Abstract
ABSTRACT The evolution of glyphosate-resistant and -tolerant weeds has caused changes in weed management around the world. Residual herbicides are crucial tools for weed management, but the rate of adoption by soybean growers remains very low in Brazil. In this research, we used glyphosate tolerant Ipomoea triloba as a model weed species to evaluate the advantages of using residual herbicides on soybeans in multiple years and locations of transition and Cerrado regions of Brazil, rather than relying only on post-emergence control. Most residual herbicides provided enough residual activity to allow a longer application window in post-emergence. Treatments with residual herbicides increased overall weed control, preventing weed interference and increasing soybean yield. When two residual herbicides were used as opposed to only one, a better I. triloba control was achieved, reflecting in higher crop yield, especially in conditions of high weed infestation. The use of pre-emergence herbicides allows growers to have a longer application window for the post-emergence treatment, which is particularly important in Brazilian Cerrado large fields when logistic could be an issue.
Highlights
Brazil plays a key role in global soybean production with the largest cultivated area in the world in 2018-2019
For São Paulo (SP), Minas Gerais (MG) and BA locations with I. triloba infestations of up to 80 plants m-2 (Table 2), the combination of a residual herbicide followed by one glyphosate application provided 75 to 97% weed control (Table 5)
These values differed for each herbicide, but no significant differences were observed between glyphosate treatments at 21 and 28 days after emergence (DAE), except in SP
Summary
Brazil plays a key role in global soybean production with the largest cultivated area in the world in 2018-2019. Among all factors affecting soybean productivity, weeds are considered the number one issue around the world, accounting for 37% yield losses on average, while only. Weed management in Brazilian soybean production has changed significantly in the past few decades. Pre- (e.g. metribuzin) and post-emergence herbicides (e.g. ACCase and ALS inhibitors) were rapidly adopted by soybean growers. When the Roundup Ready soybeans (Monsanto Company, St. Louis, MO) were released in 2005, weeds resistant to ALS inhibitors and ACCase inhibitors were managed by glyphosate (Braz et al, 2011). The high efficacy, broadspectrum activity, and low cost provided by glyphosate prompted growers to reduce the use of residual herbicides in their weed management programs (Peterson et al, 2018; Powles, 2008)
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