getting the most out of glyphosate - kansas state university · getting the most out of glyphosate...

Getting the Most Out of Glyphosate

Dallas PetersonDepartment of Agronomy

K-State Research & Extension

Glyphosate IssuesProduct Confusion & Appropriate Rates

Factors that Affect Performance

AMS Requirements and Replacement Products

Application Timing and Yield Protection

Expanded Crop Uses

Weed Shifts and Glyphosate Resistant Weeds

New Glyphosate ProductsMany glyphosate products Different concentrations, formulations, and adjuvant requirementsNeed to read labels carefully and follow rate and adjuvant recommendationsKSU research: few or no differences among most glyphosate products when applied at same acid equivalent rates and with recommended adjuvants.

Active Ingredient (a.i.)vs. Acid Equivalent (a.e.)

Glyphosate acid is the active form of glyphosate in plants.Nearly all glyphosate products formulated as salts, ie. isopropylamine (IPA), diammonium (DA), or potassium (K).Salt portions of formulated molecules have different weights.Active ingredient weight includes the salt part of the molecule, while acid equivalent weight does not.Acid equivalent weight provides a better comparison of the herbicidal component of the different glyphosate salts.

Glyphosate ProductsTrade name Salt lb ai/gal lb ae/gal 0.75 lb ae/ARoundup Original IPA 4 3 1 qtRoundup Original MAX K 5.5 4.5 22 ozRoundup WEATHERMAX K 5.5 4.5 22 ozTouchdown DA 3.75 3 1 qtTouchdown Total K 5 4.2 24 ozTouchdown HiTech K 6 5 19 ozDurango IPA 5.4 4 26 ozGlyphomax XRT IPA 5.4 4 26 ozMost Generics IPA 4 3 1qt

Surfactant Requirements with Glyphosate

Some glyphosate products always recommend using surfactant, some indicate the addition of surfactant is optional, while other products do not need additional surfactant.READ THE LABEL.KSU generally recommends adding a source of ammonium sulfate to all glyphosate applications, to condition the water carrier.

Application FactorsEnvironment

TemperatureHumidityDrought Stress

Rainfree Interval Time of Day

Spray VolumeWater QualityWater ConditionersDustWheel Tracks

Roundup Application Time of DayMaterial and Methods

Roundup rate: 1 pt/A

Application Stages: P: 4-8 inch velvetleaf and Palmer amaranthLP: 6-12 inch velvetleaf and Palmer amaranth

Application time of day:6 am, 10 am, 1:30 pm, 5 pm, 9 pm

The influence of application time of day on Roundup performance, Manhattan, KS, 1999.Application Palmer amaranth VelvetleafTime of Day Post LP Post LP

--------------(% control)-------------

6:00 am 96 85 96 47 10:00 am 99 100 99 99 1:30 pm 100 100 99 99 5:00 pm 100 99 97 97 9:00 pm 99 88 95 47

LSD 3 9

Late Postemergence - 6 am

Late Postemergence - 10 am

Late Postemergence - 9 pm

Application Time of Day

Weed control with Roundup was less when applied pre-dawn or post sundown than during the middle of the day.Possible reasons:

presence of dewlight influence on physiological interactionsplant leaf orientation

Leaf Orientation During the day and at Night

Day:

Night:

Velvetleaf Palmer amaranth

Late postemergence glyphosate applied with spray volumes of 5, 10, and 20 gpa, Manhattan, KS 2000.

5 gpa 10 gpa 20 gpa

0

20

40

60

80

100

5 gpa 10 gpa 20 gpa

Spray Volume

% C

ontr

ol

LSD=5

Oat control 2 WAT with a reduced rate of glyphosate as influenced by spray volume, Manhattan, KS 2001.

AMS with Glyphosate in Soft Water

Without AMS With AMS

AMS Replacements with Glyphosate in Hard Water

5% v/v Liquid AMS(2% w/w, or 17 lb/100gal)

0.5% v/vAMS Replacement

AMS Replacements

with Glyphosate

AMS Replacements with GlyphosateMaterials & Methods

Spray Volume: 15 gpa

Water Hardness: 103 Total Hardness as CaCO3

~6 grains/gal

Application: 7/12/05, 89F, 55% RH

Velvetleaf: 6-12” 5-10 leaf

Sorghum: 16” V6

Corn: 20” V6

Sunflower: 12-16” 8-10 leaf

Weed control with glyphosate plus AMS replacement adjuvants at 4 WAT, Manhattan, KS (MS200508).

