2007 Corn Weed 2007 Corn Weed Control UpdateControl Update

Eric P. Prostko

Extension Weed Specialist

Department of Crop & Soil Sciences - UGA

Changes in 2007 Pest Control HandbookChanges in 2007 Pest Control Handbook

Added Sequence Added Expert Added generic metolachlors but still included the following

warning: The generic formulations of metolachlor (Parallel, Stalwart, Me-Too-Lachlor) have not provided the same length of residual control of certain weeds as similar rates of Dual Magnum formulations in some UGA field trials.

Added Firestorm Added rain-free periods Added a burndown table for reduced tillage. Added Propel Post-harvest control rec's for tropical spiderwort Table of metolachlor and s-metolachlor products Added Callisto to POST section Table for ALS/GR-resistant pigweed

Burndown Control OptionsBurndown Control Options

glyphosateParaquatIgnite (glufosinate) tank-mixes with?

2,4-D atrazine

Need a clean seed-bed at planting

Ryegrass Control - BurndownRyegrass Control - Burndown

Hard to kill with 1 shot Option # 1

Glyphosate @ 1.125 lb ae/A + atrazine @ 3 pts/A

Option #2 Gramoxone Inteon @ 1.9

pts/A – 2 WBP fb Gramoxone Inteon @ 1.9 pts/A + atrazine @ 3 pts/A - planting

RR corn systems Accent????

Conventional or RR Systems?Conventional or RR Systems?

Conventional SystemsConventional Systems

Atrazine still THETHE major player in any system

Prowl in cheap but …….

One of my favorites is Accent + AtrazineIf Texas panicum is main problem

many Pre-mixes

Why do you not want to spend the money on an AccentWhy do you not want to spend the money on an Accent + Atrazine treatment in field corn? + Atrazine treatment in field corn?

168

113

0

40

80

120

160

200

Bu/

A

Accent + Atrazine Untreated

Data from 18 irrigated weed control trials conducted in Georgia from 2001-2006.At $2.00 to 3.00/bu, it only takes a 9 to 14 bu/A increase to pay for the treatment!!!

Corn Yield Response to Various POST Corn Yield Response to Various POST Herbicide TreatmentsHerbicide Treatments

131

95

179

139

193207

184

212

0

50

100

150

200

250

low (11/ft2) high (27/ft2)

Texas Panicum Density

Bu/

A

Untreated Prowl Accent RR-split

Average of 2 tests conducted in 2003 and 2004 (Tifton, Attapulgus)Average of 2 tests conducted in 2003 and 2004 (Tifton, Attapulgus)Where Texas panicum is the main weed problemWhere Texas panicum is the main weed problemAtrazine PRE @ 1.5 qt/AAtrazine PRE @ 1.5 qt/A

e

d

ab a

b

a aa

Conventional Weed Management SystemsConventional Weed Management SystemsMany Pre-Mixes AvailableMany Pre-Mixes Available

Bicep II Magnum (atrazine + Dual II Magnum) Lariat/Bullet (atrazine + Lasso) Lexar (atrazine + Dual Magnum + Callisto) many others preemergence a good choice if many different weed species are

present need 0.5” of rainfall or irrigation within 7-10 days

for activation

Post-Directed Options for Field CornPost-Directed Options for Field Corn

EvikGramoxone

Inteon/FirestormLorox/LinexAim

tropical spiderwortpigweedsmorningglory

Should you use the RR corn system?Should you use the RR corn system?

advantages Inexpensive easy Broad spectrum Reduced drift concerns No soil insecticide issues

disadvantages No residual over-reliance on a single

product Herbicide resistance

concerns Volunteer in other RR crops

How would I use RR corn systems?How would I use RR corn systems?

If you are unwilling to use a PRE application of atrazine or something else….

2 applications of glyphosate1st application: 21-28 DAP + atrazine (1.5-2.0 qt/A)2nd application: 35-40 DAP

SequenceSequence (s-metolachlor + glyphosate) ExpertExpert (s-metolachlor + atrazine + glyphosate) Do not forget to include extra seed costs/A in

your budgets! Irrigated @ 30,000/A = $12-13.00/ADryland @ 18,000/A = $7-8.00/A

Texas Panicum Control At Harvest with Single Texas Panicum Control At Harvest with Single or Split Applications of Roundup WM - IIor Split Applications of Roundup WM - II

CN-04-04 (Attapulgus)

UntreatedRoundup WM @ 22 ozs/A

21 DAP

Roundup WM @ 22 ozs/A21 + 35 DAP

125

164

181

0

30

60

90

120

150

180

210

Untreated Single Split

Bu/

A

Corn Yield Response to Single or Split Applications Corn Yield Response to Single or Split Applications of glyphosate (4.5 lb ae/gal) @ 22 ozs/A.of glyphosate (4.5 lb ae/gal) @ 22 ozs/A.

Average of 7 locations (2003-06)DKC67-60RR

Glyphosate Resistance Around the World (12 Glyphosate Resistance Around the World (12 species)species)

rigid ryegrass (1996) goosegrass (1997) horseweed (2000) Italian ryegrass (2001) hairy fleabane (2003) buckhorn plantain (2003) common ragweed (2004) giant ragweed (2004) Palmer amaranth (2005) common waterhemp (2005) johnsongrass (2005) wild poinsettia (2005)

** Can be found in the US

2005 GR-Pigweed Survey

47 of 100 sitesWith Confirmed Resistance to glyphosate!!

