Flumioxazin and Flufenacet as possible options for the control of multiple herbicide-resistant littleseed canarygrass (Phalaris minor Retz.) in wheat

Rajender Singh Chhokar Ramesh Kumar Sharma Subhash Chander Gill and Gyanendra Pratap Singh

Keywords:

wheat, flumioxazin, flufenacet, littleseed canarygrass, Phalaris minor, clodinafop, herbicide resistance, isoproturon, pendimethalin, sulfosulfuron

Abstract:

We conducted field trials and pot experiment to evaluate the effectiveness of two herbicides - flumioxazin and flufenacet - for weed control in wheat (Triticum aestivum L.), particularly targeting littleseed canarygrass (Phalaris minor Retz.). In the field studies, conducted over four seasons (2012-13 to 2015-16), the littleseed canarygrass populations encountered in the fields were sensitive to herbicides. In the pot studies, the responses of both multiple herbicide-resistant (resistant to isoproturon, clodinafop, and sulfosulfuron) and sensitive populations were examined against flumioxazin and flufenacet. In the field trials, application of preemergence flumioxazin at 125-150 g a.i./ha effectively controlled littleseed canarygrass and several broadleaved weeds, such as toothed dock (Rumex dentatus L.) and bur clover (Medicago denticulata Willd). However, flumioxazin was less effective against a second dominant grass weed, wild oat (Avena ludoviciana Dur.), which infested the field plots. Pendimethalin, which was used in the trials for comparison, at 1000 g a.i./ha, was less effective than flumioxazin in controlling wild oat. Compared with the unweeded control (weedy check) and the plots that received the pendimethalin treatments, the treatments with flumioxazin, at 125-150 g a.i./ha, produced much higher grain yields (i.e., up to 159% and up to 49% increased yield gain, respectively). The highest rate of flumioxazin (250 g a.i./ha) did not increase the weed control achieved, compared with the lower rates, but caused average crop phytotoxicity of 31% at 40 days after the herbicide application or 20 days after the first irrigation. In other field experiments, flufenacet (200-300 g a.i./ha), applied as early post-emergence at 20 days after sowing (one day before the first irrigation), was highly effective in the control of both littleseed canarygrass and wild oat. However, flufenacet was not effective in controlling broad-leaved weeds. Overall, the weed control and the wheat yield obtained with flufenacet 250 g a.i./ha were not significantly different from those obtained with the standard treatment used in the study (i.e., clodinafop, 60 g a.i./ha at 35 days after sowing). In pot bioassay studies, flumioxazin and flufenacet were tested against multiple herbicide-resistant littleseed canarygrass, known to be resistant to acetyl-coA carboxylase (ACCase), acetolactate synthase (ALS) and photosystem II site A (PS-II) inhibitor herbicides, such as clodinafop, sulfosulfuron, and isoproturon, respectively. The results of the pot study indicated effective control (up to 100%) of the herbicide-resistant littleseed canarygrass population by both flumioxazin and flufenacet. Our combined studies of field trials and pot experiment, therefore, indicate that both flumioxazin and flufenacet have the potential to be alternative herbicide options in wheat, particularly for littleseed canarygrass control. As discussed in this paper, while we have demonstrated the potential, further studies are needed, incorporating other agronomic practices in wheat cultivation with flumioxazin and flufenacet, to explore their full potential for the control of multiple herbicide-resistant littleseed canarygrass.