Abstract
Abstract Background: The application of Acetyl CoA carboxylase (ACCase) inhibitors prior to sowing of grass crops may result in crop damage due to residual effect of these herbicides in soil. The hypotheses was that different corn hybrids and ACCase herbicides can result in different plant-back intervals after burndown treatments. Objective: This work was planned to determine safe plant-back periods for three corn hybrids where ACCase herbicides clethodim and haloxyfop-methyl are applied. Methods: Herbicides were sprayed at 21, 14, 7, 2 and 0 days before sowing (DBS) at 192 g a.i. ha-1 (clethodim) and 120 g a.i. ha-1 (haloxyfop-methyl). Individual experiments were carried out with three hybrids: KWS9110 and 2B587 with glyphosate and glufosinate tolerance and Enlist with aryloxyphenoxypropionate tolerance. Results: Haloxyfop-methyl resulted in higher damage potential compared to clethodim for the hybrids KWS9110 and 2B587. For these hybrids, significant crop stand and grain yield reductions were observed mainly when haloxyfop was applied closer to sowing date (7, 2 and 0 DBS). Conclusions: Based on the effects on corn grain yield, a safe plant-back period for haloxyfop was estimated to be 8 and 11 days for the hybrids KWS9110 and 2B587, respectively. For the Enlist corn hybrid, there were no yield decreases, even when haloxyfop was applied at 0 DBS. Clethodim did not affect corn yield of any hybrid in any application time.
Highlights
In addition to glufosinate- and glyphosate- tolerance, Enlist corn hybrids carry the aryloxyalkanoate dioxygenase trait (AAD-1), obtained from the bacteria Sphingobium herbicidovorans (Ruen et al, 2017)
The experiments were conducted in a factorial scheme (5 x 2) + 1, including five periods of time between herbicide application and corn sowing (21, 14, 7, 2 and 0 days before sowing - DBS), two herbicides, and an additional treatment represented by a non-sprayed check
For the hybrid 2B587, crop injuries caused by clethodim at 0 DAS ranged from 10 to 20% and by haloxyfop-methyl were >60%
Summary
In addition to glufosinate- and glyphosate- tolerance, Enlist corn hybrids carry the aryloxyalkanoate dioxygenase trait (AAD-1), obtained from the bacteria Sphingobium herbicidovorans (Ruen et al, 2017). The Acetyl-CoA carboxylase (ACCase) inhibitors remain the most important group of herbicides for post-emergence grass control (Sanafar et al, 2017). These herbicides block the synthesis of fatty acids in monocots due to the inhibition of the target ACCase enzyme, leading to plant death (Burton et al, 1989). A third chemical group is the Phenylpyrazolines (DEN’s), which includes the herbicide pinoxaden, that has been used mainly to provide grass control in winter cereals (Locke et al, 2002). Results: Haloxyfop-methyl resulted in higher damage potential compared to clethodim for the hybrids KWS9110 and 2B587 For these hybrids, significant crop stand and grain yield reductions were observed mainly when haloxyfop was applied closer to sowing date (7, 2 and 0 DBS). Clethodim did not affect corn yield of any hybrid in any application time
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