Simulated Drift Research Articles

Robotic Label-Free Precise Oocyte Enucleation for Improving Developmental Competence of Cloned Embryos.

The invisibility of domestic oocyte nucleus in bright field currently forces operators to blindly aspirate nucleus out in oocyte enucleation, usually causing large cytoplasm losses and poor developmental competences of cloned embryos. Although fluorescent labeling of nucleus allows for nucleus localization, the involved photobleaching problems and barriers to the execution of enucleation process limit its online-application in oocyte enucleation. This paper reports a novel label-free oocyte enucleation method for precise removal of the nucleus with less cytoplasm loss. The relative positions between the injection pipette and nucleus for complete removal of nucleus with less cytoplasm loss were determined through a finite element modeling of nucleus aspiration. To position injection pipette to the above positions relative to nucleus, the appropriate oocyte orientation and trajectory of injection pipette inside oocyte were derived according to the offline-calibrated 3-D distribution of nucleus and the simulated dynamic drift of nucleus that occurs as injection pipette is maneuvered inside oocyte. Finally, a robotic label-free precise enucleation procedure was established. The experimental results on more than 1000 porcine oocytes proved that this system is capable of reducing cytoplasm loss by 60% at the same level of enucleation success rate and almost doubling the cleavage rate of clone embryos in comparison to blind aspiration method. The results prove that our method significantly improves the developmental competence of cloned embryos in comparison to manual enucleation method. Our method is expected to improve the extremely low success rate of animal cloning in the future.

Damage to lemon tree caused by simulated drift of herbicides

The use of herbicides, in particular clomazone and glyphosate, applied in isolation or in a tank mix, is very common in rice, soybeans, corn and sugarcane fields and the drift of these herbicides can cause damage in sensitive species grown nearby. The purpose of this work was to evaluate the effects of the simulated drift of clomazone and glyphosate applied in an isolated way or mixed in a spray on lemon tree plants. The experiment was installed in a greenhouse in pots with a capacity of 15 L containing sieved soil and an experimental design of randomized blocks was adopted, arranged in a 3 x 5 factorial scheme, with four replications. Plants with two years of development were used. The treatments tested were, clomazone, glyphosate and both mixed, and the decreasing doses of the recommended commercial product: 100, 75, 50, 25 and 0% to simulate herbicide drift. Was evaluated variables, phytotoxicity at 14, 28, 46 and 100 days after application of treatments; plant height, crown volume, the trunk diameter of the rootstock, trunk diameter of the graft and trunk diameter at the grafting point at 0 and 100 days after application of treatments; and liquid assimilation of CO2 at 10 and 60 days after application of treatments. Among the tested herbicides, the one that presented the highest phytotoxicity and the lowest liquid assimilation of CO2 in lemon tree plants was the glyphosate + clomazone mixture. Increases in trunk diameter of the rootstock, grafting point, graft and crown volume did not show significant effects with simulated drift. The plant height presented a greater reduction with the increase of the herbicide doses, mainly glyphosate. That there are considerable losses in lemon tree plants when herbicide drift occurs, mainly by glyphosate and its mixture with clomazone.

Simulated derive of glyphosate in green onion plants (Allium fistulosum L.)

The effect of simulated glyphosate drift on common chives (Allium fistulosum L.) was evaluated. The work was developed in a private garden, in Confresa-MT, from January to February 2016. The experiment consists of 6 treatments with 4 repetitions, arranged in a completely randomized design (DIC). The treatments were formed b 6 sub doses of glyphosate: 0,54,108,162,216 and 270 g.i.a ha-1 . At 7 and 14 days after application of the sub doses of the herbicide glyphosate, the plants were subjected to visual analysis of phytointoxication, using notes, on a scale ranging from 0 to 10. At 14 days after application of herbicide, the number total leaves, number of dead leaves, number of tillers, fresh weight of commercial leaf and root length.

