WEED MANAGEMENT ISSUES

• Pigweeds

• Marestail Control

• Volunteer Corn

• Herbicide Update

Turn Out the Lights -The Party’s Over

Turn Out the Lights -The Party’s Over

Aaron G. HagerDepartment of Crop Sciences

University of Illinois

Aaron G. HagerDepartment of Crop Sciences

University of Illinois

LyricsLyrics

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

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

??

Waterhemp Spp.

• Common Waterhemp (Amaranthus rudis)

• Tall Waterhemp (Amaranthus tuberculatus)

Waterhemp Spp.

Source: Dr. Aaron Hager, Univ of IL

Palmer Amaranth

Palmer Amaranth in Fulton County - 2009

Dr. Bill Witt Cam Kenimer

Vegetative Characteristics of Pigweeds In KY

SPECIES CHARACTERISTICS

Smooth Pigweed Hairy stems

Redroot Pigweed Hairy stems

Waterhemp Smooth stemsLeaves long, narrow, & waxy

Palmer Amaranth Smooth stems, Long petiolesSymmetrical leaf arrangement

Spiny Amaranth Smooth stemsSpines at leaf nodes

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

DIOECI

OUS

Waterhemp spp. Long, slender, & smooth

Palmer Amaranth Very long (males smooth / females prickly)

COMPARASION OF FLOWERING STRUCTURES

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.

TYPES OF HERBICIDE RESISTANCE IN MAJOR PIGWEED SPECIES IN THE US

MODE/SITE OF ACTION

SMOOTH PIGWEED

WATERHEMP SPP

PALMER AMARANTH

ALS X X XGLYCINE - X XPS II X X XDNA - - XALS + GLYCINE - X XALS + PS II X X -ALS + PPO - X -ALS + PS II + PPO - X -ALS + PPO + GLYCINE - X -

Most of these confirmed based on criteria in International Survey of Herbicide Resistant Weeds (11-07-09)

X = Resistance has been documented.

HERBICIDE OPTIONS FOR WATERHEMP CONTROL IN SOYBEAN

• Authority Assist• Authority First / Sonic• Authority MTZ• Boundary• Envive• Gangster• Linex• Prefix• Spartan• Valor Sx / Encompass• Valor XLT

• Cobra• Flexstar• Reflex• Ultra Blazer

SOIL APPLIED POSTEMERGENCE

HERBICIDE OPTIONS FOR WATERHEMP CONTROL IN SOYBEANS

• Authority Assist• Authority First / Sonic• Authority MTZ• Boundary• Envive• Gangster

SOIL APPLIED

POSTEMERGENCE

• Cobra• Flexstar

• Linen• Prefix• Spartan• Valor Sx / Encompass• Valor XLT

• Reflex• Ultra Blazer

HERBICIDE OPTIONS FOR PALMER AMARANTHCONTROL IN SOYBEANS

• Authority First/Sonic• Authority MTZ• Valor Sx / Encompass• Valor XLT

SOIL APPLIED

POSTEMERGENCE

• Dual• Intrro• Prefix• Prowl• Sencor• Treflan

>

• Ignite in LL soybeans>

• Cobra• Flexstar• Ultra Blazer

Burndown Control of Marestail

• 2,4-D ester• Sharpen• Optill• Ignite

UK Weed Sci

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

VOLUNTEER CORN IS A WEED

Herbicide Options for Controlling Unwanted Corn Plants Prior to Planting Field Corn

Herbicide Approx.Cost/A

Previous Corn Hybrid

Conventional

Hybrid

Roundup

Ready

Liberty Link

ClearfieldIMI-Corn

Glyphosate $ 4 - 15/A ++ X ++ ++

Paraquat + Photo System II Inhibitor(e.g.. Atrazine, Linex, Metribuzin) $ 11 - 22/A + + + +

Select MAX * $9/A + ++ + +

+ = Recommended ++ = Highly recommended X = No control

UK Weed Sci* SELECT MAX Replant no sooner than 6 days after application

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) $ 5.25 - 7.75/A 24”

Poast (0.75 pt/A) $ 6.75/A 20”

Select Max,etc (6 / 9 / 12 oz/A) $ 6.25- 12.50/A (12”) (24”) (36”)

** Glyphosate (0.56 to 10.75 lbae/A) $ 2.50 - 7.75/A 12” to 20”

** Sequence (2.5 pt/A) $?/A 18”

* * Will not Control Glyphosate -Tolerant Volunteer Corn.

* Price does not include cost of application or adjuvants

UK Weed Sci

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

Soybean Herbicide Update

– Sharpen (saflufenacil) *– Optill (saflufenacil + imazethapyr) *– Envive (chlorimuron + thifensulfuron + flumioxazin)– Ignite 280 (glfosinate ) Burndown & Post in LL soybean

* Kixor technology

Wheat Herbicide Update

– PowerFlex (pyroxsulam)