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Jingqian Huo - One of the best experts on this subject based on the ideXlab platform.

  • hapten synthesis antibody development and a highly sensitive indirect competitive chemiluminescent enzyme immunoassay for detection of Dicamba
    Journal of Agricultural and Food Chemistry, 2019
    Co-Authors: Jingqian Huo, Bogdan Barnych, Debin Wan, Natalia Vasylieva, Stevan Z Knezevic, Adewale O Osipitan, Jon E Scott, Jinlin Zhang, Bruce D Hammock
    Abstract:

    Although Dicamba has long been one of the most widely used selective herbicides, some U.S. states have banned the sale and use of Dicamba because of farmers complaints of drift and damage to nonresistant crops. To prevent illegal use of Dicamba and allow monitoring of nonresistant crops, a rapid and sensitive method for detection of Dicamba is critical. In this paper, three novel Dicamba haptens with an aldehyde group were synthesized, conjugated to the carrier protein via a reductive-amination procedure and an indirect competitive chemiluminescent enzyme immunoassay (CLEIA) for Dicamba was developed. The assay showed an IC50 of 0.874 ng/mL which was over 15 times lower than that of the conventional enzyme immunoassay. The immunoassay was used to quantify Dicamba concentrations in field samples of soil and soybean obtained from fields sprayed with Dicamba. The developed CLEIA showed an excellent correlation with LC-MS analysis in spike-and-recovery studies, as well as in real samples. The recovery of Dicamba ranged from 86 to 108% in plant samples and from 105 to 107% in soil samples. Thus, this assay is a rapid and simple analytical tool for detecting and quantifying Dicamba levels in environmental samples and potentially a great tool for on-site crop and field monitoring.

  • Hapten Synthesis, Antibody Development, and a Highly Sensitive Indirect Competitive Chemiluminescent Enzyme Immunoassay for Detection of Dicamba
    2019
    Co-Authors: Jingqian Huo, Bogdan Barnych, Debin Wan, Natalia Vasylieva, Stevan Z Knezevic, Adewale O Osipitan, Jon E Scott, Jinlin Zhang
    Abstract:

    Although Dicamba has long been one of the most widely used selective herbicides, some U.S. states have banned the sale and use of Dicamba because of farmers complaints of drift and damage to nonresistant crops. To prevent illegal use of Dicamba and allow monitoring of nonresistant crops, a rapid and sensitive method for detection of Dicamba is critical. In this paper, three novel Dicamba haptens with an aldehyde group were synthesized, conjugated to the carrier protein via a reductive-amination procedure and an indirect competitive chemiluminescent enzyme immunoassay (CLEIA) for Dicamba was developed. The assay showed an IC50 of 0.874 ng/mL which was over 15 times lower than that of the conventional enzyme immunoassay. The immunoassay was used to quantify Dicamba concentrations in field samples of soil and soybean obtained from fields sprayed with Dicamba. The developed CLEIA showed an excellent correlation with LC-MS analysis in spike-and-recovery studies, as well as in real samples. The recovery of Dicamba ranged from 86 to 108% in plant samples and from 105 to 107% in soil samples. Thus, this assay is a rapid and simple analytical tool for detecting and quantifying Dicamba levels in environmental samples and potentially a great tool for on-site crop and field monitoring

Mithila Jugulam - One of the best experts on this subject based on the ideXlab platform.

  • Dicamba resistance in kochia from Kansas and Nebraska evolved independently.
    Pest Management Science, 2020
    Co-Authors: Todd A. Gaines, Phillip W. Stahlman, Allan K. Fritz, Mithila Jugulam
    Abstract:

