Peanut Weed Control Update 2001

Dr. Eric P. Prostko

Extension Weed Specialist

University of Georgia

Tifton

Topic for Discussion

• Cadre * reduced rates

* cotton rotations

• paraquat• Strongarm• Valor• other stuff

Reduced Rates of Cadre?

• efficacy issues

• rotation issues

• liability

The Response of Weeds to Various Cadre Rates in Georgia

0

20

40

60

80

100

P. nutsedge Y. nutsedge sicklepod P. sida

0.36 oz/A0.72 oz/A1.1 oz/A1.44 oz/A

Webster et al. 1997 Applied EPOST (C-2L)

The Response of Weeds to Various Cadre Rates in Georgia

0

20

40

60

80

100

smallflowermorningglory

annualmorningglory

cocklebur bristly starbur

0.36 oz/A0.72 oz/A1.1 oz/A1.44 oz/A

Webster et al. 1997 Applied EPOST (C-2L)

The Response of Weeds to Various Cadre Rates in Georgia

0

20

40

60

80

100

coffee senna Florida beggarweed

0.36 oz/A0.72 oz/A1.1 oz/A1.44 oz/A

Webster et al. 1997 Applied EPOST(C-2L)

Reduced rates of Cadre work if…...

• the weed is susceptible

• good growing conditions exist

• the application is timely (small weeds)

Full rates help to overcome variability of application dueto weed size, improper sprayer calibration, environmental conditions, etc.

Cadre/Cotton Rotation Issue

• new research results

Cotton Response to Cadre Residues in North Carolina

0

1000

2000

3000

4000

5000

1992 1993-94

Year

Yie

ld (

lbs/

A)

Untreated Cadre (0.5x) Cadre (1X) Cadre (2X)

York et al., 2000 DES 119

Cotton Yield Response to PPI Applications of Cadre

0

1000

2000

3000

4000

0.032 0.016 0.008 0.004 0.002 0.001 0

Cadre Rate (lb ai/A)

Seed

Cot

ton

Yie

ld (

lbs/

A)

Averaged over 2 varieties(DP33B, SG501BG/RR) Tifton, GA 2000LSD 0.05 = 336

**

Cotton Yield Response to PRE Applications of Cadre

0

1000

2000

3000

0.032 0.016 0.008 0.004 0.002 0.001 0

Cadre Rate (lb ai/A)

Seed

Cot

ton

Yie

ld (

lbs/

A)

Averaged over 2 varieties(ST4892RR/BG, ST4691BG) Plains, GA 2000LSD 0.05 = 712

**

*

Cotton Variety Response to Cadre at 8 PPB - 9 WAT

0 10 20 30 40 50 60

Delta Pearl

DP33B

DP5415

DP458

ST4892

STX9903

BXN47

FM989

AP6101

GA161

SG125

Injury (%)

Culpepper, 2000Tifton, GA LSD 0.05 = 17

Cotton Variety Response to Cadre at 16 PPB - 9 WAT

0 20 40 60 80 100

Delta Pearl

DP33B

DP5415

DP458

ST4892

STX9903

BXN47

FM989

AP6101

GA161

SG125

Injury (%)

Culpepper, 2000Tifton, GA LSD 0.05 = 17

Cadre Carryover in CottonBrooks County - 2000

674 lbs 770 lbs 770 lbs

1540 lbs 1348 lbs 1220 lbs

738 lbs/A(lint yield)

1369 lbs/A

6/09/006/09/00

Cadre/Cotton RotationsWhat can growers do?

• follow 18 month restriction

• reduced rates of Cadre?

• Cadre on irrigated fields only?

• optimum pH and nutrient levels

• plant suspect fields last

Paraquat Formulations

Boa GramoxoneMax

Starfire

manufacturer Griffin Syngenta Syngenta

lb ai/gal 2.5 3.0 1.5

ozs/A 6.6 5.5 11

Cost/A $1.50 $1.59 $2.75

Smallflower Morningglory Control with Various Formulations of Paraquat

Test 1 - 15 DAT

83 87 83

0

20

40

60

80

100

Con

trol

(%

)

Starfire Boa GramoxoneMax

Averaged over 3 rates of Basagran

(P = 0.15)

