Impact of volatility reduction agents on dicamba and glyphosate spray solution pH , droplet dynamics, and weed control

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Two low-dose dicamba exposure trials were conducted on container-grown peach trees in Fayetteville, AR. Peach trees were ‘July Prince’ scions grafted onto ‘Guardian’ rootstock and were transplanted into 19 L containers and received experimental dicamba treatments in each year. Container trials were initiated in 2020 and repeated on new trees in 2021. In the repeated application trial, dicamba was applied at 5.6 g ae ha-1 (1/100× field rate) in five sequences: an untreated control receiving no herbicide, one treatment receiving only initial application, and three treatments receiving initial application plus sequential applications at the same rate occurring 14 d, 28 d, 14 d + 28 d after initial treatment (DAT). A separate trial assessed peach tree responses to dicamba applied at 11.2 g ae ha-1 (1/50× field rate) using a selection of nozzles with differing droplet spectrum characteristics: Turbo TeeJet® Induction (TTI11002), Air Induction Turbo TeeJet® (AITTJ60-11002), AIXR TeeJet® (AIXR11002, air induction extended range), XR TeeJet® (XR11002, extended range flat fan), and XR TeeJet® (XR1100067, extended range flat fan). Peach tree height, tree cross sectional area (TCSA) and leaf chlorophyll content were not reduced in response to any sequence of dicamba application or nozzle selection. Repeated applications of dicamba at 1/100× rate did not increase peach injury after 28 DAT. By 84 DAT, no effect of nozzle type on peach tree injury was discernable, and all treatments caused below 4% injury. No dicamba or dicamba metabolites were observed in leaf samples collected at 14, 69, or 85 DAT from trees treated with XR1100067 nor in untreated controls. While peach tree injury was observed throughout the experiment, dicamba residues were only detected consistently in 2020 from leaf samples of trees treated with dicamba at 1/50× rate using TTI1102, AITTJ60-11002, AIXR11002, and XR11002 nozzles.

Section: Methodsmentioning

confidence: 99%

Peach tree response to low dosages of dicamba as repeated application or with various spray nozzles

Bertucci,

Butts,

Kouame

et al. 2023

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“…where V is the cumulative % volume of droplets with the diameter lower than a certain value ( d ); c is the characteristic droplet diameter, defined as the diameter at which the cumulative volume fraction is 63.2%; and m is a constant indicating the uniformity of the distribution (Kouame et al 2022b; Nie et al 2019).…”

Section: Methodsmentioning

confidence: 99%

“…Droplet dynamics were measured using the VisiSize P15 Portable Particle/Droplet Image Analysis System (Oxford Lasers, Oxford, UK), and the experiment was conducted as a completely randomized design with three replications. The VisiSize P15 system was installed within a Generation 4 Research Track Sprayer (Devries Manufacturing, Hollandale, MN) as described previously by Kouame et al (2022b). The distance between the nozzle tip and the measurement zone was set to 51 cm to allow droplet size and velocity to be measured from the entire spray plume when it crossed the space between the main body and the light delivery block.…”

Section: Droplet Dynamics Laboratory Experimentsmentioning

confidence: 99%

“…The DV 0.1 , DV 0.5 , and DV 0.9 values (representing 10%, 50%, and 90% of the spray volume being composed of droplets of a smaller diameter, respectively), the relative span (RS) (Kouame et al 2022b), and the average and maximum droplet velocity data were also subjected to ANOVA using the GLIMMIX procedure with SAS software assuming a gamma distribution (Butts et al 2019b). Treatment means were separated using Tukey's adjustment (α = 0.05).…”

Section: Data Processing and Analysismentioning

confidence: 99%

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Palmer amaranth (Amaranthus palmeri) control affected by weed size and herbicide spray solution with nozzle type pairings

Kouame,

Butts,

Norsworthy

et al. 2023

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Palmer amaranth can grow 4.2 mm in height per degree day; hence, delays of a few days in weed control deployment can result in applications to larger than labeled weeds. Therefore, it is critical to understand the impact of plant size at the time of application in conjunction with herbicide spray solution and nozzle type pairings on the effectiveness of weed management programs in the Enlist E3 and XtendFlex production systems. Field experiments were conducted in 2020, in no-crop conditions, at the Milo J. Shult Agricultural Research & Extension Center in Fayetteville, AR, and the Jackson County Extension Center near Newport, AR, to evaluate the influence of Palmer amaranth size on its control with glufosinate, dicamba, and 2,4-D applied alone and in mixture with specific nozzle pairings as mandated by label requirements. Also, a laboratory experiment was conducted at the Lonoke Extension Center (Lonoke, AR) to evaluate the droplet size and velocity of the spray solutions and nozzles used for the field experiment. A 5- and 10-percentage point reduction in control was observed when applying dicamba (66%) and 2,4-D (63%) alone, respectively compared to each mixed with glufosinate (71% and 73%, respectively). Palmer amaranth density increased to 55, 73, 100, 115, and 140 plants m-2 when 15-, 25-, 41-, 61-, and 76-cm tall plants were sprayed, respectively, compared to when 5-cm tall plants were sprayed (9 plants m-2). Nozzle types did not impact weed control and density. The addition of glufosinate to 2,4-D increased the percentage of driftable fines compared to 2,4-D alone. Effective short- and long-term chemical control of Palmer amaranth will require growers to be timely with their weed management programs, overlay residuals, and expect the need for sequential applications.

“…Measurements were made using the VisiSize P15 Portable Particle/ Droplet Image Analysis System (Oxford Lasers, Imaging Division, Oxford, UK) using similar methods to previous research (Kouame et al 2022). The system was installed within a Generation 4 Research Track Sprayer (Devries Manufacturing, Hollandale, MN).…”

Section: Droplet Size and Velocity Experimentsmentioning

confidence: 99%

Evaluation of row width and nozzle selection on spray coverage and weed control in flooded rice

Reed,

Butts,

Norsworthy

et al. 2024

Barnyardgrass and other troublesome weeds have become a major problem for producers in a flooded rice system. Cultural control options and more efficient herbicide applications have become a priority to increase efficiency and weed control in rice. This study aimed to determine the effects of row width and nozzle selection on spray coverage and weed control in a flooded rice system. A field experiment was conducted at 7 site-years (Lonoke, AR, in 2021 and 2022; Pine Tree, AR, in 2021 and 2022; Rohwer, AR, in 2022; and Stoneville, MS, in 2021 and 2022) as a randomized complete block split-plot design. Five nozzles (XR, AIXR, TTI, TTI60, and AITTJ60) (subplot factor) were used for herbicide applications, and plots were drill-seeded in four row widths (whole plot factor) (13, 19, 25, and 38 cm). A droplet size experiment was conducted to evaluate the droplet size and velocity of each nozzle type used in the field experiment. Overall, as row width increased, barnyardgrass density increased. The rice grown in a wider width took longer to generate canopy closure, allowing weed escapes in the crop. For example, the 13-cm width had a 12 percentage point canopy coverage increase compared to the 38-cm row width at the preflood timing resulting in a reduction of six barnyardgrass plants per square meter. The smallest droplet size-producing nozzle (XR) provided greater weed control throughout the study but is more prone to drift. The dual-fan nozzles (AITTJ60 and TTI60) had variable weed control impacts, and it was difficult to predict when this might occur; however, they did have increased deposits on water-sensitive cards compared to single-fan counterparts (AIXR and TTI). In conclusion, a narrower row width (e.g., 19-cm or less) and a smaller droplet size producing nozzle (XR) are optimal for barnyardgrass control in a flooded rice system.