what we’ll talk about…...what we’ll talk about… 5/1/2018 7 dislodgeable foliar residues •...

5/1/2018

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Travis Gannon, PhDNorth Carolina State University

Department of Crop and Soil Sciences

• What is pesticide environmental fate?• Why is it important?

• Dislodgeable foliar residues• Why is it important???• Current research• Research implications• Best management practices

• Optimizing pesticide applications• Glyphosate• Questions

What We’ll Talk About…





Photo courtesy of: Sorochan and Brosnan Photo courtesy of: Sorochan and Brosnan

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Athletic Field Management

• Weeds (and other pests) can reduce playing surface strength and uniformity… • SAFETY CONCERNS!!!

Pesticide fate in turfgrass

Off-Target Pesticide Movement

1% 5% 10%

Hydrangeas treated with 1, 5 or 10% of 1X 2,4-D rate (1.42 lbs ai / A)

Off-Target Pesticide Movement

1% 5% 10%

Hydrangeas treated with 1, 5 or 10% of 1X fluroxypyr rate (0.15 lbs ai / A)

Preserve tools today, while providing information required

for the implementation of best application practices in the future

Pesticide Fate Research in Turfgrass…Why is it Important???

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• Keeping the right products on shelves• Reduces potential adverse effects on

off-target areas and species• Environmental, ecological

• Groundwater, surface water bodies

• Human health effects• Worker and non-worker exposure


• Keeping the right products on shelves• Reduces potential for adverse effects on





• Keeping the right products on shelves• MSMA

• August 10, 2006: EPA proposed ban on all organic arsenicals• January 16, 2009: MAA research task force reaches agreement with EPA• September, 2012: EPA announced continued use of stocks

• Athletic fields not on current labels

• 2,4-D• Public concerns intensifying regarding its use• Re-registered in 2013

• Imidacloprid• Linked to bee colony collapse• 2013 – European Union bans its use

• Glyphosate• IARC (WHO) classified as probable carcinogen (Group 2A)

• Sulfonylurea herbicides• Recent risk assessment


Arsenic from MSMA - Porewater

Figure 2. Arsenic concentrations in porewater from MSMA‐treated and non‐treated lysimeters.

• Through 200 DAT, porewater arsenic does not exceed 2 μg/L

• No difference in porewater arsenic concentrations for nontreatedand MSMA-treated lysimeters

Keeping the wrong products off shelves too…


Objective #2: Determine the effect of simulated herbicide drift into non-target areas.

• Aminocyclopyrachlor (AMCP)• Recently registered synthetic auxin herbicide• Thought to possess more favorable environmental profile• Highly active compound• Widely used in cool-season turf• Limited e-fate and off-target research available

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• Keeping the right products on shelves• Reduces potential for adverse effects on





Public Concern• Public concern about pesticide use

• “For the price of a green lawn, we are poisoning our children.” (Family Circle Magazine, 1991)

• Legislative bans introduced• Montgomery County, Maryland has become first major

municipality to ban use of pesticides on private lawns (Washington Post, Oct. 2016)

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OrganicMovementinSocietyinSomePartsofWorld Technology fears

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Some individuals are concerned

about a problem that doesn’t exist, yet not

concerned about an actual problem.





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Dislodgeable Foliar Residues

• “Residues that may be transferred to the skin as a result of contact and are available for dermal absorption or ingestion.” (EPA 1997)

Dislodged Pesticide = Human Exposure???

• It depends… (on a lot of things)

• Pesticide risk = toxicity + exposure• “The dose makes the poison” - Paracelsus

• Toxicity• LD50 – lethal dose required to kill 50% of a population

• Decreasing value = increasing toxicity

• Exposure• Acute

• Single exposure or multiple exposures in < 24 hr period• Chronic

• Repeated exposure over an extended period of time

Dislodged Pesticide = Human Exposure???

