In an attempt to refine calibration procedures for greenhouse spray chambers, the effects of an herbicide adjuvant, operating pressure, and travel speed on the static and dynamic spray patterns of single flat-fan hydraulic nozzle tips were studied. The volume output in the central 15 cm of the spray pattern (where target plants would ordinarily be positioned) was used as an indicator of the relative dosages received from both a tapered flat-fan tip (8001 VS) and an even-spray tip (8001 EVS). All tested variables significantly altered the spray pattern. Specifically, dynamic spray patterns differed from static patterns, and speed of travel affected the dynamic pattern for both tapered and even flat-fan sprays. Increasing the travel speed from 0.375 to 0.75 m/s reduced spray deposit in the central 15 cm of the spray pattern by up to 19% for water, and by up to 34% for water containing 0.1% v/v nonionic surfactant. Increasing surfactant concentration to 1% decreased the magnitude of the speed effect. Higher pressure sprays tended to reduce the effect of increased travel speeds. These results show that changes in physicochemical properties of the spray solution as well as air turbulence introduced by nozzle movement can affect the pesticide dosage to which a target plant is exposed in a spray chamber. For proper treatment comparison, delivery systems for greenhouse spray experiments should be calibrated with end-use spray liquids, operating pressures, and nozzle travel speeds.

Research was conducted in 2007 and 2008 to evaluate weed-control options in an imazethapyr-resistant rice production system. Raised beds were formed, and imidazolinone-resistant hybrid rice ‘CL 730’ was drill-seeded on beds. Five herbicide programs applied up to the four- to six-leaf stage of rice were evaluated with and without additional “as-needed” herbicide at later stages. All the herbicide combinations and as-needed herbicides tested in this research were labeled for rice, and only minor transient injury (< 5%) was initially observed. Weeds emerged throughout the growing season, and as-needed herbicides were applied after the four- to six-leaf stage of rice to control these late-emerging weeds and weeds not effectively controlled with earlier applications, primarily Palmer amaranth. Most of the Palmer amaranth at this site was insensitive to imazethapyr (possibly acetolactate synthase resistant). Therefore, application of as-needed herbicides with different modes of action, such as 2,4-D, were used to improve Palmer amaranth control. Rice yields were often numerically higher in plots that received additional herbicide after the six-leaf stage of rice, but yields were not significantly improved.

Dr. Homer M. LeBaron is Senior Research Fellow in the New Technology and Basic Research Department of CIBA-GEIGY Corporation, where He has the responsibility for coordinating and directing outside basic research on all of CIBA-GEIGY agricultural products. He has been employed in various R&D positions with Geigy and CIBA-GEIGY for 27 years. From 1960 to 1964, Dr. LeBaron was employed as a plant physiologist at the Virginia Tech Experiment Station in Norfolk, Virginia, mainly researching weed problems in vegetables and fruit crops.

LeBaron was born May 13, 1926 in Southern Alberta, Canada, the third in a family of 10 children, and grew up on a diversified irrigation farm. He obtained his B.S. and M.S. degrees from Utah State University in 1955 and 1957. He received his Ph.D. degree from Cornell in 1960.

LeBaron, in addition to WSSA, is a member of the American Society of Agronomy, American Chemical Society, Entomological Society of America, American Phytopathological Society, CAST, Sigma Xi, Aquatic Plant Management Society, European Weed Research Society, and all of the regional weed science societies.

He has held numerous positions in several of these and other scientific societies. Homer served as president of NEWSS in 1969–70 and as president of the SWSS in 1986–87. He served on several WSSA committees, including the Executive Board of Directors. In 1978, Dr. LeBaron was elected a Fellow in the WSSA, and received the Distinguished Service Award in the SWSS in 1984.

