Tropical Spiderwort Management in

Peanut, Corn, and Soybean

Eric P. Prostko

Extension Weed Specialist

Dept. Crop & Soil Sciences

University of Georgia

Tifton

Control Strategies in Peanut• row spacing

* twins vs. singles• residuals

* Dual Magnum

* Strongarm• POST’s

* Gramoxone Max

* Cadre

* Basagran

Tropical spiderwort control in peanut as influenced by row spacing

8274

0

20

40

60

80

100

Twin Single

Row Spacing

Con

trol

- %

Source: Yoder et al. 2003 (FL)

a b

Tropical spiderwort control in peanuts with Dual Magnum applied preemergence, Grady Co., 2003.

94 9486 88

96

0

20

40

60

80

100

12 DAT 26 DAT 41 DAT 64 DAT 109 DAT

Rating Date

Contr

ol -

%

Dual Magnum 7.64EC @ 1.33 pts/A

Tropical spiderwort control with Gramoxone Max + Dual Magnum Tank-Mixes

0

20

40

60

80

100

14 29-32 52-62 96-98

Time (DAT)

Con

trol

- %

2002 2003

Gramoxone Max @ 5.5 ozs/A +Dual Magnum @ 1.33 pts/A Grady County

A B

Tropical spiderwort control in peanuts. A = untreated; B= Gramoxone Max + Dual Magnum applied 17 DAP. Photos taken 49 DAP.

How much Dual Magnum can we use?

• 1-1.33 pt/A

• 2.8 pts/year

• 90 day PHI

• cost/A

– $90/gal

– $31.50/2.8 pts

Other Metolachlor Formulations• Cinch

– Dupont

– same as Dual II Magnum– cannot use POST

• Stalwart C

– Sipcam Agro USA Inc.

– “old” Dual EC formulation (7.8 lbs/gal)– not labeled for peanut

• Me-Too-Lachlor– Drexel– “old Dual EC formulation (8 lbs/gal)– rates are too low

Strongarm in Peanut

• PPI or PRE

• thru cracking*

• not labeled for POST use at this time but working on this issue

* cracking = soil displaced by germinating seedlings just prior to emergence

Tropical spiderwort control in peanuts with Strongarm @ 0.45 ozs/A, Grady Co., 2003.

7568

11

9790

7588

78

60

0

20

40

60

80

100

46 DAP 69 DAP 114 DAP

Rating Date

Contr

ol -

%

PRE EPOST LPOST

PRE = 5 DAPEPOST = 17 DAP (2”, 3 leaf)LPOST = 31 DAP (up to 6”)

aab a

abcd

b abcc

e

Untreated Strongarm applied17 DAP

Strongarm applied31 DAP

PE-24-0346 DAP

Tropical spiderwort control withPOST applied Strongarm, 2003

Gramoxone Max and CadreTank-Mixed or Split Applications?

Tropical spiderwort control withGramoxone Max and Cadre

8476

36

9287

61

0

20

40

60

80

100

46 DAP 69 DAP 114 DAP

tank-mixsplit

Tank-mix applied 17 DAP/Split applied 17 and 31 DAP

(LSD 0.05 = 11) (LSD 0.05 = 15) (LSD 0.05 = 22)

Tropical spiderwort control in peanuts. A = untreated; B= Cadre applied 7 DAP. Photos taken 49 DAP.

A B

What About Cadre + Dual Combos?

Tropical Spiderwort Control with Cadre + Dual Magnum

61

85

0102030405060708090

GM fb Cadre GM fb Cadre + Dual Magnum

Treatment

Con

trol

- %

114 DAP LSD 0.05 = 22

Tropical spiderwort control in peanuts with Valor applied preemergence, Grady Co., 2003.

95

6863

40

00

20

40

60

80

100

12 DAT 26 DAT 41 DAT 64 DAT 109 DAT

Rating Date

Contr

ol -

%

Valor 51 WP @ 3 ozs/A

Tropical Spiderwort in Field Corn

* preemergenceDual II MagnumAtrazine (?)

* postemergence2,4-DBasagran

* post-directedGramoxone MaxAimEvik

Tropical Spiderwort in Soybeans

* narrow rows* preemergence

SencorDual MagnumBoundaryCanopy SPCanopy XL

* postemergenceBasagran

* post-directedGramoxone Max

Post-Harvest Control Strategies

• prevent seed production

• re-growth after harvest

• time before first frost

• Gramoxone Max

• 2,4-D

• tillage

Tropical spiderwort control with various herbicides - 14 DAT

28 2629

58

21

63

48 51

75

60

01020304050607080

Applied October 31, 20036” tall spiderwort LSD 0.05 = 13

Tropical Spiderwort in AustraliaTropical Spiderwort in Australia • Weed problem for

20-30 years• control in other

crops important• corn

– 2,4-D

– Dual

• peanut– Pursuit

– Dual

– 2,4-D

E.P. with Australian peanut farmer, Wayne Learmonte