• It depends… (on a lot of things)

• Pesticide risk = toxicity + exposure• “The dose makes the poison” - Paracelsus

• Toxicity• LD50 – lethal dose required to kill 50% of a population

• Decreasing value = increasing toxicity

• Exposure• Acute

• Single exposure or multiple exposures in < 24 hr period• Chronic

• Repeated exposure over an extended period of time

2,4-Dimethylamine Salt (2,4-D)• POST broadleaf weeds• Registration dates

• 1944: United States (US)• 1950’s: Internationally

• Turfgrass use sites• Golf courses, sod farms, home

lawns, athletic fields, etc.• 2006 to 2007

• 34% of US use (7.3 million kg) was applied to non-cropland areas including turfgrass

2,4-dimethylamine salt

2,4-D Can Dislodge from Turfgrass

HIGH water solubilityKs = 796,000 mg L-1 (pH 5)

LOW soil sorptionKoc = 20 mL g-1

(Ks = 796,000 mg L-1 at pH 5)

(Koc = 20 mL g-1)

6:00:00 8:00:00 10:00:00 12:00:00

(Ks = 796,000 mg L-1 at pH 5)

(Koc = 20 mL g-1)

6:00:00 8:00:00 10:00:00 12:00:00

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• 24 hr prior to initiation area was: • Mown (clippings collected)• Irrigated to field capacity

• 2,4-D was applied: • to 2.5 x 13.3 ft plots (3 ft alleys)• via a single nozzle (8004 E), CO2-pressurized sprayer calibrated

to deliver 20 gal A-1 (lowest labeled carrier volume)• at 1.9 lb ai A-1 (highest labeled application rate)• at 14:00 to ensure foliage was dry and allow > 5 hr sunlight

Experiment Initiation Following Initiation• For 6 days plots were:

• not mown• covered during rainfall

• Dislodge measured 0, 1, 2, 3, 6, 12 & 24 d after treatment

• 2,4-D dislodge via soccer ball roll• Size 4 soccer ball for ages 8 to 12 yr (FIFA)

• Double-wrapped with a 5 by 120 cm absorbent material• Rolled over a 12 ft distance

2,4-D Dislodge Measurement

• Modified EPA method MRID 420453-01• High performance liquid chromatography–Diode array detector• LOD = 1 mg kg-1

Objectives

• Compare dislodgeable foliar residues:• over days after treatment (DAT) and time within a day

(TWD)• in overseeded vs non-overseeded bermudagrass• when irrigated vs. non-irrigated after treatment

Objectives

• Compare dislodgeable foliar residues:• over days after treatment (DAT) and time within a day

(TWD)• in overseeded vs non-overseeded bermudagrass• when irrigated vs. non-irrigated after treatment

6:00 8:00 10:00 12:00

• Dislodge measured daily at 5:00, 7:00, 9:00, 11:00 or 13:00 EST

Daily Fluctuations

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Effect of Time Within a Day (TWD) on Dislodgeable 2,4-D Over Time.a-c

____________________________________ DATd ___________________________________

TWDe 1 2 3 6 12f

________________________________ % of applied _________________________________

5:00 4.0 2.2 0.8 0.2 ND

7:00 3.7 2.0 1.0 ND ND

9:00 3.5 1.7 0.8 ND ND

11:00 0.5 0.0 0.0 ND ND

13:00 0.0 0.0 0.0 ND ND

LSD0.05____ 1.1 ____ ____ 1.3 ____ ____ 0.9 ____ NS ---

a Cheesecloth strip (104 in2) was wrapped twice around a soccer ball and rolled over a unique 2,4-D treated area (720 in2) at each collection timing.b (0 DAT – 0 hr – 11.3 % of applied) (0 DAT – 1 hr – 0.5% of applied)c Data averaged over two experimental runs.d Abbreviations: DAT, days after treatment; ND, non-detectable.e TWD presented are eastern standard time.f Data from 12 DAT not included in statistical analysis.