He is author of over 70 scientific publications, and has been editor and author of five books on herbicide and pesticide resistance and biotechnology. He is currently serving on the parent Herbicide Resistance Action Committee (HRAC) under GIFAP, as well as on the ALS/AHAS Inhibitors Resistance Working Group and as Chairman of the Triazine Resistance Working Group. He is on the Planning Committee and Co-Chair of the Weed Resistance Management Working Group within the International Organization for Pest Resistance Management (IOPRM). In addition to his busy professional schedule, Dr. LeBaron has always been involved in church and community affairs. He has 7 children and 20 grandchildren.

Component yields and forage quality were evaluated in established stands of alfalfa seeded alone and in binary mixtures with smooth bromegrass, orchardgrass, or timothy. Forage yields and quality were determined at three annual harvests in the third and fourth years after seeding. Weed yields in alfalfa seeded alone were significantly greater than those in the alfalfa–orchardgrass mixture. Average weed content was 24, 17, 2, and 15% for the alfalfa seeded alone, alfalfa–bromegrass, alfalfa–orchardgrass, and alfalfa–timothy, respectively. Seeding alfalfa with orchardgrass increased first harvest and annual forage yields while reducing alfalfa yield. Yields of orchardgrass often exceeded those of bromegrass or timothy. In the first harvest each year, crude protein was reduced and acid detergent fiber and neutral detergent fiber increased by including orchardgrass. Neutral detergent fiber was greater in alfalfa–orchardgrass than in the alfalfa seeded alone at most harvests. There were no consistent differences among the alfalfa seeded alone and the other mixtures in yield or quality.

Experiments compared the effect on weed control and potato yield of banded applications of metolachlor plus linuron with or without flex-tine, rolling, and shovel cultivation prior to hilling. Cultivation without banded herbicide resulted in greater prehilling in- and between-row weed densities and reduced late-season weed control as compared to broadcast herbicides or cultivation with banded herbicides. Although the flex-tine and rolling cultivators were expected to provide improved in-row weed control, there were few differences between these and the other cultivation implements. Despite reduced weed control with cultivation alone, potato yields were not reduced.

Field experiments were conducted to evaluate pyridine herbicides for Virginia buttonweed control and turfgrass tolerance. Treatments included clopyralid and fluroxypyr applied at 35, 70, 140, 280, and 560 g ae/ha, compared to a three-way combination of 2,4-D plus dichlorprop plus dicamba (840 + 840 + 210 g ae/ha, respectively). Fluroxypyr applied at 140 g/ha or greater controlled Virginia buttonweed 80% or greater through 10 wk after treatment. A second experiment evaluated 280 g/ha clopyralid or 140 g/ha fluroxypyr alone or in combination with 0.25 or 0.50% (v/v) nonionic surfactant, compared to 280 g/ha dicamba or 1,120 g/ha 2,4-D alone or in combination with nonionic surfactant. The addition of nonionic surfactant to clopyralid or fluroxypyr did not increase Virginia buttonweed control. Fluroxypyr at 280 g/ha and higher produced 22 to 53% injury to bermudagrasses 2 wk after treatment. Common centipedegrass was injured through 3 wk after treatment with 4,470 g/ha fluroxypyr or greater. Zoysiagrass exhibited injury with 4,470 g/ha fluroxypyr at 2 wk after treatment; however, injury was less than 8% at 3 wk. Common St. Augustinegrass was severely injured with 2,235 g/ha or greater fluroxypyr through 7 wk after treatment. Clopyralid did not cause injury to any turfgrass species.

Field experiments were conducted in Tifton, Midville, and Athens, GA to determine economic net returns from PRE-broadcast, PRE-banded, POST, and POST-directed herbicide treatments and inter-row cultivation in conventional-tillage soybean. Metribuzin applied PRE-broadcast was more effective for sicklepod and morningglory control than PRE-banded. Soybean net returns were not significantly reduced in two of three years in plots treated with metribuzin applied PRE-banded compared with broadcast application. The addition of POST or POST-directed herbicides increased treatment net returns over PRE-broadcast and PRE-banded metribuzin two of the three years of the study. No significant soybean injury was observed.

