Using Quinclorac to Control Annual Grasses and Palmer Amaranth in Grain Sorghum (Sorghum bicolor L.)

James Grichar,Travis Janak

doi:10.24297/jaa.v12i.8950

Abstract

Field studies were conducted during the 2015 and 2016 growing seasons in south-central Texas to determine control of Palmer amaranth and annual grasses along with grain sorghum tolerance to quinclorac alone and in various combinations when applied to weeds < 5 cm (EPOST) or 10 to 16 cm tall (LPOST). When evaluated late-season quinclorac alone at 0.43 kg ae ha-1 controlled broadleaf signalgrass 72% when applied EPOST and 91% when applied LPOST. Combinations of quinclorac with either atrazine, pyrasulfotole + bromoxynil, dicamba, or dimethenamid-P controlled Palmer amaranth 88 to 100% when applied EPOST or LPOST; however, broadleaf signalgrass control with these combination was better when applied LPOST (75 to 95%) compared with EPOST (37 to 72%) applications. Texas millet control with quinclorac was poor in both years and was never greater than 54%. Quinclorac plus either atrazine, pyrasulfotole + bromoxynil, dicamba, or atrazine + dimethenamid-P caused at least 20% sorghum injury at one of three locations. No yield reductions from the untreated check were noted in either year; however, in 2016 all treatments with the exception of quinclorac alone at 0.29 kg ha-1 applied EPOST, quinclorac + pyrasulfotole + bromoxynil applied LPOST, quinclorac + atrazine + pyrasulfotole + bromoxynil applied LPOST, and quinclorac + dicamba at either application timing produced yields that were greater than the untreated check.

Highlights

Quinclorac is an auxinic herbicide belonging to the quinolinic acid class recommended for control of broadleaf weeds and grass species in rice (Oryza sativa L.), corn (Zea mays L.), soybean (Glycine max L.), sorghum [Sorghum bicolor (L.) Moench], and pastures [1] and is readily absorbed by germinating seeds, roots, and leaves [2]
Wheeler] biotype to herbicides presenting this mode of action, finding no differences in the absorption, transport or metabolism of auxin-mimic herbicides between the resistant and susceptible biotypes
The Yoakum site was infested with a natural population of Texas millet, 10 to 15 plants/m2, and Palmer amaranth, 20 to 30 plants/m2, while broadleaf signalgrass populations at the Ganado site ranged from 8 to 12 plants/m2

Summary

Introduction

Quinclorac is an auxinic herbicide belonging to the quinolinic acid class recommended for control of broadleaf weeds and grass species in rice (Oryza sativa L.), corn (Zea mays L.), soybean (Glycine max L.), sorghum [Sorghum bicolor (L.) Moench], and pastures [1] and is readily absorbed by germinating seeds, roots, and leaves [2]. Quinclorac is selective to relatively well-known species, its mode of action in weeds and mechanism of selectivity for crops are not completely understood [3,4]. Zheng and Hall [5] proposed that a group of proteins named ABP (auxin-binding proteins) is the site of the auxin-mimic herbicides. They characterized biochemically and physiologically the resistance of a wild mustard [Brassica kaber (DC.) L. Wheeler] biotype to herbicides presenting this mode of action, finding no differences in the absorption, transport or metabolism of auxin-mimic herbicides between the resistant and susceptible biotypes

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Conclusion