CONTROL OF VOLUNTARY SOYBEAN PLANTS WITH HERBICIDES RECOMMENDED FOR COTTON

Abstract

In part of the Midwest region of Brazil, cotton has been grown in second crop, sown after
soybean harvest. In these areas, the occurrence of voluntary soybean plants has been
common, interfering in the development of cotton crop. In this sense, the objective of this
work was to evaluate the effectiveness of herbicides applied post-emergence in cotton for
the control of voluntary soybeans containing different transgenics. Two experiments were
carried out in a greenhouse, using a soybean cultivar with Liberty Link® technology (LL®),
which confers tolerance to glufosinate, and the other Roundup Ready® (RR®) cultivar,
which has tolerance to glyphosate. In both experiments, a randomized completely block
design was used, in a 7 x 2 factorial arrangement, with 4 replications. The first factor
consisted of herbicides registered for cotton: 2,4-D, dicamba, glyphosate, pyrithiobac,
trifloxysulfuron, S-metolachlor, in addition to a control without application; while the
second factor consisted of the association or not with glufosinate. To assess the performance
of herbicide treatments, evaluations were made of the percentage of control, height and
shoot dry mass of soybean plants. For LL® voluntary soybeans, dicamba and glyphosate
alone, in addition to the association of glufosinate with dicamba, 2,4-D or glyphosate, they
consisted of the most effective treatments, providing control levels above 80.0%. For RR®
soybeans, dicamba, trifloxysulfuron and 2,4-D isolated showed efficacy in the control of
voluntary plants, with increases in control levels being seen when the addition of
glufosinate was applied to the spray solution of these herbicides.