A. S. Culpepper, J. Kichler, A. C. York and J. Smith
Advancement in cotton weed management by growers has been miraculous; however, an economical solution to the control of Palmer amaranth is still elusive. Efforts for 2015 focus on critical components of a successful management program while emphasizing factors that influence excessive crop injury and/or insufficient Palmer control. Additionally, detailed programs for Liberty-based and Roundup-based systems are provided.
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Critical Steps For A Roundup-based System
1. No pigweed emerged at planting.
2. Plant seed into moist soil.
3. Apply two effective residual herbicides plus paraquat PRE.
4. Apply Roundup plus a residual within 13 d of planting; use Staple/Pyrimax as residual if resistance is not present.
5. Apply Roundup plus a residual 13 d after POST 1.
6. Apply layby about 18 d after POST 2 when Palmer < 5″.
7. Activate PRE (30-48 hr) and POST (12-24 hr) residuals.
8. Palmer present at harvest often emerge within 17 d of planting, timeliness of POST 1 herbicides critical.
9. Hand-weed Palmer escapes prior to seed production.
Critical Steps For A Liberty-based System
1. No pigweed emerged at planting
2. Plant seed into moist soil.
3. Apply two effective residual herbicides plus paraquat PRE.
4. Apply Liberty plus a residual when the largest pigweed is 3″; < 12 d if PRE not activated and about 17 d if activated.
5. Apply Roundup plus a residual about 13 d after POST 1; if Palmer is up Liberty again at about 17 d is the better option.
6. Apply layby about 18 d after POST 2 when Palmer < 5″.
7. Activate PRE (30-48 hr) and POST (12-24 hr) residuals.
8. Palmer at harvest often emerge within 17 d of planting.
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https://www.gaweed.com/HomepageFiles/2015Palmerhandout-Final%20Dec%2015.pdf