TITLE:
Control of Glyphosate-Resistant Waterhemp with Two-Pass Weed Control Strategies in Glyphosate/Dicamba-Resistant Soybean
AUTHORS:
Brittany K. Hedges, Nader Soltani, David C. Hooker, Darren E. Robinson, Peter H. Sikkema
KEYWORDS:
Waterhemp, Soybean, Glyphosate Resistance, Glyphosate, Dicamba
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.9 No.7,
June
19,
2018
ABSTRACT: Waterhemp
is a small-seeded, dioecious, broadleaf weed that emerges throughout the
growing season. If left uncontrolled, waterhemp interference can reduce soybean
yield up to
73%. Glyphosate-resistant
(GR) waterhemp was first
discovered in one county in Ontario in 2014; as of 2017, it has been found in
two other
counties. Glyphosate/dicamba-resistant soybean can be sprayed with glyphosate and/or dicamba
preplant (PP), preemergence (PRE) and/or postemergence (POST). The objective of
this study was to determine the control of GR waterhemp in
glyphosate/dicamba-resistant soybean with PRE residual herbicides,
glyphosate/dicamba applied POST or
a two-pass
program of a PRE residual herbicide followed by glyphosate/dicamba applied POST. At 8 weeks after application
(WAA), pyroxasulfone (150 g ai ha-1), S-metolachlor/metribuzin
(1943 g ai ha-1),
pyroxasulfone/sulfentrazone (300 g ai ha-1) and flumioxazin/pyroxasulfone
(240 g ai ha-1),
applied PRE, resulted
in 71%, 85%, 82% and 90% GR waterhemp
control, respectively. The same PRE herbicides, followed by glyphosate/dicamba
(1800 g ae ha-1) POST,
improved control to greater than 96%. This study concludes that
a two-pass program of an effective soil applied residual herbicide followed by
glyphosate/dicamba POST controlled GR
waterhemp in glyphosate/dicamba-resistant soybean.