Forced Patterns of Sea Level Rise in the Community Earth System Model Large Ensemble From 1920 to 2100

AbstractTo provide context for observed sea level rise, the forced response (FR) in dynamic sea level (DSL) during the 20th and 21st centuries is examined in the Community Earth System Model Large Ensemble (LE). After accounting for simulation drift, which in the LE is sizable, the DSL FR is found to be complex, both in space and time. Its evolving character is suggested to arise from both the diversity and transient evolution of climate forcing agents and the slow adjustment timescales of the intermediate and deep oceans. Nonetheless, various intervals of spatially coherent change simulated for the recent past and near future are identified, and their characteristics and associated driving mechanisms are identified and discussed. The mid‐ to late‐20th century DSL FR is characterized by an hemispherically asymmetric pattern of change, with depressed rates of rise in the northern oceans. There is also a dipole of change in the Southern Ocean caused by changes in near‐surface zonal winds. Through the late 20th and early 21st centuries, a different pattern of rise emerges with elevated rates in the tropics and depressed rates at high latitudes. Zonal and interbasin variations characterize both intervals and involve the pattern and depth of anomalous ocean heat content storage and spatial contrasts in the expansion coefficient tied mainly to base state temperature, with greater rates of rise in warm regions per unit warming. The relative roles of surface flux and ocean convergence anomalies are examined.

Evaluation of Arctic sea ice drift and its dependency on near-surface wind and sea ice conditions in the coupled regional climate model HIRHAM–NAOSIM

Abstract. We examine the simulated Arctic sea ice drift speed for the period 2003–2014 in the coupled Arctic regional climate model HIRHAM–NAOSIM 2.0. In particular, we evaluate the dependency of the drift speed on the near-surface wind speed and sea ice conditions. Considering the seasonal cycle of the Arctic basin averaged drift speed, the model reproduces the summer–autumn drift speed well but significantly overestimates the winter–spring drift speed, compared to satellite-derived observations. Also, the model does not capture the observed seasonal phase lag between drift and wind speed, but the simulated drift speed is more in phase with the near-surface wind. The model calculates a realistic negative correlation between drift speed and ice thickness and between drift speed and ice concentration during summer–autumn when the ice concentration is relatively low, but the correlation is weaker than observed. A daily grid-scale diagnostic indicates that the model reproduces the observed positive correlation between drift and wind speed. The strongest impact of wind changes on drift speed occurs for high and moderate wind speeds, with a low impact for rather calm conditions. The correlation under low-wind conditions is overestimated in the simulations compared to observation/reanalysis data. A sensitivity experiment demonstrates the significant effects of sea ice form drag from floe edges included by an improved parameterization of the transfer coefficients for momentum and heat over sea ice. However, this does not improve the agreement of the modeled drift speed / wind speed ratio with observations based on reanalysis data for wind and remote sensing data for sea ice drift. An improvement might be achieved by tuning parameters that are not well established by observations.

Integrating dissipative particle dynamics with energy conservation.

To suppress secular energy drift in dissipative particle dynamics simulations with energy conservation, we introduce an additional pairwise particle dynamics that allows for a microscopic energy fluctuation while conserving the total linear momentum of the system exactly. The pairwise dynamics may be regarded as an adaptation of the thermostat in isothermal dissipative particle dynamics, but leads to microcanonical instead of canonical ensemble at equilibrium and allows for a nonuniform temperature field at a steady state. The method is also effective in suppressing secular energy drift when used in combination with reverse nonequilibrium molecular dynamics moves. All of the equilibrium and transport properties we computed were unaffected by this additional pairwise dynamics.

Simulated drift of dicamba and 2,4-D on soybeans: effects of application dose and time

The use of soybean varieties resistant to the herbicides dicamba and 2,4-D may lead to drifts towards areas grown with non-resistant varieties. The aim of this study was to evaluate the effects of dicamba and 2,4-D underdoses applied at the phenological stages V4 and R2 of soybeans. Two experiments were conducted with dicamba or 2,4-D in a randomized block design with four replications. The 4 × 2 + 1 factorial scheme was composed of four doses (0.028, 0.28, 2.8, and 28 g ae ha−1) of dicamba or 2,4-D applied at two phenological stages (V4 and R2) + a control treatment (without herbicide application). Dicamba underdoses caused damage to soybean crop affecting its vegetative growth and yield; the injuries caused by 2,4-D were neither enough to damage crop nor affect yield components. Dicamba underdoses applied at V4 caused injuries of up to 41%, while in R2 they reached 70%. Plant height decreased by up to 61% when treated with dicamba. Soybean yield was reduced by 29 and 76% when the simulated drift occurred at V4 and R2, respectively, and at a dose of 28 g ae ha−1 of dicamba. For the tested underdoses, only 2,4-D had no effect in soybean crop yield.

