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OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

 

PC Code: 080818

DP Barcodes: 356140, 367446

 Date: April 15, 2010

MEMORANDUM

SUBJECT: Memorandum: Revised Spray Drift Modeling and Terrestrial Plant Risk 

Characterization in Support of the Section 3 Registration of the New Chemical 

Indaziflam (BCS-AA10717)

TO: Erik Kraft, Chemical Review Manager

Jim Tompkins, Risk Manager 

Registration Division (7505P)

FROM: Alicia Korol, Biologist

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

REVIEWED

BY: Melissa Panger, Acting Risk Assessment Process Leader

Chuck Peck, Environmental Engineer

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

APPROVED

BY: Mark Corbin, Acting Branch Chief

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)
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EFED has re-evaluated the spray drift exposure of indaziflam on terrestrial plants based 

on registrant-proposed label revisions (Attachment 1). Changes to the AgDRIFT modeling have 

been made to the exposure inputs, while the effects endpoints used to determine spray drift 

buffers have remained unchanged (Table 1). The exposure inputs for AgDRIFT are presented in 

Table 2. Four broad categories of uses were modeled based on applications to food (i.e., citrus 

fruit, stone fruit, pome fruit, grapes, tree nuts, pistachios, and olives), turf, forested areas

(including Christmas tree farms), and a combination exposure scenario reflecting applications to

roadsides, rights-of-ways, site preparation and others. Based on proposed ground application 

labeling revisions to droplet size specification, all ground applications were modeled assuming 

an American Society of Agricultural & Biological Engineers Standard 572 (ASAE)

1 MediumCoarse distribution. Additionally, based on proposed turf use label restrictions for release 

heights of no greater than (≤) 2-3 feet, turf use was modeled assuming a low boom height. 

EFED chose to model the ≤ 2-3 feet requirement as a low boom height (20 in) rather than high 

boom height (50 in), the only release height parameter inputs in Tier I AgDRIFT, to avoid 

overestimating exposure. Recommendations for potential label revisions to the ≤ 2-3 feet release 

height language are provided under the Labeling Recommendations section below.

In re-evaluating the spray drift exposure estimates, EFED reconsidered the protectiveness 

of employing AgDRIFT’s orchard scenario to model food use applications; a ground application 

exposure was found to be a more appropriate modeling scenario for these uses. Modeling inputs

are presented in Table 2. 

For purposes of investigating the influence of input parameters on exposure estimates,

EFED modeled three exploratory scenarios that would reduce overall spray drift exposure. An 

alternative ground application exposure for food uses was modeled assuming a low boom height. 

Two alternative aerial application exposures were modeled assuming ASAE Medium to Coarse 

and ASAE Coarse to Very Coarse droplet size distributions. These scenarios are highlighted in 

Table 2. 

Table 1: Toxicity Endpoints used to Determine a Spray Drift Buffer for Terrestrial Plants

Test Type / Crop Most Sensitive 

Study Species

NOAEC 

(lbs a.i./A)

EC25

(lbs a.i./A)

Most Sensitive 

Parameter

Seedling Emergence:

Dicot

Oilseed Rape 0.00011 0.000062 Emergence

Table 2: AgDrift Exposure Input Parameters

Use Application 

Type

Label Application 

rate (lbs a.i./A)

Droplet Size Boom

Height1

Food Ground Indaziflam 200 

SC; Indaziflam 

500 SC

0.085 ASAE FineMedium/

Coarse

Low Boom

Ground Indaziflam 200 

SC; Indaziflam 

500 SC

0.085 ASAE FineMedium/

Coarse

High Boom

 

1 The American Society of Agricultural Engineers (ASAE) became the American Society of Agricultural and 

Biological Engineers (ASABE) in 2005. ASABE standards are labeled "ASAE" rather than "ASABE" since 

standards were developed before the name change.
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Use Application 

Type

Label Application 

rate (lbs a.i./A)

Droplet Size Boom

Height1

Turf2 Ground BCS-AA 

10717 20WSP

0.017 ASAE FineMedium/

Coarse

Low Boom3

Roadsides/Rightsof-way/Site 

Preparation/

Other3

Ground Esplanade 200 

C

0.089 ASAE FineMedium/

Coarse

High Boom

Forested Areas Ground Esplanade F 0.125 ASAE FineMedium/

Coarse

High Boom

Aerial Esplanade F 0.125 ASAE FineMedium4N/A

Aerial Esplanade F 0.125 ASAE 

MediumCoarse

N/A

Aerial Esplanade F 0.125 ASAE CoarseVery CoarseN/A

1 Tier I Low boom height = 0.508 m (20 in); Tier I High boom height = 1.27 m (50 in) 

2 Established turf in areas such as parks, cemeteries, gold courses, sod farms, sports fields, home and commercial 

lawns. 