____________________________________ DATd ___________________________________

TWDe 1 2 3 6 12f

________________________________ % of applied _________________________________

5:00 4.0 2.2 0.8 0.2 ND

7:00 3.7 2.0 1.0 ND ND

9:00 3.5 1.7 0.8 ND ND

11:00 0.5 0.0 0.0 ND ND

13:00 0.0 0.0 0.0 ND ND

LSD0.05____ 1.1 ____ ____ 1.3 ____ ____ 0.9 ____ NS ---



____________________________________ DATd ___________________________________

TWDe 1 2 3 6 12f

________________________________ % of applied _________________________________

5:00 4.0 2.2 0.8 0.2 ND

7:00 3.7 2.0 1.0 ND ND

9:00 3.5 1.7 0.8 ND ND

11:00 0.5 0.0 0.0 ND ND

13:00 0.0 0.0 0.0 ND ND

LSD0.05____ 1.1 ____ ____ 1.3 ____ ____ 0.9 ____ NS ---



____________________________________ DATd ___________________________________

TWDe 1 2 3 6 12f

________________________________ % of applied _________________________________

5:00 4.0 2.2 0.8 0.2 ND

7:00 3.7 2.0 1.0 ND ND

9:00 3.5 1.7 0.8 ND ND

11:00 0.5 0.0 0.0 ND ND

13:00 0.0 0.0 0.0 ND ND

LSD0.05____ 1.1 ____ ____ 1.3 ____ ____ 0.9 ____ NS ---


Effect of TWD on Dislodgeable 2,4-D Over Time

0

1

2

3

4

5

% o

f ap

plie

d 2

,4-D

• Following application, 2,4-D dislodgeability decreases as:• TWD increases

• Trend only observed through 3 DAT• DAT increases

• 5 times more 2,4-D was dislodged at 5:00, 1 DAT than 5:00, 3 DAT

• More 2,4-D dislodged in subsequent morning than previous afternoon

• Dislodgeability changes as atmospheric conditions change• 2,4-D dislodgeability increases as:

• Relative humidity increases• (Air temperature – dew point) decreases• Leaf wetness increases• Time from sunrise decreases

Conclusions Days After Treatment and Time Within Day

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• Why is 2,4-D more dislodgeable in AM compared to PM???



• Why is 2,4-D more dislodgeable in AM compared to PM???• 2,4-D’s high water solubility coupled with climatic conditions favoring

wet turfgrass

• System characteristics affect 2,4-D dislodge• Can vary between turfgrass species• Canopy moisture presence increases dislodge• Can vary by sampling method

• To reduce 2,4-D dislodge• Irrigate areas 24 hours after treatment• Increase spray carrier volume

• 80 GPA > 40 GPA = 20 GPA• Use nozzles delivering coarse spray droplets

• AIXR > DG = XR

2,4-D Dislodge Conclusions Implications

So what does this all mean for human exposure?!?!?

Potential Human Exposure

1 ball roll = 2 in by 12 ft = 0.07% of field area*

15 y

d

20 yd

* Minimum recommended dimensions for < 6 yr children (US Youth Soccer Organization)*


• EPA 2,4-D doses for human risk assessment:• Short term dermal (< 30 d) = 25 mg kg-1 d-1

• Intermediate term dermal (1 – 6 mo) = 15 mg kg-1 d-1

• Long term dermal (> 6 mo) = 5 mg kg-1 d-1

• Average body mass of U.S. children, ages 2-3 = 14 kg• Short term: 25 mg kg-1 d-1 x 14 kg = 350 mg 2,4-D d-1

• Intermediate term: 15 mg kg-1 d-1 x 14 kg = 210 mg 2,4-D d-1

• Long term: 5 mg kg-1 d-1 x 14 kg = 70 mg 2,4-D d-1

E = 57 mg d-1 (one ball roll)Dermal absorption factor (EPA) = 10% = 5.7 mg 2,4-D d-1

Short term = 1.6% of allowanceIntermediate term = 2.7% of allowance

Long term = 8.1% of allowance

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• EPA 2,4-D doses for human risk assessment:• Short term dermal (< 30 d) = 25 mg kg-1 d-1

• Intermediate term dermal (1 – 6 mo) = 15 mg kg-1 d-1

• Long term dermal (> 6 mo) = 5 mg kg-1 d-1

• Average body mass of U.S. children, ages 2-3 = 14 kg• Short term: 25 mg kg-1 d-1 x 14 kg = 350 mg 2,4-D d-1

• Intermediate term: 15 mg kg-1 d-1 x 14 kg = 210 mg 2,4-D d-1

• Long term: 5 mg kg-1 d-1 x 14 kg = 70 mg 2,4-D d-1

E = 57 mg d-1 (one ball roll)Dermal absorption factor (EPA) = 10% = 5.7 mg 2,4-D d-1

Short term = 1.6% of allowanceIntermediate term = 2.7% of allowance

Long term = 8.1% of allowance

Best Management Practices to Minimize 2,4-D Dislodgement

• Turfgrass managers and athletic field schedulers should coordinate 2,4-D (and other pesticides) applications with events to provide an appropriate buffer period to minimize human exposure.

• Workers and non-workers should enter athletic fields treated with 2,4-D with caution for 2-3 d following application.• Data suggest afternoon hours are safe for re-entry

• Irrigate 2,4-D treated areas 24 hr following application




What We’ll Talk About… Pesticide Fate and Behavior

Cases of failed pest control!!!

