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4 results on '"Wesley C. Hoffmann"'

1. Dicamba off‐target movement from applications on soybeans at two growth stages

Author

Greg R. Kruger, Guilherme S. Alves, Kasey Schroeder, Jeffrey A. Golus, Daniel B. Reynolds, Darrin M. Dodds, Ashli E. Brown, Bradley K. Fritz, and Wesley C. Hoffmann

Subjects
Agriculture, Environmental sciences, GE1-350
Abstract

Abstract The objective of this study was to evaluate dicamba off‐target movement during and after applications over soybean at two growth stages. Dicamba‐tolerant soybean [Glycine max (L.) Merr.] at V3 and R1 growth stages in Nebraska and Mississippi fields were treated with diglycolamine salt of dicamba (560 g ae ha−1), potassium salt of glyphosate (1260 g ae ha−1), and a drift‐reducing adjuvant (0.5% v v−1). Filter papers positioned outside the sprayed area were used to determine primary movement and air samplers positioned at the center of sprayed area were used to calculate dicamba flux from 0.5 up to 68 hours after application (HAA). Flux was calculated using the aerodynamic method. Soybean growth stage did not affect dicamba deposition on filter papers from 8 to 45 m downwind from the sprayed areas. At 33 m downwind (i.e., distance of the labeled buffer zone), a spray drift of less than 0.0091% (0.05 g ae ha−1) of applied rate is estimated. Dicamba secondary movement may not be affected by soybean growth stage during the application. Although dicamba was detected in air samples collected at 68 HAA, the majority of the secondary movement was observed in the first 24 HAA. Dicamba cumulative loss was lower than 0.77% of applied rate. Results suggest the more stable the atmospheric conditions, the higher the dicamba flux. Thus, meteorological conditions after applications must be considered, and tools to predict the occurrence of temperature inversion are needed to minimize secondary movement of dicamba.

Published
2023
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2. Nozzle Selection and Adjuvant Impact on the Efficacy of Glyphosate and PPO-Inhibiting Herbicide Tank-Mixtures

Author

Jesaelen G. Moraes, Thomas R. Butts, Vitor M. Anunciato, Joe D. Luck, Wesley C. Hoffmann, Ulisses R. Antuniassi, and Greg R. Kruger

Subjects
air inclusion nozzle, crop oil concentrate, drift reducing adjuvant, methylated seed oil, non-air inclusion nozzle, non-ionic surfactant, Agriculture
Abstract

PPO-inhibiting herbicides in combination with glyphosate for postemergence applications is a common approach to manage glyphosate- and ALS-inhibitor-resistant weeds. PPO-inhibitors can reduce glyphosate translocation when applied in tank-mixtures, but adjuvants may be used to overcome this effect. Additionally, optimal droplet size may be affected by tank-mixtures of different herbicides and it can be crucial to herbicide efficacy. Field and greenhouse studies were conducted to investigate the impact of nozzle selection and adjuvants on weed control and interactions when applying PPO-inhibitors (fomesafen or lactofen) alone or in tank-mixture with glyphosate to five weed species using six nozzle types. Ultra-coarse droplets were just as effective as medium droplets regardless of the spray solution, but have a lower likelihood of off-target movement. Tank-mixtures applied were consistently antagonistic to common lambsquarters, horseweed, and Palmer amaranth. Only fomesafen was antagonistic to kochia whereas synergistic interactions were observed when glyphosate plus lactofen were applied in combination with COC, DRA + COC, or NIS. Separate applications are advisable with herbicide- and weed-specific situations to avoid antagonism, which is necessary to achieve optimum weed control and maintain the effectiveness of PPO-inhibitors. Future research should continue to look at these important interactions across a wide range of weed species.

Published
2021
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3. Impact of electrostatic and conventional sprayers characteristics on dispersion of barrier spray

Author

Muhammad, Farooq, Todd W, Walker, Bryan P, Heintschel, Wesley C, Hoffmann, Bradley K, Fritz, Vincent L, Smith, Cathy A, Robinson, and Trey, English

Subjects
Aerosols, Insecticides, Mosquito Control, Static Electricity, Animals
Abstract

A study was conducted to analyze the performance of 3 electrostatic (Electrolon BP-2.5, Spectrum Electrostatic 4010, and Spectrum Electrostatic head on a Stihl 420) and 2 conventional (Buffalo Turbine CSM2 and Stihl 420) sprayers for barrier sprays to suppress an adult mosquito population in an enclosed area. Sprayer characteristics such as charge-mass ratio, air velocity, flow rate, and droplet spectra were measured while spraying water. Dispersion of the spray cloud from these sprayers was determined using coverage on water-sensitive cards at various heights (0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m, and 3.0 m) and depths (1 m, 3 m, and 5 m) into the under-forest vegetation while spraying bifenthrin (Talstar 7.9% AI; FMC Corporation, Philadelphia, PA) at the rate of 21.8 ml/300 m of treated row. The charge-mass ratio data show that Electrostatic head on a Stihl 420 did not impart enough charge to the droplets to be considered as an electrostatic sprayer. In general, the charged spray cloud moved down toward the ground. The Electrolon BP 2.5 had significantly lower spray coverage on cards, indicating lack of spray dispersion. This sprayer had the lowest air velocity and did not have the air capacity needed to deliver droplets close to the target for electrostatic force to affect deposition. The analysis shows that these 2 sprayers are not a suitable choice for barrier sprays on vegetation. The results indicate that the Buffalo Turbine is suitable for barriers wider than 3 m, and the Spectrum 4010 and Stihl 420 are suitable for 1-3-m-wide barriers.

Published
2011

4. Mortality and reproductive effects of ingested spinosad on adult bollworms

Author

Juan D, López, Mohamed A, Latheef, and Wesley C, Hoffmann

Subjects
Male, Drug Combinations, Eating, Insecticides, Reproduction, Animals, Female, Macrolides, Moths
Abstract

Upon emergence from their pupal cells, bollworm, Helicoverpa zea (Boddie), adults actively seek and feed on plant exudates before they disperse and reproduce on suitable host plants. This nocturnal behavior of the bollworm may be exploited as a pest management strategy for suppression of the insect by using an attractant/stimulant mixed with an insecticide to induce feeding to cause adult mortality or reproductive reduction/inhibition. This study aimed to determine in the laboratory whether or not spinosad when mixed with sucrose solution as a feeding stimulant and ingested by bollworm could influence mortality and reproduction of the insect.Sublethal concentrations of spinosad fed to laboratory-reared females confined with males significantly reduced percentage hatch of eggs at 0.1 mg L(-1), and it was reduced to near zero at 2.5 mg L(-1) when compared with females fed 2.5 M sucrose solutions only. The lethal concentration (LC(99)) for males captured from the field in sex-pheromone-baited traps was 73 mg L(-1) for 24 h response. Proboscis extension response was not inhibited significantly even at 10 g L(-1). In spite of a 137-fold increase in lethal dose concentration, spinosad did not inhibit feeding.A detailed study of laboratory-reared and field-collected bollworm adults relative to mortality and reproduction after ingestion of spinosad indicates that spinosad would be useful in an attract-and-kill strategy to control the insect when mixed with a feeding attractant/stimulant. Field validation of the data is warranted.

Published
2010

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