3 Other uses include: railroads, railway yards, bareground, landscape plantings on roadsides, ornamentals, dormant 

woody or conifer plant species, hardscapes

4 Label specifies droplet size of 150-200 microns

Dissipation to the EC25 and no effect level was modeled in order to provide potential 

buffer distances that are protective of nonlisted and listed terrestrial plant species, respectively

(Table 3). As in Table 2, exploratory scenarios are highlighted. The results of AgDRIFT 

modeling show that levels of concern (LOC) for terrestrial plants are exceeded from 62 ft to 

greater than ~1,000 feet from the site of application, with risk extending furthest for forested 

area uses and extending the least for turf uses. The AgDISP model was used to refine spray drift

exposure estimates from aerial applications to forested areas based on proposed management 

practices, e.g., boom length along aircraft wing and spray volume rate; however, the refined 

estimates were not found to reduce the LOC for terrestrial plants below ~1000 feet from the 

application site.

Using the proposed labeled spray drift restrictions, spray drift buffers of 62 feet for turf

uses would be necessary to reduce spray drift deposition below the non-listed species LOC, 

while for listed species these buffers would need to be 131 feet. These distances are lower than 

the previously calculated turf use buffer distances of 341 feet for nonlisted species and 528 feet 

for listed species, based on assumptions of an ASAE Very Fine to Fine spray droplet distribution 

and a high boom height. For food uses, buffers ranging from 466 to 640 feet would be necessary

to create spray drift deposition below the level of concern for non-listed plants, and at a 

minimum of 843 feet for listed species. Buffers at, or greater than, 666 feet are needed for 

ground and aerial applications to roadsides/rights-of-ways/site preparation/other and forested 

areas. 

To further characterize the exposure to terrestrial plant species, RQs per use pattern were 
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developed for spray drift exposures ranging from distances of 0 (on the field) to 950 feet off the 

field. Figure 1 depicts the nonlisted species RQs relative to distances off field, while Figure 2

depicts the listed species RQs relative to distances off field. 

Table 3: Summary of AgDRIFT Modeling Results for Listed and Non-Listed Terrestrial

Plant Species By Use Pattern

Use1

(Single Max 

Application Rate)

Distance (ft) from edge of field where 

LOC is no longer exceeded –

Ground Application 

Distance (ft) from edge of field 

where LOC is no longer exceeded 

— Aerial Applications

Non-listed Plants2 Listed Plants3 Non-listed 

Plants2

Listed Plants3

Food – Low Boom

(0.085 lbs ai/A) 466 843 - -

Food – High Boom

(0.085 lbs ai/A) 640 >997 - -

Turf

(0.017 lbs ai/A) 62 131 - -

Roadsides/Rights-ofway/Site Preparation/ 

Other 

(0.089 lbs ai/A)

666 >997 - -

Forested Areas 

Fine-Med/Coarse

(0.125 lbs ai/A)

896 >997 >997 >997

Forested Areas 

Med-Coarse 

(0.125 lbs ai/A)

-- -- >997 >997

Forested Areas 

Coarse-Very Coarse 

(0.125 lbs ai/A)

-- -- >997 >997

1 Only proposed uses of indaziflam for broadcast spray via ground or aerial methods were modeled with AgDrift. 

2 Most sensitive terrestrial plant EC25 = 0.00011 lbs a.i./A (1.1x10E-4 lbs a.i.A)

3 Most sensitive terrestrial plant NOAEC = 0.000062 lbs a.i./A (6.2x10E-5 lbs a.i./A)
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0

1

10

100

1000

0 100 200 300 400 500 600 700 800 900 1000

Distance from Edge of Field

RQ

Food_Low Boom

Food_High Boom

Turf

Roadsides/Rights-of-way/Site Preparation/Other

Forested Areas_Ground

Forested Areas_Aerial_Fine/Medium

Forested Areas_Aerial_Medium/Coarse

Forested Areas_Aerial_Coarse/Very Coarse

Figure 1: RQs for the most sensitive nonlisted terrestrial plant exposed to spray drift from 

proposed broadcast uses of indaziflam. The risk to nonlisted species LOC is 1.0 (RQ = 1.0).

