Managing Tropical Spiderwort (Commelina benghalensis) In Roundup Ready Cotton A.S. Culpepper, J.T....
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Transcript of Managing Tropical Spiderwort (Commelina benghalensis) In Roundup Ready Cotton A.S. Culpepper, J.T....
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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
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Spiderwort response to Roundup UltraMax*
20 oz 0 oz 30 oz 0 oz
40 oz 0 oz 50 oz 0 oz*Pictures 15 d after treatment. No plants died from any treatment. Six inch at time of application.
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Typical RR Cotton Grower Program:
1) DNA at planting
2) Roundup at 3- to 4-leaf
3) Roundup at layby
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Tropical Spiderwort Infestation
Red = severeOrange = moderateGreen = lightYellow = exist Gray = not found
2002 Prostko agent survey
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Spiderwort’s Rank as Georgia’s Most Troublesome Weeds in Cotton
1998: not ranked*
2001: ninth*
2003: number 1
*Published in SWSS annual proceedings.
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Tropical spiderwort infestation, Cairo, GA, 2001.
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Grady Co. 2002
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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
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*
Location
Two on farm trials in 2001 and 2002
***
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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
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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
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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)
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0
20
40
60
80
100
RU + Staple + Dual
21 DAT
Tropical Spiderwort Control with Topical Applications.
53 c60 b
80 a
% c
ontr
ol
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UltraMax @ 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.
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0
20
40
60
80
100
RU + Staple + Dual
21 DAT
Late-season*
Tropical Spiderwort Control with Topical Applications.
49 b 48 b
69 a
% c
ontr
ol
53 c60 b
80 a
*Late-season control pooled over directed applications.
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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 0.016 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.
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Mid-Season Tropical Spiderwort Control with Directed Applications (21 DAT).
0
20
40
60
80
100
70 e
80 bcd
% c
ontr
ol
Roundup
+ Aim
+ Direx
+ Harvade
+ Valor
MS
MA
+ Direx
+ Valor
Data pooled over four locations. Directed main effect means presented.
79 bcd 75
de
85 ab 78
cd
83 abc
89 a
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Prowl pre, glyphosate POST, glyphosate directed. 17 day after directed.
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Prowl pre, glyphosate POST, MSMA directed. 17 day after directed.
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Late-Season Tropical Spiderwort Control with Directed Applications.
0
20
40
60
80
100
44 c 42 c
80 a
% c
ontr
ol
Roundup
+ Aim
+ Direx
+ Harvade
+ Valor
MS
MA
+ Direx
+ Valor
Data pooled over four locations. Directed main effect means presented.
57 b
43 c
64 b
45 c
64 b
76 a
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Four Most Effective Spiderwort Systems at Harvest. Pooled over 4 locations.
Herbicide system Control (%)
Herbicide cost ($/A)
Prowl, RU + Dual, Valor + MSMA 80 35.23
Prowl, RU + Dual, Direx + MSMA 75 29.57
Prowl, RU + Dual, Roundup + Direx 78 29.58
Prowl, RU + Dual, Roundup + Valor 73 31.93
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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.
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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.