3 results
Impact of reduced rates of 2,4-D and glyphosate on sweetpotato growth and yield
- Thomas M. Batts, Donnie K. Miller, James L. Griffin, Arthur O. Villordon, Daniel O. Stephenson IV, Kathrine M. Jennings, Sushila Chaudhari, David C. Blouin, Josh T. Copes, Tara P. Smith
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- Journal:
- Weed Technology / Volume 34 / Issue 5 / October 2020
- Published online by Cambridge University Press:
- 08 June 2020, pp. 631-636
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Commercialization of 2,4-D–tolerant crops is a major concern for sweetpotato producers because of potential 2,4-D drift that can cause severe crop injury and yield reduction. A field study was initiated in 2014 and repeated in 2015 to assess impacts of reduced rates of 2,4-D, glyphosate, or a combination of 2,4-D with glyphosate on sweetpotato. In one study, 2,4-D and glyphosate were applied alone and in combination at 1/10, 1/100, 1/250, 1/500, 1/750, and 1/1,000 of anticipated field use rates (1.05 kg ha−1 for 2,4-D and 1.12 kg ha−1 for glyphosate) to ‘Beauregard’ sweetpotato at storage root formation (10 days after transplanting [DAP]). In a separate study, all these treatments were applied to ‘Beauregard’ sweetpotato at storage root development (30 DAP). Injury with 2,4-D alone or in combination with glyphosate was generally equal or greater than with glyphosate applied alone at equivalent herbicide rates, indicating that injury is attributable mostly to 2,4-D in the combination. There was a quadratic increase in crop injury and quadratic decrease in crop yield (with respect to most yield grades) with increased rate of 2,4-D applied alone or in combination with glyphosate applied at storage root development. However, neither the results of this relationship nor of the significance of herbicide rate were observed on crop injury or sweetpotato yield when herbicide application occurred at storage root formation, with a few exceptions. In general, crop injury and yield reduction were greatest at the highest rate (1/10×) of 2,4-D applied alone or in combination with glyphosate, although injury observed at lower rates was also a concern after initial observation by sweetpotato producers. However, in some cases, yield reduction of U.S. no.1 and marketable grades was also observed after application of 1/250×, 1/100×, or 1/10× rates of 2,4-D alone or with glyphosate when applied at storage root development.
Impact of reduced rates of dicamba and glyphosate on sweetpotato growth and yield
- Thomas M Batts, Donnie K. Miller, James L. Griffin, Arthur O. Villordon, Daniel O Stephenson IV, Kathrine M. Jennings, Sushila Chaudhari, David C. Blouin, Josh T. Copes, Tara P. Smith
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- Journal:
- Weed Technology / Volume 35 / Issue 1 / February 2021
- Published online by Cambridge University Press:
- 19 May 2020, pp. 27-34
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A major concern of sweetpotato producers is the potential negative effects from herbicide drift or sprayer contamination events when dicamba is applied to nearby dicamba-resistant crops. A field study was initiated in 2014 and repeated in 2015 to assess the effects of reduced rates of N,N-Bis-(3-aminopropyl)methylamine (BAPMA) or diglycloamine (DGA) salt of dicamba, glyphosate, or a combination of these individually in separate trials with glyphosate on sweetpotato. Reduced rates of 1/10, 1/100, 1/250, 1/500, 1/750, and 1/1,000 of the 1× use rate of each dicamba formulation at 0.56 kg ha−1, glyphosate at 1.12 kg ha−1, and a combination of the two at aforementioned rates were applied to ‘Beauregard’ sweetpotato at storage root formation (10 d after transplanting) in one trial and storage root development (30 d after transplanting) in a separate trial. Injury with each salt of dicamba (BAPMA or DGA) applied alone or with glyphosate was generally equal to or greater than glyphosate applied alone at equivalent rates, indicating that injury is most attributable to the dicamba in the combination. There was a quadratic increase in crop injury and a quadratic decrease in crop yield (with respect to most yield grades) observed with an increased herbicide rate of dicamba applied alone or in combination with glyphosate applied at storage root development. However, with a few exceptions, neither this relationship nor the significance of herbicide rate was observed on crop injury or sweetpotato yield when herbicide application occurred at the storage root formation stage. In general, crop injury and yield reduction were greatest at the highest rate (1/10×) of either salt of dicamba applied alone or in combination with glyphosate, although injury observed at lower rates would be cause for concern after initial observation by sweetpotato producers. However, in some cases yield reduction of No.1 and marketable grades was observed following 1/250×, 1/100×, or 1/10× application rates of dicamba alone or with glyphosate when applied at storage root development.
Development of a model to predict soybean yield loss from dicamba exposure
- Matthew R. Foster, James L. Griffin, Josh T. Copes, David C. Blouin
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- Journal:
- Weed Technology / Volume 33 / Issue 2 / April 2019
- Published online by Cambridge University Press:
- 25 March 2019, pp. 287-295
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Although dicamba-resistant crops can provide an effective weed management option, risk of dicamba off-site movement to sensitive crops is a concern. Previous research with indeterminate soybean identified 14 injury criteria associated with dicamba applied at V3/V4 or R1/R2 at 0.6 to 280 g ae ha−1. Injury criteria rated on a 0 to 5 scale (none to severe), along with percent visible injury and plant height reduction, and canopy height collected 7 and 15 d after treatment (DAT) were analyzed using multiple regression with a forward-selection procedure to develop yield prediction models. Variables included in the 15 DAT models (in order of selection) for V3/V4 were lower stem base lesions/cracking, plant height reduction, terminal leaf epinasty, leaf petiole droop, leaf petiole base swelling, and stem epinasty, whereas for R1/R2 variables were lower stem base lesions/cracking, terminal leaf chlorosis, leaf petiole base swelling, stem epinasty, terminal leaf necrosis, and terminal leaf cupping. To validate the models, experiments including the same dicamba rates and application timings used in previous research were conducted at two locations. For the variables specific to each model, data collected for the dicamba rates were used to predict yield. For the V3/V4 15 DAT model, predicted yield reduction (compared with the nontreated control for dicamba at 0.6 to 4.4 g ha−1) underestimated or overestimated observed yield reduction by an average of 1 and 3 percentage points. For 8.8 g ha−1, predicted yield reduction overestimated observed yield reduction by 8 points and for 17.5 g ha−1 by 20 points. For the R1/R2 15 DAT model, predicted yield reduction for 0.6 to 4.4 g ha−1 overestimated observed yield reduction by an average of 3 to 5 percentage points. For dicamba at 8.8 g ha−1, predicted yield reduction underestimated observed yield reduction by 8 points and for 17.5 g ha−1 overestimated by 6 points.