### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

### WASHINGTON

. D

. C

. 20460

June I

, 2 01 5 OFFICE OF CHEMICAL SAFETY AND POLLUTION P REVENTION

PC Co d es: 1 0900 1

MEMORANDUM DP Barcode : 425886

SUBJECT: E P A R es p o n se t o Comme nt s Rel ated to the "'Oxa dia zo n Pr e limina ry Work Pl an : Re g i s trati o n R eview ·· 

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Mohammed Ruhm an. Ph.D

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n v i ro nm en t al Ri s k Branch Y FROM:

E nvironmental Fate and Effect s Divi s i o n (7507 P ) 

# w**THRO UG~1**  Shamim, Branch Chief, Ph.D. 

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TO: E n viron m e ntal Fat e and Effect s D i vis i o n (75 0 7P)

Kath e rin e St. C lair. Ri s k Manager R ev i ewer Tom M ye r s. Team Lea d er Ri s k Mana ge m e nt and Im p l eme nt a ti o n Branc h 2 Pe s ticide R e-Eva lu ati o n Divi s i o n (7508 P

In r esponse t o th e p os tin g in the pub l i c d oc ket o r · ·oxadia zo n Pr e liminal) ' Work Plan: R egistration R

ev i ew: Initi a l D oc ket. D ece mber 2014 " ( D oc ket N umb e r E P A- H Q-O PP -20 1 4-0782)

. the r egistrant Bayer Env i ro nm e ntal Science produc ed comments during th e public co mm e nt period. T he pu r p ose o f this m e m ora ndum i s t o a ddr ess the se co mm e nt s

. Listed below a r e the E P A r es p o n ses

.

### 2 1. Comment from Bayer on EPA Statement (p. 5) “Outstanding Data Requirements from GDCI

109001

- 24733”

“ For GDLN 835.4300, a new Aerobic Aquatic Metabolism study (MRID 49405201) was submitted in June 2014. For GDLN 850.1400, Bayer is working with the EPA to fulfill the raw data request. For the GDLN 850.4100, a Seedling Emergence study (MRID46676502) was submitted in 2005 and determined to be acc eptable. For GDL N 850.4150, a Vegetative Vigor study (MRID 46676503) was submitted in 2005 and determined to be acceptable.”

EPA Response:

Two studies were submitted for the aerobic aquatic metabolism, the first one was under MRID 465947

- 01 and was considered in the problem formulation document. In this study relatively high un

extracted residues we re observed. Following the issuance of the problem formulation another study was submitted ( MRID 49405201) in which a different extraction system was used . This extraction system appears to be more efficient in extraction of the residues than the system used in the previous study. T he EPA will consider the results of both studies and no longer require data related to oxadiazone fate in aerobic aquatic syste ms.

EPA acknowledges the submittal of Seedling Emergence Study (MRID 46676502) and Vegetative Vigor Study ( MRID 46676503) classification as acceptable and no longer considers them to be outstanding data requirements

.

2. Bayer provided General Background on Use as a comment to EPA Statement (p.4) “Anticipated Data Needs”

“ Bayer Oxadiazon end

- use products can be categorized as granular formulations or as formulations that are applied as liquid s prays. The granular formulations range from 0.86% to 2% active ingredient with and without fertilizer. The formulations that are applied as liquid sprays are a 50% wettable powder (WP), with and without water soluble packaging, and a liquid formulation at a concentration of 3.17 lb a.i./ gallon. All of the Bayer oxadiazon products are labeled for application to turf or ornamentals.

The turf applications are predominately to golf course turf but can include application to park turf and commercial lawn turf. All labels expressly prohibit any application to residential turf. The maximum turf application rate is 4 lb a.i./A for both granular and spray applied formulations. The ornamental applications can be made to woody ornamental shrubs, vines and trees to control weeds. Applications to ornamental beds on residential property are permitted. Oxadiazon is a pre

- emergent herbicide for the control of annual grasses and broadleaf weeds, and as such, the ornamental applications are ground directed for the granular applications and primarily g round directed for the liquid sprays. The liquid sprays do permit over the top applications to ornamentals, but require an immediate watering to remove foliar residues and prevent ornamental plant damage or death. “

EPA Response:

EPA will ta ke this ba ckground information labelled use into consideration in the future risk

assessment.

