸ conidia/m²), the required dew period was reduced to 12 h, and the effect of the temperature during the dew period was minimized. In the field, C. dematium f.sp. epilobii alone or when amended with an oil emulsion failed to control fireweed growth. When the oil formulation of C. dematium f.sp. epilobii was tank mixed with a low rate of glyphosate, high levels of control were consistently achieved. Growth reduction achieved with this formulation was more than additive, suggesting a synergistic interaction. The effectiveness of the formulated conidial suspension of C. dematium f.sp. epilobii decreased with plant maturity, and 15-wk-old plants were not controlled. C. dematium f.sp. epilobii alone has limited potential as a candidate bioherbicide, but when formulated in an oil/water emulsion and combined with low rates of glyphosate, suppression of fireweed can be attained in the field.

Nomenclature: Glyphosate; fireweed, Epilobium angustifolium L. #³ CNAAN.

Additional index words: Bioherbicide, biological weed control, mycoherbicide.

Abbreviations: PDA, potato dextrose agar; SNK, Student-Newman-Keuls Multiple Range test.

Abstract: Sulfonylurea herbicide residues in soil can affect rotational crops even at low concentrations. Although analytical methods are efficient enough to measure them, the lack of an efficient herbicide extraction technique makes bioassays useful for determining the presence of phytotoxic levels of sulfonylurea residues in soil. A growth chamber bioassay using sunflower was developed to detect MON-37500 and triasulfuron residues in two different soils. Root length was measured 15 d after the treatment. A sigmoid equation described plant root length response as a function of herbicide concentration. The nonlinear regression established a range of I₅₀ values from 0.9 to 2.9 ppb ai for both sulfonylureas.

Nomenclature: MON-37500 (proposed common name, sulfosulfuron), 1-(4,6-dimethoxypyrimidin-2-yl)-3-[(2-ethanesulfonyl-imidazo[1,2-a]pyridine)sulfonyl]urea; triasulfuron; sunflower, Helianthus annuus L. ‘Albani’.

Additional index words: Dose–response curves, I₅₀, phytotoxicity, rotational crops, sulfonylurea herbicides.

Abbreviations: I₂₀, dose required for 20% inhibition; I₅₀, dose required for 50% inhibition; OM, organic matter.

Abstract: Herbicide efficacy, coverage, and retention were evaluated for spray applied through Drift Guard, Turbo TeeJet, AI TeeJet, and TurboDrop drift-reducing nozzles compared to a conventional flat-fan nozzle. Percentage spray coverage detected on water-sensitive cards was greater for conventional and Drift Guard nozzles than for Turbo TeeJet, AI TeeJet, and TurboDrop nozzles. Spray without adjuvants was retained better by redroot pigweed for treatments applied with conventional and Drift Guard nozzles than Turbo TeeJet, AI TeeJet, and TurboDrop nozzles. However, spray with adjuvants was retained similarly for all nozzle types when averaged over spray adjuvant and two weed species. The efficiency of spray retention was greater for spray applied in 47 than in 190 L/ha spray volume for all nozzles. Paraquat and glyphosate, representing contact and translocated herbicides, respectively, provided similar grass species control for all nozzle types, regardless of spray volume. Paraquat and glyphosate were also equally or more effective in 47 compared to 190 L/ha spray volume.

Nomenclature: Glyphosate; paraquat; common lambsquarters, Chenopodium album L. #³ CHEAL; foxtail millet, Setaria italica (L.) P. Beauv.; oat, Avena sativa L.; proso millet, Panicum miliaceum L.; redroot pigweed, Amaranthus retroflexus L. # AMARE.

Additional index words: Application methods, droplet size, spray coverage, spray drift, spray retention, spray volume.

Abbreviations: ATV, all-terrain vehicle; MVO, methylated vegetable oil; NIS, nonionic surfactant; VMD, volume median diameter.

Abstract: Volunteer potato plants are difficult to control in rotational crops, and they harbor harmful diseases, nematodes, and insects. Five herbicide treatments were evaluated for control of volunteer potato in field corn grown under no-till and conventional tillage in 1994 and 1995. In mid-June, potato control was greater in conventionally tilled corn than no-till corn primarily due to the reservoir tillage that followed postemergence (POST) herbicide applications in the conventional system. Final potato tuber weight was not different between tillage levels in 1994 or 1995. Herbicide treatments reduced potato tuber weight 64 to 96% in no-till corn and 85 to 99% in conventionally tilled corn compared to nontreated checks. Atrazine applied preemergence at 1.1 kg ai/ha followed by dicamba plus 2,4-D applied POST at 0.28 plus 1.1 kg ae/ha, respectively, reduced potato tuber weight greater than 95% in both years and both tillage systems. Corn yield was not affected by tillage level or herbicide treatments in 1994 or 1995 and averaged 10.5 MT/ha in 1994 and 15.1 MT/ha in 1995. In a separate experiment, glyphosate, dicamba plus 2,4-D, or fluroxypyr applied at the eight-leaf stage to potato grown without a corn crop, and followed by cultivation 10 d later, reduced the number of potato tubers produced 79 to 95% compared to nontreated potato.

