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)

	 

≤) 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 Fine-Medium/

Coarse	Low Boom

	Ground	Indaziflam 200 SC; Indaziflam 500 SC	0.085 	ASAE Fine-Medium/

Coarse	High Boom

Turf2	Ground	BCS-AA 10717 20WSP	0.017 	ASAE Fine-Medium/

Coarse	Low Boom3

Roadsides/Rights-of-way/Site Preparation/

Other3	Ground	Esplanade 200 C	0.089 	ASAE Fine-Medium/

Coarse	High Boom

Forested Areas

	Ground	Esplanade F	0.125 	ASAE Fine-Medium/

Coarse	High Boom

	Aerial	Esplanade F	0.125 	ASAE Fine-Medium4 	N/A

	Aerial	Esplanade F	0.125 	ASAE Medium-Coarse	N/A

	Aerial	Esplanade F	0.125 	ASAE Coarse-Very Coarse	N/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 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-of-way/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)

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).

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).

	

	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.

  

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

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 fixed-wing 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. 

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 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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