Corn Weed Management for New County Extension Agents

1
Corn Weed Management for New County Extension
Agents

• Eric P. Prostko
• Extension Weed Specialist
• Department of Crop Soil Sciences - UGA

April 2007
2
Cultural Practices

• Planting Date
• Row Spacing
• Fertility
• give the crop a competitive edge against weeds

3
Mechanical Cultivation

• Time
• Diesel fuel prices
• Strip-tillage

4
Insecticide/Herbicide Interactions

• Insecticides
• Organophosphates (OPS)
• Counter, Lorsban, Thimet
• Herbicides
• Accent, Beacon, Option, Callisto, Steadfast,
  Basis

5
Weed/Disease Interactions

• Maize Dwarf Mosaic Virus (MDMV)
• Maize Chlorotic Dwarf Virus (MCDV)
• johnsongrass
• aphid/leafhoppers
• Accent/Beacon
• hybrid tolerance

6
Corn Stages of Growth
7
Specific Herbicides

• Atrazine
• Prowl
• Accent

8
Atrazine Use in Field Corn

• Since 1958
• foundation
• inexpensive
• excellent crop tolerance
• PPI, PRE, POST (12)
• broad-spectrum
• up to 2.5 lb ai/A/year
• easily tank-mixed
• weak on T. panicum
• does not last full season in SE

9
Conventional Weed Management SystemsMany
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

10
Prowl Use in Field Corn

• since 1975
• pendimethalin
• DNA or yellow
• inexpensive but.
• do not apply PRE
• early-post (EPOST)
• up to 30 tall or V8
• crop injury concerns
• Planting depth (1.5)
• Furrow closure

11
Optimum Prowl/Pendimax Timing Field Corn
Prowl will not control emerged grasses!!!
12
Prowl Injury In Field Corn
Prowl
Control
13
Accent Use in Field Corn

• since 1991
• nicosulfuron
• sulfonylurea
• ALS-inhibitor
• POST
• up to 20 tall or V6
• 20-36 (PDIR)
• Pigweed, Texas panicum
• Weak on crabgrass
• Hybrid sensitivity
• OP interaction
• Tank-mix with atrazine
• cost

14
Corn Hybrid/Herbicide Tolerance

• Pioneer
• http//www.pioneer.com/CMRoot/Pioneer/usa/agronomy
  /corn/herb_table.pdf

15
Why do you not want to spend the money on an
Accent Atrazine treatment in field corn?
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!!!
16
Know Your Grasses
broadleaf signalgrass
large crabgrass
johnsongrass
fall panicum
Source SWSS Weed ID Guide
17
Texas Panicum vs. Crabgrass
Fringe of hairs
membranous
WSSA
Southern crabgrass
Texas panicum
18
Post-Directed Applications
19
Post-Directed Options for Field Corn

• Evik
• Gramoxone Inteon/Firestorm (paraquat)
• Lorox/Linex
• Aim
• tropical spiderwort
• pigweeds
• morningglory

20
Herbicide Resistant Corn Technologies
21
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

22
How would I use RR corn systems?

• If you are unwilling to use a PRE application of
  atrazine or something else.
• 2 applications of glyphosate
• 1st application 21-28 DAP atrazine (1.5-2.0
  qt/A)
• 2nd application 35-40 DAP
• Sequence (s-metolachlor glyphosate)
• Expert (s-metolachlor atrazine glyphosate)
• Do not forget to include extra seed costs/A in
  your budgets!
• Irrigated _at_ 30,000/A 12-13.00/A
• Dryland _at_ 18,000/A 7-8.00/A

23
Texas Panicum Control At Harvest with Single or
Split Applications of Roundup WM - II
Untreated
Roundup WM _at_ 22 ozs/A 21 35 DAP
Roundup WM _at_ 22 ozs/A 21 DAP
CN-04-04 (Attapulgus)
24
Corn Yield Response to Single or Split
Applications of glyphosate (4.5 lb ae/gal) _at_ 22
ozs/A.
Average of 7 locations (2003-06) DKC67-60RR
25
What about Liberty-Link Corn?

• Glufosinate
• Liberty (corn)
• Ignite (cotton)
• No tech fee
• up to 24 tall corn or V7
• Tank-mix with atrazine
• Liberty ATZ
• good on morningglory, Texas millet, sicklepod
• Hybrid performance???
• Garst 8353CB/LL, Hytest 7729Hx/LL

2007 Rebate Program Buy 20 gals and get a
5-6/A rebate
26
Dont Forget Liberty-Link Corn!
83 Bu/A
114 Bu/A
Untreated
Liberty 1.67SL _at_ 32 ozs/A Atrazine _at_ 90WG _at_ 1.0
lb/A AMS _at_ 3 lbs/A Applied 26 DAP
CN-10-06 (Croplan Genetics 731 HX/LL) Ponder
Farm 52 DAP
27
Clearfield Corn Systems

