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1 December 2018 Tolpyralate Efficacy: Part 1. Biologically Effective Dose of Tolpyralate for Control of Annual Grass and Broadleaf Weeds in Corn
Brendan A. Metzger, Nader Soltani, Alan J. Raeder, David C. Hooker, Darren E. Robinson, Peter H. Sikkema
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Abstract

Tolpyralate is a new 4-hydroxyphenyl-pyruvate dioxygenase (HPPD)-inhibiting herbicide for POST weed management in corn; however, there is limited information regarding its efficacy. Six field studies were conducted in Ontario, Canada, over 3 yr (2015 to 2017) to determine the biologically effective dose of tolpyralate for the control of eight annual weed species. Tolpyralate was applied POST at six doses from 3.75 to 120 g ai ha-1 and tank mixed at a 1:33.3 ratio with atrazine at six doses from 125 to 4,000 g ha-1. Regression analysis was performed to determine the effective dose (ED) of tolpyralate, and tolpyralate + atrazine, required to achieve 50%, 80%, or 90% control of eight weed species at 1, 2, 4, and 8 wk after application (WAA). The ED of tolpyralate for 90% control (ED90) of velvetleaf, common lambsquarters, common ragweed, redroot pigweed or Powell amaranth, and green foxtail at 8 WAA was ≤15.5 g ha-1; however, tolpyralate alone did not provide 90% control of wild mustard, barnyardgrass, or ladysthumb at 8WAAat any dose evaluated in this study. In contrast, the ED90 for all species in this study with tolpyralate + atrazine was ≤13.1 + 436 g ha-1, indicating that tolpyralate + atrazine can be highly efficacious at low field doses.

Nomenclature: Atrazine; tolpyralate; barnyardgrass, Echinochloa crus-galli (L.) P. Beauv. ECHCG; common lambsquarters, Chenopodium album L. CHEAL; common ragweed, Ambrosia artemisiifolia L. AMBEL; green foxtail, Setaria viridis (L.) P. Beauv. SETVI; ladysthumb, Persicaria maculosa Gray POLPE; Powell amaranth, Amaranthus powelli S. Watson AMAPO; redroot pigweed, Amaranthus retroflexus L. AMARE; velvetleaf, Abutilon theophrasti Medik. ABUTH; wild mustard, Sinapis arvensis L. SINAR; corn, Zea mays L.

© Weed Science Society of America, 2018.
Brendan A. Metzger, Nader Soltani, Alan J. Raeder, David C. Hooker, Darren E. Robinson, and Peter H. Sikkema "Tolpyralate Efficacy: Part 1. Biologically Effective Dose of Tolpyralate for Control of Annual Grass and Broadleaf Weeds in Corn," Weed Technology 32(6), 698-706, (1 December 2018). https://doi.org/10.1017/wet.2018.82
Received: 11 May 2018; Accepted: 17 August 2018; Published: 1 December 2018
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KEYWORDS
Dose response
HPPDinhibiting herbicides
hydroxyphenylpyruvate dioxygenase (HPPD)
photosystem II-inhibiting herbicides
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