Junglerice control with glyphosate and clethodim as influenced by dicamba and 2,4-D mixtures

Clay M Perkins,Lawrence E Steckel,Thomas C Mueller

doi:10.1017/wet.2021.5

Clay M Perkins, Lawrence E Steckel + Show 1 more

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https://doi.org/10.1017/wet.2021.5

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Journal: Weed Technology	Publication Date: Jan 22, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: University of Tennessee at Knoxville

Abstract

AbstractJunglerice has become a major weed in the mid-south and other areas of the United States. Glyphosate resistance has been documented in junglerice populations and is part of the reason for the increase in its prevalence. However, reduced junglerice control with glyphosate + dicamba and clethodim + dicamba mixtures has been observed in many production fields where glyphosate resistance has not yet evolved. Therefore, research was conducted to assess reduced junglerice control with glyphosate and clethodim when applied with dicamba. Adding dicamba to the spray tank with glyphosate reduced junglerice control by 27%. Adding dicamba to the spray tank with clethodim reduced junglerice control by 11%. The use of Turbo Teejet Induction (TTI) nozzles reduced junglerice control an additional 8% compared to applications with an air induction extended range (AIXR) nozzle. When a drift reduction agent (DRA) was added to dicamba mixtures with glyphosate or clethodim, junglerice control was reduced 36%. Junglerice control was similar with the glyphosate + dicamba treatment compared to the glyphosate + 2,4-D mixture. There was no interaction between nozzles and herbicide treatment. Regardless of herbicide treatment junglerice control was always lower when applied with the ultracourse TTI nozzle. Many applicators in Tennessee prefer to make one application of glyphosate + dicamba in a mixture to save time (authors’ personal experience). These results show that the addition of dicamba to glyphosate or clethodim applied with labeled nozzles and a DRA results in reduced junglerice control and should be avoided.

Highlights

Junglerice has become one of the top two prevalent weeds in soybean [Glycine max (L.) Merr.] and cotton (Gossypium hirsutum L.) in much of Tennessee and across the mid-south (Perkins et al 2021; Tahir 2007)
Many field reports from cotton and soybean growers in Tennessee suggest that grass weed control, junglerice, from glyphosate þ dicamba or clethodim þ dicamba applications has been unacceptable (Perkins et al 2021)
The objective of this research was to 1) assess junglerice control with mixtures containing dicamba and 2) assess whether labeled nozzles and drift reduction agent (DRA) used in dicamba applications are reducing control; and 3) examine whether increased rates of dicamba in these mixtures resulted in less junglerice control

Summary

Introduction

Junglerice has become one of the top two prevalent weeds in soybean [Glycine max (L.) Merr.] and cotton (Gossypium hirsutum L.) in much of Tennessee and across the mid-south (Perkins et al 2021; Tahir 2007). Several populations of junglerice have been tested for glyphosate and clethodim resistance (Perkins et al 2021). Those studies have indicated that 15% of the populations have a 2-fold to 8-fold resistant to glyphosate, which is consistent with a report by Nandula et al (2018) who studied selected Mississippi and Tennessee populations. Many field reports from cotton and soybean growers in Tennessee suggest that grass weed control, junglerice, from glyphosate þ dicamba or clethodim þ dicamba applications has been unacceptable (Perkins et al 2021)

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