Biološki odgovori hibrida kukuruza na drift glifosata

The effect of simulated glyphosate drift on six maize hybrids (NS 6102, as 334, Lucius, Confites, DKC 5031 and P0216) was investigated in Kulpin during the vegetation season of 2018. Glyphosate was applied in two growth stages: in stages 3-4 and 6-7 of fully formed maize leaves, with five different sublethal doses of the herbicide: 10, 20, 40, 80, 160 g ha-1. Phytotoxicity assessments of glyphosate were performed 7, 14, and 21 days after herbicide application. Analysis of the results has shown that glyphosate in the dose of 160 g ha-1 in the phase of 3-4 maize leaves caused only slight damages, without affecting the height and grain yield, while phytotoxicity was not observed at lower applied doses. Significant phytotoxicity on maize plants in the form of chlorosis, leaf curling and notable necrotic area was found when applying glyphosate in the dose of 160 g ha-1 in the phase of 6-7 leaves. Maize hybrids tested in this treatment have achieved an 81% lower yield on average, when compared to the control. Hybrids treated with the dose of 80 g ha-1 of glyphosate had a reduced yield by 30%, while in other lower doses the reduction in yield ranged between 25 and 18%, compared to the control.

Simulated drift of dicamba: effect on the physiological quality of soybean seeds

Abstract: The release of soybean varieties resistant to dicamba herbicide leads to the possibility of dicamba herbicide drift into soybean seed production fields and reduction in the physiological quality of soybean seeds. The aim of this study was to evaluate the physiological quality of soybean seeds as a function of the application of reduced rates of dicamba in two phenological phases. A randomized block experimental design was used, with four replications. The 4 × 2 + 1 factorial arrangement consisted of four reduced rates (0.028, 0.28, 2.8 and 28 g.ha-1) of dicamba applied in the V4 and R2 stages + a control. The physiological quality of the seeds was evaluated after harvest and at six months after storage at 20 °C. At the rate of 28 g.ha-1 of dicamba applied in the V4 and R2 stages, seed germination declined by 15% and 42%, respectively. After storage, seeds under the 28 g.ha-1 dicamba treatment had 64% lower germination compared to the lowest application rate evaluated, and electrical conductivity doubled in relation to the control. The physiological quality of soybean seeds declines under these reduced rates of dicamba applied in the V4 and R2 stages, both before and after storage.

Tank contamination and simulated drift effects of dicamba‐containing formulations on soybean cultivars

AbstractThe objectives of this study were to (a) investigate the spray drift potential of dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) formulations with different nozzles in a low‐speed wind tunnel and (b) evaluate the effects of sublethal rates of dicamba‐containing formulations on non–dicamba‐tolerant (DT) soybean [Glycine max (L.) Merr.] cultivars. The dicamba formulations used were diglycolamine (DGA), N,N‐Bis‐(3‐aminopropyl)methylamine, and diglycolamine with VaporGrip (DGAvg). The wind tunnel drift study was conducted with these three dicamba formulations, two nozzle types (AIXR110015 and TTI110015), and five downwind distances from the nozzle (1, 2, 4, 8, and 12 m). The dicamba rate was 560 g ae ha−1, simulating a 140 L ha−1 carrier volume. The soybean exposure study was conducted in two experimental runs with three sublethal dicamba rates (0.112, 0.56, and 5.6 g ae ha−1), the three dicamba formulations aforementioned, and five non‐DT soybean cultivars (Asgrow A3253, Asgrow AG2636, Credenz CZ2601LL, DynaGro 39RY25, and Hoegemeyer 2511NRR). Applications were made using a spray chamber with a single AI9502EVS even nozzle that delivered 140 L ha−1. During applications, soybean plants were at three‐leaf growth stage. Dicamba formulations had different drift deposition across the AIXR and TTI nozzles. The soybean cultivars had different levels of sensitivity to dicamba and depended on rate vs. formulation interaction. The DGA caused greater biomass reduction on soybean cultivars compared with DGAvg, especially for Credenz CZ2601LL, which was one of the most dicamba‐sensitive cultivars along with Hoegemeyer 2511NRR. Additional care must be taken to mitigate off‐target movement from dicamba applications with these cultivars nearby.