Experiments were conducted in Florida from 1998 through 2000 to evaluate trifloxysulfuron-sodium applied POST for weed control in cotton. The addition of 0.25% (v/v) nonionic surfactant (NIS) to trifloxysulfuron-sodium, regardless of rate, increased sicklepod control 10 to 50% 6 and 19 wk after planting (WAP). All trifloxysulfuron-sodium treatments controlled Florida beggarweed and redweed 70 to 100% 6 and 19 WAP. Pitted morningglory was controlled 68 to 100% by trifloxysulfuron-sodium treatments; however, control was higher for treatments that contained 0.25% v/v NIS. Trifloxysulfuron-sodium provided poor control of smallflower morningglory. A sequential application of fluometuron PRE followed by trifloxysulfuron-sodium POST provided better control of smallflower morningglory than trifloxysulfuron-sodium alone 19 WAP. Cotton treated with trifloxysulfuron-sodium yielded higher than the nontreated check and early POST treatments that included 0.25% v/v NIS yielded approximately 20% higher than non-NIS treatments. Trifloxysulfuron-sodium applied POST provided season-long control of Florida beggarweed, pitted morningglory, redweed, and sicklepod with the addition of 0.25% v/v NIS but did not control smallflower morningglory in cotton.

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

Spurred anoda is an increasing weed problem in Colorado pinto bean production. This research was designed to evaluate reduced rates of bentazon and imazethapyr applied at various times for spurred anoda control and profitability. In 1993, spurred anoda control with early applications of either bentazon or imazethapyr was superior to late applications. Bentazon provided better spurred anoda control than imazethapyr in June. Spurred anoda control in 1993 was better than in 1994 due to late-emerging weeds and herbicide treatments not providing residual control. In 1994, bentazon controlled spurred anoda better than imazethapyr 1 and 3 wk after late POST, but no treatment provided commercially acceptable full-season control. The number of treatments with gross margins greater than the untreated check increased as pinto bean prices increased, but ranking of gross margin did not change due to pinto bean prices.

Conventional lentil, because it is relatively noncompetitive, requires effective weed control. In conventional lentil, metribuzin should be applied by the four-node stage to avoid crop injury. This is earlier than the critical period of weed control (CPWC) of lentil, which is between the five- and 10-node stage. However, imidazolinone herbicides potentially can be applied later in imidazolinone-resistant lentil, which might allow lentil to be kept weed-free for the CPWC. The objective of this experiment was to determine the best herbicide choice and application timing necessary to achieve the CPWC in lentil. To do this we tested herbicides differing in efficacy and residual control. The herbicides imazethapyr/imazamox, imazamox, and metribuzin + sethoxydim were applied at the two- and six-node lentil stage. Of the three herbicide treatments, metribuzin + sethoxydim resulted in grain yield that was on average 31% lower than the other herbicides. This occurred because of greater broadleaf biomass (composed primarily of wild mustard) in lentils treated with these herbicides regardless of application timing. Because of this, the CPWC was not attained with metribuzin + sethoxydim. Late applications of imazethapyr/imazamox or imazamox resulted in grain yields 30% higher than with early application of these herbicides. Early applications of the imidazolinone herbicides gave poor control of grass weeds (wild oat and green foxtail), but late applications resulted in grass weed control equivalent to metribuzin + sethoxydim. Imazethapyr/imazamox or imazamox should be applied at the five- to six-node stage of lentil to achieve the CPWC.

Kochia poses a challenge to vegetation management in both agricultural and noncrop areas. This species has developed widespread resistance to several herbicides with differing modes of action, including acetolactate synthase inhibitors and photosynthesis inhibitors. Resistance is also beginning to appear against the synthetic auxins and glycines. Therefore, alternative PRE and POST herbicides are needed for effective kochia management, especially in roadside bare-ground zones. Both PRE and POST herbicides were screened on rights-of-way in Pennsylvania. Mixtures containing diuron, flumioxazin, sulfentrazone, pendimethalin, prodiamine, and bromacil were evaluated for PRE activity in combination with glyphosate. POST kochia control was assessed for 15 noncrop herbicides. Results from all trials varied with kochia size and vigor at time of treatment. Although diuron is the current industry standard for PRE control in tank mixes, sulfentrazone appeared to have the most POST activity against vigorously growing kochia. All PRE herbicides evaluated performed better than the standard, sulfometuron plus chlorsulfuron alone. Dicamba, dicamba plus diflufenzopyr, fluroxypyr, and glyphosate performed best against kochia when applied POST. The recently available chemistries saflufenacil and aminocyclopyrachlor require further evaluation of application timing and use rates, respectively, for POST activity on kochia.

