Increased Absorption and Translocation Contribute to Improved Efficacy of Dicamba to Control Early Growth Stage Palmer amaranth <i>(Amaranthus palmeri)</i>

Cuvaca, Ivan; Currie, R. S.; Roozeboom, Kraig L.; Fry, Jack D.; Jugulam, Mithila

doi:10.1017/wsc.2019.67

Cited by 6 publications

(9 citation statements)

References 36 publications

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“…This result was not expected for treatments with dicamba programmes (T2, T3 and T4), considering that this herbicide has been reported as providing high levels of control (>90%) of A. palmeri (Cahoon et al, 2015;Tehranchian et al, 2017). There are, however, several conditions that can reduce the control of auxin herbicides, such as the type of tissue, plant species, growth stage (Grossman, 2010) and height (Cuvaca et al, 2020). Also, when dicamba is applied mixed with glyphosate to A. palmeri, there is an antagonism that is expressed as a decrease in glyphosate uptake and translocation (Meyer et al, 2020).…”

Section: Weed Species Favoured By Herbicide Programmesmentioning

confidence: 87%

Population growth rates of weed species in response to herbicide programme intensity and their impact on weed community

et al. 2021

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The adoption of dicamba-tolerant crops has reduced the challenge of controlling glyphosate-resistant Amaranthus palmeri in these crops. However, introducing herbicide programmes with new mechanisms of action and different intensities can favour major shifts in weed communities. This can affect not only the functionality of the agroecosystem, but also resource availability to the most problematic species. The objectives of this work were to evaluate how herbicide programme structure and intensity affect (a) weed diversity, (b) population growth rate (λ) of weed species and (c) weed community structure based on λ dynamics in a dicamba-tolerant cotton monoculture. To achieve these objectives, a cotton field experiment was established to compare four herbicide programmes from 2011 to 2018. The herbicide programmes differed in the first 4 years (i.e. glyphosate every year, alternating glyphosate and glyphosate plus dicamba every other year, glyphosate plus dicamba every year, and residual herbicide and glyphosate plus dicamba every year). During the last 4 years, all programmes received glyphosate plus dicamba. The weed seedbank was evaluated every spring and λ calculated. Environmental variation from year to year was more important in determining weed richness than herbicide programmes, which exhibited similar richness across all treatments during the eight years of the study. Regardless of herbicide programme, most species maintained λ between zero and one. Only a few species were the exception with λ values above one, such as A. palmeri, Mollugo verticillata and Eleusine indica. Although glyphosate plus dicamba reduced λ for several species, this herbicide mix was less effective in reducing λ for other weeds compared with glyphosate alone, suggesting a potential antagonism that could change weed community composition. The limited changes in λ for most species suggest the capacity of weeds to adjust reproduction and survival to overcome changes in mortality rates caused by increases in herbicide use intensity.

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Section: Weed Species Favoured By Herbicide Programmesmentioning

confidence: 87%

Population growth rates of weed species in response to herbicide programme intensity and their impact on weed community

et al. 2021

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“…Although new technology is available allowing broadcast applications of synthetic auxins and glufosinate in cotton and soybeans during the growing season, Palmer amaranth control can be variable among years and locations [19,24]. Herbicide efficacy can be significantly impacted by Palmer amaranth size, maturity, and growing conditions [23,[32][33][34]. Height and biomass of Palmer amaranth in this study was similar in nontreated control plots among years with heights averaging from 133 and 135 cm and biomass of 13,569 and 10,175 kg ha −1 at maturity in 2018 and 2019, respectively.…”

Section: Field Study: Dicamba-based Programsmentioning

confidence: 99%

“…Larger plants may have thicker plant cuticles which could reduce herbicide penetration resulting in poor control [27,36,39]. Furthermore, mature plants have reduced sugar transport which may decrease translocation of some systemic herbicides [34,40,41]. Highest label rate of glufosinate (880 g ai ha −1 ) plus ammonium sulfate and application under optimal environmental conditions may be required to provide additional control of large Palmer amaranth plants [42,43].…”

Section: Field Study: Dicamba-based Programsmentioning

confidence: 99%

Sequential Applications of Synthetic Auxins and Glufosinate for Escaped Palmer Amaranth Control

