Focus Meeting for Norflurazon: 

Registration Review and Endangered Species 

April 11 2013
2

Overview of Meeting Topics●Review of Use / Usage of Norflurazon

- Potential for pre-assessment label clarificatio

●Ecological Risk Assessment Considerations

- Geospatial analysis- Exposure refinements- Ecotoxicological refinements
Norflurazon Use
4

General Information: Overview

● First Registered in the U.S. in 1974● Currently approved for controlling weeds in:

- Aerial or ground applications

- cotton, peanut, soybean, alfalfa 

- Ground applications only

- almond, pecan, filbert, walnut- citrus, apple, apricot, avocado, cherry, nectarine, peach, pear, plum, p

- blackberry, raspberry, blueberry, cranberry, grape, hops, asparagus

- non-agricultural farmstead areas (other non-crop uses such as field gr

rights-of-way were cancelled in February 2013 by NuFarm/Riverdale

- no residential uses

● Used to control certain annual broadleaf weeds, grasses and sedges anof certain perennial weeds● Preplant Incorporated (PPI) and Preemergence (Pre) / No Postemerg● Section 24(C) for Solicam® DF in Arizona

Allows use via chemigation on alfalfa in LaPaz, Maricopa, GraMojave, Pinal, Cochise counties
5

Technical EPA Reg. 

No. Registrant Activ

Norflurazon Technical 100-839 Syngenta Crop Protection, LLC No

End Use Products

Solicam®

(WDG) 100-849 Syngenta Crop Protection, LLC No

Evital® 5G (Granular) 5481-506 AmVac Ag (Cranberry use Only) No

Recent Norflurazon Product Registration Cancellation :

- Predict® : Riverdale Product, EPA Reg. No. 228 – 399

(Federal Register vol. 78, No. 25, Feb. 6, 2013)

Cancellation Request Pending (Per Syngenta Letter to EPA February 6, 2

- Zorial® Rapid 80 : Syngenta Crop Protection, LLC, EPA Reg. No. 100-8

Registered Products
6

General Information: Overview

● Mechanism of Action: Inhibitor of phytoene desaturase (PDS

in the pathway for carotenoid production

● Bleaching symptoms● Uptake of norflurazon is solely through the root system● Weed Resistance to this mode of action has only been docume

weedy species in the United States:

- Hydrilla resistant to fluridone in aquatic systems (Internat

of Resistant Weeds: weedscience.com), but norflurazon hauses

● Only herbicide with this mechanism of action in tree crops● Provides a tool for a herbicide resistance management progra
7

Norflurazon Maximum Rates and Application 

Use

Max. Single Appl. 

Broadcast Rate

lb. product/acre

(lb. a.i./acre)

M

Peanut 1.8 (1.4) 

Alfalfa, Cotton and Soybean 2.5 (2.0) 

Almond, Pecan, Filbert, Walnut, 

Apple, Apricot, Avocado, Cherry, Nectarine, Peach, 

Pear, Plum, Prune, Grape 

Blackberry, Raspberry, Blueberry, Hops and Asparagus 

5 (3.9) 

Citrus (broadcast, band, ring drench, chemigation) 5.0 [10.0*] (3.9) 

Cranberry (AmVac, 5GR) 160 (8.0) 

Non-Agricultural Farmstead Areas 5 (3.9) 

* Newly planted non-bearing trees as a ring drench, FL only.
8

Norflurazon – Use for Newly Planted Non-Beari

in Florida

Treated Citrus trees with SolicamRings 3, 4 or 5 ft. diameterExample: mix 2.6 ounces Solicam in 500 gal. water

Apply 5 gallons per tree in a 3-foot diameter circle a
9

Label Considerations for Risk Assessm

Use Restrictions (Example)

● Crop use rates and number of applications vary greatly depending on g

type, organic matter

Region Soil Texture

Broadcast 

Rate

(lb. Product 

/Treated acre)

(lb. a.i./A)

Oth

Cotton

Solicam DF can be used for weed control in all cotton producing states except CA

clay loam, silty clay loam, silty clay, clay 2.5 (2.0) single o

loam, silt loam, silt, sandy clay loam, sandy clay and Coastal Plains Soils (SE US)

0.95 – 1.9

(0.75 – 1.5)

Do not uthan 1.2on coarsPlains s

sand, loamy sand, sandy loam 0.625 – 1.25

(0.50 - 0.98)

Special directions for TX (West of I-35), Southwest OK and NM

0.60 – 1.0

(0.47 – 0..79)

