The current state of The current state of herbicidal weed controlherbicidal weed control

Micheal D. K. OwenMicheal D. K. OwenIowa State UniversityIowa State UniversityAmes, IA 50011 USAAmes, IA 50011 USAmdowen@iastate.edumdowen@iastate.edu

www.weeds.iastate.eduwww.weeds.iastate.edu

IntroductionIntroduction Glyphosate-based weed control systems predominate in Glyphosate-based weed control systems predominate in

soybeans and are increasing in cornsoybeans and are increasing in corn The benefits of glyphosate are intuitively obviousThe benefits of glyphosate are intuitively obvious Pseudo-benefits of glyphosate-based systems reflect Pseudo-benefits of glyphosate-based systems reflect

incorrect assumptions by growers (i.e. simplicity and cost incorrect assumptions by growers (i.e. simplicity and cost compared to “conventional” systems)compared to “conventional” systems)

Risks of glyphosate-based systems are no different than Risks of glyphosate-based systems are no different than with other herbicide systemswith other herbicide systems• Selection pressure imposed on weed communities resulting in Selection pressure imposed on weed communities resulting in

evolved resistant populations or weed population shiftsevolved resistant populations or weed population shifts• Application timelinessApplication timeliness

What alternatives exist?What alternatives exist?

Grower perception is the problemGrower perception is the problem

Recent survey conducted by Dr. Bill Johnson Recent survey conducted by Dr. Bill Johnson (Purdue University) quantifies the extent of the (Purdue University) quantifies the extent of the problem (see www.weeds.iastate.edu)problem (see www.weeds.iastate.edu)

90% of soybeans and 30+% of corn are RR90% of soybeans and 30+% of corn are RR® ®

varieties/hybridsvarieties/hybrids Multiple applications of glyphosate yearly Multiple applications of glyphosate yearly

imposes selection pressure on weeds resulting in imposes selection pressure on weeds resulting in evolved resistance or weed population shiftsevolved resistance or weed population shifts

Growers (~66%) indicate they are not concerned Growers (~66%) indicate they are not concerned about changes (current or future) in weeds about changes (current or future) in weeds attributable to glyphosate selection pressureattributable to glyphosate selection pressure• new herbicides will be available soonnew herbicides will be available soon• Problem does not exist if it is not on my farmProblem does not exist if it is not on my farm

WRONG!!!WRONG!!!

Glyphosate stewardshipGlyphosate stewardship

Glyphosate stewardship should be a key Glyphosate stewardship should be a key consideration in order to preserve the utility of consideration in order to preserve the utility of the technologythe technology

Continuing misperceptions about simplicity of Continuing misperceptions about simplicity of glyphosateglyphosate• Flexibility of application timing provides a false sense of Flexibility of application timing provides a false sense of

security security • Ability to control larger weeds results in treatment after Ability to control larger weeds results in treatment after

weeds have reduced potential yieldweeds have reduced potential yield Increased adoption in corn will result in greater Increased adoption in corn will result in greater

selection pressure resulting in “new” weed selection pressure resulting in “new” weed management issuesmanagement issues

Evolution of glyphosate resistant weeds continues Evolution of glyphosate resistant weeds continues to escalateto escalate

Glyphosate Stewardship: pollen drift provides a Glyphosate Stewardship: pollen drift provides a new management “opportunity”new management “opportunity”

Glyphosate stewardshipGlyphosate stewardship Clean fields do not necessarily equate to good weed Clean fields do not necessarily equate to good weed

managementmanagement• The objective of weed management is to protect The objective of weed management is to protect

crop yield potentialcrop yield potential Diversified weed management tactics provide Diversified weed management tactics provide

significant benefits to glyphosate-based systemssignificant benefits to glyphosate-based systems• Residual herbicides applied EPP or PRE are Residual herbicides applied EPP or PRE are

important components of a corn and soybean weed important components of a corn and soybean weed management programmanagement program

• Mechanical weed control tactics should be includedMechanical weed control tactics should be included Timely application of tactics is critical for all weed Timely application of tactics is critical for all weed

management programsmanagement programs

Role of Pre-emergent Herbicides inRole of Pre-emergent Herbicides inRR (LL, etc.) SystemsRR (LL, etc.) Systems

Broaden spectrum of controlBroaden spectrum of control Improve consistencyImprove consistency Protect yieldsProtect yields