    BACKGROUND Evolution and spread of resistance to glyphosate in kochia [Bassia scoparia (L.) A.J. Scott] is a major challenge for the sustainability of glyphosate-resistant crop technology in this region. Dicamba offers a viable option to manage glyphosate-resistant kochia. However, the recent and rapid evolution of Dicamba resistance in glyphosate-resistant kochia populations in Kansas (KS), and other states in the USA is a threat to the management of this weed. Our previous research suggests that two distinct mechanisms confer Dicamba resistance in KS (KSUR) and NE (CSUR) kochia. CSUR kochia is Dicamba-resistant due to a double mutation in an auxin and Dicamba coreceptor gene (Aux/IAA16), and CSUR kochia plants show reduced Dicamba translocation. However, the mechanism of Dicamba resistance in KSUR is not known. The objective of this research was to determine if Dicamba resistance in KSUR is due to a different mechanism and therefore evolved independently from CSUR by measuring whether the resistance traits are chromosomally linked. RESULTS The F1 and F2 progenies from KSUR × CSUR were generated. Single Dicamba rate tests were conducted using the F1 and F2 progeny. The results indicate that two different genes confer Dicamba resistance in KSUR and CSUR; importantly, these two genes are not linked. CONCLUSION This research provides evidence that different populations of kochia have independently evolved resistance to Dicamba by different mechanisms, and we confirmed that the genes conferring resistance to the same herbicide in different populations are not chromosomally linked.

  • Glyphosate- and Dicamba-Resistant Genes Are Not Linked in Kochia ( Bassia scoparia )
    Weed Science, 2018
    Co-Authors: Allan K. Fritz, Phillip W. Stahlman, Randall S. Currie, Mithila Jugulam
    Abstract:

    Kochia [ Bassia scoparia (L.) A. J. Scott] is one of the most troublesome weeds throughout the North American Great Plains. Herbicides such as glyphosate and Dicamba have been used widely to control B. scoparia for decades. However, many B. scoparia populations have evolved resistance to these herbicides due to selection. Especially, Dicamba-resistant B. scoparia populations are often also found to be glyphosate-resistant. The objective of this research was to determine whether these two herbicide resistances are linked in B. scoparia. Reciprocal crosses were performed between glyphosate- and Dicamba-resistant (GDR) and glyphosate- and Dicamba-susceptible (GDS) B. scoparia to produce F 1 and F 2 progeny. Two F 1 and seven F 2 progeny families were screened with various doses of Dicamba or glyphosate. All the F 1 progeny survived both Dicamba and glyphosate treatments. Chi-square analyses of F 2 progeny suggest (1) glyphosate and Dicamba resistances in B. scoparia are inherited via single, dominant nuclear genes; and (2) glyphosate- and Dicamba-resistant genes are not linked. Thus, the Dicamba and glyphosate resistances appear to have evolved independently due to intense selection but do not seem to spread together.

  • increased chalcone synthase chs expression is associated with Dicamba resistance in kochia scoparia
    Pest Management Science, 2018
    Co-Authors: Dean Pettinga, Mithila Jugulam, Philip Westra, Eric L. Patterson, Todd A. Gaines
    Abstract:

    BACKGROUND Resistance to the synthetic auxin herbicide Dicamba is increasingly problematic in Kochia scoparia. The resistance mechanism in an inbred Dicamba-resistant K. scoparia line (9425R) was investigated using physiological and transcriptomics (RNA-Seq) approaches. RESULTS No differences were found in Dicamba absorption or metabolism between 9425R and a Dicamba-susceptible line, but 9425R was found to have significantly reduced Dicamba translocation. Known auxin-responsive genes ACC synthase (ACS) and indole-3-acetic acid amino synthetase (GH3) were transcriptionally induced following Dicamba treatment in Dicamba-susceptible K. scoparia but not in 9425R. Chalcone synthase (CHS), the gene regulating synthesis of the flavonols quertecin and kaemperfol, was found to have two-fold higher transcription in 9425R both without and 12 h after Dicamba treatment. Increased CHS transcription co-segregated with Dicamba resistance in a forward genetics screen using an F2 population. CONCLUSION Prior work has shown that the flavonols quertecin and kaemperfol compete with auxin for intercellular movement and vascular loading via ATP-binding cassette subfamily B (ABCB) membrane transporters. The results of this study support a model in which constitutively increased CHS expression in the meristem produces more flavonols that would compete with Dicamba for intercellular transport by ABCB transporters, resulting in reduced Dicamba translocation.