Treatment

Rate

Velvet- Leaf

Sorghum

Corn

Sun-flower

---------------(% control)-------------- Roundup WMax +: 8 oz +: None 40 60 52 73 AMS 2 % w/w 77 90 83 92 Class Act NG 2.5% v/v 72 90 82 90 Alliance 1.25% v/v 65 83 77 90 Choice 0.5% v/v 30 47 42 60 Request 0.5% v/v 37 58 50 75 Speedway 0.5% v/v 42 50 50 85 Blendmaster 1% v/v 43 57 53 80 US 500 0.25% v/v 33 50 47 70 Citron 2.2 lb/100G 37 40 40 78 N-Tank 0.5% v/v 62 68 67 90 LSD (10%) 7 9 7 7

Weed control with glyphosate as influenced by AMS

No AMS 17 lb AMS/100 Gal Low Rate AMS Replacement

Weed control with glyphosate plus AMS replacement adjuvants at 4 WAT, Manhattan, KS , 2006 (MS200606).

Treatment

Rate

Velvet- Leaf

Sorghum

Corn

Sun-flower

---------------(% control)-------------- Roundup WMax +: 8 oz +: None 0 0 0 3 AMS 2 % w/w 50 67 70 85 Class Act NG 2.5% v/v 30 73 68 78 Alliance 1.25% v/v 17 57 57 43 Choice WM 0.5% v/v 3 0 0 5 Request 0.5% v/v 8 0 7 7 Flame 0.5% v/v 5 2 3 10 Cayuse Plus 0.5% v/v 10 5 3 7 Loadout 0.5% v/v 3 3 3 7 Citron 2.2 lb/100G 3 3 5 3 N-Tank 0.5% v/v 30 22 37 23 LSD (10%) 10 9 10 11

Weed control with glyphosate plus AMS replacement adjuvants at 9 DAT, Tribune, KS 2006 (0613Fall).

Treatment

Rate

Sorghum

Corn

Sunflower

---------(% control)---------- Roundup WMax +: 8 oz +: None 56 74 84 AMS 2 % w/w 83 90 89 Class Act NG 2.5% v/v 80 87 90 Alliance 1.25% v/v 83 78 90 Choice WM 0.5% v/v 63 69 85 Request 0.5% v/v 60 73 85 Flame 0.5% v/v 69 84 86 Cayuse Plus 0.5% v/v 69 86 86 Loadout 0.5% v/v 68 78 86 Citron 2.2 lb/100G 69 80 86 N-Tank 0.5% v/v 83 86 87 LSD (10%) 16 11 5

Applicator Tracks

Glyphosate + AMS

Low Rate Full Rate

Weed Control and Yield Protection

Weed PressureWeed Control StrategyTiming of Weed ControlLevel of Weed Control

Late Roundup Application

Glyphosate4 WAP

Early season weed competition with soybeans.

Soybean yield as influenced by time of weed removal, 1998.(Peterson&Regehr)

0

5

10

15

20

25

30

35

Weed Free 22 DAP 27 DAP 31 DAP 35 DAP No Removal

Herbicide Application Timing (Days after Planting)

Soyb

ean

yiel

d (B

u/A

) Glyphosate, sequential

Glyphosate, single

Soybean Stage /Weed SizeV1/<4” V2/<12” V4/<24” V5/<30”

Critical Period of Weed ControlGrowth Stage or critical period to remove weeds from a crop before significant yield loss occurs.Highly variable and dependent on:

Weed Species PresentWeed PopulationsTime of Weed Emergence Relative to Crop EmergenceCrop Management Practices

– fertility, row spacing, population, etcEnvironmental Conditions

Often 3 to 4 WAP with heavy weed pressure

Hard to Control Weeds with Glyphosate

Naturally Tolerant Species:Prairie cupgrass, tumble windmillgrass, yellow nutsedge, annual spurges, wild buckwheat, lambsquarters, Russian thistle, velvetleaf, morninnglory, waterhemp

Glyphosate Resistant Weeds

Glyphosate Resistant weeds?Annual ryegrass: 1996 - Australia, California, South

America,S. AfricaGoosegrass: 1997 - Malaysia Horseweed/marestail: 2000 - East and SE US.

probably in KansasCommon Ragweed: 2004 - MissouriPalmer Amaranth: 2005 - Georgia, TennesseeWaterhemp: 2005 - MissouriJohnsongrass: 2006 - ArgentinaGiant Ragweed: 2006 - Ohio, IndianaLambsquarters?