Nomenclature: Atrazine; cyanazine; 2,4-D, dicamba, dimethylamine salt; fluroxypyr; glyphosate, nicosulfuron; primisulfuron; triclopyr, triethylamine salt; corn, Zea mays L ‘Pioneer 3394’; potato, Solanum tuberosum L. ‘Russet Burbank.’

Additional index words: No-till, reservoir tillage (dammer diking).

Abbreviations: DAT, days after treatment; EPOST, early postemergence; LPOST, late postemergence; PRE, preemergence; POST, postemergence; WAT, weeks after treatment.

Abstract: Field trials were conducted in 1998 and 1999 to determine the effect of delayed burndown timings on weed control and yield of no-tillage glyphosate-resistant corn planted into soybean residue and into a wheat cover crop. Burndown treatments containing glyphosate were applied to both trials when the corn was planted (PRE), when the corn began to emerge (SPIKE), or when the corn had three visible leaves (3-LEAF). As burndown timing was delayed, velvetleaf control increased in corn planted into soybean residue. Glyphosate applied at 0.84 kg ae/ha at the SPIKE or 3-LEAF timing followed by a sequential application of glyphosate at 0.84 kg/ha controlled velvetleaf 91% and corn yields were similar to the weed-free plots. Corn yields among the burndown treatments were directly related to velvetleaf control. In the wheat cover crop trial, wheat treated at the PRE timing was completely controlled and corn yields were similar to the weed-free plots. As burndown timings were delayed, corn emergence and yields were severely reduced. Glyphosate applied at 0.84 kg/ha to 25-cm-wide strips over the corn row at planting and followed with delayed burndown timings increased corn emergence and yield.

Nomenclature: Glyphosate, N-(phosphonomethyl)glycine; corn, Zea mays L. DK 493RR; velvetleaf, Abutilon theophrasti Medicus #³ ABUTH; winter wheat, Triticum aestivum L.

Additional index words: Herbicide-tolerant crops, living mulch, residual herbicides.

Abbreviations: PRE, preemergence; SPIKE, at corn emergence; 3-LEAF, corn with three visible leaves.

Abstract: Greenhouse and field experiments were conducted in North Dakota to determine the effect of adjuvants applied with imazapic on the control of leafy spurge and production of various grass species and to determine the most effective fall-application timing of imazapic for optimum leafy spurge control with minimal effect on herbage. Imazapic applied with a methylated seed oil (MSO) adjuvant tended to provide greater leafy spurge control than when applied with other types of adjuvants. Imazapic applied alone or with adjuvants reduced production of some grass species in the greenhouse, but it did not decrease herbage production in the field. Imazapic at 140 g/ha applied with MSO or with 28% N plus MSO averaged 72% leafy spurge control 12 mo after treatment, compared to 33% control from imazapic alone and 40% control from picloram plus 2,4-D. Imazapic at 140 g/ha applied with MSO in mid-September provided greater leafy spurge control compared to August or October applications.

Nomenclature: Imazapic; leafy spurge, Euphorbia esula L. #3 EPHES.

Additional index words: Invasive weed control, rangeland weeds.

Abbreviations: DAT, days after treatment; MAFT, months after first treatment; MAT, months after treatment; MSO, methylated seed oil.

Abstract: Field studies were conducted from 1995 through 1998 to evaluate citronmelon control with postemergence (POST) herbicides. Imazapic at any application timing and late postemergence (LPOST) applications of 2,4-DB were the only herbicides that provided >80% control of citronmelon late season. Other herbicides such as acifluorfen, imazethapyr, lactofen, and pyridate provided acceptable (>75%) early-season control of citronmelon, but control was inadequate at harvest.

Nomenclature: Acifluorfen; imazapic; imazethapyr; lactofen; pyridate; 2,4-DB; citronmelon, Citrullus lanatus var. citroidas #³ CITCL; peanut, Arachis hypogaea L. ‘GK-7’.

Additional index word: Groundnut.

Abbreviations: DAP, days after planting; EPOST, early postemergence; LPOST, late postemergence; POST, postemergence.