  • reduced absorption of glyphosate and decreased translocation of Dicamba contribute to poor control of kochia kochia scoparia at high temperature
    Pest Management Science, 2018
    Co-Authors: Phillip W. Stahlman, Mithila Jugulam
    Abstract:

    BACKGROUND Plant growth temperature is one of the important factors that can influence postemergent herbicide efficacy and impact weed control. Control of kochia (Kochia scoparia), a major broadleaf weed throughout the North American Great Plains, often is unsatisfactory when either glyphosate or Dicamba are applied on hot summer days. We tested effects of plant growth temperature on glyphosate and Dicamba phytotoxicity on two Kansas kochia populations (P1 and P2) grown under the following three day/night (d/n) temperature regimes: T1, 17.5/7.5°C; T2, 25/15°C; and T3, 32.5/22.5°C. RESULTS Visual injury and above-ground dry biomass data from herbicide dose–response experiments indicated greater susceptibility to both glyphosate and Dicamba when kochia was grown under the two cooler temperature regimes, i.e. T1 and T2. At T1, the ED50 of P1 and P2 kochia were 39 and 36 g ha−1 of glyphosate and 52 and 105 g ha−1 of Dicamba, respectively. In comparison, at T3 the ED50 increased to 173 and 186 g ha−1 for glyphosate and 106 and 410 g ha−1 for Dicamba, respectively, for P1 and P2. We also investigated the physiological basis of decreased glyphosate and Dicamba efficacy under elevated temperatures. Kochia absorbed more glyphosate at T1 and T2 compared to T3. Conversely, there was more Dicamba translocated towards meristems at T1 and T2, compared to T3. CONCLUSION Reduced efficacy of Dicamba or glyphosate to control kochia under elevated temperatures can be attributed to decreased absorption and translocation of glyphosate and Dicamba, respectively. Therefore, it is recommended to apply glyphosate or Dicamba when the temperature is low (e.g. d/n temperature at 25/15°C) and seedlings are small (less than 12 cm) to maximize kochia control. © 2016 Society of Chemical Industry

  • Reduced Translocation of Glyphosate and Dicamba in Combination Contributes to Poor Control of Kochia scoparia: Evidence of Herbicide Antagonism
    Scientific Reports, 2018
    Co-Authors: Junjun Ou, Curtis R. Thompson, Nicholas Bloedow, Phillip W. Stahlman, Mithila Jugulam
    Abstract:

    Kochia scoparia is a troublesome weed across the Great Plains of North America. Glyphosate and Dicamba have been used for decades to control K. scoparia . Due to extensive selection, glyphosate- and Dicamba-resistant (GDR) K. scoparia have evolved in the USA. Herbicide mixtures are routinely used to improve weed control. Herbicide interactions if result in an antagonistic effect can significantly affect the management of weeds, such as K. scoparia . To uncover the interaction of glyphosate and Dicamba when applied in combination in K. scoparia management the efficacies of different doses of glyphosate plus Dicamba were evaluated under greenhouse and field conditions using GDR and a known glyphosate- and Dicamba-susceptible (GDS) K. scoparia . The results of greenhouse and field studies suggest that the combination of glyphosate and Dicamba application controlled GDS, but glyphosate alone provided a better control of GDR K. scoparia compared to glyphosate plus Dicamba combinations. Furthermore, investigation of the basis of this response suggested glyphosate and Dicamba interact antagonistically and consequently, the translocation of both herbicides was significantly reduced resulting in poor control of K. scoparia . Therefore, a combination of glyphosate plus Dicamba may not be a viable option to control GDR K. scoparia .

Bruce D Hammock - One of the best experts on this subject based on the ideXlab platform.

  • hapten synthesis antibody development and a highly sensitive indirect competitive chemiluminescent enzyme immunoassay for detection of Dicamba
    Journal of Agricultural and Food Chemistry, 2019
    Co-Authors: Jingqian Huo, Bogdan Barnych, Debin Wan, Natalia Vasylieva, Stevan Z Knezevic, Adewale O Osipitan, Jon E Scott, Jinlin Zhang, Bruce D Hammock
    Abstract:

    Although Dicamba has long been one of the most widely used selective herbicides, some U.S. states have banned the sale and use of Dicamba because of farmers complaints of drift and damage to nonresistant crops. To prevent illegal use of Dicamba and allow monitoring of nonresistant crops, a rapid and sensitive method for detection of Dicamba is critical. In this paper, three novel Dicamba haptens with an aldehyde group were synthesized, conjugated to the carrier protein via a reductive-amination procedure and an indirect competitive chemiluminescent enzyme immunoassay (CLEIA) for Dicamba was developed. The assay showed an IC50 of 0.874 ng/mL which was over 15 times lower than that of the conventional enzyme immunoassay. The immunoassay was used to quantify Dicamba concentrations in field samples of soil and soybean obtained from fields sprayed with Dicamba. The developed CLEIA showed an excellent correlation with LC-MS analysis in spike-and-recovery studies, as well as in real samples. The recovery of Dicamba ranged from 86 to 108% in plant samples and from 105 to 107% in soil samples. Thus, this assay is a rapid and simple analytical tool for detecting and quantifying Dicamba levels in environmental samples and potentially a great tool for on-site crop and field monitoring.