PHYTOTOXICITY AND GROWTH OF COFFEE PLANTS AS A FUNCTION OF THE APPLICATION OF HERBICIDE 2,4-D

Weed control in coffee is of great importance for there is a great interference, standing out the competition for water, light and nutrients. Among the control methods, chemical control is highlighted as a function of its efficiency. However, the incorrect application of herbicides may imply the occurrence of drift, resulting in damage to coffee development due to phytotoxicity. In this context, the objective of this study was to evaluate the symptoms and phytotoxicity effects caused by the herbicide 2,4-D drift on the morphological, physiological and anatomical characteristics of coffee seedlings. The experiment was carried out in a greenhouse with ‘Topázio MG1190’ coffee seedlings (<em>Coffea arabica</em> L.), planted in 11-L pots. A randomized block design with four treatments and four replicates was used. The treatments were: 0%; 10%; 25% and 50% of the recommended commercial dose of 2,4-D (2.5 L.ha<sup>-1</sup>). Each plot consisted of three plants. The evaluations were performed at 74 days after implantation. Morphological, physiological, anatomical and phytotoxicity symptoms were evaluated as a function of the simulated herbicide drift. Coffee seedlings intoxicated by the herbicide 2,4-D presented hyponastic, chlorosis, shriveling and leaf anomalies. In the orthotropic branch, bending was observed in its extension, besides thickening in the collar region; in the plagiotropic branch, cracking was observed. Herbicide drift negatively affects the development of coffee plants. The coffee physiology was affected as a function of herbicide drift, but without damage to the leaf anatomy.

Sensitivity of Ice Drift to Form Drag and Ice Strength Parameterization in a Coupled Ice–Ocean Model

ABSTRACTA pan-Arctic sea-ice–ocean prediction system is assessed in terms of its ability to predict sea-ice velocity. This system is based on the Regional Ice Ocean Prediction System running operationally at the Canadian Centre for Meteorological and Environmental Prediction. A form drag parameterization is implemented in the system to allow spatially and temporally varying neutral drag coefficients depending on the sea-ice morphological characteristics. Simulated ice velocity is assessed using data from the International Arctic Buoy Programme, as well as ice motion derived from Environment and Climate Change Canada’s synthetic aperture radar automated ice-tracking system. Results indicate that introducing the form drag parameterization systematically increases the sea-ice velocity and exacerbates a positive bias in summer already present in the previous version in which constant neutral drag coefficients were used. The ice strength parameterization used in the model rheology is found to affect the simulated ice drift significantly. Introducing modifications to the ice strength formulation and the empirical parameters helped alleviate the ice velocity bias.

A hyperspectral experiment over tropical forests based on the EO-1 orbit change and PROSAIL simulation

ABSTRACTWe designed a unique hyperspectral experiment from the Earth Observing One (EO-1) orbit change to evaluate solar illumination effects over tropical forests in Brazil. Ten nadir-viewing Hyperion images collected over a fixed site and period of the year (July to August) were selected for analysis. We evaluated variations in reflectance and in 16 narrowband vegetation indices (VIs) with increasing solar zenith angle (SZA) from the pre-drift (2004–2008) to the EO-1 drift period (2011–2016). To detect changes in reflectance and shadows, we applied spectral mixture analysis (SMA) and principal component analysis (PCA) and calculated the similarity spectral angle (θ) between the vegetation spectra measured with variable SZA. The magnitude of the illumination effects was also evaluated from change-point analysis and nonparametric Mann-Whitney U tests applied over the time series. Finally, we complemented our experiment using the PROSAIL model to simulate the VIs variation with increasing SZA resultant from satellite drift. The results showed significant changes in Hyperion reflectance and VIs, especially when the EO-1 crossed the study area at earlier times and larger SZA in 2015 (9:05 a.m.; SZA = 59°) and 2016 (8:30 a.m.; SZA = 67°). Compared to the pre-drift period (10:30 a.m.; SZA = 45°), the SZA differences of 14° (2015) and 22° (2016) increased the shade fractions and decreased the vegetation brightness. PCA separated the pre-drift and drift reflectance datasets, showing shifts in scores due to changes in brightness. θ increased with SZA, indicating changes in the shape of the vegetation spectra with drift. For most VIs, the change-point analysis indicated 2015 (SZA = 59°) as the predominant year of detected changes. Compared to the EO-1 original orbit, the Plant Senescence Reflectance Index (PSRI), Anthocyanin Reflectance Index (ARI) and Structure Insensitive Pigment Index (SIPI) presented the largest positive changes during drift, while the Photochemical Reflectance Index (PRI), Visible Atmospherically Resistant Index (VARI) and Enhanced Vegetation Index (EVI) had the largest negative changes. The effect size of the illumination geometry on these VIs was large, as indicated by increasing values of the Cohen’s r metric toward 2016. The anisotropy of the Hyperion VIs was generally consistent with that from PROSAIL in the simulated pre-drift and drift periods. Focusing on structural indices, it affected the relationships between VIs and simulated leaf area index (LAI) at large SZA.

