Abstract
Tolpyralate, an HPPD (4-hydroxyphenyl-pyruvate dioxygenase) inhibitor, is a relatively new herbicide for weed control in corn. Field studies were conducted in 2015 and 2016 to evaluate the effective dose of tolpyralate applied alone or mixed with atrazine for weed control in corn. The treatments included seven rates (0, 5, 20, 29, 40, 50 and 100 g ai ha-1) of tolpyralate applied alone or mixed with a constant rate (560 g ai ha-1) of atrazine. The evaluated weed species were common waterhemp (Amaranthus rudis Sauer), common lambsquarters (Chenopodium album L.), velvetleaf (Abutilon theophrasti Medik), henbit (Lamium amplexicaule L.) and green foxtail (Setaria viridis L.). Overall, POST-application of tolpyralate resulted in 58-94% visual weed control when applied alone; whereas, addition of atrazine provided 71-100% control of same species. Calculated dose of 19-31 g ai ha-1 (ED90) of tolpyralate applied alone provided 90% visual control of waterhemp, lambsquaters, henbit, and velvetleaf. Whereas, addition of atrazine resulted in significantly lower dose of 11-17 g ai ha-1 for the same level of control, suggesting synergy between the two herbicides.
Highlights
There is an increase in minimum and no-till systems in United States, which in reality depends heavily on herbicides as the main tool for weed control in corn (Heap & Duke, 2018)
There was no significant interaction between years and treatments on weeds and corn yield responses, data from both years were combined and regression curves fit to 30 and 60 days after treatment (DAT) observation dates for each weed species
Addition of atrazine resulted in better weed control, suggesting potential synergy between tolpyralate and atrazine
Summary
There is an increase in minimum and no-till systems in United States, which in reality depends heavily on herbicides as the main tool for weed control in corn (Heap & Duke, 2018). Tolpyralate, an HPPD (4-hydroxyphenyl-pyruvate dioxygenase) inhibitor is a relatively new post-emergence herbicide for weed control in corn (Kikugawa et al, 2015; Morris et al, 2018). This new active ingredient blocks biosynthesis of carotenoids in plants through inhibition of HPPD enzyme resulting in the disruption of photosynthesis followed by death of sensitive plants (Kikugawa et al, 2015). A tank mix of tolpyralate with commonly used herbicides such as chloro-acetamides, dicamba, glyphosate and glufosinate provided excellent weed control (Tonks et al, 2015). Information is lacking on the effectiveness of tolpyralate applied alone or in mixture with atrazine for weed control in corn
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