A Multy-Year Study Reveals the Importance of Residual Herbicides on Weed Control in Glyphosate-Resistant Soybean

Abstract

-A 3-year field study was conducted to assess the potential for using pre-emergent (PRE) herbicides tank mixed with glyphosate as a means of controlling weed species in soybean. In 2011/12, 2012/13 and 2013/14 growing sessions soybean cultivar Brasmax Apollo RR was planted under residues of rye. The herbicide treatments glyphosate (gly) (1,296 g a.i. ha -1 ), gly + S-metolachlor (1,296 + 1,920), gly + imazaquin (1,296 +161), gly + pendimethalin (1,296 + 1,000), gly + metribuzin (1,296 + 480), gly + 2.4-D amine (1,296 + 1,209) was applied in pre-emergence (PRE) over rye crop residues two days before soybean sowing. In addition, full season weed-free and weedy control plots were included. Gly + S-metolachlor and gly + pendimethalin reduced the horseweed density from 48 to 3 and 6 plants m -2 , respectively. The mix containing gly + metribuzin and gly + 2.4-D amine and gly applied alone had no effect in the horseweed control. The mix containing gly + metribuzin, gly + 2.4-D amine, gly + imazaquin and gly applied alone had no effect in the crabgrass control. In contrast gly + S-metolachlor and gly + pendimethalin reduced the crabgrass density from 70 to 0 and 1 plant m -2 , respectively. The soybean yield was higher with weed-free, S-metolachlor and metribuzin treatments. The use of an herbicide with residual effect had impact on weed management and soybean yield. In conclusion, a greater control of horseweed and crabgrass occurred when S-metolachlor or pendimethalin was applied PRE.Keywords: Glycine max; 2.4-D; metribuzin; S-metolachlor; Conyza spp. 2011/12, 2012/13 e 2013/14, o RESUMO -Um estudo de campo de três safras foi conduzido para avaliar o potencial de uso de herbicidas pré-emergentes misturados com glyphosate como meio de controlar as espécies de plantas daninhas na cultura da soja. Nas safras

Conyza bonariensis growth and development according to thermal time accumulation and photoperiod

“…In this sense, changes in the vegetative growth and development of plants are related to emergency timing, and the decision for post-emergence control based on days, or according to plant height, may not represent the period of greatest weed sensitivity to hairy fleabane. Thus, an important weed management practice is the application of pre-emergent herbicides (Nunes et al, 2018) that can reduce infestation by retarding emergence. (1) Means followed by equal letters, lowercases in the lines and uppercases in the rows, do not differ by the Tukey's test, at 5% probability.…”

Weed control and soybean agronomic performance in response to application of sulfentrazone + diuron in pre-emergence

“…When implemented IWM minimize the impact of weeds and it could delay the evolution of herbicide resistant weeds HARKER, 2017). Within the chemical method, the use of pre-emergent herbicides has been presented as a good alternative to significantly reducing infestations of weeds after some years of use (NUNES et al, 2018). Among the advantages of using pre-emergent are the reduction in the number of herbicide applications, the lower development of weeds, making them more sensitive to post-emergence applications, the absence of weeds during the critical interference prevention period, and increase the diversity of herbicide sites of action (LOPES OVEJERO et al, 2013).…”

Soybean tolerance to sulfentrazone and diclosulam in sandy soil

“…The strategies to prevent and manage herbicide resistance include crop rotation, integration of control methods, and mixture or sequential use of herbicides with different mechanisms of action in order to reduce the selection pressure exerted by a single herbicide (Baucom, 2016). Alternative pre-emergent soybean herbicides, which were widely used in the past, are considered an important weed control tool for areas with glyphosate resistance (Osipe et al, 2014;Nunes et al, 2018). The use of these chemistries was significantly reduced after the introduction of RR soybeans varieties.…”