Peanut Weed Management Issues - 2006

Eric P. ProstkoExtension Weed Specialist

Department of Crop & Soil SciencesThe University of Georgia

Tifton

GA Peanut Farm Show - 2006

Topics for Discussion

• What’s new for 2006?

• Herbicide resistance– ALS– Glyphosate

• Tropical spiderwort

• Reduced tillage systems

What is new for 2006?

• A new formulation of paraquat• 2 lbs ai/gallon• Safer formulation

– alginate– alerting agent (decaying grass odor)– purgative– emetic– green dye

G-Max G-Inteon

Lbs ai/gal 3.0 2.0

Normal Rates

(peanuts)

5.4-8.0 ozs/A 8.0-12.0 ozs/A

Maximum/year

(in-crop peanuts)

10.8 ozs/a 16.0 ozs/A

vs.

Cadre 70DG vs. Cadre 2AS

Cadre 70DG Cadre 2AS

Normal use rate

1.44 oz/A 4.0 oz/A

Reduced rate(not supported by BASF)

1.00 oz/A 2.8 oz/A

What about ALS-resistant pigweed?

Causes of Herbicide Failures

• weed size**

• moisture

• temperature

• humidity

• rate

• nozzle type

• GPA

• calibration

• bad luck

• herbicide resistance

All possible reasons for poor performance should be investigatedbefore considering the possibility of resistance!!!

Herbicide Resistant WeedsSelection Pressure

Source: J.L. Gunsolus. Herbicide Resistant Weeds. 1998. North Central Region Extension Publication 468.

Commonly Used ALS Herbicides

• Accent• Ally• Beacon• Cadre • Classic• Envoke• Exceed• Express • Finesse

• FirstRate • Harmony Extra • Osprey• Peak• Permit/Sandea• Pursuit• Python• Scepter• Staple• Strongarm

All have the same mode of action!!!!!!!

ALS-Resistant pigweed has been identified in at least 4 counties!

2005 ALS-Resistant Pigweed Survey61 samples, 21 counties

If ALS-Resistance is Suspected• Prowl or Sonalan

– What about DNA-resistance?

• Cautious use of ……– Classic– Cadre– Pursuit– Strongarm

• Consider adding…..– Valor– Dual Magnum– Outlook

• Don’t be afraid of Gramoxone

• Ultra Blazer or Cobra– Tank-mix with Cadre

Do you need Gramoxone?

PE-07-05July 18, 2005 (69 DAP)Ponder Farm

Untreated(374 lbs/A)

Gramoxone Max+ Pledge + NIS

@ (15 DAP)Fb Cadre + COC

@ (28 DAP)(2170 lbs/A)

Cadre + COC @ (28 DAP)(1212 lbs/A)

Glyphosate Resistance Around the World (8 species)

• rigid ryegrass (1996)• goosegrass (1997)• horseweed (2000)• Italian ryegrass (2001)• hairy fleabane (2003)• buckhorn plantain (2003)• common ragweed (2004)• Palmer amaranth (2005)

– In Central Georgia

* Can be found in US

WeatherMax 66 oz/A

Worried About Hard to Kill Weeds?

67% of 600 Indiana growers are not overly concerned that some weeds are shrugging off Roundup as farmers expect chemical companies to develop new herbicides for weeds that do not respond to Roundup.

Purdue University, Nov 29, 2005, Herbicide-defiant weeds causing anxious moments

Timeliness the Key!!!!

Tropical spiderwort (a.k.a. Benghal dayflower)Commelina benghalensis

• tropical Africa native• annual or perennial• seeds and rhizomes• above and below ground

flowers• 1,600 seeds/plant• alternate host of southern root-

knot nematode• Reservoir for southern stem

blight (white mold)

TSW in GeorgiaCurrent Known Distribution

* confirmed in 29 counties by GA Dept. of Ag and UGA in 2004 (blue)

* identified in 4 morecounties in 2005 (black)

Tropical Spiderwort Control

• Conventional vs. strip-tilllage

• Twin rows vs. single rows

• Prowl or Sonalan (PPI or PRE)

• Gramoxone Inteon (12 oz/A) + Basagran (8 oz/A) + Dual Magnum (11-16 oz/A)

• Followed by Cadre (1.44 oz/A) or Strongarm (0.45 oz/A) + Dual Magnum (11-16 oz/A)

• Cost/A = ~$44-51

Tillage Impact on Tropical SpiderwortCotton & Peanut Rotation

92

28

0

20

40

60

80

100

Conventional Strip-Till

Tillage Method

TS

W C

on

tro

l -

%

Dr. B. BreckeUniversity of Florida2005 Conventional = Moldboard plow (12”), disk-harrow, field cultivator

How do we manage the yellow herbicides in strip-tillage systems?

• Use Prowl/Pendimax

• Increase rate to at least 3 pts/A

• Apply broadcast

• Split application– 1 pt/A – Burndown– 2 pt/A – at-planting

• Gramoxone at-plant

• Will still need a POST grass herbicide

Strip-Tillage and Grass Weeds

www.gaweed.com