SAPS in the 17 March 2013 Storm Event: Initial Results From the Coupled Magnetosphere‐Ionosphere‐Thermosphere Model

AbstractSubauroral polarization stream (SAPS) is latitudinally narrow flow channels of large westward plasma drifts in the subauroral ionosphere. In this study, the global structure and dynamic evolution of SAPS are investigated by using the Coupled Magnetosphere‐Ionosphere‐Thermosphere model with ring current extension, namely, the Lyon‐Fedder‐Mobarry‐Thermosphere Ionosphere Electrodynamics General Circulation Model‐Rice Convection Model, to simulate the 2013 St. Patrick's Day storm event. This is the first time that the global distribution and temporal evolution of SAPS are investigated using first‐principle models. The model shows a strong westward ion drift channel formed equatorward of the auroral electron precipitation boundary on the duskside, which is identified as the SAPS structure. The simulated ion drift velocity and auroral electron precipitation sampled along the trajectory of the Defense Meteorological Satellite Program F18 satellite are in good agreement with the satellite measurements. SAPS initiate in the predusk sector when the interplanetary magnetic field turns southward. SAPS latitude generally decreases with magnetic local time from dusk to midnight. The SAPS channel shows wedge, inverse wedge, and crescent morphologies during the storm and becomes discontinuous when the interplanetary magnetic field is weakly southward. The SAPS mean latitude has a correlation coefficient of 0.77 with the Dst index. The mean latitude moves equatorward, and the flow channel broadens in the storm main phase. The simulation results illustrate both the global distribution and highly dynamic behavior of SAPS that are not readily apparent from the observation data.

Simulated Single Drift Events of 2,4-D and Dicamba on Pecan Trees

A large number of agronomic and horticultural crops are susceptible to injury and yield loss from drift-level exposures to synthetic auxin herbicides. A new generation of genetically modified crops including cotton (Gossypium hirsutum), field corn (Zea mays), soybean (Glycine max), and canola (Brassica napus) with resistance to dicamba and 2,4-D herbicides has been developed to address the problem of glyphosate-resistant weeds. In the few years since their commercial introduction, these technologies have been rapidly adopted. The objective of this study was to determine the potential effects of simulated, single drift events of 2,4-D and dicamba on pecan (Carya illinoinensis) trees. 2,4-D amine [3.8 lb/gal acid equivalent (a.e.)] or dicamba-Diglycolamine salt (4.0 lb/gal a.e.) were applied in 1.0%, 0.1%, and 0.01% by volume spray solutions to pecan trees in June 2013. In 2016 and 2017, 2,4-D choline (3.8 lb/gal a.e.) or dicamba-N,N-Bis-(3-aminopropyl) methylamine (5.0 lb/gal a.e.) were applied in 1.0%, 0.1%, and 0.01% by volume spray solutions to pecan trees in May. These results suggest that serious injury can occur to pecan trees receiving a drift application of 1.0% by volume dicamba or 2,4-D. This injury includes deformed foliage, dead foliage, dead limbs, and/or branches, and arrested nut development. There were no major differences in the response of pecan to either dicamba or 2,4-D at similar rates in this study. Pecan damage resulting from off-target movement of 2,4-D and dicamba at rates ≥1% by volume has the potential to cause significant injury. Yield was not negatively affected by any of the treatments, suggesting that pecan trees can compensate for the observed injury to some extent. The effect of treatments on percent kernel was variable.