Tifton, GA 2000

Weed Control with Various Paraquat Formulations

Test 2 - 5 DAT

75

100 100

73

10092

78

100 97

0

25

50

75

100

smallflower mg Fla. Pusley annual grass

Starfire Boa GramoxoneMax

Tifton, GA 2000Averaged over 3 rates of Basagran

(P = 0.72) (P = 0.45) (P = 0.15)

Weed Control with Various Paraquat Formulations

Test 2 - 14 DAT

8797

56

8797

51

8697

51

0

25

50

75

100

smallflower mg Fla. Pusley y. nutsedge

Starfire Boa GramoxoneMax

Tifton, GA 2000Averaged over 3 rates of Basagran

(P = 0.53) (P = 0.82) (P = 0.40)

Improving At-Crack Applications

• calibrate sprayer

• SMALL WEEDS (2”)

• nozzle selection (XR TeeJet, TwinJet)

• higher water volumes (15 GPA+) improve coverage

• lower pressures (30 PSI) reduce drift and evaporation

How would you rate the overall performance of Strongarm in your county?

8

4943

00

15

30

45

60

75

Poor Fair Good Excellent

%

2000 UGA County Agent Survey

What were the weeds that most frequently escaped control of Strongarm?

7872

2217

0

20

40

60

80

100

sicklepod nutsedge beggarweed pigweed

%

2000 UGA County Agent Survey

Strongarm - Does it work?Attapulgus - 7 WAP

Untreated Strongarm + Prowl (PPI)

PE-01-00

Untreated Strongarm ($23.50/A)

Strongarm fb Cadre - 1 oz/ACOC - 1% v/v

($44.77/A)Gramoxone Max - 5.5 oz/A

Storm - 1 pt/A2,4-DB - 1 pt/A

NIS - 0.125% v/vfb Cadre - 1 oz/A

COC - 1% v/v($35.14/A) 28 DAT

StrongarmHow Should It Be Used in GA?

• use where starbur, eclipta, poinsettia, and copperleaf are problems

• tank-mix with DNA

• irrigate in if possible

• variable on nutsedge

• poor sicklepod control

Strongarm Label Update2001

“at cracking” applications

split applications

snapbean rotation = 9 months

Strongarm/Cadre CombinationsConcerns?

• cost/A

• rotations

* peanut (anytime)

* soybeans (9 m)

* snapbean (9 m)

* IR corn (10 m)

• ALS resistance

Valor 50WDG

• Valent

• flumioxazin• N-phenylphthalimide derivative• PPO oxidase inhibitor• PRE• 2-3 ozs/A • label in April 2001 (I hope!!)

Why do we need Valor??

• Florida beggarweed

• rotation restrictions

• mode of action

• reduced costs/A?

• market competition

But, it is not the Holy Grail!!

Why does Valor have to be applied PRE in peanuts?

• PPI treatments less effective

Bristly Starbur Control with Valor @ 3 ozs/A

77

58

20

9280

58

0

20

40

60

80

100

5 WAP 8 WAP 13 WAP

Time

Con

trol

(%

)

PPIPRE

Attapulgus, 2000

Why does Valor have to be applied PRE in peanuts?

• PPI treatments less effective

• POST treatments can cause excessive crop injury!

Valor Injury on Peanuts

Although Valor has many strengths, growers/dealers need to be made aware of

its weaknesses such as . . . .

• cocklebur

• nutsedge

• sicklepod

• increased crop injury with delayed applications

Do soil applied herbicides cause yield reductions?

Peanut Yield As Influenced By PRE Herbicides

5767 57695456

5838

0

1500

3000

4500

6000

Untreated Strongarm Valor Spartan

Herbicide

lbs/

A

Averaged over 2 varieties (GA Green, C99R) * LSD (0.05) = 561 weed-free

Reduced Tillage Weed Control Research Results

• 2,4-D, Clarity, and Harmony Extra

Peanut yield response to preplant herbicide applications in Georgia, 2000.

0

1000

2000

3000

4000

5000

2,4-D amine(1.1 pt/A)

2,4-D ester(1.1 pt/A)

Clarity HarmonyExtra

Herbicide

lbs/

A

30 DBP 15 DBP 7 DBP 0 DBP None

*Averaged over 4 locations (P = 0.45)

(0.5 pt/A)(0.6 oz/A)

University ofGeorgia

ExtensionWeed Science(gaweed.com)