Peanut Weed Management Update 2008

Eric P. ProstkoExtension Weed Specialist

Department of Crop & Soil SciencesThe University of Georgia

Topics For Discussion

• Resistance Update

• Modes of Action Info

• Aim – Harvest Aid label

• Palmer Amaranth

• Herbicide/Fungicide Tank-mix Issues

– Provost

• 2,4-DB issues

• Classic Update

GA Confirmed Glyphosate-Resistant Palmer SitesGA Confirmed Glyphosate-Resistant Palmer Sites

2005

2006

Current Testing2007

GA Confirmed ALS-Resistant Palmer SitesGA Confirmed ALS-Resistant Palmer Sites

Herbicide Modes of Action Info

• New Table in 2008 Pest Control Handbook

• MOA’s listed in crop sections

• www.gaweed.com

diclosulam (Strongarm) 84WG 0.45 oz

0.024 Provides general broadleaf weed control. Incorporate into top 1-3" of final seedbed. Goodto excellent control of many species includingbristly starbur, wild poinsettia, eclipta, andcopperleaf. Should be tank-mixed with a grassherbicide. Poor control of sicklepod. Controlof nutsedge has been variable and inconsistent. Can also be applied preemergence. Croprotation restrictions: cotton = 10 months;soybeans = 0 months; wheat, barley = 4months; oats, rye = 6 months; corn = 18months (10 months - IR hybrids); tobacco,sorghum = 18 months; other crops = 30months. MOA = 2.

• September 2007

• 1-2 oz/A

• NIS or COC

• 7 day PHI

• Morningglory

• Pigweed

• Spiderwort

Harvest Aid Label

Managing Palmer Amaranth• Know the enemy

– Lots of seed– Grows 1-2”/day– Very competitive

• Resistant or not??– ALS or GR

• Residual herbicide– Activation

• irrigation or incorporation

• Timely POST’s

• Avoid overusing PPO’s

Palmer Amaranth Control in Peanut with PRE Herbicides

0

20

40

60

80

100

11 18 23 38 53 94

Time (DAT)

Cont

rol -

%

.

Valor Dual Magnum Stalwart Outlook

Valor @ 3 oz/ADual Magnum @ 1 pt/AStalwart @ 1 pt/AOutlook @ 1 pt/A

Palmer Amaranth Control in PeanutsMacon County, GA – 2007 (38 DAT)

NTC Valor SX 51WG @ 3 oz/A

Palmer Amaranth Control in PeanutsMacon County, GA – 2007 (38 DAT)

NTC Dual Magnum 7.62EC@ 1 pt/A

Residual Herbicides Must Be Activated!!!!!!

• Rainfall• Irrigation• Herbicide incorporation

– Conventional tillage– Dryland fields– No chance of rain– will help but not a guarantee– 2X, angle– Some herbicides should not

be incorporated• Valor

This is what a 2” pigweed looks like!!!!

Provost (10.7 oz/A) + Fulbor + Penatrator Plus + 2,4-DB

Richard McDaniel, 2007

Probable Provost Label Changes

• No surfactants

• No tank-mixes with 2,4-DB

• No tank-mixes with EC pyrethroids

• Others??

Herbicide/Fungicide Tank-Mixeshttp://www.peanut.ncsu.edu/ag653_web.pdf

• Possible combinations are endless

• Avoid 3-way mixes if possible

• Regional Publication

– AGW-653

– NCSU

– Updated in May 2007

Contaminated Lots

• Contamination if exceeds 250 ppm• Tested Lots

– FB-01 = 2,4-D acid (0.294%)– EC-16 = dicamba (0.17%) + 2,4-D acid

(0.11%)– EC-16 = Dicamba (0.198%) + 2,4-D acid

(0.104%)– EL-31 = 101-117 ppm 2,4-D (3 samples)– CE-04 = 56 ppm of 2,4-D

What will 2,4-D and dicamba do to peanuts????

• Research in GA conducted over the past few years would suggest that 2 oz/A of 2,4-D would not cause many problems.– If contaminated product was applied at

24 oz/A then 2,4-D rate would only be 0.05-0.18 oz/A.

What will 2,4-D and dicamba do to peanuts????• No data exists for peanut response to

dicamba.– Peanuts are more sensitive to dicamba

than 2,4-D.– Dicamba rate was equivalent to 0.08-

0.1 oz/A (Normal rate for corn is 8 oz/A)

Why is this important?

• Peanut response to dicamba

– Dicamba resistant crops are in the pipeline

– More contamination/drift problems are likely

Classic/Peanut Issues

• How much does it really effect TSWV?

• How much does it really influence yields?

Classic Research in Georgia

• 2000-2007• 15 locations• 6 varieties

– GA Green, GA-02C, GA-03L, AP-3, C-99R, AT-201

• weed-free trials• Results

– No interaction between variety and Classic timing

– TSWV increased an average of 9%– No effect on peanut yield

The Influence of Classic on the Incidence of TSWV (2000-2007)

28

3537

34 3430

0

8

16

24

32

40

NTC 60-69 70-79 80-89 90-99 100+

Classic Timing (DAE)

TSW

V (%

) .

Classic @ 0.5 oz/A + NIS @ 0.25% v/vAveraged over 6 varieties and 15 locations*Significantly different from NTC (P = 0.05.)

* **

The Influence of Classic on Peanut Yield (2000-2007)

41853844 3728

4820

39943670

0

1000

2000

3000

4000

5000

NTC 60-69 70-79 80-89 90-99 100+

Classic Timing (DAE)

lbs/

A .

Classic @ 0.5 oz/A + NIS @ 0.25% v/vAveraged over 6 varieties and 15 locationsP = 0.3321

www.gaweed.com