Evaluation of POST-Harvest Herbicide Applications for Seed Prevention of Glyphosate-Resistant Palmer amaranth (Amaranthus palmeri)

Abstract

Recent increases in the prevalence of glyphosate-resistant (GR) Palmer amaranth mandate that new control strategies be developed to optimize weed control and crop performance. A field study was conducted in 2012 and 2013 in Jackson, TN, and in 2013 in Knoxville, TN, to evaluate POST weed management programs applied after harvest (POST-harvest) for prevention of seed production from GR Palmer amaranth and to evaluate herbicide carryover to winter wheat. Treatments were applied POST-harvest to corn stubble, with three applications followed by a PRE herbicide applied at wheat planting. Paraquat alone or mixed with S-metolachlor controlled 91% of existing Palmer amaranth 14 d after treatment but did not control regrowth. Paraquat tank-mixed with a residual herbicide of metribuzin, pyroxasulfone, saflufenacil, flumioxazin, pyroxasulfone plus flumioxazin, or pyroxasulfone plus fluthiacet improved control of regrowth or new emergence compared with paraquat alone. All residual herbicide treatments provided similar GR Palmer amaranth control. Through implementation of POST-harvest herbicide applications, the addition of 1,200 seed m À2 or approximately 12 million seed ha À1 to the soil seedbank was prevented. Overall, the addition of a residual herbicide provided only 4 to 7% more GR Palmer amaranth control than paraquat alone. Wheat injury was evident (, 10%) in 2012 from the PRE applications, but not in 2013. Wheat grain yield was not adversely affected by any herbicide application. Nomenclature: Pyroxasulfone, 5-(difluoromethoxy)-1-methyl-3-(trifluoromethyl)pyrazol-4-ylmethyl 4,5-dihydro-5,5-dimethyl-1,2-oxazol-3-yl sulfone; Palmer amaranth, Amaranthus palmeri S. Wats; corn, Zea mays L.; wheat, Triticum aestivum L. Key words: Glyphosate resistance, herbicide resistance, weed control.Aumentos recientes en la prevalencia de Amaranthus palmeri resistente a glyphosate (GR) requiere que nuevas estrategias de control sean desarrolladas para optimizar el control de malezas y el desempeño de los cultivos. Se realizó un estudio de campo en 2012 y 2013, en Jackson, Tennessee, y en 2013 en Knoxville, Tennessee, para evaluar programas de manejo de malezas POST aplicados después de la cosecha (POST-cosecha) para la prevención de la producción de semilla de A. palmeri GR y para evaluar la residualidad de los herbicidas durante el trigo de invierno. Los tratamientos fueron aplicados POST-cosecha a campos después de la cosecha del maíz, con tres aplicaciones seguidas por un herbicida PRE aplicado al momento de la siembra del trigo. Paraquat solo o en mezcla con S-metolachlor controló 91% del A. palmeri existente 14 d después del tratamiento, pero no controló el rebrote de la maleza. La mezcla en tanque de paraquat con un herbicida residual ya sea metribuzin, pyroxasulfone, saflufenacil, flumioxazin, pyroxasulfone más flumioxazin, o pyroxasulfone más fluthiacet mejoró el control de rebrotes o nueva emergencia de plántulas al compararse con paraquat solo. Mediante la implementación de aplicaciones de herbicidas POST-cosecha se previno ...

Economics of Management of Photosystem II‐ and HPPD‐inhibitor‐Resistant Palmer amaranth in Corn

“…Growers should consider rotating different HR cultivars such as glufosinate-and glyphosate-resistant corn and utilize the effective PRE followed by POST herbicide programs investigated in this study for controlling PS II-and HPPD-inhibitor-resistant Palmer amaranth and to reduce the chances of evolution of HR weeds. Growers also need to adopt an integrated weed management approach that includes the use of different site of action PRE followed by POST herbicides, crop rotation, narrow row spacing, the rotation of different HR cultivars with conventional crop cultivars, tillage, and POSTharvest weed seed control to mitigate the evolution and spread of multiple HR Palmer amaranth (Crow et al, 2015;Price et al, 2012;Wiggins et al, 2016).…”

Integrating Herbicide Programs with Harvest Weed Seed Control and Other Fall Management Practices for the Control of Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri)

“…Additionally, its ability to establish large seedbanks through prolific seed production and extended germination window (Ward et al 2013) ensures persistence in crop production systems (Sparks et al 2003). Species like Palmer amaranth with biological attributes such as these mentioned above and the ability to evolve resistance to numerous herbicides have led to implementing a zero-tolerance seed production policy (Crow et al 2015;Norsworthy et al 2014).…”

Improving soil seed bank management

“…Postharvest herbicides, too, have been used to prevent seed dispersal. Postharvest applications of broad‐spectrum herbicides, such as paraquat and glyphosate, reduce annual weed seed production by over 90% in several cropping systems and weed species . Postharvest tillage may be nearly as effective as postharvest glyphosate at reducing weed seed production .…”

“…Postharvest applications of broad-spectrum herbicides, such as paraquat and glyphosate, reduce annual weed seed production by over 90% in several cropping systems and weed species. 57,58 Postharvest tillage may be nearly as effective as postharvest glyphosate at reducing weed seed production. 59 Preharvest herbicides can also prevent weed seed set, as with crop topping, although their use as a harvest aid is often for helping the crop dry down.…”