Abstract
Palmer amaranth and pitted morningglory are difficult to manage weeds present in South Carolina soybean production fields. Glyphosate and ALS-resistant Palmer amaranth biotypes have spread rapidly throughout South Carolina making the control of these weeds more difficult. Recently, soybean varieties with tolerance to dicamba have been introduced along with several new ultra-low volatility formulations of dicamba to help with the problem. Field experiments were conducted near Blackville, SC in 2012 and 2013 to evaluate dicamba herbicide programs for broadleaf weed management in dicamba tolerant soybean. At 2 weeks after POST1 (2 WAP1), Palmer amaranth control ranged from 93% to 100% across the PRE followed by POST treatments in 2012 and 2013. By 2 weeks after POST2 (2 WAP2), control was 95% or better. Treatments containing two or three herbicide applications (PRE, POST1 and POST2) offered good to excellent (92% - 100%) pitted morningglory control. No differences in weed control were observed among treatments with 3 application times compared to those applied twice. In general, all treatments with a PRE followed by at least one POST application provided good to excellent control of Palmer amaranth and pitted morningglory. Overall, a PRE (either dicamba or flumioxazin) followed by a dicamba or a non-dicamba containing POST treatment provided good to excellent control of Palmer amaranth and pitted morningglory when applied at the correct growth stage.
Highlights
As the world’s population increases, there is an increasing pressure upon the farmers to produce enough food and fiber for the world today
Treatments containing two or three herbicide applications (PRE, POST1 and POST2) offered good to excellent (92% - 100%) pitted morningglory control; the PRE followed by POST1 were slightly less effective in 2012 than 2013
A PRE followed by a dicamba + glyphosate POST tank mix provided excellent control of Palmer amaranth and pitted morningglory in these studies. Those containing 2 applications (PRE followed by POST1) were similar in effectiveness as those containing 3 applications (PRE followed by POST1 and POST2)
Summary
As the world’s population increases, there is an increasing pressure upon the farmers to produce enough food and fiber for the world today. Farmers have looked to researchers to develop better crop cultivars that are superior to the traditional landrace or heirloom strains that have been cultivated before modern agriculture. These improvements in crop varieties have allowed for an increased level of crop productivity. Among these breeding advances was the development of higher yielding crops which allowed farmers to plant on the same acreage with greater yield [1] [2]. The advantage of weed control achieved by the introduction of herbicides eventually led to the selection of herbicide resistant weeds
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