Abstract: Field experiments were conducted to determine the influence of nozzle type, spray volume, and adjuvants on herbicide efficacy. Carfentrazone and imazamox, representing contact and translocated herbicides, respectively, were equally or more effective when applied with drift-reducing TurboDrop or Drift Guard nozzles than the conventional flat-fan nozzle in 95% of the comparisons. Imazamox was equally effective when applied in 47, 94, or 190 L/ha spray volume, regardless of nozzle type or adjuvant. Carfentrazone applied in 47 L/ha spray volume controlled flax and sunflower as well as in 94 or 190 L/ha, provided urea ammonium nitrate fertilizer and either nonionic surfactant or methylated vegetable oil were included in the spray mixture. Conversely, carfentrazone with only urea ammonium nitrate was less effective when applied in 47 than in 94 or 190 L/ha spray volume. Carfentrazone and imazamox applied in low spray volumes (47 L/ha) gave consistent control when an effective adjuvant was included in the spray mixture.

Nomenclature: Carfentrazone; imazamox; flax, Linum usitatissimum L.; sunflower, Helianthus annuus L.

Additional index words: Application methods, droplet size, nitrogen fertilizer, spray coverage, spray drift.

Abbreviations: DAT, days after treatment; MVO, methylated vegetable oil, NIS, nonionic surfactant; UAN, urea ammonium nitrate fertilizer; VMD, volume median diameter.

Abstract: Field research was conducted at three locations in Iowa to determine the effectiveness of glyphosate for velvetleaf control in glyphosate-resistant soybean. Velvetleaf survival ranged from 46 to 81% when treated with 420 g ae/ha glyphosate, whereas survival ranged from 13 to 37% at the 840 g/ha rate. At two locations, velvetleaf survival was greater when treated at the 12- to 17-cm height compared with application to either 8- to 10- or 20- to 30-cm-tall plants. Growth of plants surviving glyphosate application was greatly reduced, with the high glyphosate rate reducing velvetleaf aboveground biomass by over 90% compared to untreated plants. A linear relationship between biomass and capsule number was observed for both control plants and plants surviving glyphosate, both having slopes of approximately one. Velvetleaf surviving glyphosate treatment should have minimal impact on soybean yield due to reduced growth; however, surviving plants may replenish the seed bank, leading to future management problems.

Nomenclature: Glyphosate; soybean, Glycine max (L.) Merr. #³ GLYMA; velvetleaf, Abutilon theophrasti Medik. # ABUTH.

Additional index word: Reproductive fitness.

Abstract: A field experiment was conducted over 2 yr to study efficacy of bromoxynil mixtures with pyrithiobac or MSMA applied postemergence (POST) with and without fluometuron or fluometuron plus pendimethalin preemergence (PRE) for control of broadleaf weeds in ultra narrow row bromoxynil-resistant cotton in the Mississippi Delta. Bromoxynil applied POST (single or sequential) provided variable control of common purslane (<9%), sicklepod (<35%), Palmer amaranth (<46%), prickly sida (>75%), hyssop spurge (>79%), hemp sesbania (>96%), and pitted morningglory (100%) at 4 wk after early POST (WAT). Broadleaf weed control increased when PRE herbicides were followed by bromoxynil or bromoxynil plus pyrithiobac or MSMA POST. Weed control generally decreased at harvest compared to 4 WAT, and the decrease was greater in bromoxynil POST-only programs compared to bromoxynil POST following PRE programs. Seed cotton yield with bromoxynil POST-only programs was lower (400 to 2,810 kg/ha) compared to bromoxynil POST programs following PRE herbicides (2,150 to 3,720 kg/ha). Early-season weed interference and variable control of weeds in bromoxynil POST-only programs resulted in greater cotton stand reduction and lower open bolls per plant compared to bromoxynil POST programs following PRE herbicides.

Nomenclature: Bromoxynil; fluometuron; MSMA; pendimethalin; pyrithiobac; common purslane, Portulaca oleracea L. #³ POROL; cotton, Gossypium hirsutum L. ‘BXN 47’; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A. W. Hill # SEBEX; hyssop spurge, Euphorbia hyssopifolia L. # EPHHS; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; sicklepod, Senna obtusifolia (L.) Irwin & Barneby # CASOB.

Additional index word: Transgenic cotton.

Abbreviations: EPOST, early postemergence; fb, followed by; LPOST, late postemergence; POST, postemergence; PRE, preemergence; UNR, ultra narrow row; WAT, weeks after EPOST application.

Abstract: Desiccants are used in potato production to remove vines before harvest to make harvest easier. We evaluated the new herbicide glufosinate-ammonium for potential as a vine desiccant, for its effect on seed tuber sprouting, and plant growth the following season. Glufosinate-ammonium was applied at 0, 0.3, 0.45, 0.6, and 0.75 kg ai/ha and compared with diquat at 0.84 kg ai/ha when applied as desiccants in mid-September in 1997 and 1998. Potato leaf and vine desiccation were rated 3, 7, and 14 d after treatment (DAT). Yields were obtained at maturity and tubers retained and stored over winter at 3 C and 95% relative humidity for determination of stem end discoloration (SED), tuber sprouting in March, and plant growth of daughter tubers planted the following year. Application of glufosinate-ammonium resulted in slower leaf and stem desiccation at 3 and 7 DAT than did diquat. By 14 DAT leaf desiccation was the same but stem desiccation was slightly less than with diquat. Tuber SED and marketable tuber yield were no different with either desiccant. At higher rates of application, glufosinate-ammonium reduced daughter tuber sprout weight but had no effect on number of sprouts in growth room sprouting tests when compared with untreated controls. Daughter tubers from glufosinate-ammonium-treated plants planted the next growing season had markedly slower emergence and established full emergence 7 to 14 d later than diquat-desiccated tubers.