The genus Conium is comprised of two or three temperate species of biennial herbs with highly divided leaves and compound umbels of small white flowers. All parts of C. macula tum have long been recognized as being highly poisonous; it was the plant used to kill Socrates in BC 399 (Gledhill 1985; Holm et al. 1997; Hyam and Pankhurst 1995). Conium is a member of the Umbelli ferae or Apiaceae, the carrot family, which accommodates 300 genera and between 2,500 and 3,000 species.

Experiments were conducted to determine peanut tolerance to CGA-362622 applied preemergence (PRE) and postemergence (POST) and to determine the potential for CGA-362622 applied PRE and POST to cotton to injure peanut grown in rotation the following year. CGA-362622 at 3.75 and 7.5 g ai/ha applied PRE visually injured peanut 11 and 16%, respectively, at 5 wk after treatment (WAT) but did not influence peanut yield. POST treatments at 3.75 and 7.5 g/ha injured peanut 63 and 93%, respectively, at 4 WAT and reduced peanut stand by 53 and 89% at 11 WAT, respectively. Peanut pod yield was reduced 73.1 and 97.9% by CGA-362622 POST at 3.75 and 7.5 g/ha, respectively, compared with the untreated weed-free control. CGA-362622 PRE at 3.75 and 7.5 g/ha reduced peanut pod yield 7.5 and 12.6%, respectively. Cotton was injured 9% or less by CGA-362622 PRE or POST at 3.75 or 7.5 g/ha and up to 25% with CGA-362622 POST at 15 g/ha. However, CGA-362622 did not influence weed-free cotton lint yields, regardless of method or rate of application. Peanuts grown in rotation were not injured, and yields were not influenced by CGA-362622 applied PRE or POST the previous year to cotton.

Laboratory and field studies were conducted to determine the effect of the drift control adjuvants HM 2005B and HM 9752 on the droplet spectra and efficacy of spray mixtures of a potassium salt formulation of glyphosate. Droplet spectra were examined using a laser spray droplet analyzer. The addition of each adjuvant decreased the percentage of the spray volume in small diam spray droplets (<141μm) and either had no effect or increased glyphosate efficacy. These adjuvants could prove useful for providing management in potential drift situations.

Field studies were conducted to examine the effects of the sulfonylurea-tolerant (ST) soybean and fall tillage on reducing rotational soybean response to soil-applied prosulfuron across a range of soil pH values. Prosulfuron (10 and 20 g ai/ha) was applied in the fall to simulate the maximum amount of carryover theoretically possible from corn weed control systems. ST soybean reduced effects of prosulfuron soil residues on soybean grain yield. Increased soil pH led to greater prosulfuron carryover as indicated by the differential in ST and non-ST soybean and grain yield responses. Tillage (chisel plow) did not decrease non-ST soybean response to prosulfuron soil residues. Soybean injury 30 d after emergence was well correlated with eventual yield losses in non-ST soybean. Greater soybean injury and yield loss was observed on a silt loam soil with 0.8% organic carbon than on silt loams with greater than 2.5% organic carbon.

Alfalfa seed yield and Canada thistle densities were measured in 10 fields in southern Alberta to assess the effect of thistles on seed yield. Thistle density and seed yield from each field were fitted to the Weibull, hyperbolic, and linear equations and a random coefficient and linear equation were used to obtain an “average yield loss curve”. Estimated average losses in alfalfa seed yield were >34% and >48% at thistle densities of 10 and 20 shoots m–2, respectively.