Continuous soybeans for many years, RR soybeans with at least one application of glyphosate since 1996Waterhemp also ALS and PPO resistant, but not triazineresistant

Glyphosate-Resistant Waterhemp Biotype in NW MOKevin Bradley, University of Missouri

Kevin Bradley, University of Missouri

None 1 pt 1 qt 2 qt 1 gal 2 gal(Rate of 3# ae glyphosate/A)

Kevin Bradley, University of Missouri

Susceptible Moderately Tolerant Resistant

Common Waterhemp Biotype Response to 0.75 lb ae Glyphosate/A

WeatherMax 88 oz at 1 inch



Glyphosate Resistant Palmer Amaranth Stanley Culpepper, University of Georgia

0 3 12 24 486Roundup WeatherMax oz/A

Sus.

WMax: oz/A

Res.

Stanley Culpepper, University of Georgia

Glyphosate Resistant Palmer Amaranth in Georgia

Glyphosate-resistant Palmer amaranth: Stanley Culpepper, Georgia, 2005.

Current Glyphosate Resistance Evaluations at KSU

Common Waterhemp (2 populations)Marestail (2 populations)Giant Ragweed (2 populations)Kochia

Glyphosate Resistant Marestail Assay

Sumner Co.

Miami Co.

Check

Glyphosate Rate: 1 pt 1 qt 1.5 qt 0

Glyphosate Resistant Giant Ragweed Assay

R?

S

Rate: 8X 4X 3X 2.5X 2X 1.5X 1X 1/2X 1/4X 0X

Differential Waterhemp Response to Glyphosate

Glyphosate Resistant Kochia?Poor control of a wandering row of kochia with glyphosate was observed in a field of Roundup Ready cotton in Stevens county, KS in the summer of 2007.Kochia seed was collected from the uncontrolled plants in the cotton field in Stevens county and from an uncropped area in Finney county in the fall of 2007. Greenhouse experiments were conducted to compare the efficacy of glyphosate at various rates on the two kochia populations.

Materials and MethodsS and R biotypes of kochia were grown in the greenhouse and treated when plants were 4 to 6 inches tall.Kochia plants were treated with Roundup Weather Max at 0.38, 0.75, 1.12, 1.5, 2.25 and 3 lb ae/a (11,22, 33, 44, 66, & 88 oz/A).Weed control was visually evaluated 2 and 4 weeks after treatment.

Kochia biotype response to glyphosate , 2 WAT.

4499331.12“

84100662.25“3

1.5

0.750.38

(lb/a)ae

Rate Biotype

(% control)

6LSD (5%)9610088“

6010044“

348822“01511Roundup WMax + AMS

(oz/a)StevensFinney ProductHerbicide


085331.12“

30100662.25“3

1.5

0.750.38

(lb/a)ae

Rate Biotype

(% Mortality)

14LSD (5%)8510088“

010044“




76100331.12“

100100662.25“3

1.5

0.750.38

(lb/a)ae

Rate Biotype

(% control)

LSD (5%)10010088“

9210044“




45100331.12“

100100662.25“3

1.5

0.750.38

(lb/a)ae

Rate Biotype

(% Mortality)

LSD (5%)10010088“

7510044“



Glyphosate Resistant Kochia?(2 WAT)

Finney Co.

0.75 lb(22 oz)

0.38 lb(11 oz) Untreated

Stevens Co.

1.5 lb(44 oz)

3 lb(88 oz)

Roundup WMax:

2.25 lb(66 oz)

Glyphosate Resistant Kochia?(5 WAT)

Finney Co.

0.75 lb(22 oz)

0.38 lb(11 oz) Untreated

Stevens Co.

1.5 lb(44 oz)

3 lb(88 oz)Roundup WMax:

2.25 lb(66 oz)

1.13 lb(33 oz)

SummaryA biotype of kochia in southwestern Kansas has developed a low level of resistance to glyphosate.Exclusive use of glyphosate, especially at reduced rates may result in increased tolerance by weeds.Producers should use labeled rates, tank-mix and/or rotate herbicides with different modes of action to manage and minimize the risk of further development of glyphosate resistant weeds.

Volunteer glyphosate-tolerant corn in High Plains wheat /

corn / fallow

Best defense against developing glyphosate resistant weeds:

Avoid continuous, exclusive use of glyphosate for weed control

Crop rotation, especially with non RR cropsRotate and/or tankmix herbicides with different sites of action, within and across yearsInclude other control tactics (cultivation, prevention, crop competition, cultural practices)“Use the proper rate at the proper time”

Herbicide and Weed Information on Internet

KSU Weed Management: www.oznet.ksu.edu/weedmanagement/Pesticide labels, supplements, and MSDS sheets: www.cdms.net/Kansas Department of Agriculture: www.ksda.gov/default.aspx?tabid=1Weed Science Society of America: www.wssa.net/K-State Research & Extension: www.oznet.ksu.edu/

Dallas PetersonExtension Weed Specialist

[email protected]

getting the most out of glyphosate - kansas state university · getting the most out of glyphosate...

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