• Widen application windowWiden application window Reduce selection pressureReduce selection pressure

2005 Critical Period Studies2005 Critical Period Studies

Three pre treatmentThree pre treatment• ControlControl• Corn: 0.6 or 1.2 qt Harness Xtra 6.0Corn: 0.6 or 1.2 qt Harness Xtra 6.0• Soybean: 1 or 2 qt INTSoybean: 1 or 2 qt INTRRRROO

Four post timingsFour post timings• ControlControl• V2V2• V4V4• V6V6

Effect of preemergence Harness Xtra 6.0 and Effect of preemergence Harness Xtra 6.0 and INTINTRRRRO in weed density at V6 applicationO in weed density at V6 application

0

5

10

15

20

25

Nu

mb

er w

eed

s p

er s

qu

are

ft

Corn Soybean

Control

Low

High

Harness Xtra: Low = 0.6 qt, High = 1.2 qtINTRRO: Low = 1 qt, High = 2 qt

Relationship Between Weed BiomassRelationship Between Weed Biomassand Soybean Yield Lossand Soybean Yield Loss

Weed biomass (g.m-2)

0 200 400 600 800 1000 1200 1400 1600

Rel

ativ

e y

ield

(%

)

0.0

0.2

0.4

0.6

0.8

1.0Ames

Nashua

Kanawha

Adj. R2 = 0.7092Y = 1.0126 - 0.0006x

2 qt INTRRO

Control

Data include three preemergence herbicide treatments.

Weed Growth Rate vsWeed Growth Rate vsYield Loss RateYield Loss Rate

Weed heightWeed height Growth RateGrowth Rate(inches/day)(inches/day)

Yield Loss/day Yield Loss/day (%)(%)

2 to 4”2 to 4” 0.40.4 0.50.5

4 to 6”4 to 6” 0.50.5 0.80.8

6 to 8”6 to 8” 0.70.7 1.51.5

New productsNew products A dearth of “opportunities”A dearth of “opportunities” This represents a partial list of that which This represents a partial list of that which

is “new”is “new” Many “new” companies taking an Many “new” companies taking an

increasingly active role in re-introducing increasingly active role in re-introducing old products or marketing generic versions old products or marketing generic versions of existing herbicidesof existing herbicides

In corn and soybeans, still some discovery In corn and soybeans, still some discovery activity by the major companiesactivity by the major companies

No “silver bullets” in the foreseeable No “silver bullets” in the foreseeable future (if ever there was a “silver bullet” – future (if ever there was a “silver bullet” – see workshop 9)see workshop 9)

MilestoneMilestone (aminopyralid) (aminopyralid)

Pastures, CRP, non-cropPastures, CRP, non-crop

Growth regulator – pyridine familyGrowth regulator – pyridine family

Particularly strong on composites (thistles)Particularly strong on composites (thistles)

No grazing restrictions (3 day flush out)No grazing restrictions (3 day flush out)

Non-volatileNon-volatile

MilestoneMilestone

ProductProduct Product Product RateRate

Lb ai/ALb ai/A Half-LifeHalf-Life

(days)(days)

MilestoneMilestone 4-7 fl oz4-7 fl oz 0.06-0.10.06-0.1 2525

StingerStinger

(clopyralid)(clopyralid)0.6 -1.3 pt0.6 -1.3 pt 0.2-0.40.2-0.4 4040

Tordon Tordon (picloram)(picloram)

1-2 pt1-2 pt(2-4 pt (2-4 pt Grazon)Grazon)

0.25 – 0.50.25 – 0.5(0.13-0.27)(0.13-0.27) 9090

BanvelBanvel 1 pt1 pt 0.50.5 55

Impact 2.8SCImpact 2.8SC(topramezone)(topramezone)

Postemergence in field corn, seed Postemergence in field corn, seed corn, popcorn and sweet corncorn, popcorn and sweet corn

HPPD inhibitor (bleacher)HPPD inhibitor (bleacher) Broadleaf (3-8”) and grass (3-4”)Broadleaf (3-8”) and grass (3-4”) 0.75 fl oz/A (0.02 lb ai/A) 0.75 fl oz/A (0.02 lb ai/A) MSO or COC +UANMSO or COC +UAN 0.25 to 1.0 lb atrazine recommended0.25 to 1.0 lb atrazine recommended

Impact 2.8SCImpact 2.8SC One application per yearOne application per year 45 day harvest restriction45 day harvest restriction Do not tank mix or use sequential application Do not tank mix or use sequential application

with isoxaflutole (Balance, etc.) or mesotrione with isoxaflutole (Balance, etc.) or mesotrione (Callisto, etc.)(Callisto, etc.)