In AZ, apply Solicam DF preplant incorporated only

0.65 – 1.25

(0.51 – 0.98)
10

Label Considerations for Risk Assessme

Drift Management

● Ground Application (min. 10 gpa)

- Intend to add spray drift reduction measures for ground applications

- Boom must not be higher than 20” above canopy- Use nozzles that product coarse spray droplets and provide uniform cov

- Wind speed and direction requirements

● Aerial Application (min. 5 gpa)

- Use a drift control agent such as Nalco-Trol®- Outermost nozzles should not exceed 3⁄4 of the wingspan or rotor- Apply large droplets

- High flow rate nozzles- Spray released parallel to airflow- Narrow spray angle nozzles, low-drift nozzles

- Apply no higher than 10 ft. above the canopy- Adjust swath for crosswind- Avoid application if wind is < 3mph, minimal drift when wind is 3-10mph

- In low humidity, increase droplet size to compensate for evaporation

- Do not apply during temperature inversion- Only apply when the potential to drift to adjacent sensitive areas is minima

blowing away from the sensitive area)
11

Potential Early Risk Reductio

Measures

• Remove all non-agricultural farmstead uses from • Clarify DFU’s for ring drench applications to new

nonbearing citrus in Florida

• Label clarification for ground applications to min

spray drift potential 

• Improve application directions in regard to wind 

aerial applications
Application of Geospatial Analysis 

& Refinement 
Geographic Scope of Potential Norflurazon Use

Counties 

● Major uses based on recent survey data are citrus, a

almond

* The maps show citrus, apple, and almond production counties reported in the 2007 Census of Agriculture. 
14

Geographic Scope of Norflurazon Uses –So

● GfK Kynetec use survey data provides annual pesticide product use d

Crop Reporting District (CRD) level 

● California Pesticide Use Reporting (PUR) Data ● Confidential marketing sales data can be shared under CBI● Information from growers and other experts
15

Norflurazon Use Pattern in CA: Total Annu

(2001 to 2010)

Use (Lb A.I.)

Use (Lb A.I.)
16

Considering Geographically Specific Label 

(CA example)

Use Use in CA EFED Crop Group Max. Annual Appl. Rate (lb a.i./ acre) 

Citrus Y Orchards and grapes 3.9Citrus N Orchards and grapes 7.9 Irrigated Citru

Apples Y Orchards and grapes 3.9

Avocado Y Orchards and grapes 3.9 depends 

Filbert Y Orchards and grapes 3.9 depends 

Nectarine Y Orchards and grapes 3.9 depends 

Peach Y Orchards and grapes 3.9 depends Pecan Y Orchards and grapes 3.9 depends 

Apricot Y Orchards and grapes 3.9 depends 

Pear Y Orchards and grapes 3.9 depends 

Prune Y Orchards and grapes 3.9 depends 

Walnut Y Orchards and grapes 3.9 depends 

Almond Y Orchards and grapes 3.9 depends 

Cherry Y Orchards and grapes 3.9 depends 

Grape Y Orchards and grapes 3.9 depends 

Blueberry Y Vegetables and ground fruit 3.9 depends 

Blackberry Y Vegetables and ground fruit 3.9 depends 

Raspberry Y Vegetables and ground fruit 3.9 depends 

Asparagus Y Vegetables and ground fruit 3.9 depends 

Hop Y Other crops 3.9 depends 

Cranberry N Vegetables and ground fruit 8.0 depends 

Cotton N Cotton 2.0 Br

Soybean N Corn/soybeans 2.0 Br

Alfalfa Y Hay/forage/silage 2.0 Br

Peanuts N Other row crops 1.4 Br

Non-Ag uses Y No Ag 3.9 depends 
19

Geospatial Data (Species)

• Species Information available at National Level 

 Federally Listed Species Information: U.S. Fish and Wildlife Service Threatened and E

Species System (TESS, accessible at URL: http://ecos.fws.gov/tess_public/) 

 Threatened & Endangered Species

 Critical Habitats: U.S. FWS Critical Habitat Portal [URL: http://criticalhabitat.fws.gov]

 Additional spatial data digitized by Syngenta GIS Lab

• Work products of FIFRA Endangered Species 

Task Force (FESTF)

 Information Management System (IMS): The 

IMS system contains the county-level species data provided from US EPA/US FWS and crop data from the USDA Census of Agriculture & Biological information. 

 Multi-Jurisdictional Database (MJD): The 

FESTF MJD provides an extensive database that contains location-specific information provided by NatureServe, along with its member Natural Heritage Programs and Conservation Data Centers.