1 location in Lee CountyConfirmed in 2006

**

Preserving the Value of GlyphosatePreserving the Value of Glyphosate

tank-mix 2,4-D in burndown when glyphosate will be used in-cropConsider paraquat or Ignite if appropriate

Alternate glyphosate use with other herbicide modes of actionTank-mix with atrazine

Use other practices such as cultivation

Do not allow weed escapes to produce seed

New Products that have been testedNew Products that have been tested

Syngenta POST 3 oz/A + COC + UAN or AMS

($13-15/A) Up to 30” tall or 8-leaf corn Palmer amaranth up to 5” If 2,4-D is undesirable or ALS-

resistance Tank-mix with atrazine also good on horsenettle Interaction with OP’s

Texas Panicum ControlTexas Panicum Control

OR OR

•About 30% of the time, Accent has provided better control of Texas panicumAbout 30% of the time, Accent has provided better control of Texas panicum•But, yields have not been different.But, yields have not been different.

What about Liberty-Link Corn?What about Liberty-Link Corn?

GlufosinateLiberty (corn)Ignite (cotton)

No tech feeup to 24” tall corn or V7Tank-mix with atrazine

Liberty ATZ good on morningglory, Texas millet,

sicklepodHybrid performance???

Garst 8353CB/LL, Hytest 7729Hx/LL

2007 Rebate Program2007 Rebate Program* Up to $6.25/A* Up to $6.25/A

Don’t Forget Liberty-Link Corn!Don’t Forget Liberty-Link Corn!

Untreated Liberty 1.67SL @ 32 ozs/AAtrazine @ 90WG @ 1.0 lb/A

AMS @ 3 lbs/AApplied 26 DAP

CN-10-06 (Croplan Genetics 731 HX/LL)Ponder Farm52 DAP

83 Bu/A 114 Bu/A

Morningglory Control in CornMorningglory Control in Corn

as much atrazine as possible

1.0 lb/A – PRE fb 1.5 lb/A – POST small grain rotations tank-mix with Aim (POST)

2,4-D, Clarity Liberty-Link Corn Systems split applications of

glyphosate (RR corn)* 1st application + atrazine

Pigweed Control in CornPigweed Control in Corn preemergence

AtrazineDual/genericsOutlook

postemergenceAtrazineAccentCallisto2,4-DPermitAimglyphosate (RR corn)

Timing is critical!

Sicklepod Control in CornSicklepod Control in Corn

Conventional SystemsAtrazine2,4-DClarity

Herbicide-ResistantRR corn systemLL corn system

Nutsedge ControlNutsedge Control

not very competitive800 plants/100 row feet

only reduce yields by 2%

Eradicane or Sutan - PPIDual II Magnum or

generic – PRE Glyphosate – RR corn

Split applications

Basagran Permit

Tropical spiderwort (a.k.a. Benghal dayflower)Tropical spiderwort (a.k.a. Benghal dayflower)Commelina benghalensisCommelina 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 GeorgiaTSW in Georgia

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

* identified in 4 morecounties in 2005 (black)

*identified in 6 more counties in 2006 (dark blue)

TSW Control in Field CornTSW Control in Field CornDepends on planting

date2,4-D or Aim – POSTSequence or Expert in

RR cornAim/Gramoxone/Evik +

Dual Magnum – laybyPost-harvest may be

more important than in-cropTillage2 applications of 2,4-D,

Gramoxone, or Aim

Post-Harvest Control of Tropical SpiderwortPost-Harvest Control of Tropical Spiderwort

Untreated 2,4-D @ 1.5 pt/APOST1 + POST 2

($14.41/A)POST1: 8-10” tall COMBEPOST2: 2 weeks laterPhoto 1 week after POST2

Post-Harvest Control of Tropical Post-Harvest Control of Tropical SpiderwortSpiderwort

Untreated Gramoxone Inteon @ 1 qt/A + COC POST1 + POST2

($25.40/A)POST1: 8-10” tall COMBEPOST2: 2 weeks laterPhoto 1 week after POST2

Johnsongrass Control in CornJohnsongrass Control in Corn

Accent no OP soil insecticide hybrid tolerance to

Accent hybrid resistance to

MDMV

Glyphosate in RR corn

New Products Tested in 2006New Products Tested in 2006

Impact (toprazamene) Amvac POST Poor control of Texas panicum and sicklepod

Resolve (rimsulfuron) DuPont PRE and POST Crop Injury problems

Stout (Accent + Harmony GT) DuPont POST Crop Injury problems

Resolve 25WG (rimsulfuron) Injury to Field CornResolve 25WG (rimsulfuron) Injury to Field Corn 1.0 oz/A Applied PRE

Pictures @ 18 DAT

Stout Injury on Pioneer 3167 - 6 DATStout Injury on Pioneer 3167 - 6 DAT

CN-08B-06Attapulgus, GA

Future ProductsFuture Products

KIH-485 Kumiai similar activity to Dual

and Prowl but different structure and lower use rates

good on Palmer amaranth

Not yet been tested in Georgia

Texas Panicum Control in Field Corn in Texas

02040

6080

100

4 WAT 6 WAT 8 WAT

Time

Co

ntr

ol

- %

K- 0.22 lb ai/A DM - 0.95 lb ai/A

Source: Steele et al. 2005. WeedTechnology 19:866-869

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