Peter H Sikkema - One of the best experts on this subject based on the ideXlab platform.

  • Off-target movement assessment of Dicamba in North America
    Weed Technology, 2020
    Co-Authors: Nader Soltani, Jason K. Norsworthy, Christy L. Sprague, Maxwel C. Oliveira, Guilherme S. Alves, Rodrigo Werle, Bryan G. Young, Daniel B. Reynolds, Ashli Brown, Peter H Sikkema
    Abstract:

    Six experiments were conducted in 2018 on field sites located in Arkansas, Indiana, Michigan, Nebraska, Ontario, and Wisconsin to evaluate the off-target movement (OTM) of Dicamba under field-scale conditions. The highest estimated percentages of Dicamba injury in non–Dicamba-resistant (DR) soybean were 55%, 44%, 39%, 67%, 15%, and 44% injury for noncovered areas and 55%, 5%, 13%, 42%, 0%, and 41% injury for covered areas during Dicamba application in Arkansas, Indiana, Michigan, Nebraska, Ontario, and Wisconsin, respectively. The level of injury generally decreased as the downwind distance increased under covered and noncovered areas at all sites. There was an estimated 10% injury in non-DR soybean at 113, 8, 11, 8, and 8 m; and estimated 1% injury at 293, 28, 71, 15, and 19 m from the edge of treated fields downwind when plants were not covered during Dicamba application in Arkansas, Indiana, Michigan, Ontario, and Wisconsin, respectively. Assessment of filter-paper collectors placed from 4 to 137 m downwind from the edge of the sprayed area suggested the Dicamba deposition reduced exponentially with distance. The greatest injury to non-DR soybean from Dicamba OTM occurred at Nebraska and Arkansas (as far as 250 m). Non-DR soybean injury was greatest adjacent to the Dicamba sprayed area, but injury decreased with no injury beyond 20 m downwind or in any other direction from the Dicamba sprayed area in Indiana, Michigan, Ontario, and Wisconsin. The presence of soybean injury under covered and noncovered areas during the spray period for primary drift suggests that secondary movement of Dicamba was evident at five sites. Additional research is needed to determine the exact forms of secondary movement of Dicamba under different environmental conditions.Nomenclature: Dicamba; soybean, Glycine max (L.) Merr

  • Influence of Glyphosate/Dicamba Application Rate and Timing on the Control of Glyphosate-Resistant Horseweed in Glyphosate/Dicamba-Resistant Soybean
    Weed Technology, 2018
    Co-Authors: Brittany Km Hedges, Nader Soltani, David C Hooker, Darren E Robinson, Peter H Sikkema
    Abstract:

    Dicamba may be an efficacious option for the control of glyphosate-resistant (GR) horseweed in glyphosate/Dicamba-resistant soybean; research is needed to optimize the application rate based on horseweed height at the time of application. The purpose of this study was to determine the effect of glyphosate/Dicamba rate and application timing for the control of GR horseweed. Glyphosate/Dicamba was applied at three rates (900, 1,350, and 1,800 g ae ha-1) at three horseweed application timings (5, 15, and 25 cm) in a factorial design. There was no interaction between glyphosate/Dicamba rate and timing for GR horseweed control or soybean yield; however, there was an interaction for GR horseweed density and biomass. At 2 and 4 wk after application (WAA), there was a decrease in GR horseweed control as the height at the time application increased. At 4 WAA, the application of glyphosate/Dicamba to GR horseweed that was 5-, 15-, and 25-cm tall provided 87%, 76%, and 62% control, respectively. There was no impact of glyphosate/Dicamba application timing on soybean yield. At 2, 4, and 8 WAA, there was an increase in GR horseweed control as the rate of glyphosate/ Dicamba was increased. At 8 WAA, glyphosate/Dicamba applied at 900, 1,350, and 1,800 g ae ha-1 controlled GR horseweed 76%, 87%, and 92%, respectively. Earlier application timings and higher rates of glyphosate/Dicamba caused the greatest reduction in GR horseweed density and biomass. Reduced GR horseweed competition resulted in a 100% to 144% increase in soybean yield, but there was no difference in soybean yield among glyphosate/Dicamba rates tested.Nomenclature: Dicamba; glyphosate; horseweed, Erigeron canadensis L. Cronq.; soybean, Glycine max (L.) Merr.