Sensitivity and Recovery of Grain Sorghum to Simulated Drift Rates of Glyphosate, Glufosinate, and Paraquat

A field experiment was conducted in 2017 and 2018 to evaluate the sensitivity and recovery of grain sorghum to the simulated drift of glufosinate, glyphosate, and paraquat at two application timings (V6 and flag leaf growth stage). Paraquat drift caused maximum injury to sorghum plants in both years, whereas the lowest injury was caused by glyphosate in 2017. Averaged over all herbicide treatments, injury to grain sorghum from the simulated herbicide drift was 5% greater when herbicides were applied at flag leaf stage, as compared to herbicide applications at the six-leaf stage in 2017. In 2018, injury from glyphosate drift was higher when applied at the six-leaf stage than at the flag leaf stage. Paraquat and glufosinate drift caused more injury when applied at flag leaf stage than at six-leaf stage at 14 days after application in 2018. About 21% to 29% of injury from the simulated drift of paraquat led to a 31% reduction in grain sorghum yield, as compared to a nontreated check in 2017. The simulated drift of glyphosate and glufosinate did not result in any significant yield reduction compared to the nontreated check in 2017, possibly due to the recovery of sorghum plants after herbicides’ drift application.

A deriva de glyphosate interfere no desenvolvimento e produtividade de arroz irrigado

Objetivo do trabalho foi avaliar os danos ao desenvolvimento e produtividade de cultivar de arroz irrigado de ciclo precoce (IRGA 430), ocasionados por deriva simulada de glyphosate. O experimento foi realizado a campo na Estação Experimental do Arroz – IRGA na safra 2016/17 e os tratamentos foram arranjados em esquema fatorial 3x2+1 cujo fator A constou da simulação de deriva de glyphosate nas doses de 135; 270 e 540g ha-1 e.a.; o fator B de duas doses de nitrogênio (N), sendo eles 90 e 121,5 kg ha-1 de N; mais testemunha sem aplicação de glyphosate e com aplicação de 90kg ha-1 de N. O aumento na dose de glyphosate resultou em maiores danos à cultura, como sintomas de fitotoxicidade, redução no número de panículas por área e no rendimento de grãos que foi de aproximadamente 60% na maior dose estudada. De acordo com o aumento da dose de glyphosate também ocorreu o prolongamento no número de dias entre a emergência da cultura até o estágio de desenvolvimento de antese (R4). A deriva simulada de glyphosate evidencia que o herbicida causa elevada fitotoxicidade a cultura, menor estatura as plantas e aumento do ciclo de desenvolvimento, interferindo negativamente na produtividade da cultura do arroz irrigado.

Detection of Bispyribac-sodium Residues in Walnut Leaves after Simulated Drift

Walnut (Juglans regia) and rice (Oryza sativa) are among the most important crops grown in the Sacramento Valley of California. Because rice herbicides are often applied by air, there are occasional allegations of rice herbicide drift onto walnut trees. This study was established to investigate bispyribac-sodium residues on walnut leaves after simulated drift treatments. The objectives were to determine whether bispyribac-sodium can generate visual symptoms on walnut trees without leaving detectable residues in leaf tissues and to evaluate the subsequent impacts on walnut yield. Two experiments were conducted in a 3-year-old walnut orchard. In the first experiment bispyribac-sodium was applied to walnut trees at 0.125%, 0.25%, 0.5%, and 1% of the normal use rate in rice (45 g·ha−1). In the second experiment, rates were 1%, 3%, 10%, and 100% of the normal use rate in rice. Bispyribac-sodium caused general leaf chlorosis and discrete yellow spotting on walnut leaves even at very low concentrations; symptoms were recorded on trees exposed to rates as low as 0.125% of the normal use rate in rice. However, based on high-performance liquid chromatography analysis, the lowest simulated drift treatment from which bispyribac-sodium could be detected 10 d after treatment was 1% of the rice use rate. In general, visual injury symptoms remained constant over time, or even worsened, whereas bispyribac-sodium residues decreased or became not detectable. There was no measurable impact on walnut yield from any of the simulated drift treatments in these experiments.

