Is There a Benefit of Adding Atrazine to HPPD-Inhibiting Herbicides for Control of Multiple-Herbicide-Resistant, Including Group 5-Resistant, Waterhemp in Corn?

Abstract

The evolution of multiple-herbicide-resistant (MHR) waterhemp (resistant to Groups 2, 5, 9, and 14) in Ontario, Canada is challenging for growers. The complementary activity of the co-application of hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides with atrazine has been well documented. The objective of this research was to determine if the addition of atrazine to 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides applied postemergence improves their consistency of MHR waterhemp (including Group 5 resistance) in corn. Five field trials were conducted over a two-year period (2018, 2019) in Ontario, Canada. Five HPPD-inhibiting herbicides [isoxaflutole (105 g ha-1), mesotrione (100 g ha-1), topramezone (12.5 g ha-1), tembotrione (90 g ha-1), and tolpyralate (30 g ha-1)] were applied postemergence with and without atrazine to 10-cm-tall waterhemp. Corn injury (≤ 10%) was observed at specific sites where the application of tembotrione, isoxaflutole and isoxaflutole + atrazine resulted in characteristic white bleaching of corn foliage; however, yield was not affected. Averaged across field sites, the addition of atrazine to isoxaflutole, mesotrione, topramezone, or tembotrione improved MHR waterhemp control 15%, 11%, 7%, and 7%, respectively at 4 weeks after application (WAA). Averaged across herbicide treatments and sites, the addition of atrazine reduced the standard error of MHR waterhemp control by 13% to 100%. This study concludes that the co-application of atrazine with HPPD-inhibitors applied postemergence reduced the risk of herbicide failure and resulted in greater and more consistent control of MHR waterhemp.

4-Hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides: past, present, and future

“…In research plots throughout North America, mixing atrazine with tembotrione reduced variability in weed control and sweet corn yield variation (Williams et al 2011a, 2011b). Similar findings were observed with atrazine + isoxaflutole, mesotrione, topramezone, tembotrione, or tolpyralate for waterhemp control in field corn (Willemse et al 2021a). Furthermore, atrazine improved the efficacy of pyrasulfotole + bromoxynil for weed control in grain sorghum (Reddy et al 2013).…”

“…Field corn production systems rely extensively on a mixture of HPPD and PS II inhibitors. Considerable field research demonstrates excellent crop tolerance with their mixtures (Johnson et al 2002; Osipitan et al 2018; Stephenson et al 2004; Whaley et al 2006; Willemse et al 2021a). Additional research shows that the synergistic effect of HPPD and PS II inhibitors for weed control was not observed on sweet corn response (Choe et al 2014).…”