  • Single and sequential applications of Dicamba for the control of glyphosate-resistant common ragweed in glyphosate- and Dicamba-resistant soybean
    Canadian Journal of Plant Science, 2018
    Co-Authors: Holly P. Byker, Darren E Robinson, Annemarie C. Van Wely, Nadar Soltani, Mark B. Lawton, Peter H Sikkema
    Abstract:

    Confirmation of glyphosate-resistant (GR) weeds in southwestern Ontario has led to a change in weed management practices, particularly in soybean. Registered soil-applied herbicides have been identified that have activity on GR common ragweed; however, due to the long emergence period of common ragweed, additional postemergence options are required. The recent development of glyphosate- and Dicamba-resistant soybean (Roundup Ready Xtend soybean) allows for the preplant and postemergence application of Dicamba. Three field studies were conducted in Ontario, Canada, in a field with confirmed GR common ragweed. Glyphosate-resistant common ragweed interference resulted in 75% yield loss in soybean compared with the weed-free check. At 4 wk after application, Dicamba tank-mixed with glyphosate applied preplant only, postemergence only, or preplant followed by postemergence controlled GR common ragweed up to 94%, 87%, and 99%, respectively. The availability of Dicamba for use in glyphosate- and Dicamba-resistan...

  • control of glyphosate resistant waterhemp amaranthus tuberculatus var rudis with Dicamba and dimethenamid p in ontario
    Canadian Journal of Plant Science, 2017
    Co-Authors: Mike G Schryver, Nader Soltani, David C Hooker, Darren E Robinson, Patrick J Tranel, Peter H Sikkema
    Abstract:

    Glyphosate-resistant (GR) waterhemp is the fifth confirmed GR weed in Canada and was first confirmed in 2014 in the province of Ontario. In 2015 and 2016, two field experiments were conducted across four site–years each to determine the effectiveness of Dicamba at two rates (300 and 600 g a.i. ha−1) in addition to dimethenamid-P (693 g a.i. ha−1) in a single and sequential management program. Due to traited soybean seed availability, all treatments were applied in corn. Waterhemp density, biomass, visual control estimates, and corn yield were collected. Waterhemp density and dryweight were found to be lower in treatments including a sequential application of dicamaba and those that included dimethenamid-P. The sequential management strategy provided >95% control of GR waterhemp at 12 weeks after application. Dicamba applied after emergence at 300 and 600 g a.i. ha−1 controlled GR waterhemp 80% and 91%, respectively; in contrast, Dicamba applied before emergence at 300 and 600 g a.i. ha−1 provided only 9% ...

  • response of glyphosate resistant soybean to Dicamba spray tank contamination during vegetative and reproductive growth stages
    Canadian Journal of Plant Science, 2016
    Co-Authors: Nader Soltani, Robert E Nurse, Peter H Sikkema
    Abstract:

    The anticipated availability of Dicamba-resistant crops will increase the potential for crop injury to non-Dicamba-resistant soybean due to Dicamba spray tank contamination. A total of eight field trials were conducted at various locations in Ontario, Canada during 2012-2014 to determine the response of non-Dicamba-resistant soybean to Dicamba spray tank contamination at 0, 0.75, 1.5, 3, 6, 15, 30, and 60 g a.e. ha-1 applied postemergence (POST) at the V2-3 (2-3 trifoliate) or R1 (1st flower) stage. At one week after treatment (WAT), Dicamba applied at 0.75, 1.5, 3, 6, 15, 30, and 60 g a.e. ha-1 at V2-3 caused 12, 18, 25, 31, 43, 53, and 66% visible injury in soybean, respectively. Injury increased at 2 and 4 WAT and decreased by 8 WAT with 68% visible injury observed at the highest dose. Dicamba applied at R1 caused 23, 28, 36, 40, 48, 61, and 73% visible injury in soybean at 0.75, 1.5, 3, 6, 15, 30, and 60 g a.e. ha-1, respectively. The predicted dose of Dicamba to reduce soybean seed yield 1, 5, 10, 20...