Nomenclature: Diquat; glufosinate-ammonium; potato, Solanum tuberosum, #³ SOLTU.

Additional index words: Tuber sprouting test, daughter tuber replant test, Russet Burbank, Shepody, Kennebec.

Abbreviations: DAE, days after emergence; DAP, days after planting; DAT, days after treatment; RH, relative humidity; SED, stem end discoloration.

Abstract: Field studies were conducted with fresh market spinach to examine crop tolerance and weed control with S-metolachlor. S-metolachlor was applied preemergence (PRE) at rates of 0.56, 0.72, 1.06, and 1.41 kg/ha and compared with the commercial standard cycloate at 3.4 and 4.5 kg/ha. Spinach was generally tolerant of S-metolachlor at rates up to 1.06 kg/ha on all soil types. S-Metolachlor at 0.56 to 0.72 kg/ha and cycloate at 3.4 kg/ha provided >88% control of common purslane, nettleleaf goosefoot, and shepherd's purse. Control of common chickweed with S-metolachlor at ≥0.56 kg/ha was >80%, whereas cycloate at 3.4 to 4.5 kg/ha was ineffective. Hand-weeding times in plots treated with S-metolachlor at 0.56 and 0.72 kg/ha were similar or lower than hand-weeding times in plots treated with cycloate at 3.4 kg/ha. Greenhouse studies were conducted to compare the relative tolerance of fresh market spinach to S-metolachlor and metolachlor. The GR₁₀ values for S-metolachlor and metolachlor were 1.57 and 2.03 kg/ha, respectively. At rates above 2.2 kg/ha S-metolachlor is less selective in spinach than metolachlor. S-metolachlor is safe for PRE use in fresh market spinach at rates up to 1.06 kg/ha.

Nomenclature: Cycloate; metolachlor; S-metolachlor; S-enantiomer; common chickweed, Stellaria media L. Vill. #³ STEME; common purslane, Portulaca oleracea L. # POROL; nettleleaf goosefoot, Chenopodium murale L. # CHEMU; shepherd's-purse, Capsella bursa-pastoris L. Medik # CAPBP; spinach, Spinacia oleracea L. # SPQOL.

Additional index words: Herbicide tolerance, weed control, CAPBP, CHEMU, POROL, SPQOL, STEME.

Abbreviations: GR₁₀, herbicide concentration required to reduce shoot dry weight by 10%; PRE, preemergence.

Abstract: Early canopy closure and manipulation of crop row spacing or density can reduce the amount and frequency of herbicide use in corn. Field studies were conducted at Woodstock, ON from 1996 to 1999 to evaluate the effect of corn row spacing, plant density, and frequency of glufosinate application on weed biomass and corn yield in glufosinate-resistant corn. Treatments included row width, corn density, and herbicide. The effect of row width and corn density on weed biomass was variable among years. In a wet year (1996), narrow (38 cm) rows provided greater weed suppression than wide (76 cm) rows regardless of crop density. In a dry year (1998), narrow-row high-density (100,000 plants/ha) corn had the lowest weed biomass. In other years, either narrow row or high density was equally successful in suppressing weeds. Effectiveness of herbicides in reducing weed biomass was not influenced by row width or corn density. Corn yield was influenced by row width or corn density. Although weed biomass was lowered by two applications of glufosinate in comparison with a single application, corn grain yields were similar between the two treatments. Planting corn at higher densities may help in reducing early-season weed competition, whereas narrow rows may help in controlling later-emerging species.

Nomenclature: Glufosinate; glyphosate; metolachlor; dicamba; corn, Zea mays L. Pride X2650LL.

Additional index words: Corn row spacing, corn density.

Abbreviations: EPOST, early postemergence; IWM, integrated weed management; LPOST, late postemergence; POST, postemergence.