### 3 3. Comment from Bayer on EPA Statement (p.4 ) “Anticipated Data Needs, GDLN 850.6100 Terrestrial field dissipation study (for turf)”

“The existing laboratory study shows very little degradation (half

- life of about 841 days), while existing field dissipation studies show significantly faster degradation (overall half

- lives of 115 and 145 days) with longer and shorter half

- lives during portions of the study. These studies w ere conducted with ornamental crops in place so they are more indicative of behavior in turf rather than the standard bare ground field dissipation studies and clearly demonstrate that the laboratory studies are a conservative estimate of degradation compa re to actual use conditions. Also since EPA’s practice is to use laboratory data in risk assessment, the conduct of a turf terrestrial dissipation study will not produce information that will be used in the risk assessments conducted by EPA. Based on the existing information, Bayer will be requesting a waiver for the terrestrial field dissipation study conducted with turf.”

EPA Response:

EPA will look into the basis of the waiver request when submitted and respond accordingly.

4. Comment from Bayer on EPA Statement (p.4) “Anticipated Data Needs, non

- GDLN Special Studies, Acute oral toxicity to adult and larval honeybees, Chronic toxicity to adult and larval honeybees.”

“Professionally managed turf is free of flowering weeds making this environment not bee attractive. For ornamentals, the spray and granular use is soil directed. The majority of the oxadiazon use on ornamentals is granular and oxadiazon is not systemic. Therefore, there is minimal exposure and hence minimal risk t o pollinators for use on turf or ornamentals.”

EPA Response:

There are a number of weeds that may be present within a t urf environment that would qualify as bee attractive, including but not limited to clover. Presence of flowering weeds would result in the presence of bees that are actively foraging. Exposure to bees with respect to a turf application cannot be considered minimal and risk cannot be discounted.

5. Bayer provided the name, toxicity, structure, and CAS number for each of the degradates l isted in Section 5 of the EFED Problem Formulation as requested (p. 8).

EPA Response:

Thank you for the information, EPA will utilize the name, toxicity, structure, and CAS for risk characteriza tion in future assessments, not ing that data was not provided for three degradates.

6. Com ment from Bayer:

### 4 “Typically oxadiazon is applied in the late winter/early spring for pre

- emergent control of weeds. Applications are either made as a single sprayable application at 3

- 4 lb a.i/A or as a granular with 2 applications at 2 lb a.i./A rate. Granular applications to landscape or nursery plants are made in the Spring or Fall. Most applications are in the South East United States. 73% of all applications we re made in seven states: FL, NC, GA, TX, TN and AL. Timing of the first application depends on weed seed germination in different geographies of the US. Intervals between applications are made 30

– 60 days for the split application in the spring (2 lb ai /A).

Further information on the applications for Bayer Labels is provided in the attached pdf. (Oxadiazon EFED Table 1 Use Patters Bayer Pre

- lim Comment.)”

Bayer’s comment is in reference to the following excerpt from EFED Problem Formulation (p. 8 and 9 ):

“Certain oxadiazon labels are unclear with respect to application parameters. Without further information, EPA expects to use conservative assumptions to approximate these parameters in order to conduct a quantitative risk assessment. However, the Ag ency will work with registrants to clarify information on oxadiazon product labels, especially the maximum annual application rates for non

agricultural uses including golf courses, turf and ornamental lawns.

Confirmation of the following label informatio n: sites or application; formulations; application methods and equipment; maximum application rates; frequency of application, application intervals, and maximum number of applications per season; and geographic limitations on use.

Typical application t iming (date of first application and application intervals)

– national, state and county.

The following usage/use information for non

- agricultural uses: total pounds a.i. applied; percent crop/site treated; application rates (typical and maximum); frequen cy of application by region of the country; methods of application; target or niche pests; efficacy i n formation/product performance;
t ypical application interval (days).”

EPA Response:

EFED will take the expanded version of Table 1 provided by the registrant, which includes label clarification

, into consideration in the risk assessment

.