 Proximity Database: The access database includes 

proximity distance calculation using nature serve location data and 2006 NLCD.
An Example of Geospatial Data Matr

Pesticide Use/ Crop Area 

Hydrology Land use

Species 

Local States Regional National 

2006 NLCD

High 

Resolution 

Elevation 

State Use 

Reports 

NS-MJD

NS-IMS

GAP Land Cover 

Recovery Plan NOAA Regional office

FWS Regional 

office

FWS CH portal

NHD Plus

CAL Water

CAL Fish

Ag Census data

NASS CDL

CNDDB (CA)

NWI Data 

State land 

cover data 

Other Spatial 

Data 

NAWQA/NWIS/STORET 

Monitoring Data 

Satellite/ 

Aerial 

Images 

Steamnet.org

GfK Survey 

State or research water quality 

monitoring program 

Bird Migration 

Monitoring data

PUR 

Database

Data Layers 

• Standardizing/updating best available spatial data matrix is necessary to ens

“the best scientific and commercial data available”. 

FWRI (FL) 

Label 

Biological 

Data 

Elevation 

(NED)
23

Quantitative Image Analysis Approach to Monitor Vegetation Changes in Riparian 

• Long-term free satellite images collected from historical product use locations. • Using Vegetation Index (indicator of vegetation health/biomass growth), proved no changes in vegetation stability within riparian zone near our product use areas. 
Examples of exposure refinements
25

Aquatic Exposure

● Potential refinement to the standard EPA PRZM/EXAMS modeling (

pond):

- Selection of a more appropriate SAMSON weather station.- Use of more representative weather data.- Selection of a crop/use scenario that is more appropriate for the no

being modeled.

- Identification of a soil that is more representative of the norflurazo

within habitat of concern.

● The level of refinement performed will vary over the different uses be

Some uses may require no refinement, while some may require that alabove be considered. 

● Simulated application dates are based on historical data when availab

or supplementary information) to describe the likely application dates

● Simulation using flowing water body when applicable.
26

Example Refinement of Standard Scenar

Norflurazon use on Almonds in CA 

● EPA standard scenario for almonds (CAalmond_WirrigSTD):

- Weather station: Sacramento (1961 – 1990)- Representative location: San Joaquin County - Soil: manteca fine sandy loam, hydrologic group C- Application rate: 5 lb/acre (product) 3.93 lb/acre (ai)

● Refinements applied:

- Weather station: highest concentration of potential almond use sit

CRLF habitat occurs in northern San Benito County and Southern County. 

- Application rate: norflurazon use on almonds requires application 

dependent upon soil texture. 

- Runoff potential: curve numbers for the almond scenario were mo

more accurately reflect the vegetation characteristics of the orchar
27

Example Location of Standard and Refined 

Stations Relative to Almonds in CRLF H

● The Sacramento weather station is close 

to almond growing areas, however, the Salinas weather station is closest to the concentration of almond growing areas within CRLF habitat.
28

Example Refinement of Standard Scenario for Norfluraz

Almonds in CA, Results 

● Refinement of the weather station to one more representative o

in CRLF habitat resulted in a modest (~4 ug/L) reduction in th

● Using the correct application rate for the soil type, had a signif

on the peak EEC, lowering it further by ~ 50%.

● The use of more appropriate CN values for typical orchard agr

practices resulted in additional ~25% reduction in the peak EE

Scenario

App Rate

(lb ai/ac) Weather Curve Numbers

90th %‐

EEC (

CAalmond_WirrigSTD 3.93 Sacramento (EPA) Standard 30

CAalmond_WirrigSTD 3.93 Salinas, 1981 ‐ 2010 Standard 26

CAalmond_WirrigSTD 1.96 Salinas, 1981 ‐ 2010 Standard 13

CAalmond_WirrigSTD 1.96 Salinas, 1981 ‐ 2010 Adjusted 9.
29

A Probabilistic Static Pond Modeling App

● The EPA standard farm pond scenarios are based on a hypothetical p

single “representative” soil. The soil may be more associated with the modeled than the geographic location it is intended to represent.

