TITLE:
Palmer Amaranth (Amaranthus palmeri S. Wats.) and Pitted Morningglory (Ipomoea lacunosa L.) Control in Dicamba Tolerant Soybean (Glycine max L.)
AUTHORS:
Dwayne D. Joseph, Michael W. Marshall, Colton H. Sanders
KEYWORDS:
Weed Resistance, Soybean, Dicamba, Glyphosate, Broadleaf Weeds
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.13,
December
22,
2017
ABSTRACT: Palmer amaranth and pitted morningglory are
difficult to manage weeds present in South Carolina soybean production fields.
Glyphosate and ALS-resistant Palmer amaranth biotypes have spread rapidly
throughout South Carolina making the control of these weeds more difficult.
Recently, soybean varieties with tolerance to dicamba have been introduced
along with several new ultra-low volatility formulations of dicamba to help
with the problem. Field experiments were conducted near Blackville, SC in 2012
and 2013 to evaluate dicamba herbicide programs for broadleaf weed management
in dicamba tolerant soybean. At 2 weeks after POST1 (2 WAP1), Palmer amaranth
control ranged from 93% to 100% across the PRE followed by POST treatments in
2012 and 2013. By 2 weeks after POST2 (2 WAP2), control was 95% or better.
Treatments containing two or three herbicide applications (PRE, POST1 and
POST2) offered good to excellent (92% - 100%) pitted morningglory control. No
differences in weed control were observed among treatments with 3 application
times compared to those applied twice. In general, all treatments with a PRE
followed by at least one POST application provided good to excellent control of
Palmer amaranth and pitted morningglory. Overall, a PRE (either dicamba or
flumioxazin) followed by a dicamba or a non-dicamba containing POST treatment provided
good to excellent control of Palmer amaranth and pitted morningglory when
applied at the correct growth stage.