Greg R. Kruger - One of the best experts on this subject based on the ideXlab platform.

  • Off-target Movement of DGA and BAPMA Dicamba to Sensitive Soybean
    Weed Technology, 2019
    Co-Authors: Gordon T. Jones, Jason K. Norsworthy, Tom Barber, Edward E. Gbur, Greg R. Kruger
    Abstract:

    It is well established that Dicamba can cause severe injury to soybean that is not resistant to Dicamba. Dicamba-resistant (DR) cotton became available in 2015, followed by DR soybean in 2016; in late 2016 came the release of new Dicamba formulations approved for topical use in cotton and soybeans. Until this approval, use of Dicamba was limited to primarily corn, small grains, range and pasture, and eco-fallow acres. Hence, studies were conducted in 2015 and 2016 to examine off-target movement of two Dicamba formulations using non-DR soybean as a bio-indicator. Diglycolamine (DGA) and N,N-Bis(3-aminopropyl)methylamine (BAPMA) Dicamba were applied simultaneously at 560 g ae ha–1 in the center of two side-byside 8-ha fields to vegetative glufosinate-resistant soybean. On the same day, a rate response experiment was established encompassing nine different Dicamba rates of each formulation. Results from the rate response experiment indicate that soybean is equally sensitive to DGA and BAPMA Dicamba. In 2015, a rain event occurring 6 to 8 h after application of the large drift trial probably limited off-target movement by incorporating some of the herbicide into the soil. As a result, secondary drift was less in 2015 than in 2016. However, minimal secondary injury (

  • off target movement of dga and bapma Dicamba to sensitive soybean
    Weed Technology, 2019
    Co-Authors: Gordon T. Jones, Jason K. Norsworthy, Tom Barber, Edward E. Gbur, Greg R. Kruger
    Abstract:

    It is well established that Dicamba can cause severe injury to soybean that is not resistant to Dicamba. Dicamba-resistant (DR) cotton became available in 2015, followed by DR soybean in 2016; in late 2016 came the release of new Dicamba formulations approved for topical use in cotton and soybeans. Until this approval, use of Dicamba was limited to primarily corn, small grains, range and pasture, and eco-fallow acres. Hence, studies were conducted in 2015 and 2016 to examine off-target movement of two Dicamba formulations using non-DR soybean as a bio-indicator. Diglycolamine (DGA) and N,N-Bis(3-aminopropyl)methylamine (BAPMA) Dicamba were applied simultaneously at 560 g ae ha–1 in the center of two side-byside 8-ha fields to vegetative glufosinate-resistant soybean. On the same day, a rate response experiment was established encompassing nine different Dicamba rates of each formulation. Results from the rate response experiment indicate that soybean is equally sensitive to DGA and BAPMA Dicamba. In 2015, a rain event occurring 6 to 8 h after application of the large drift trial probably limited off-target movement by incorporating some of the herbicide into the soil. As a result, secondary drift was less in 2015 than in 2016. However, minimal secondary injury (<5%) occurred 12m farther into DGA Dicamba plots in 2015. In 2016, secondary movement was decreased by 72m when BAPMA Dicamba was used compared to DGA Dicamba. Appreciable secondary movement of both DGA and BAPMA Dicamba is possible following in-crop applications of either formulated product to soybean in early to mid-summer. Additionally, the risk for secondary movement of BAPMA Dicamba is slightly less than for DGA Dicamba.Nomenclature: Dicamba; glufosinate; cotton, Gossypium hirsutum L.; soybean, Glycine max (L.) Merr.

