Giant Ragweed Control in Cotton Larry Steckel and Chris Main University of Tennessee

Giant Ragweed Moves into Fields from Borders

Giant Ragweed Begins to Spread

2 Shots of Roundup Original Max

Spreads Throughout the Field

40 (2”) + 88 (6”) + 88 (18”) oz/A Roundup WM

2008 Weed Control Manual for Tennessee Field Crops • Forage Crops • Pastures • Farm Ponds • Harvest Aids Contents 4 Burndown Herbicides 6 Tobacco 56 Calibration 83 Resistant Horseweed 7 Wheat 59 Herbicide Drift 87 Corn 10 Sunflowers 63 Grazing Restrictions 96 Grain Sorghum 23 Forage & Pastures 66 Price List 104 Cotton 29 Farm Ponds 79 Rotation Restrictions 108 Soybeans 47 Sprayer Cleaning 82 Herbicide Index 114

Giant Ragweed Biology

Giant Ragweed Moves into Fields from Borders

Objectives Evaluate several Pre applied herbicides for giant ragweed control Caparol, Cotoran, Direx and Staple Determine if Envoke or Staple applied Post-emergence could help provide giant ragweed control

Application Information & Design Pre Study Randomized Complete Block 4 replications Herbicides were applied with backpack CO2 charged sprayer 10 gpa 80015VS Applications were made: Pre - May 1 Horseweed control ratings taken 7, 21 and 40 DAT

Objectives Evaluate several Pre applied herbicides for giant ragweed control Can Pre applied herbicides provide giant ragweed control? Determine if Envoke or Staple applied Post-emergence could help provide giant ragweed control

NO…Not in 2007!

Objectives Evaluate several Pre applied herbicides for giant ragweed control Determine if Envoke or Staple applied Post-emergence could help provide giant ragweed control

Application Information & Design Post Study Randomized Complete Block 4 replications Herbicides were applied with backpack CO2 charged sprayer 10 gpa 80015VS Applications were made: Roundup WeatherMax applications OT applied 1st and 4th cotton node Post – June 1 Hooded – June 25 Horseweed control ratings taken 7, 14, 21, 30 and 40 DAT

Giant Ragweed Control Applications made to 8 node cotton 20 40 60 80 Roundup WeatherMax applied at 22 ozs/A at 1st and 4th nodes Applications made to 8 node cotton Staple LX 3.8 oz/A Envoke 0.15 oz/A LSD = 13 20 40 60 80 100 % Control 40 DAT

Staple LX

Summary of Post Applications Envoke and Staple LX provided about 60 to 70% control Not enough Would that much control help with follow-up hooded Ignite applications?

Envoke over the top + Ignite hooded

22 oz/RWM 1st/4th nodes fb 0.15 oz Envoke fb 29 oz Ignite hooded 22 oz/RWM 1st/4th nodes fb Ignite hooded 22 oz/RWM 1st/4th nodes fb 0.15 oz Envoke fb 29 oz Ignite hooded

Summary of Timing Envoke or Staple LX provided enough giant ragweed suppression to allow better control with follow-up hooded applications of Ignite Ignite in mid-summer applications can provide very effective control of giant ragweed Post direct Over the top of LL varieties

County Std. Test #1 Main et al 2007 Gin Turnout Lint Yield Length Strength Uni-formity Leaf Loan Value Rank Company Variety (%) (lb./acre) Mic (inches) (g/tex) Grade (¢/lb.) 1 Phytogen 310 R 39.2 771 3.8 1.04 26.3 80.3 4 48.76 2 Delta & Pine Land 444 BG/RR 39.0 769 3.5 1.06 26.8 79.5 49.53 3 370 WR 38.6 740 3.9 26.5 80.4 48.15 445 BG/RR 39.5 725 3.7 1.07 29.2 80.1 51.35 5 Stoneville 4554 B2RF 36.6 712 27.5 80.9 49.05 6 4427 B2RF 37.3 705 3.6 26.1 47.08 7 Croplan Genetics 3520 B2RF 36.4 644 3.4 1.08 24.2 79.7 46.16 8 Americot 1532 B2RF 36.3 641 80.2 47.32 9 Dyna-Gro 2242 B2RF 35.7 635 24.1 46.14 10 2100 B2RF 34.7 604 3.2 1.05 24.0 79.0 45.84 11 4020 B2RF 35.4 572 47.14 12 117 B2RF 37.9 560 27.3 80.5 44.26   Mean 37.2 673 25.9 80.0 47.57 LSD (0.05) 1.4 56 0.1 0.01 0.9 0.6 0.38 2.37 CV 7.06 35.08 12.10 3.43 9.31 1.40 19.20 10.03 Main et al 2007 23

County Std. Test #3 Main et al 2007 Gin Turnout Lint Yield Length Strength Uni-formity Leaf Loan Value Rank Company Variety (%) (lb./acre) Mic (inches) (g/tex) Grade (¢/lb.) 1 FiberMax 1600 LL 34.0 645 3.7 1.11 27.8 80.6 4 51.43 2 1735 LLB2 29.9 586 3.4 29.0 80.3 49.58 3 955 LL 29.7 527 3.6 1.07 30.8 80.9 50.96 958 LL 30.4 500 1.10 80.7 52.90 5 966 LL 30.1 469 1.09 30.2 80.8 52.75   Mean 545 29.5 51.55 LSD (0.05) 3.3 108 0.1 0.22 2.3 0.9 0.39 1.92 CV 11.16 36.46 17.49 3.72 9.36 0.97 16.57 7.24 Main et al 2007 24

Giant Ragweed Management Contain it at the field edges!!! Staple and Envoke can help control giant ragweed Ignite is the most effective post option in cotton Post direct Post over the top (variety selection issues)

Questions