Abstract: Dicamba is a herbicide used for the control of broadleaf weeds in wheat. Dicamba, applied within the recommended growth stage interval, reduced the grain yield of Wakefield winter wheat by 95% in a herbicide sensitivity study at Michigan State University. Growers have also reported yield loss when using dicamba on Wakefield. Field and greenhouse experiments were conducted to characterize the response of Wakefield winter wheat to dicamba and to compare this response to that of ‘Harus’ winter wheat, a cultivar that is not considered sensitive to dicamba. This research was conducted to characterize the sensitivity of Wakefield to dicamba and to develop visual methods for detecting sensitivity of wheat cultivars to dicamba. Field experiments confirmed that dicamba affects the number of spikelets and the seed weight of Harus and Wakefield similarly. However, dicamba, applied within the recommended application interval, caused small, shriveled (underdeveloped) seeds to occur in Wakefield in the field and greenhouse. These seeds weighed very little, did not contribute to grain yield, and could not be harvested mechanically. Dicamba reduced the number of fully developed seeds of Wakefield by as much as 62% in the field and 92% in the greenhouse when applied within the recommended application interval. The number of fully developed seeds of Harus was reduced in the field only when dicamba was applied later than the recommended application interval. Decreases in grain yield due to dicamba were caused primarily by decreases in the number of fully developed seeds. Greenhouse experiments indicated that pollen abnormalities were only a minor cause of the development of underdeveloped seeds.

Nomenclature: Dicamba; winter wheat, Triticum aestivum L. ‘Harus’, ‘Wakefield’.

Additional index words: Herbicide sensitivity, growth regulators.

Abbreviations: F2, Feekes stage 2; F3, Feekes stage 3; F5, Feekes stage 5; F9, Feekes stage 9; F10, Feekes stage 10.

Abstract: Field studies were conducted from 1997 to 1999 to evaluate the influence of weed competition and herbicides on glyphosate-resistant soybean at the Belleville Research Center at Belleville, IL. Season-long weed competition did not delay maturity or reduce soybean population. However, season-long weed competition reduced soybean height by 10% and grain yield by 68%. Competition from weeds 30 cm in height or less did not increase days to maturity or reduce plant population, height, or grain yield. Chlorimuron plus thifensulfuron caused 6% height reduction at 21 d after treatment. Despite the injury from herbicides, none increased days to maturity or reduced plant height, population, or grain yield of soybean. The soil-applied herbicides alachlor, imazaquin, and pendimethalin and the postemergence herbicides acifluorfen, bentazon, chlorimuron, imazethapyr, and thifensulfuron did not reduce yield of glyphosate-resistant soybean.

Nomenclature: Acifluorfen; alachlor; bentazon; chlorimuron; glyphosate; imazaquin; imazethapyr; pendimethalin; thifensulfuron; soybean, Glycine max (L.) Merr. ‘Asgrow 4401 RR’.

Additional index words: Herbicide injury, soil-applied herbicides, preemergence, postemergence.

Abbreviations: DAT, days after treatment; POST, postemergence; PRE, preemergence; UAN, urea ammonium nitrate.

Abstract: Small-scale African farmers typically have few resources for the management of weeds and soil fertility. Weed composition varies with soil properties and crops compete with weeds for available nutrients. We conducted field surveys in four districts to study the effects of cropping systems, fallow, landscape position, and soil characteristics on weed composition and evaluated the value of weed species density in predicting soil fertility conditions. Weed density was higher with annual than for banana-based cropping systems with higher relative densities of hairy beggarticks and garden spurge and lower relative densities for Cyperus spp. and johnsongrass in the banana-based systems. The relative densities of weed species varied with the length of the postfallow period, landscape position, drainage, and soil properties. Long-term rotation of annual and perennial cropping systems may be more effective than fallow in reducing total weed numbers, but fallow may be effectively used to reduce the relative densities of tropical spiderwort, Cyperus spp., and goosegrass. Relative densities of blue couch, goosegrass, garden spurge, Cyperus spp., oxalis, and johnsongrass varied more with nutrient supply than for other species. Soil properties had less effect on the distributions of tropic ageratum, hairy beggarticks, tropical spiderwort, and smallflower galinsoga. High relative densities of blue couch and garden spurge were generally associated with low soil nutrient levels. Goosegrass, johnsongrass, and oxalis were associated with higher nutrient levels. Information on the relationship of soil nutrient levels with weed flora was used to develop a decision guide to aid farmers in the identification of areas in their fields with severe nutrient deficiencies.

Nomenclature: Banana, Musa spp.; blue couch, Digitaria scalarum (Schweinf) Chiov #³ DIGSC; garden spurge, Euphorbia hirta L. # EPPHI; goosegrass, Eleusine indica (L.) Gaertn # ELEIN; hairy beggarticks, Bidens pilosa L. # BIDPI; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; oxalis, Oxalis latifolia; smallflower galinsoga, Galinsoga parviflora Cav. # GASPA; tropic ageratum, Ageratum conyzoides # AGECO; tropical spiderwort, Commelina benghalensis L. # COMBE.

Additional index words: Banana, decision guides, indicator plants, relative density, soil fertility management, weed flora composition, weed management.

Abbreviation: RD, relative density.