● Alternative approach:

- Identifies a population of representative ponds within a geographi

interest

- Links local weather conditions with each pond - Characterizes actual crop potential use site extent (PCA) for each - Characterizes actual soil conditions co-occurring with use sites aro

pond

● PRZM/EXAMS simulations are run for each pond

- Standard farm pond characteristics are unaltered - Weather, soils, crop uses, and PCA vary for each pond

● Ponds can be ranked according to EEC and overall “risk” assessed.
30

Ponds in CRLF Habitat (Example from Pr

CRLF Assessment)

● Approximately 5,000 small ponds are found within CRLF habit● A relatively small fraction of those are within close proximity to 

areas and potential pesticide use sites.
31

Flowing Water Body

Hydrologic flow should be incorporated in modeling exposure concentrflowing water bodies.

0.00.20.40.60.81.0

Relative concentration (C/Cmax) 012345678

Year

PRZM/EXAMS predicted normalized concentration using low flow 

static versions of EPA farm pond compared with observed residu

Flowing farm pond No flow farm pond Observed re
Flowing Water Body (Example from Prom

CRLF Assessment)

Inclusion of physically based watershed scale model such as SWAT. ProCRLF modeling indicated highest peak EEC of 63.2 μg/L (static), 8.1 μ(flowing, SWAT) and 3.1 μg/L (monitoring data).
Norflurazon Surface Water Monitoring D

• An extensive database of environmental monitoring results was com

from nine federal, state and other monitoring programs.

• 25,998 surface water samples collected between August 1983 and Fe

2012
Source Sampling Duration /Number of samples % Detection (# of detect/ # of total samples) Maximum Concentration in μg/L (State of sample location) 

USGS NAWQA

18 years, 

8052 samples

7.5% 

(600/8052) 7.3 (MS) 

5 years,

557 samples

51%

(284/557) 6.1 (MS) 

USGS NWIS

29 years,

11650 samples

7.0% 

(812/11650) 96 (MS) 

4 years,

628 samples

54% 

(339/628) 7.38 (MS) 

EPA STORET 9 years, 588 samples 22.3% (131/588) 87 (FL) 

CDPR 17 years, 1199 samples 11.8% (141/1199) 1.49 CEDEN 3 months, 111 samples 6.3 % (7/111) 0.256 CILRP 5 years, 224 samples 22.8% (51/224) 1.4 OR DEQ

10 years, 

1329 samples

3.4% 

(45/1329) 0.489 

1 year, 

1 sample

100% 

(1/1)

0.021 

WA EIM 19 years, 2845 samples 8.5% (242/2845) 9.5 

SFWMD 

(Schuler and Rand, 2008)

17 years

2063 samples na 3.9 

Water Quality Monitoring Data: Basic Sta

* Bold values for the monitoring data statistics for demethyl-norflurazon (meta
35

Agency

Number of 

samples 

(sites)

Sites with > 

100 

samples

Sites with > 

25 samples Frequency descr

USGS NAWQA 380 (33) 0 4 Few days apart, weekly, bi-w

frequency is dependent on the 

USGS NWIS 550 (68) 0 6

Dependent on site location, raweekly, bi-weekly, monthly, sand yearly

EPA STORET None NA NA Irregular, ranges from 1 per s

month for a few months

CA DPR 1199 (96) 2 9 Ranges from 2 days, weekly, 

irregular spaced sampling

CA CEDEN 111 (29) 0 0 Ranges from 2 weeks apart to 

several times per year

CA ILRP 224 (22) 0 0 Ranges from 2 weeks apart to 

several times per year

Water Quality Monitoring Data in CA

Sampling Frequency
Surface Water Monitoring Data in Califo

CA DPRMax 1.49 μg/L, 95thpercentile 0.648 μg/L CRLF boundaries: 3 sites, 17 samplesNo detects CEDENMax 0.256 μg/L , 95thpercentile 0.256 μg/L CRLF species habitats boundaries: No samples and detects

E9 sN

CILRPMax 1.4 μg/L, 95th percentile 

1.34 μg/LCRLF species habitats 

boundaries: No samples and detects
37

Example Terrestrial Plant Exposure: Runoff R

Using PRZM Runoff Flux

Input Parameter Value (lb/A)

Application Rate 2

Runoff Fraction 0.02 

Drift Fraction 0.01

Input parameters for TerrPlant used to derive EECs

EEC = TerrPlant Runoff Fractions + TerrPlant Drift Fraction

Refined EEC = PRZM Runoff Fractions + TerrPlant Drift Fraction

EEC = 0.02 (2 lb/A) + 0EEC = 0.04 lb/A + 0.02 EEC = 0.06 lb/A 

Input Parameter Value (lb/A)

Application Rate 2

Runoff Fraction

Output from 

PRZM 

Scenario

Drift Fraction 0.01

EEC = 0.0014 lb/A + 0.0EEC = 0.0014 lb/A + 0.0EEC = 0.0214 lb/A 

Input parameters for TerrPlant and output from 

PRZM runoff used to derive EECs

Hypothetical scenario
Ecotoxicological Refinements
39

0.00.20.40.60.81.0

1 10 100 1000 

Proportion of Taxa Affected

Concentration (μg

Effects: Species Sensitivity Distributions (

SSDs are useful for assessing effects at the community-level. Functional redundancy is prevalent in many ecosystems and therefore the reduction or loss of a species is unlikely to alter ecosystem function. Structural shifts ≠ Functional 

change.

