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Managing Glyphosate-Resistant Palmer Amaranth in Conventional and Strip-Till Roundup Ready Cotton Culpepper, Kichler, MacRae, Whitaker, York, Davis.

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Presentation on theme: "Managing Glyphosate-Resistant Palmer Amaranth in Conventional and Strip-Till Roundup Ready Cotton Culpepper, Kichler, MacRae, Whitaker, York, Davis."— Presentation transcript:

1 Managing Glyphosate-Resistant Palmer Amaranth in Conventional and Strip-Till Roundup Ready Cotton Culpepper, Kichler, MacRae, Whitaker, York, Davis

2 Management Program For Glyphosate-Resistant Palmer Amaranth if Things Are Not Perfect

3 Strip-Till Cotton Acreage Estimates for Georgia and North Carolina % Acres

4 Conservation Tillage is Very Important To the Southeast

5 2004 Common Horseweed Burndown Program Photo credit: Larry Steckel

6 Hypothesis  Glyphosate-resistant Palmer amaranth will put cotton farmers out of conservation tillage production?

7 2006 Locations Rocky Mount * Macon Co. **

8 Materials and Methods Split Plot Design 2 tillage practices 7 herbicide systems Plot size GA = 4 rows by 45 feet NC = 4 rows by 30 feet

9 Herbicide Systems* PREPOST Prowl Roundup + Dual Mag. Prowl + Cotoran Prowl + Staple Prowl + Reflex Prowl Roundup + Staple Prowl + Cotoran Prowl + Reflex *Direx + MSMA applied at layby for each herbicide program.

10 Herbicides and Rates 2.5 pt/AProwl H20 2 pt/ACotoran 1.7 fl ozStaple LX 1 pt/AReflex 22 oz/AWeatherMax 1 ptDual Mag. 1.7 fl ozStaple LX PRE POST Layby Direx 2 pt + MSMA 2 lb

11 Tillage Systems Conventional: no weeds or residue Strip Tillage: cover controlled several weeks ahead of planting followed by Gramoxone PRE

12 Residues Rocky Mount * Macon Co. ** weeds (little residue) Grazed wheat (little cover) Thick wheat (heavy cover)

13

14 Impact of Tillage on Locations with Little Cover* Georgia strip till = 67 conven = 69 North Carolina strip till = 77 conven = 74 *Averaged over all herbicide systems.

15 Direx + MSMA directed over entire trial area. Percent late-season glyphosate-resistant Palmer amaranth control. Macon Co., GA * 90 ab +Cotoran +Reflex +Cotoran+Reflex+Staple 84 bc WeatherMax + Dual 54 d 60 d 80 c 95 a WeatherMax + Staple Prowl <25% resistant

16 Direx + MSMA directed over entire trial area. Percent late-season glyphosate-resistant Palmer amaranth control. Wayne Co, NC * 91 a +Cotoran +Reflex +Cotoran+Reflex+Staple WeatherMax + Dual 69 b 76 b 91 a 94 a 90 a 93 a WeatherMax + Staple Prowl <25% resistant

17 Direx + MSMA directed over entire trial area. Seed cotton yield (lb/A). Wayne Co, NC * 1420 a +Cotoran +Reflex +Cotoran+Reflex+Staple WeatherMax + Dual 1160 c 1225 bc 1360 abc 1315 abc 1462 a 1536 a WeatherMax + Staple Prowl

18 Residue= 9760 lb/A

19 Number of plants in the non- treated control at harvest. strip till = 8 conven = 32 # plants per sq. yard

20 75+% Resistant

21 Percent glyphosate-resistant Palmer amaranth control. Macon Co * Direx + MSMA directed over entire trial area Cotoran +Reflex +Cotoran+Reflex+Staple 62 WeatherMax + Dual 61 WeatherMax + Staple Prowl 75+% resistant

22 Glyphosate-resistant Palmer amaranth response to herbicides and tillage. Macon Co * Direx + MSMA directed over entire trial area. 0 f3 f 30 d 73 b 3 f 13 e +Cotoran +Reflex +Cotoran+Reflex+Staple 62 c WeatherMax + Dual 60 c 66 bc 61 c 74 b 85 a 88 a WeatherMax + Staple Prowl

23 Prowl + Cotoran PRE fb Roundup + Staple

24 Prowl + Cotoran PRE fb Roundup + Dual 4 inch fb Direx + MSMA PD ConvStrip-Till

25 Prowl + Reflex PRE fb Roundup + Dual 4 inch fb Direx + MSMA PD ConvStrip-Till

26 Direx + MSMA directed over entire trial area. Asterick denotes similar yield among systems. Seed cotton yield (lb/A). Macon Co * +Cotoran +Staple +Reflex+Cotoran+Reflex WeatherMax + Dual * WeatherMax + Staple Prowl * * * * *

27 Conclusions 1.Low levels of dead residue did not impact herbicidal control. 2.Heavy residue improved control. A. Reduced pigweed emergence B. Delayed pigweed emergence and growth 3.Heavy residue likely eliminated much of the activity of PRE herbicides placing more “pressure” on Staple POST

28 Staple LX fl oz/A

29 Staple Wmax fl oz/A

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