Abstract: Several herbicide-based weed management programs for glyphosate-tolerant cotton were compared in eight field studies across Alabama during 1996 and 1997. Weed management programs ranged from traditional, soil-applied residual herbicide programs to more recently developed total postemergence (POST) herbicide programs. Pitted morningglory and sicklepod control was best achieved with fluometuron applied preemergence (PRE) followed by (fb) a single POST over-the-top (POT) application of glyphosate fb a POST-directed application of glyphosate. Annual grass control was better with the preplant incorporated (PPI) programs at two of three locations in both years. Treatments that included at least one glyphosate POT application gave increased grass control over no glyphosate or pyrithiobac POT. Velvetleaf control was improved with the addition of glyphosate POT. A herbicide program using no POST herbicides yielded significantly less seed cotton than any program using POST herbicides at one location. PRE- and POST-only weed management programs at another location produced more seed cotton and gave greater net returns than PPI programs. Similarly, net returns at that same location were equivalent for both PRE- and POST-only programs, and less for PPI programs. POST-only programs yielded highest amounts of seed cotton and netted greater returns.

Nomenclature: Fluometuron; glyphosate; pyrithiobac; cotton, Gossypium hirsutum L. ‘Deltapine 5415RR’, ‘Deltapine 5690RR’; pitted morningglory, Ipomoea lacunosa L. #³ IPOLA; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; velvetleaf, Abutilon theophrasti Medik. # ABUTH.

Additional index words: Cotton yields, herbicide costs, herbicide-resistant crops, transgenic cotton.

Abbreviations: ANOVA, analysis of variance; EPDS, early postemergence-directed spray; EPOT, early postemergence over-the-top; fb, followed by; GCS, Gulf Coast Research and Education Center; LPDS, late postemergence-directed spray; LPOT, late postemergence over-the-top; LSD, least significant difference; PDS, postemergence-directed spray; PEF, Prattville Experimental Field; POST, postemergence; POT, postemergence over-the-top; PPI, preplant incorporated; PRE, preemergence; TVS, Tennessee Valley Research and Education Center; WGS, Wiregrass Research and Education Center.

Abstract: Greenhouse studies were conducted to evaluate weed control from various formulations of glyphosate alone and in combination with postemergence herbicides. Tank mixtures did not increase barnyardgrass control 2 wk after treatment (WAT) when compared with glyphosate alone; however, tank mixtures did reduce barnyardgrass fresh weight 4 WAT when compared with glyphosate alone in several instances. Antagonism was observed when chlorimuron was combined with all formulations of glyphosate 4 WAT, but control was not reduced when compared with glyphosate alone. Selective herbicides added to glyphosate had an additive or antagonistic effect on prickly sida fresh-weight reductions. Antagonism of pitted morningglory fresh-weight reductions occurred when glyphosate was combined with all herbicides except acifluorfen, which had an additive effect. Fomesafen or lactofen effectively controlled hemp sesbania 2 WAT without the addition of glyphosate. Acifluorfen and chlorimuron combined with glyphosate Cheminova, Monsanto, or Zeneca reduced hemp sesbania fresh weight nearly twofold more than glyphosate alone.

Nomenclature: Acifluorfen; chlorimuron; fomesafen; glyphosate; lactofen; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #³ ECHCG; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex. A. W. Hill # SEBEX; pitted morningglory, Ipomea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP.

Additional index words: Additive effects, antagonism, reduced rates, synergism.

Abbreviations: ALS, acetolactase synthase; C, Cheminova; LSD, least significance difference; M, Monsanto; POST, postemergence; WAT, weeks after treatment; Z, Zeneca.

Abstract: Spot treatments with hexazinone (0.03, 0.046, and 0.06% ai [v/v]) were evaluated for their effects on thistle density, seed production, and crown vetch vigor from 1991 to 1994 to determine if long-term usage of hexazinone caused damage to the vetch and exacerbated the thistle problem. Thistle densities were reduced within a year at any concentration of hexazinone and seed production was reduced or eliminated. Environment had a large impact because initial thistle densities varied widely among years. The amount of precipitation during July of the previous year accounted for 89% of the variation in initial thistle densities in the subsequent year. Vetch injury from hexazinone was also best explained by the amount of precipitation during July. Vigorously growing crown vetch in wet years may have suppressed the thistles enough to reduce density the following year while drought years reduced the competitiveness of the crown vetch, resulting in higher initial densities of thistles in the following year.

Nomenclature: Hexazinone; Canada thistle, Cirsium arvense (L.) Scop. #³ CIRAR; crown vetch, Coronilla varia L.

Additional index words: Herbicide selectivity, interspecific plant competition, weather effects.

Abbreviation: PPFD, photosynthetic photon flux density.