Evaluating risks of plant growth regulator–resistant soybean technologies to horseradish production

AbstractOff-target movement of dicamba and 2,4-D may injure and reduce the yield of many fruit and vegetable crops, impacting specialty crop producers and herbicide applicators alike. Two field experiments were established, using plant growth regulator–resistant soybean herbicide technologies, to evaluate drift and carryover risks to horseradish production. The drift experiment was conducted in 2015 and 2016 to evaluate impact of dicamba and 2,4-D simulated drift on horseradish production with a mid-POST application in soybean. Simulated drift rates were 1/10,000X, 1/1,000X, and 1/100X, with 1/2X, 1X, and 2X of standard application rates. Injury and yield loss was greater following application of 2,4-D than with dicamba. Yield reductions were observed beginning at the 1/1,000X rate of 2,4-D, with complete crop loss occurring when rates exceed 1/2X. In comparison, dicamba only reduced yields when applied at the 1X and 2X rates. Only horseradish roots from plants treated with dicamba at the 2X rate had greater dicamba residue than the nontreated control, and the amount detected, 0.32 parts per billion (ppb), was lower than the EPA tolerance of 100 ppb in root crops. There was little to no harvestable tissue for 2,4-D residue analysis for plants treated with 2,4-D at rates above 1/2X. The carryover experiment was a 2-yr rotational evaluation conducted in 2014, 2015, and 2016 to assess dicamba carryover to horseradish following application to dicamba-resistant soybean the previous season. Observations taken at 4, 6, and 8 wk after planting indicated no significant horseradish injury, nor was height, stand, or root weight reduced. These results suggest that horseradish growers should have few concerns about injury from dicamba drift or carryover. While 2,4-D applicators may need to be cautious when making applications near horseradish fields, 2,4-D may be an effective tool for controlling volunteer horseradish in 2,4-D–resistant soybean.

Glyphosate‐Resistant Soybean Response to Micro‐Rates of Three Dicamba‐Based Herbicides

Core Ideas The impact of simulated dicamba drift on growth and yield of glyphosate‐resistant soybean was similar among dicamba formulations. The impact of dicamba drift on soybean could be influenced by moisture condition of the environmental field. Late vegetative or early flowering stage of soybean was the most sensitive growth stage to dicamba drift. New dicamba‐based herbicides such as Engenia (N,N‐bis‐(3‐aminopropyl) methylamine salt) and XtendiMax (diglycolamine salt) with VaporGrip technology were developed to reduce dicamba volatility and drift; however, there are claims that these products can still volatilize or drift. Field studies were conducted to evaluate glyphosate (N‐(phosphonomethyl)glycine))–resistant (GR) soybean response to micro‐rates (0, 1/1000, 1/500, 1/100, 1/50, and 1/10 of the label rate, 560 g a.e. ha−1) of the two new dicamba products compared with Clarity (diglycolamine salt) applied at three growth stages. The GR soybean [Glycine max (L.) Merr.] was equally impacted by the micro‐rates of all three products as measured by visual injury, height reduction, delayed physiological maturity, and yield reduction. The greatest visual injury (80%), plant height reduction (65%), maturity delay (22 d), and soybean yield loss (96%) was caused by 1/10 of the dicamba label rate when applied at V7/R1 soybean growth stage. In addition, estimation of effective dose for 5, 10, or 20% yield reduction suggested that V7/R1 was the most sensitive soybean growth stage to the three dicamba products. For example, 10% yield reduction occurred when 1.83 to 1.85 g a.e. ha−1 (∼1/300 of the label rate) of Engenia was applied at V2 or R2, whereas, a lower dose of 0.32 g a.e. ha−1 (1/1750 of the label rate) of Engenia caused the same level of yield reduction when applied at V7/R1. Similar doses were estimated for Clarity and XtendiMax; therefore dicamba drift should be avoided at all costs, because GR soybean was equally sensitive to low rates of all three tested products with different formulations or technologies.