  • Effect of Low Doses of Dicamba Alone and in Combination with Glyphosate on Parent Soybean and Offspring
    Weed Technology, 2018
    Co-Authors: Gordon T. Jones, Jason K. Norsworthy, Tom Barber, Edward E. Gbur, Greg R. Kruger
    Abstract:

    It is well established that soybean that does not contain the Dicamba-resistant (DR) trait is highly sensitive to off-target exposure to Dicamba. However, there is limited information on the effect of low doses of Dicamba plus glyphosate mixtures on Dicamba-sensitive soybean—a mixture likely to be used on a vast acreage of Dicamba/glyphosate-resistant soybean. The objective of this research was to examine leaf and pod malformation, along with height and yield effects, when Dicamba, glyphosate, or a mixture of the two was applied to soybean sensitive to both Dicamba and glyphosate at sublethal doses. Field applications were made at three growth stages (R1, R3, and R5) at multiple locations. Two glyphosate rates (1/64 and 1/256 of the labeled rate of 870 g ae ha ⁻¹) and two Dicamba rates (1/64 and 1/256 of the labeled rate of 560 g ae ha ⁻¹) were used. Adding glyphosate to Dicamba increased leaf malformation by 6% more than Dicamba alone when applied at the R1 soybean growth stage. After R3 applications, pod malformation was 10% greater in treatments containing Dicamba and glyphosate than Dicamba alone. Applications at R5 showed minimal leaf and pod malformation. Seed from field trials was planted in the greenhouse to evaluate the offspring. The number of offspring plants showing Dicamba-like symptomology was not increased with the addition of glyphosate to Dicamba. Overall, injury to offspring was similar in Dicamba alone and Dicamba plus glyphosate treatments; however, the number of plants injured increased when parent plants were exposed to sublethal doses of Dicamba at R3 and R5 compared with R1 growth-stage exposure. Vigor was reduced in Dicamba-containing treatments, but not glyphosate-alone treatments. Glyphosate addition to Dicamba had no effect on vigor of soybean offspring. Although there is increased injury to parent plants when glyphosate is added to Dicamba, this research demonstrates that glyphosate does not contribute to the negative effects of Dicamba on soybean offspring. Nomenclature: Dicamba; glyphosate; soybean, Glycine max (L.) Merr

  • Dicamba Spray Drift as Influenced by Wind Speed and Nozzle Type
    Weed Technology, 2017
    Co-Authors: Guilherme Sousa Alves, Greg R. Kruger, João Paulo Arantes Rodrigues Da Cunha, Denise Garcia De Santana, Luís André T. Pinto, Frederico Guimarães, Milos Zaric
    Abstract:

    With the release of Dicamba-resistant crops, it is necessary to understand how technical and environmental conditions affect the application of Dicamba. This study sought to evaluate drift from Dicamba applications through flat-fan nozzles, under several wind speeds in a wind tunnel. Dicamba applications were performed through two standard (XR and TT) and two air induction (AIXR and TTI) 110015 nozzles at 0.9, 2.2, 3.6 and 4.9ms-1 wind speeds. The applications were made at 276 kPa pressure and the Dicamba rate was 561 g ae ha-1. The droplet spectrum was measured using a laser diffraction system. Artificial targets were used as drift collectors, positioned in a wind tunnel from 2 to 12m downwind from the nozzles. Drift potential was determined using a fluorescent tracer added to solutions, quantified by fluorimetry. The air induction TTI nozzle produced the lowest percentage of Dicamba drift at 2.2, 3.6 and 4.9m s-1 wind speeds at all distances. Dicamba spray drift from XR, TT and AIXR nozzles increased ex...

  • Dose Response of Glyphosate and Dicamba on Tomato (Lycopersicon esculentum) Injury
    Weed Technology, 2012
    Co-Authors: Greg R. Kruger, William G. Johnson, Douglas J. Doohan, Stephen C. Weller
    Abstract:

    Abstract Field studies were conducted to determine the response of sublethal glyphosate and Dicamba doses to processing tomato flowering loss and marketable yield. Dose–response studies for both herbicides were conducted on four commercial processing tomato lines (two different lines within each study) and plants were sprayed at either the vegetative stage or the early bloom stage. Both glyphosate and Dicamba caused higher yield losses when sprayed at the early bloom stage. A 25% yield loss was observed with 8.5 and 7.5 g ae ha−1 for glyphosate and Dicamba, respectively, at the early bloom stage and 43.9 and 11.9 g ae ha−1 for glyphosate and Dicamba, respectively, at the early vegetative stage. Overall, these tomato cultivars were more sensitive to Dicamba than to glyphosate. We conclude that glyphosate and Dicamba drift could have serious implications on tomato yields especially if the drift occurs during flowering. Nomenclature: Glyphosate; Dicamba; tomato, Lycopersicon esculentum Mill.