Abstract: Field studies were conducted to evaluate the effects of glyphosate and conventional herbicides on purple and yellow nutsedges. Tubers collected from the field were counted and tested for viability via growth chamber or triphenyl tetrazolium chloride test to determine the effect of herbicides on tuber density and viability. With purple nutsedge, herbicide treatments containing glyphosate at 0.84 kg/ha followed by (fb) glyphosate at 0.56 kg/ha reduced viable and total tuber density. Among conventional herbicides, treatments containing metolachlor at 2.2 kg/ha plus sulfentrazone at 0.26 kg/ha plus chlorimuron at 0.05 kg/ha applied preemergence (PRE) and metolachlor at 2.2 kg/ha plus imazaquin at 0.14 kg/ha applied PRE fb bentazon at 0.84 kg/ha applied postemergence (POST) reduced total and viable tuber density compared to the nontreated. Metolachlor at 2.2 kg/ha plus sulfentrazone at 0.26 kg/ha plus chlorimuron at 0.05 kg/ha applied PRE fb bentazon applied POST also reduced viable tuber density of purple nutsedge. With yellow nutsedge, all herbicide treatments reduced total and viable tuber density over the nontreated check.

Nomenclature: Tetrazolium red; 2,3,5-triphenyl tetrazolium chloride; purple nutsedge, Cyperus rotundus L. #³ CYPRO; soybean, Glycine max (L.) Merr. ‘Asgrow 4701RR’, ‘Hartz 4998’; yellow nutsedge, Cyperus esculentus L. # CYPES.

Additional index word: Perennial weeds.

Abbreviations: fb, followed by; POST, postemergence; PRE, preemergence; WAP, weeks after planting.

Abstract: Field studies were conducted in 1998 and 1999 to evaluate the sensitivity of a common sunflower population to acetolactate synthase (ALS)-inhibiting herbicides and evaluate alternative control methods for ALS-resistant common sunflower in soybean. Imazaquin, imazethapyr, imazamox, flumetsulam, chlorimuron, cloransulam, and CGA277476 provided 35 to 73% control of common sunflower with labeled rates. Postemergence glyphosate and sequential applications of bentazon effectively controlled ALS-resistant common sunflower. Although pendimethalin imazaquin imazethapyr preemergence followed by glyphosate postemergence with and without cultivation provided 100% control of ALS-resistant common sunflower, sequential applications of glyphosate provided net incomes approximately $50 to $110/ha higher than the alternative control methods. Pendimethalin preemergence followed by acifluorfen bentazon postemergence followed by bentazon 10 d later provided the lowest overall weed control and net income. In treatments with a soil-applied herbicide followed by glyphosate postemergence, cultivation generally did not improve weed control. Soybean yields were the same comparing glyphosate with a soil-applied herbicide followed by glyphosate.

Nomenclature: Acifluorfen, bentazon, chlorimuron ethyl, cloransulam, flumetsulam, glyphosate, imazamox, imazaquin, imazethapyr, CGA277476, pendimethalin, common sunflower, Helianthus annuus L. #³ HELAN; soybean, Glycine max (L.) Merr. ‘Asgrow 3601 RR*STS’.

Additional index words: Cultivation, herbicide resistance, sulfentrazone, Amaranthus rudis Sauer, Ipomoea hederaceae (L.) Jacq., Setaria faberi Herrm., Xanthium strumarium L., AMATA, IPOHE, SETFA, XANST.

Abbreviations: ALS, acetolactate synthase; cec, cation exchange capacity; CV, coefficient of variation; MPOST, mid postemergence; OM, organic matter; PRE, preemergence; WAT, weeks after treatment.

Abstract: Alternative methods are needed to control weeds in no-till corn and soybean which minimize herbicide contamination of surface or ground water. The objective of this research was to determine whether between-row (BR) mowing band-applied herbicide could help reduce herbicide use, without sacrificing summer annual weed control or yield, in no-till soybean and field corn. Glyphosate was applied shortly before or at planting to control emerged winter annual weeds in all treatments. In the BR mowing weed management system, the band-applied soil residual herbicides imazaquin alachlor in soybean or atrazine alachlor in corn were applied shortly before or after planting followed by two or more between-row mowings to control summer annual weeds. Annual weeds were first mowed when they were about 8 cm tall and again just before crop canopy closure. Between-row mowing weeds very close to the soil surface two or three times killed or suppressed summer annual grass and broadleaf weeds, chiefly giant foxtail, common cocklebur, and horseweed, when timed properly. The BR mowing weed management system increased yield above a weedy check in these no-till crops. It also controlled weeds and yielded as well as or better than broadcast-applied herbicide at the same rates. Use of soil residual herbicides to control summer annual weeds was reduced 50% by banding because only 50% of the field area was sprayed.

Nomenclature: Alachlor, atrazine; glyphosate; imazaquin; common cocklebur, Xanthium strumarium L. # XANST; corn, Zea mays (L.) #³ ZEAMX, ‘Pioneer 3394’; giant foxtail, Setaria faberii (L.) Beauv. # SETFA; horseweed, Conyza canadensis (L.) Cronq # CONCA; soybean, Glycine max (L.) Merr. # GLYMA, ‘Pioneer 9461’.

