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UGA Programs for Controlling Glyphosate-Resistant Palmer Amaranth in 2015 Cotton

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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http://www.gaweed.com/HomepageFiles/2015Palmerhandout-Final%20Dec%2015.pdf