Browne

Price

et al. 2020

Agronomy

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Field and greenhouse studies were conducted to investigate the influence of sequence and timing of synthetic auxins and glufosinate on large Palmer amaranth (Amaranthus palmeri) control. Field studies were performed in Henry County, AL where treatments were applied to Palmer amaranth with average heights of 37 and 59 cm in 2018 and 2019, respectively. Sequential applications of 2,4-D/dicamba + glyphosate followed by (fb) glufosinate at labeled rates 3 or 7 days after initial treatment (DAIT) were used in addition to the reverse sequence with a 7-day interval. Time intervals of 3 or 7 days between applications did not influence Palmer amaranth control. Palmer amaranth was controlled 100% by dicamba + glyphosate fb glufosinate and 2,4-D + glufosinate fb glufosinate 7 DAIT in 2018. However, herbicide performance was reduced due to delayed application and taller plants in 2019 with up to 23% less visual injury. To further investigate Palmer amaranth response to dicamba and glufosinate applied sequentially, a greenhouse study was conducted in 2019 where physiological measurements were recorded over a 35-day period. Treatments were applied to Palmer amaranth averaging 38 cm tall and included dicamba + glyphosate fb glufosinate 7 DAIT, the reverse sequence, and a single application of dicamba + glufosinate + glyphosate. Glufosinate severely inhibited mid-day photosynthesis compared to dicamba with up to 90% reductions in CO2 assimilation 1 DAIT. In general, Palmer amaranth respiration and stomatal conductance were not affected by herbicides in this study. Applications of dicamba + glyphosate fb glufosinate 7 DAIT was the only treatment hindered Palmer amaranth regrowth with 52% reduction in leaf biomass compared to nontreated control. These data suggest Palmer amaranth infested fields are more likely to be rescued with sequential applications of synthetic auxins and glufosinate, but consistent control of large Palmer is not probable.

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“…As a result, dicamba, does not typically translocate to the lower parts of the plant, resulting in symptomology being primarily concentrated near the area of application for the roller wiper applications. Conversely, the broadcast applications provided a more uniform distribution of herbicide on the plant, thus increasing the amount of the plant that was exposed to dicamba and resulting in more uniform dicamba uptake and Palmer amaranth control, as reported by Cuvaca et al 37 ; Butts et al 26 ; and Meyer et al 34,36 Palmer amaranth control in Keiser was also influenced by the number of herbicide applications (with or without the sequential treatment) (Table 6). Averaged over all other factors, the addition of a second application resulted in 83% Palmer amaranth control at 28 DAFT (Table 7).…”

Section: Herbicide Placement Studymentioning

confidence: 66%

Utility of roller wiper applications of dicamba for Palmer amaranth control in soybean

Farr

Norsworthy

Barber

et al. 2022

Pest Management Science

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BACKGROUND: The commercialization of dicamba-resistant soybean has resulted in increased concern for off-target movement of dicamba onto sensitive vegetation. To mitigate the off-target movement through physical drift, one might consider use of rope wicks and other wiper applicators. Although wiper-type application methods have been efficacious in pasture settings, the utility of dicamba using wiper applicators in agronomic crops is not available in scientific literature. To determine the utility of roller wipers for dicamba applications in dicamba-resistant soybean, two separate experiments were conducted in the summer of 2020 and replicated in both Keiser and Fayetteville, AR, USA. RESULTS: Utilizing opposing application directions and a 2:1:1 ratio of water: formulated glyphosate: formulated dicamba were the most efficacious practices for controlling Palmer amaranth. The high herbicide concentrations and wiping in opposing directions increased dicamba-resistant soybean injury when the wiper contacted the crop, but no yield loss was observed because of this injury. Broadcast applications resulted in greater Palmer amaranth mortality than roller wiper applications, and the most effective roller wiper treatments were when two sequential applications were made inside the crop canopy.CONCLUSIONS: Dicamba applications require adequate coverage for optimum weed control. While efforts can be made to increase roller wiper efficacy by optimizing coverage and timing of applications, broadcast applications are superior to roller wiper applicators for weed control. Roller wiper applications did not reduce soybean yield, thus wiper-type applications may be safely used in dicamba-resistant soybean, albeit the likelihood for off-target damage caused by volatilization of these treatments would need to be investigated.

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Increased Absorption and Translocation Contribute to Improved Efficacy of Dicamba to Control Early Growth Stage Palmer amaranth (Amaranthus palmeri)

Cited by 6 publications

References 36 publications

Population growth rates of weed species in response to herbicide programme intensity and their impact on weed community

Population growth rates of weed species in response to herbicide programme intensity and their impact on weed community

Sequential Applications of Synthetic Auxins and Glufosinate for Escaped Palmer Amaranth Control

Utility of roller wiper applications of dicamba for Palmer amaranth control in soybean

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