Additional index words: Band application, defoliation, mowing, mechanical weed control, no-till, no-tillage, tillage, topping.

Abbreviations: DAP, days after planting; BR, between row.

Abstract: Sulfometuron was applied over the top of recently planted oak seedlings in three separate studies. Both preemergent (PRE) and postemergent (POST) timings were utilized in all studies. In 1997, six species of oaks were planted and evaluated, and two species were planted in the 1998 and 1999 studies. Sulfometuron was applied at rates of 0.1 and 0.2 kg ai/ha in 1997 PRE and at 0.1 kg ai/ha POST. In 1998 and 1999, treatment rates were 0.1 and 0.15 kg ai/ha for PRE and 0.1 kg ai/ha POST. Results indicate that sulfometuron is effective for competition control and can be applied PRE with total safety with the tested oaks. However, sulfometuron should not be applied POST over white oak seedlings, as mortality will result.

Nomenclature: Sulfometuron; white oak, Quercus alba L.

Additional index words: Hardwoods, reforestation.

Abbreviations: DAT, days after treatment; POST, postemergent; PRE, preemergent.

Abstract: The influence of three simulated dew levels and 150, 300, and 450 L/ha spray volume on glyphosate control of oat plants was determined from pot experiments. Results showed that the effect of dew level on glyphosate efficacy was related to application volume. Glyphosate efficacy at the low and medium application volume (150 and 300 L/ha) was not affected by dew level. However, glyphosate efficacy decreased when applied at the high spray volume (450 L/ha), regardless of dew level. However, high dew level reduced efficacy only when glyphosate was applied at 450 L/ha.

Nomenclature: Glyphosate; oat, Avena sativa L.

Additional index words: Application volume, glyphosate activity, foliage water retention, foliage free water.

Abbreviations: DAE, days after emergence; HDA, homogeneous dew area.

Abstract: The effect of CGA 152005 residues in the soil on six crops grown in rotation with field corn was investigated over a 2-yr period. CGA 152005 at 10, 15, 20, and 30 g ai/ha was applied postemergence (POST) to corn in 1994. CGA 152005 at 15 and 30 g ai/ha, atrazine at 1,000 g ai/ha, CGA 152005 at 15 g plus atrazine at 500 g ai/ha, and CGA 152005 at 30 g plus atrazine at 1,000 g ai/ha were applied POST to corn in 1995. Soybean, pea, cabbage, tomato, pepper, and potato were planted each spring, 1 yr after herbicide application. Cabbage exhibited injury and yield reductions that increased with increasing application rate, and pepper exhibited slight injury at the highest rate and yield reduction in 1995. Cabbage yields were reduced by CGA 152005 plus atrazine, and tomato yields were reduced by CGA 152005 and CGA 152005 plus atrazine in 1996. Yields of other crops were not affected in either year.

Nomenclature: CGA 152005 (proposed common name, prosulfuron), 1-(4-methoxy-6-methyl-triazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)-phenylsulfonyl]-urea; cabbage, Brassica oleracea L. var. capitata L.: corn, Zea mays L.; pea, Pisum sativum L.; pepper, Capsicum annuum L.; potato, Solanum tuberosum L.; soybean, Glycine max (L.) Merr.; tomato, Lycopersicon esculentum Mill.

Additional index words: Crop injury, herbicide carryover, soil pH, soil temperature.

Abbreviations: OM, organic matter; POST, postemergence; SU, sulfonylurea.

Abstract: Dr. Lawrence R. “Dick” Oliver is University Professor and Elms Farming Chair for Weed Science at the University of Arkansas. Agriculture was the backdrop of his youth in Stuttgart, AR, which profoundly affected his career choice. Dr. Oliver received his B.S. and M.S. degrees from the University of Arkansas and his Ph.D. degree from Purdue University. He has been actively involved in weed science research and teaching in Arkansas since 1972. His research in weed biology, weed interference, reduced herbicide rate programs, and control of specific problem weeds in soybean, corn, and wheat has earned him recognition throughout the United States and especially in the southern region.

Dr. Oliver has served the Weed Science Society of America (WSSA) as member-at-large and on numerous committees before being elected Vice President in 1998. He has also been Secretary-Treasurer and President of the Southern Weed Science Society (SWSS). Dr. Oliver has received numerous awards for contributions to teaching, research, and service, such as Outstanding Teacher and Fellow in WSSA; Outstanding Young Weed Scientist, Weed Scientist of the Year, Outstanding Educator, and Distinguished Service Awards in SWSS; Outstanding Teacher and Researcher in Bumpers College of Agriculture, Food, and Life Sciences; and University of Arkansas Alumni Association Faculty Distinguished Achievement Award for Teaching and Research.