Two-Way Performance Interactions amongρ-Hydroxyphenylpyruvate Dioxygenase- and Acetolactate Synthase-Inhibiting Herbicides

Abstract

There is little information available on performance interactions for tank mixtures of topramezone and acetolactate synthase (ALS)-inhibiting herbicides. Controlled-environment and field experiments were conducted in 2006 and 2007 to determine the interactions of topramezone when tank-mixed with ALS-inhibiting herbicides. Controlled-environment experiments were conducted on four annual grass species treated at the five- to six-leaf stage. Dose–response curves for large crabgrass, barnyardgrass, yellow foxtail, and green foxtail were generated for nicosulfuron or foramsulfuron alone and in combination with label rates of topramezone or mesotrione (with or without atrazine). Eight field experiments were conducted using registered rates of two ρ-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting and three ALS-inhibiting herbicides alone and in combination. All herbicide treatments in the field were applied at the two- to three-leaf and five- to six-leaf stages of barnyardgrass, green foxtail, giant green foxtail, and witchgrass. In both the controlled environment and field experiments, antagonistic interactions were found to be species specific. In the controlled environment, nicosulfuron antagonized topramezone for the control of large crabgrass and barnyardgrass, but did not influence control of yellow or green foxtail. This antagonism was overcome with the addition of atrazine or an increased dose of nicosulfuron. Antagonism was not observed with tank mixtures of topramezone and foramsulfuron on the species tested under controlled-environment or field conditions. In the field, antagonism was not influenced by growth stage of the annual grasses. Antagonistic interactions were observed when topramezone was tank-mixed with nicosulfuron or nicosulfuron + rimsulfuron for the control of barnyardgrass and, to a lesser extent, giant green foxtail. Similar tank mixtures did not reduce control of green foxtail or witchgrass. HPPD-inhibiting herbicides are known to antagonize the activity of ALS-inhibiting herbicides for the control of annual grasses. This is the first report in the literature that an ALS-inhibiting herbicide can antagonize an HPPD-inhibiting herbicide. Thus, the chemistries of these herbicides exhibit a two-way antagonistic interaction.

Annual Grasses Control With Topramezone in Mixture With Als-Inhibiting Herbicides

“…is largely reduced when topramezone is applied in mixture with rimsulfuron or nicosulfuron, indicating that the ALS-inhibiting herbicides tested in the present study can interact to a different extent with topramezone (an HPPDinhibiting herbicide). Such interaction was firstly reported by Kaastra et al (2008) for topramezone plus nicosulfuron under controlled environment on D. sanguinalis and E. crus-galli and also under field conditions on E. crus-galli and, to a lesser extent, on S. viridis var. major.…”

“…Therefore, tank mixtures of topramezone with other herbicides used in maize are required to provide effective weed control, particularly of the monocotyledonous species. Previous research on compatibility of topramezone with other herbicides used in maize showed that nicosulfuron in mixture with topramezone antagonized topramezone activity for the control of Digitaria sanguinalis and Echinochloa crus-galli under controlled conditions, but did not affect the control of Setaria glauca or S. viridis (Kaastra et al, 2008). Additionally, antagonistic interactions were observed in the field when topramezone was mixed with nicosulfuron or nicosulfuron plus rimsulfuron for the control of E. crus-galli and, to a lesser extent, S. viridis var.…”

“…Additionally, antagonistic interactions were observed in the field when topramezone was mixed with nicosulfuron or nicosulfuron plus rimsulfuron for the control of E. crus-galli and, to a lesser extent, S. viridis var. major (Kaastra et al, 2008). Yet similar mixtures did not reduce control of S. viridis or Panicum capillare (Kaastra et al, 2008).…”

“…major (Kaastra et al, 2008). Yet similar mixtures did not reduce control of S. viridis or Panicum capillare (Kaastra et al, 2008). In another study, the activity of topramezone on volunteer potato plants was not improved when applied in combination with herbicides interfering with the photosystem II (PS-II inhibitors), and in some instances appeared to antagonize control (Koepke-Hill et al, 2010).…”

“…An understanding of how herbicides perform in mixtures is critical to the positioning of new herbicide products in the marketplace (Kaastra et al, 2008). In addition, to the best of our knowledge, postemergence activity of topramezone either alone or in mixture with ALS-inhibiting herbicides has not been studied on naturalized Echinochloa spp., such as E. oryzoides and E. phyllopogon.…”