Rotation restrictionsRotation restrictions• Soybean: North of I-80 18 monthsSoybean: North of I-80 18 months

South of I-80 9 months South of I-80 9 months

2EE label: North of I-80 (Except N of 20 and 2EE label: North of I-80 (Except N of 20 and west of US71)west of US71)

0.5 oz rate allows 9 month soybean replant0.5 oz rate allows 9 month soybean replant

ResolveResolve(rimsulfuron)(rimsulfuron)

Component of Steadfast (rim + Component of Steadfast (rim + nicosulfuron)nicosulfuron)

Current label:Current label:• Postemergence up to 12” or V6, whichever is Postemergence up to 12” or V6, whichever is

most restrictivemost restrictive• PRE label newly availablePRE label newly available

1 oz Resolve = 0.25 oz rimsulfuron1 oz Resolve = 0.25 oz rimsulfuron 0.75 oz Steadfast = 0.19 oz rimsulfuron0.75 oz Steadfast = 0.19 oz rimsulfuron

Half-life: 2-4 daysHalf-life: 2-4 days

ET Herbicide/Defoliant ET Herbicide/Defoliant

Likely to be introduced in the Midwest by Likely to be introduced in the Midwest by Ninchino America, Inc.Ninchino America, Inc.

A PPO inhibitor to be positioned as an A PPO inhibitor to be positioned as an addition to glyphosate in cornaddition to glyphosate in corn

Registered in cotton as a defoliantRegistered in cotton as a defoliant Inexpensive control of small seeded Inexpensive control of small seeded

annual broadleaf weeds (e.g. common annual broadleaf weeds (e.g. common waterhemp and common lambsquarters)waterhemp and common lambsquarters)

Injury (cosmetic) to corn a factorInjury (cosmetic) to corn a factor

ImperiumImperium

Pre-mix of EPTC plus acetochlor re-Pre-mix of EPTC plus acetochlor re-introduced by Gowan Companyintroduced by Gowan Company

Previously marketed as DoubleplayPreviously marketed as Doubleplay Requires incorporationRequires incorporation Effective on difficult annual grasses Effective on difficult annual grasses

(i.e. woolly cupgrass)(i.e. woolly cupgrass)

KIH-485 60WGKIH-485 60WG New chemistry!New chemistry! Under development by K-I Chemical USA, Inc.Under development by K-I Chemical USA, Inc.

• ISU has 4 years experience with the productISU has 4 years experience with the product• Investigations in field corn, popcorn, soybeansInvestigations in field corn, popcorn, soybeans• EPP, PRE, Fall EPP, PRE, Fall

Chemistry not released but comparisons made to other Chemistry not released but comparisons made to other chloracetamide products (i.e. Dual MAGNUM)chloracetamide products (i.e. Dual MAGNUM)

Broad spectrum controlBroad spectrum control• Woolly cupgrassWoolly cupgrass• ShattercaneShattercane• Small-seeded annualsSmall-seeded annuals• VelvetleafVelvetleaf

Excellent residual activity, very low a.i./acreExcellent residual activity, very low a.i./acre

Other Products/ChangesOther Products/Changes Radius (Bayer) flufenacet + isoxaflutoleRadius (Bayer) flufenacet + isoxaflutole

• Significantly higher ratio of fluf:isox than in Significantly higher ratio of fluf:isox than in EpicEpic

Callisto: now cleared for pre and post applications Callisto: now cleared for pre and post applications on sweet cornon sweet corn

Select Max: no additives required with ‘loaded’ Select Max: no additives required with ‘loaded’ glyphosate; greater adjuvant flexibility with other glyphosate; greater adjuvant flexibility with other posts; posts; 1 lb/gal EC rather than 2 lb/gal 1 lb/gal EC rather than 2 lb/gal

Boundary: changed from 7.8EC to 6.5ECBoundary: changed from 7.8EC to 6.5EC Propel (Rosens): new brand of dimethenamid-PPropel (Rosens): new brand of dimethenamid-P

Questions?