Managing Tropical Spiderwort (Commelina benghalensis) In Roundup Ready Cotton A.S. Culpepper, J.T. Flanders, and A.C. York University of Georgia and N. C. State

Spiderwort response to Roundup UltraMax* 20 oz0 oz 30 oz 0 oz 40 oz0 oz50 oz 0 oz *Pictures 15 d after treatment. No plants died from any treatment. Six inch at time of application.

Typical RR Cotton Grower Program: 1) DNA at planting 2) Roundup at 3- to 4-leaf 3) Roundup at layby

Tropical Spiderwort Infestation Red = severe Orange = moderate Green = light Yellow = exist Gray = not found 2002 Prostko agent survey

Spiderwort’s Rank as Georgia’s Most Troublesome Weeds in Cotton 1998: not ranked* 2001: ninth* 2003: number 1 *Published in SWSS annual proceedings.

Tropical spiderwort infestation, Cairo, GA, 2001.

Grady Co. 2002

Objectives  Compare POST over-the-top herbicide options for spiderwort control  Compare POST-directed herbicide options for spiderwort control  Develop a systems approach for spiderwort management

* Location Two on farm trials in 2001 and 2002 * **

Materials and Methods Cultivar:various RR cultivars Planted:May or June Plot size:three or four rows by 30 feet Design:split plot Treatments:factorial arrangement with 3 early POST by 8 directed options Reps:3 or 4 reps

Application Information  DNA applied at planting at each location  POST over-the-top treatments applied at 15 GPA  POST directed treatments applied at 15 to 20 GPA  Treatments applied at 3 MPH  Tropical spiderwort 1 to 4 inches, avg. 2 to 3 inch  Weed control visually estimated throughout season

POST Over-the-Top: Whole Plot 1. Roundup UltraMax (0.75 lb ae) 2. Roundup + Staple (0.032 lb ai) 3. Roundup + Dual Magnum (0.95 lb ai)

Tropical Spiderwort Control with Topical Applications. 53 c 60 b 80 a % control

4 leaf cotton + Dual Magnum 1 pt/A 1) Dayflower emerged 3 to 7 day after 4 leaf application. One inch of rain within 48 hr. 2) Prowl applied PRE. No layby.

Tropical Spiderwort Control with Topical Applications. 49 b 48 b 69 a % control 53 c 60 b 80 a *Late-season control pooled over directed applications.

POST Directed Treatments: Subplot 1. Roundup UltraMax (0.75 lb ae) 2. + Direx (0.625 lb ai) 3. + Valor (0.032 lb ai) 4. + Aim (0.012 to lb ai) 5. + Harvade (0.3 lb ai) 6. MSMA (2 lb) + NIS 7. + Direx (1 lb ai) 8. + Valor (0.064 lb ai) Timely & precise applications were made with less than 9% herbicide injury noted.

Mid-Season Tropical Spiderwort Control with Directed Applications (21 DAT). 70 e 80 bcd % control Roundup + Aim+ Direx+ Harvade+ ValorMSMA+ Direx+ Valor Data pooled over four locations. Directed main effect means presented. 79 bcd 75 de 85 ab 78 cd 83 abc 89 a

Prowl pre, glyphosate POST, glyphosate directed. 17 day after directed.

Prowl pre, glyphosate POST, MSMA directed. 17 day after directed.

Late-Season Tropical Spiderwort Control with Directed Applications. 44 c42 c 80 a % control Roundup + Aim+ Direx+ Harvade+ ValorMSMA+ Direx+ Valor Data pooled over four locations. Directed main effect means presented. 57 b 43 c 64 b 45 c 64 b 76 a

Four Most Effective Spiderwort Systems at Harvest. Pooled over 4 locations. Herbicide systemControl (%) Herbicide cost ($/A) Prowl, RU + Dual, Valor + MSMA Prowl, RU + Dual, Direx + MSMA Prowl, RU + Dual, Roundup + Direx Prowl, RU + Dual, Roundup + Valor

Conclusions 1) Early POT applications of glyphosate + Staple are more effective than glyphosate alone on emerged spiderwort. 2) However, residual control from Dual appears to be more critical in the system.

Conclusions 3) MSMA was more effective than glyphosate at layby. 4) Direx and Valor were the most effective directed tank mix options due to residual spiderwort activity.