Weed Control in Cotton by Combinations of Microencapsulated Acetochlor and Various Residual Herbicides Applied Preemergence

Abstract

Residual herbicides are routinely recommended to aid in control of glyphosate-resistant (GR) Palmer amaranth in cotton. Acetochlor, a chloroacetamide herbicide, applied PRE, controls Palmer amaranth. A microencapsulated (ME) formulation of acetochlor is now registered for PRE application in cotton. Field research was conducted in North Carolina to evaluate cotton tolerance and Palmer amaranth control by acetochlor ME alone and in various combinations. Treatments, applied PRE, consisted of acetochlor ME, pendimethalin, or no herbicide arranged factorially with diuron, fluometuron, fomesafen, diuron plus fomesafen, and no herbicide. The PRE herbicides were followed by glufosinate applied twice POST and diuron plus MSMA directed at layby. Acetochlor ME was less injurious to cotton than pendimethalin. Acetochlor ME alone or in combination with other herbicides reduced early season cotton growth 5 to 8%, whereas pendimethalin alone or in combinations injured cotton 11 to 13%. Early season injury was transitory, and by 65 to 84 d after PRE treatment, injury was no longer noticeable. Before the first POST application of glufosinate, acetochlor ME and pendimethalin controlled Palmer amaranth 84 and 64%, respectively. Control by acetochlor ME was similar to control by diuron plus fomesafen and greater than control by diuron, fluometuron, or fomesafen alone. Greater than 90% control was obtained with acetochlor ME mixed with diuron or fomesafen. Palmer amaranth control was similar with acetochlor ME plus a full or reduced rate of fomesafen. Acetochlor ME controlled large crabgrass and goosegrass at 91 and 100% compared with control at 83 and 91%, respectively, by pendimethalin. Following glufosinate, applied twice POST, and diuron plus MSMA, at layby, 96 to 99% control was obtained late in the season by all treatments, and no differences among herbicide treatments were noted for cotton yield. This research demonstrated that acetochlor ME can be safely and effectively used in cotton weed management programs.

Weed Control and Peanut (Arachis hypogaea L.) Response to Acetochlor Alone and in Combination with Various Herbicides

“…], and soybean [Glycine max (L.) Merr.] to control annual grasses and small-seeded broadleaf weeds (Anonymous, 2017b;Cahoon et al 2015;Geier et al, 2009;Steckel et al, 2002). Acetochlor inhibits geranylgeranyl pyrophosphate cyclization enzymes, which are part of the gibberellin biosynthetic pathway and controls weeds by inhibiting growth of seedling shoots (Shaner, 2014).…”

“…Grichar et al (2015) reported no negative effect of acetochlor ME application timing and rate on peanut grade and yield in runner and Spanish market type cultivars. Cahoon et al (2015) documented that acetochlor ME applied PRE caused less than 8% early season injury to cotton and at least 90% control of Palmer amaranth. Early season injury caused by acetochlor was transient and did not negatively impact cotton yield.…”

Overlapping Residual Herbicides for Control of Photosystem (PS) II- and 4-Hydroxyphenylpyruvate Dioxygenase (HPPD)-Inhibitor-Resistant Palmer amaranth (Amaranthus palmeri S. Watson) in Glyphosate-Resistant Maize

“…Several soil-residual PRE herbicides have been registered for Palmer amaranth control in maize. For instance, acetochlor, dimethenamid-P, pendimethalin, pyroxasulfone, saflufenacil, or S -metolachlor applied PRE provided >80% Palmer amaranth control up to 50 days after application (Johnson et al, 2012 ; Cahoon et al, 2015 ; Janak and Grichar, 2016 ; Meyer et al, 2016 ). In addition, some soil residual herbicides such as acetochlor, pyroxasulfone, or dimethenamid-P can be applied POST in maize up to certain growth stages (Anonymous, 2017e , f , g ).…”

Adsorption, desorption and persistence of fomesafen in soil

“…In Georgia, 18 573 kg of fomesafen was applied on 66 636 ha in 2007 and this increased to 85 164 kg on 304 330 ha by 2015 . However, cotton growers in the southern USA have frequently observed seedling injury, stunting and stand reduction caused by fomesafen application and little analytical data are available to address this issue . Fomesafen has recently received a 24C special local need label for Palmer amaranth control in several vegetables in Georgia, such as watermelon, tomatoes, squash and pepper.…”

“…19 However, cotton growers in the southern USA have frequently observed seedling injury, stunting and stand reduction caused by fomesafen application and little analytical data are available to address this issue. [20][21][22] Fomesafen has recently received a 24C special local need label for Palmer amaranth control in several vegetables in Georgia, such as watermelon, tomatoes, squash and pepper. However, because of its relatively long soil persistence, fomesafen carryover injury on the subsequent sensitive crop planted in the same bed has also been reported by Georgia vegetable growers who utilize plasticulture in their production.…”