• Not used that much or at all in Georgia
• Pursuit
• Lightning
• Pursuit Arsenal
• POST
• Non-GMO
• ALS-resistance

28
Common Weed Problems

• Texas panicum (Texas millet, buffalograss)
• sicklepod (coffeeweed)
• pigweeds
• morningglories
• nutsedges
• johnsongrass
• Tropical spiderwort (Benghal dayflower)

29
Texas Panicum Control in CornWhat works!

• Prowl/Pendimax (DPRE/EPOST)
• Accent (POST)
• Option (POST)
• RR or LL system
• post-directed
• Evik/Paraquat

30
Texas Panicum Control
OR

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

31
Texas Panicum Control (104 DAT) - IIAccent vs
Option - 2004
Untreated
Accent _at_ 0.67 ozs/A Agrioil _at_ 1 v/v
Option _at_ 1.5 ozs/A MSO _at_ 1.25 v/v AMS _at_ 3 lbs/A
CN-04-04 (Attapulgus) Applied 21 DAP PANTE
1-2, 2-4 leaf
32
Sicklepod Control in Corn

• Conventional Systems
• Atrazine
• 2,4-D
• Clarity
• Herbicide-Resistant
• RR corn system
• LL corn system

33
Pigweed Control in Corn

• preemergence
• Atrazine
• Dual/generics
• Outlook
• postemergence
• Atrazine
• Accent
• Callisto
• 2,4-D
• Permit
• Aim
• glyphosate (RR corn)
• Timing is critical!

34
Morningglory 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, Status
• Liberty-Link Corn Systems
• split applications of glyphosate (RR corn)
• 1st application atrazine
• Harvest Aids
• 2,4-D, sodium chlorate, glyphosate, Aim, paraquat

35
Nutsedge Control

• not very competitive
• 800 plants/100 row feet only reduce yields by 2
• Eradicane or Sutan - PPI
• Dual II Magnum or generic PRE
• Glyphosate RR corn
• Split applications
• Basagran
• Permit

36
Johnsongrass Control in Corn

• Accent
• no OP soil insecticide
• hybrid tolerance to Accent
• hybrid resistance to MDMV
• Glyphosate in RR corn

37
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)

38
TSW in Georgia
confirmed in 29 counties by GA Dept. of Ag and
UGA in 2004 (light blue)
identified in 4 more counties in 2005
(black) identified in 6 more counties in 2006
(dark blue)
39
TSW Control in Field Corn

• Depends on planting date
• 2,4-D or Aim POST
• Sequence or Expert in RR corn
• Aim/Gramoxone/Evik Dual Magnum layby
• Post-harvest may be more important than in-crop
• Tillage
• 2 applications of 2,4-D, Gramoxone, or Aim

40
Reduced Tillage Systems
41
Burndown Control Options

• glyphosate
• Paraquat
• Ignite (glufosinate)
• tank-mixes with?
• 2,4-D
• atrazine
• Need a clean seed-bed at planting

42
Ryegrass Control - Burndown

• Hard to kill with 1 shot
• Option 1
• Glyphosate _at_ 1.125 lb ae/A atrazine _at_ 3 pts/A
• Option 2
• Gramoxone Inteon _at_ 1.9 pts/A 2 WBP fb Gramoxone
  Inteon _at_ 1.9 pts/A atrazine _at_ 3 pts/A -
  planting
• RR corn systems
• Accent????

43
Herbicide-Resistant Weed Issues

• Glyphosate
• ALS

44
Herbicide ResistanceDefinition

• inherited ability of a weed or crop biotype to
  survive a herbicide application to which the
  original population was susceptible.

Biotype a group of plants within a species that
has biological traits that are not common to the
population as a whole.
45
Glyphosate Resistance Around the World (12
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
46

3/15/2007
47
What does ALS mean?

• Acetolactate synthase (ALS)
• Acetohydroxyacid synthase (AHAS)
• chloroplast enzyme needed to form certain amino
  acids
• Valine, leucine, isoleucine
• Herbicide families
• Imidazolinones
• Sulfonylureas
• Sulfonanalides
• benzoates

48
Commonly Used ALS Herbicides

• Accent
• Ally/Cimarron
• Beacon
• Beyond
• Cadre
• Classic
• Envoke
• Exceed
• Express
• Finesse
• FirstRate

• Glean
• Harmony Extra
• Maverick Pro
• Osprey
• Peak
• Permit
• Pursuit
• Python
• Scepter
• Staple
• Strongarm

49
ALS-Resistant Palmer Amaranth Survey
50
Where to go for more information?

• UGA Weed Science Web-Site
• www.gaweed.com
• UGA Pest Control Handbook
• UGA Corn Production Guide