Choosing the Right Formulation

Granular distribution Liquid distribution

Choosing the Right Formulation

Granular distribution Liquid distribution

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Unacceptable Annual Bluegrass control with Sulfonylurea Herbicides Applied Prior

to Overseeding Perennial Ryegrass

0

10

20

30

40

50

60

70

80

90

100

Per

cen

t C

ontr

ol

Annual Bluegrass Trials – Prior to Overseeding

Product:lb AI/A:

Product:lb AI/A:

Rim0.0039

Rim0.0039

Nic0.0078

Rim0.0078

Rim0.0078

Nic0.0078

Rim0.0078

Nic0.0156

Rim0.0156

Nic0.0078

Nic0.0156

Foram0.013

Rim0.0039

Rim0.0039

Nic0.0078

Rim0.0078

Rim0.0078

Nic0.0078

Rim0.0078

Nic0.0156

Rim0.0156

Nic0.0078

Nic0.0156

Foram0.013

0

10

20

30

40

50

60

70

80

90

100

Per

cen

t C

ontr

ol

Annual Bluegrass Trials – Prior to Overseeding

Product:lb AI/A:

Product:lb AI/A:

Rim0.0039

Rim0.0039

Nic0.0078

Rim0.0078

Rim0.0078

Nic0.0078

Rim0.0078

Nic0.0156

Rim0.0156

Nic0.0078

Nic0.0156

Foram0.013

Rim0.0039

Rim0.0039

Nic0.0078

Rim0.0078

Rim0.0078

Nic0.0078

Rim0.0078

Nic0.0156

Rim0.0156

Nic0.0078

Nic0.0156

Foram0.013

|----------------Applied Late SEP to Early OCT----------------||--------------------Applied Mid- to Late OCT--------------------|

Effect of temperature on LOLPE control (2 WAT)

Willis et al. 2007


Willis et al. 2007 Willis et al. 2007

Katana 1.5 oz/a Monument 0.33 oz/a Revolver 17.5 oz/a


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Effect of temperature on sulfonylurea herbicide efficacy

• Application timing, pest stage at time of application and environmental conditions have profound impact on efficacy– Temperature before, during and after application

affect herbicide efficacy


• Dislodgeable foliar residues• Why is it important???

• Current research

• Research implications

• Best management practices

• Optimizing pesticide applications• Glyphosate

• Questions


Glyphosate (background)• Glyphosate (Roundup®)

• Commercially released: 1974

• Highly efficacious non-selective herbicide

• Registered in >100 countries• Residential and commercial

settings

• EPSPS enzyme inhibitor • Targets shikimate acid pathway

• Pathway exclusive to plants

Glyphosate Fate• Physicochemical properties

• Very high soil–organic carbon coeff. (KOC = 24,000 mL g-1)• High to very high water solubility (KS = 15,700 mg L-1)• Moderate half-life in soil (T1/2 = 47 days) • Very low octanol–water partition coeff. (log KOW = –3.2)

• High KOC suggest glyphosate is essentially non-mobile• Leaching / runoff into water sources are not a concern

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PesticideOrganic carbon sorption coeff.

(mL g-1)

Water solubility(mg L-1)

Octanol-water partition coeff.

(log KOW)

LD50acute - oral - rat

(mg/kg-1)

Paraquat 1,000,000 620,000 -4.5 110

Cypermethrin 58,000 0.01 5.3 250

Glyphosate 24,000 15,700 -3.2 >5,000

Pendimethalin 17,200 0.275 5.2 >5,000

Halosulfuron 94 15 1.7 >5,000

Most to least toxic

Strongest to weakest



• Very low log KOW suggest, if human exposure occurs glyphosate has a very low tendency to bioaccumulate

PesticideOrganic carbon sorption coeff.

(mL g-1)

Water solubility(mg L-1)

Octanol-water partition coeff.