0

1

10

100

1000

0 100 200 300 400 500 600 700 800 900 1000

Distance from Edge of Field

RQ

Food_Low Boom 

Food_High Boom

Turf

Roadsides/Rights-of-way/Site Preparation/Other

Forested Areas_Ground

Forested Areas_Aerial_Fine/Medium

Forested Areas_Aerial_Medium/Coarse

Forested Areas_Aerial_Coarse/Very Coarse

Figure 2: RQs for the most sensitive listed terrestrial plant exposed to spray drift from 

proposed broadcast uses of indaziflam. The risk to listed species LOC is 1.0 (RQ = 1.0).
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Based on this analysis of spray drift exposure and resulting RQs at carrying distances 

from the field, non-listed species LOCs for terrestrial plants are not exceeded with buffers of ~ 

60 feet for turf uses. Likewise, for turf uses, listed species LOCs are not exceeded with buffers 

of ~130 feet. These LOC exceedances apply to direct effects to listed terrestrial plants and any

listed species that has an obligate relationship with terrestrial plants (i.e., 130 ft buffer), and 

indirect effects for listed species that rely on terrestrial plants but are not obligates (i.e., 60 ft 

buffer). Furthermore, indirect effects to other taxa that rely on terrestrial plants may also occur. 

For all other uses, buffer distances < ~450 ft would not preclude risk of indaziflam toxicity to 

off-field nonlisted and listed species of terrestrial plants, but they are expected to reduce the 

number of species ultimately affected.

Labeling Recommendations

The following label recommendations apply to proposed Esplanade F and BCS-AA10717 

20 WSP formulations.

 The proposed Esplanade F formulation label states, “To reduce the potential for drift, 

apply large droplets (i.e., 150-200 microns) under low spray pressure”. This range 

overlaps the lower drop size classification regime of ASAE Very Fine to Fine, and the 

next higher, ASAE Fine to Medium droplet size distribution. Label specification of a 

volume median diameter (VMD), Dv0.5, of 255 microns for spray droplets would reduce 

ambiguity because 255 microns is the median diameter for an ASAE Fine to Medium 

droplet size distribution

 Proposed revisions to the BCS-AA10717 20 WSP formulation label (Attachment I) 

require that “For use on golf courses and commercial lawns, the boom height must be no 

higher than 2-3 feet above the ground...” EFED modeled a ground application to turf 

assuming a low boom height (20in) rather than a high boom height (50in) to avoid 

overestimating exposure. However, the distance from the application site where the risk 

to plant species LOC is exceeded is potentially underestimated for boom heights greater 

than 20in (up to 36in). EFED recommends that the specific boom height for turf be 

restricted to boom heights no greater than 2 feet (24in). 

The following label recommendations are relevant to the exploratory, reduced exposure 

scenarios modeled above and apply to the Esplanade F, Indaziflam 200 SC, and Indaziflam 500 

SC formulations. 

 EFED recommends that the Esplanade F label explicitly specify the drop regime to be

either ASAE Medium-Coarse or ASAE Coarse-Very Coarse for aerial applications. 

Alternatively, the label could explicitly specify the Dv0.5, equal to 341 microns for ASAE 

Medium-Coarse and 439 microns for ASAE Coarse-Very Coarse.

 For the Indaziflam 200 SC and Indaziflam 500 SC labels, formulations for food use, 

EFED recommends that a boom height no greater than 2 feet (24in) be specified.

 
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Attachment 1

Indaziflam and Drift Potential with Spray Applications 

Bayer is proposing to add to their commercial end-use indaziflam labels certain spray parameters 

to reduce drift. Since spray drift is not an issue for granular applied herbicides, Bayer assumes 

that granular applications are okay to use without further spray drift language. Since homeowner 

applications are made with either hose-in or hand wand applicators, Bayer believes that label 

language on the consumer (Bayer Advanced) products is adequate. 

is a pre-emergent herbicide with very little post-emergent activity. This has been seen in efficacy 

testing with the compound and is confirmed by the seedling emergence and vegetative vigor data 

submitted to the Agency. Pre-emergent applications of indaziflam to turf are made using spray

volumes and spray pressures that are conducive to reducing the potential for spray drift. In the 

unlikely event of spray drift onto non-target plants, any small amount of spray drift from 

indaziflam applications that reaches non-target plants will have little, if any, adverse effects. In 

order for indaziflam to have any effect on non-target seeds, it would need to get through any

vegetation that is present and be moved down into the soil to the non-germinated seeds. 

