WEED MANAGEMENT ISSUES Pigweeds Marestail Control Volunteer Corn Herbicide Update

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

? 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 ?

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 Waterhemp Smooth stems Leaves long, narrow, & waxy Palmer Amaranth Smooth stems, Long petioles Symmetrical leaf arrangement Spiny Amaranth Spines 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 DIOECIOUS 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 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 (11-07-09)

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

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

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 >

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

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

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

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” * Price does not include cost of application or adjuvants * * Will not Control Glyphosate -Tolerant Volunteer Corn. 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)