(log KOW)

LD50acute - oral - rat

(mg/kg-1)

Paraquat 1,000,000 620,000 -4.5 110

Cypermethrin 58,000 0.01 5.3 250

Glyphosate 24,000 15,700 -3.2 >5,000

Pendimethalin 17,200 0.275 5.2 >5,000

Halosulfuron 94 15 1.7 >5,000

Most to least toxic

Strongest to weakest

Historical Glyphosate Usage • Most applied herbicide globally

• >8.6 billion kg ai applied from 1974 – 2014 (Benbrook, 2016)

Estim

ated

use

in m

illio

n kg

Trends in Glyphosate Herbicide Use in the United States and Globally Benbrook (2016)

Historical Herbicide Usage In US

Estim

ated

use

in m

illio

n kg

Estim

ated

use

in m

illio

n kg

Glyphosate replaced much more toxic herbicides• Glyphosate LD50 = 5600 mg/kg-1

• Alachlor LD50 = 1150 mg/kg-1• Cyanazine LD50 = 334 mg/kg-1

• Metolachlor LD50 = 2150 mg/kg-1

aAcute Oral LD50 rat; Properties from WSSA Herbicide Handbook Shaner (2014)

Risk Assessment Concept

• A highly toxic material will present little risk of harm if exposure is limited to levels below that causing a response

• A low or moderately toxic material may present a measurable risk of harm if exposure is widespread, frequent, and/or prolonged at levels causing a response

Risk is a function of exposure and response

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Quantifying EffectDetermining “allowable daily intake” (ADI)

amount of exposure that should not cause a response

• 1st : Quantify no-observed-adverse-effect level (NOAEL)• Based on chronic oral exposure: 24-mo mice: NOAEL = 175 mg/kg/d-1

• 2nd : Account for “safety factor”• 10 (account for differences between species [humans vs. test animals]) • 10 (account for differences in sensitivity between humans [25 vs. 90 yr old])

• 3rd : 175 mg/kg/d ÷ 100 (safety factor) = 1.75 mg/kg/d-1

• ADI set forth by EPA where exposure should not cause a response

=

Safety Factors and Established of Acceptable Daily Intakes Renwick (1991)

IARC Grouping System

• Caffeine/tea • Magnetic fields • Cholesterol • Hair dye products


• Coffee• Aloe vera• Baby powder• Table salt


• Hairdresser profession

• Night shift workers

• Beef, pork, lamb• Fried foods




• Cured meats (bacon)

• Alcohol• Tobacco• Sunlight



Group 1Known

Carcinogen

Group 2A

Probable Carcinogen

Group 3Not

Classifiable

Group 2BPossible

Carcinogen

IARC Grouping System















Group 1Known

Carcinogen

Group 2A

Probable Carcinogen

Group 3Not

Classifiable

Group 2BPossible

Carcinogen

Communication Breakdown• Individuals may be scared of things they are unfamiliar

with and/or do not understand• Ex.) Ethanol (alcohol), sunlight and nicotine (tobacco) are all

classified as known carcinogens with many exposed to these agents at much greater levels than glyphosate but due to their prevalence, many individuals assume the risk

Probable to be carcinogenic to known to be carcinogenic

Communication Breakdown• Glyphosate in wine / beer example:

• 14 beer analyzed for glyphosate residue • Highest glyphosate concentration found:

• 29.7 µg/L • Lowest glyphosate concentration found:

• 0.5 µg/L

• In one liter of beer with highest level• 29.7 ppb of glyphosate • 999,999,970.3 ppb not glyphosate

“La pureza de la cerveza alemana en cuestión después de que el grupo ambiental encuentre rastros de herbicidas”




• 0.5 µg/L

• In one liter of beer with highest level• To reach allowable daily intake level set for

glyphosate, a 60 kg person would have to ingest 3536 liters of beer “La pureza de la cerveza

alemana en cuestión después de que el grupo ambiental encuentre rastros de herbicidas”

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• 0.5 µg/L

• If a beer contains 6.0% alcohol then it will contain ~60,000,000 ppb of the “known carcinogen” ethanol “La pureza de la cerveza

alemana en cuestión después de que el grupo ambiental encuentre rastros de herbicidas”

Communication Breakdown• Disconnect between science and public perception?

• Individuals can find news stories and sources that reaffirm their beliefs and/or opinion (conformation bias)

• Social media plays a significant role in the digital age • Anti-glyphosate groups have won in the court of public opinion

• Researchers can distribute all the science based education plausible and the reality is that less of those articles will gain traction compared to flashy headlines, like “Glyphosate is Killing Your Child”

Communication Breakdown• What can turfgrass managers do bridge the gap?

• Educate yourself on pesticide related topics

• Try to understand why individuals have their beliefs

• Realize you cannot win an argument on social media or by aggressively attacking an individual and their beliefs

• Express empathy to individuals who truly believe pesticides usage is a major concern to human and environmental health

Questions???

what we’ll talk about…...what we’ll talk about… 5/1/2018 7 dislodgeable foliar residues •...

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