Enlist E3TM soybean cultivars permit over-the-top application of labeled glyphosate, glufosinate, and 2,4-D choline products. Increased Enlist E3TM trait adoption and use of 2,4-D choline postemergence across U.S. soybean production systems raise concerns regarding potential for 2,4-D off-target movement (OTM). A large-scale drift experiment was established near Sun Prairie, WI, and Arlington, WI, in 2019 and 2020, respectively. A 2,4-D-resistant soybean cultivar was planted in the center of the field (∼3 ha), while the surrounding area was planted with a 2,4-D-susceptible cultivar. An application of 785 ae ha−1 2,4-D choline plus 834 g ae ha−1 glyphosate was completed within the center block at R2 and V6 growth stages on August 1, 2019, and July 3, 2020, respectively. Filter papers were placed in-swath and outside of the treated area in one upwind transect and three downwind transects to estimate particle deposition. Low-volume air samplers ran for the 0.5-h to 48-h period following application to estimate 2,4-D air concentration. Injury to 2,4-D-susceptible soybean was assessed 21 d after treatment (0% to 100% injury). The 2,4-D deposition in-swath was 9,966 and 5,727 ng cm−2 in 2019 and 2020, respectively. Three-parameter log-logistic models estimated the distance to 90% reduction in 2,4-D deposition (D90) to be 0.63 m and 0.90 m in 2019 and 2020, respectively. In 2020, the 2,4-D air concentration detected was lower for the upwind (0.395 ng m−3) than the downwind direction (1.34 ng m−3), although both were lower than the amount detected in-swath (4.01 ng m−3). No soybean injury was observed in the downwind or upwind directions. Our results suggest that 2,4-D choline applications following label recommendations pose little risk to 2,4-D-susceptible soybean cultivars; however, further work is needed to understand 2,4-D choline OTM under different environmental conditions and the presence of other susceptible crops.

The use of cover crops in soybean production systems has increased in recent years. There are many questions surrounding cover crops—specifically about benefits to crop production and most effective herbicides for spring termination. No studies evaluating cover crop termination have been conducted across a wide geographic area, to our knowledge. Therefore, field experiments were conducted in 2016 and 2017 in Arkansas, Indiana, Mississippi, Missouri, and Wisconsin for spring termination of regionally specific cover crops. Glyphosate-, glufosinate-, and paraquat-containing treatments were applied between April 15 and April 29 in 2016 and April 10 and April 20 in 2017. Visible control of cover crops was determined 28 days after treatment. Glyphosate-containing herbicide treatments were more effective than paraquat- and glufosinate-containing treatments, providing 71% to 97% control across all site years. Specifically, glyphosate at 1.12 kg ha−1 applied alone or with 2,4-D at 0.56 kg ha−1, saflufenacil at 0.025 kg ha−1, or clethodim at 0.56 kg ha−1 provided the most effective control on all grass cover crop species. Glyphosate-, paraquat-, or glufosinate-containing treatments were generally most effective on broadleaf cover crop species when applied with 2,4-D or dicamba. Results from this research indicate that proper herbicide selection is crucial to successfully terminate cover crops in the spring.

Glyphosate is now the most widely used herbicide; after years of frequent utilization, resistant weeds were selected, mainly due to widespread adoption of glyphosate-resistant crops and no-tillage sowing system. Increasing difficulty in controlling Chloris polydactyla with glyphosate has been noticed in agricultural areas. Here, the susceptibility level of various C. polydactyla accessions from Brazil is examined. Two whole-plant studies were conducted to confirm the presence and extent of glyphosate susceptibility among accessions, which involved the application of seven glyphosate doses on four accessions. The four accessions showed different glyphosate susceptibilities. The “Matão” accession presented major tolerance for glyphosate compared to “Palotina” accessions. “Jaboticabal” plants showed an intermediary susceptibility. The resistance factor (RF) was 3.76 between the “Matão” and “Palotina” accessions. All biotypes died at 2,880 g ae ha−1 glyphosate.