However, any small amounts of indaziflam reaching the non-target plants will already be at sub 

lethal dosage and will be further degraded on the plant and the soil surface before reaching any

non-germinated seed. In most cases, the first contact from spray drift will be existing vegetation 

and not bare ground. Therefore, the consideration of a spray buffer for the indaziflam label 

should be based upon vegetative vigor data rather than seedling emergence. 

Proposed label language: 

SPRAY DRIFT MANAGEMENT 

Ground Application

Spray equipment and weather affect spray drift. Consider all factors when making application 

decisions. Where states have more stringent regulations, they must be observed. Avoiding spray

drift is the responsibility of the applicator or grower. To reduce the potential for drift, the 

application equipment must be set to apply medium to large droplets (i.e., ASAE Standard 572) 

with corresponding spray pressure. Use high flow rate nozzles to apply the highest practical 

spray volume. With most nozzle types, narrower spray angles produce larger droplets. Follow the 

nozzle manufacturer’s directions on pressure, orientation, spray volume, etc., in order to 

minimize drift and optimize coverage and control. 

Golf Course, Residential, and Commercial Lawns

Set the boom and make applications at the lowest height that safely permits uniform coverage of 

the soil and minimizes droplet evaporation. For use on golf courses and commercial lawns, the 

boom height must be no higher than 2-3 feet above the ground and nozzles tips must be set to 

spray out medium to very coarse spray droplets. Applications to residential lawns must be made 

by equipment that maintains coarse spray droplets (to reduce drift). 

Ornamentals
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For deciduous ornamental plants, the spray must be directed at the base of the plant or away from 

the plant but as not to come in contact with the foliage as some leaf malformations or 

discoloration may occur. Dormant deciduous trees are tolerant to Indaziflam herbicide. 

Conifers including Christmas trees are tolerant to foliar applications of indaziflam. In Christmas 

tree farm operations, the common practice is to direct the spray to the base of the trees on a band 

or broadcast application. 

Wind

Avoid making applications when spray particles may be carried by air currents to areas where 

sensitive crops and plants are growing. Do not spray near sensitive plants if wind is gusty, below 

2 mph, or in excess of 10 mph and moving in the direction of adjacent areas of sensitive crops or 

plants. Do not apply during temperature inversions. Always make applications when there is 

some air movement to determine the direction and distance of possible spray drift. 

Local terrain may influence wind patterns; the applicator should be familiar with local conditions 

and understand how they may impact spray drift. Boom or nozzle shielding can reduce the 

effects of wind or air currents on drift. Verify that the shields do not interfere with uniform 

deposition of product prior to application. 

Aerial Application 

When applying by air only, orient nozzles so that the spray is applied backwards, parallel to the 

airstream. This practice will produce larger droplets than other nozzle orientations. With fixedwing aircraft, the length of the boom should not exceed 3/4 the length of the wing. For 

helicopters, use a boom length and position that prevents the spray from entering the rotor 

vortices. Use a minimum of 5 gallons or more of spray volume when applying by air. 

Temperature Inversion 

A surface temperature inversion (i.e., increasing temperature with increasing altitude) greatly 

increases the potential for drift. Avoid application when conditions are favorable to inversion. 

Presence of ground fog is a good indicator of a surface temperature inversion. 

Sensitive Areas 

Sensitive areas are areas where the application of Indaziflam 20 WSP Herbicide is not labeled. 

These include bodies of water (ponds, lakes, rivers, streams, and ditches containing casual 

water), habitats for endangered species, and non-target plants including agricultural crop areas. 

Applications of Indaziflam 20 WSP Herbicide need to be made when wind is blowing away from 

sensitive areas. Maintain a practical and appropriate untreated buffer (15 ft) between application 

of Indaziflam 20 WSP Herbicide and any sensitive areas.