1. WEED MANAGEMENT ISSUES
Pigweeds
Marestail Control
Volunteer Corn
Herbicide Update

2. Turn Out the Lights - The Party’s Over
Aaron G. Hager
Department of Crop Sciences
University of Illinois

4. ? Lyrics Turn out the lights, the party’s over
They say that all good things must end
Let’s call it a night the party’s over
And tomorrow starts the same old thing again ?

5. Waterhemp Spp. Common Waterhemp (Amaranthus rudis)
Tall Waterhemp (Amaranthus tuberculatus)

6. Waterhemp Spp.
Source: Dr. Aaron Hager, Univ of IL

7. Palmer Amaranth

8. Palmer Amaranth in Fulton County - 2009
Dr. Bill Witt
Cam Kenimer

9. Vegetative Characteristics of Pigweeds In KY
SPECIES
CHARACTERISTICS
Smooth Pigweed
Hairy stems
Redroot Pigweed
Waterhemp
Smooth stems
Leaves long, narrow, & waxy
Palmer Amaranth
Smooth stems,
Long petioles
Symmetrical leaf arrangement
Spiny Amaranth
Spines at leaf nodes

10. Reproductive Characteristics of Pigweeds In KY
SPECIES
CHARACTERISTICS OF FLOWERING BRANCHES
MONOECIOUS
Smooth Pigweed
Compact short, slender & somewhat prickly
Redroot Pigweed
Compact short & prickly
Spiny Amaranth
Male flowers top of plants & female flowers at bottom & middle of plants
DIOECIOUS
Waterhemp spp.
Long, slender, & smooth
Palmer Amaranth
Very long (males smooth / females prickly)

11. COMPARASION OF FLOWERING STRUCTURES

12. WATERHEMP & PALMER AMARANTH BIOLOGY CREATE CHALLENGES FOR SOYBEAN GROWERS
Prolific seed producers. Seed scattered with combines.
Dioecious (male & female plants). Pollen flow contributes to dispersal.
Multiple events of plant emergence throughout the season.
Palmer grows rapidly and difficult to control:
3” tall with Flexstar
5” to 6” tall for Ignite in LL soybean.

13. TYPES OF HERBICIDE RESISTANCE IN MAJOR PIGWEED SPECIES IN THE US
MODE/SITE OF ACTION
SMOOTH PIGWEED
WATERHEMP SPP
PALMER AMARANTH
ALS X
GLYCINE -
PS II
DNA
ALS + GLYCINE
ALS + PS II
ALS + PPO
ALS + PS II + PPO
ALS + PPO + GLYCINE
X = Resistance has been documented.
Most of these confirmed based on criteria in International Survey of Herbicide Resistant Weeds ( )

14. HERBICIDE OPTIONS FOR WATERHEMP CONTROL IN SOYBEAN
SOIL APPLIED
POSTEMERGENCE
Authority Assist
Authority First / Sonic
Authority MTZ
Boundary
Envive
Gangster
Linex
Prefix
Spartan
Valor Sx / Encompass
Valor XLT
Cobra
Flexstar
Reflex
Ultra Blazer

15. HERBICIDE OPTIONS FOR WATERHEMP CONTROL IN SOYBEANS
SOIL APPLIED
Authority Assist
Authority First / Sonic
Authority MTZ
Boundary
Envive
Gangster
Linen
Prefix
Spartan
Valor Sx / Encompass
Valor XLT
POSTEMERGENCE
Cobra
Flexstar
Reflex
Ultra Blazer

16. HERBICIDE OPTIONS FOR PALMER AMARANTH CONTROL IN SOYBEANS
SOIL APPLIED
Dual
Intrro
Prefix
Prowl
Sencor
Treflan
Authority First/Sonic
Authority MTZ
Valor Sx / Encompass
Valor XLT
>
POSTEMERGENCE
Cobra
Flexstar
Ultra Blazer
Ignite in LL soybeans
>

17. Burndown Control of Marestail
2,4-D ester
Sharpen
Optill
Ignite

18. VOLUNTEER CORN IS A WEED
Corn yield reduced 42 to 60 % due to interference from volunteer corn plants
(Source Univ. of Illinois)
1 Volunteer Corn Clump/8 ft2
Reduces Soybean Yield 25% Source: Becket & Stoller 1988
UK Weed Sci

19. Herbicide Options for Controlling Unwanted Corn Plants Prior to Planting Field Corn
Approx.
Cost/A
Previous Corn Hybrid
Conventional
Hybrid
Roundup Ready
Liberty Link
Clearfield
IMI-Corn
Glyphosate
$ /A ++ X
Paraquat + Photo System II Inhibitor
(e.g.. Atrazine, Linex, Metribuzin)
$ /A +
Select MAX *
$9/A
+ = Recommended = Highly recommended X = No control
* SELECT MAX Replant no sooner than 6 days after application
UK Weed Sci

20. Soybean Herbicides Labeled For Controlling Volunteer Corn
Postemergence Herbicide
Cost/A*
Max Corn Height
Arrow (4-6 oz/A
$ 4.50 – 7.0/A
4” to 12”
Assure II (4 to 8 oz/A)
$ 4.50 – 8.75/A
18” to 30”
Fusion (4 to 6 oz/A)
$ /A
24”
Poast (0.75 pt/A)
$ 6.75/A
20”
Select Max,etc (6 / 9 / 12 oz/A)
$ /A
(12”) (24”) (36”)
** Glyphosate (0.56 to lbae/A)
$ /A
12” to 20”
** Sequence (2.5 pt/A)
$?/A
18”
* Price does not include cost of application or adjuvants
* * Will not Control Glyphosate -Tolerant Volunteer Corn.
UK Weed Sci

21. Corn Herbicide Update Sharpen (saflufenacil) *
Integrity (saflufenacil + dimethenamide) *
Corvus (isoxaflutol + thiencarbazone)
Accent Q (nicosulfuron + safener)
Steadfast Q (nicosulfuron + rimsulfuron + safener)
Valor (14-Day EPP)
* Kixor technology

22. Soybean Herbicide Update
Sharpen (saflufenacil) *
Optill (saflufenacil + imazethapyr) *
Envive (chlorimuron + thifensulfuron + flumioxazin)
Ignite 280 (glfosinate ) Burndown & Post in LL soybean
* Kixor technology

23. Wheat Herbicide Update
PowerFlex (pyroxsulam)