Examples of functional redundancy Slight structural shifts in aquatic plant communities are unlikely to alter primary productivity and shelter availability in ecosystems. Similarly, in complex freshwater food webs, the prolonged existence of predators is unlikely affected by reductions in select prey species. 

Norflurazon SSD for aq
40

Effects: Appropriate HCx value for SS

Log Concentration

% of Taxa Affected

0

100

90

8070

60

50

4030

20

10

Log Concen

% of Taxa Affected

0

100

90

8070

60

50

4030

20

10

Mode of action (Norflurazon)Non specific / narcosis

Invertebrates and Vertebrates Plants

Effect endpoints used for SSDLethality

Mode of action (Norflu

Inhibits carotenoid biosinhibiting phytoene des

Effect endpoints used 

Sublethal, growth 

Recovery following exposure

Not applicable.

Recovery following ex

Effects are reversible (W

HC5 HC
41

Effects: Probabilistic and statistical techn

Incorporation of probabilistic statistical techniques for ecological ris
42

Effects: Aquatic Plant Endpoints for SS

Erickson (2010) details issues with interpreting and applying plant toxicity test results in Proposed Methodology for Specifying Atrazine Levels of Concern for Protection of Plant Communities in Freshwater Ecosystems.ECs are affected by:

1) Test duration2) Observation interval 3) Endpoint 

- absolute biomass (AB)

- growth- specific growth rate (SGR)

Absolute biomass may be misleading. 

“When control growth is just a doubling of biomass 

over the duration of the test, an EC50 for absolute 

biomass actually represents no growth.”

Example: This illustration values derived from SGR endpoints for aquatic plannorflurazon over time. It why SGR may be more u

0

50

100150200250

Day

2 4 6 8 

0

50

100150200250

Vasc

Non-v

Absolute Growth

EC50 (μg/L) Specific Growth Rate

EC50 (μg/L)
43

Effects: Terrestrial Plant SSD

RyCoCuMuOaCa

Using data from laboratory Co

toxicity tests with crop 

species as a surrogate for 

assessing risk to terrestrial 

plant communities is likely 

highly conservative.

To account for the complexity of plant 

communities in riparian habitats, the 

use of non-crop toxicity data in SSDs 

should be considered. 
44

Duration of exposure (d)

0 20 40 60 80 100

Basing EECs on study duration

Selecting the most appropriate exposure duration for evalua

ACUTE

CHRONIC

ACUTE

CHRONIC

21-d EEC 60-d EEC

ELS

CHRONIC

Similar con

for terrestri

ACUTE/ CHRONIC

Peak EEC
45

Risk Quotient > Endangered Species Level of Concern (Acute = 0.1 / 

Effects: Risk Quotients Derived from T-REX 

The user manual for T-REX v.1.5 states:

“The risk assessment includes numerous calculations of dietary exposure for m

classes of animals. However, there are energetic considerations which suggest 

class/food item combinations are not likely to occur naturally. For example, thto be many 15 g mammals or 20 g birds that exclusively feed on vegetation. Thurged to consult such texts as the Wildlife Exposure Factors Handbook (USEPA will provide more comprehensive approaches for considering energy requiremeavailability to estimate dietary exposure.”

Will all or only environmentally relevant weight class/food item compaT-REX v.1.5. be considered for future risk assessments?

Example: Output from T-REX v.1.5 based on hypothetical mammalian toxicity endpoints 

pattern. 

15 grams

Acute Chronic

Short Grass 0.26 2.45Tall Grass 0.12 1.12Broadleaf plants 0.15 1.38Fruits/pods 0.02 0.15Arthropods 0.10 0.96Seeds 0.00 0.03

Dose-based RQs (Dose-based EEC/LD50 or 

Small mammal
46

Discussion / Next Steps●How to incorporate use clarifications / changes 

risk assessments?

●Refinements for risk assessments – process for 

changes to inputs for risk assessments?

●Future timing of assessments / meetings / discu

norflurazon?