1 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

March 2 , 2016

PC Code: 103901
MEMORANDUM DP Barcode: 431858

SUBJECT: Sodium Bentazon : Response to BASF ’s Comments on the Proposed Mitigation

Measures for Bentazon Registration Review

FROM: He Zhong, Ph.D., Biologist

Stephen Wente, Ph.D., Biologist

Environmental Risk Branch 1 Environmental Fate and Effects Division ( 7507P)

THROUGH: Sujatha Sankula, Ph.D., Branch Chief

Greg Orrick, Risk Assessment Process Leader

Environmental Risk Branch 1 Environmental Fate and Effects Division (7507P)

TO: Moana Appleyard, Chemical Review Manager

Linda Arrington, Branch Chief Risk Managem ent and Implementation Branch V

Pesticide Re

- Evaluation Division (7508P)

The purpose of this Environmental Fate and Effects Division (EFED) memo i s to address BASF’s response to the Proposed Mitigation Measures for Bentazon Registration Review that are applicable to the ecological risk a ssessment for the herbicide sodium bentazon. BASF’s

response included two submitted reports (MRIDs 49821201, 49821202) and comments in a letter

dated February 1, 2016 . In addition, BASF met with the Agency on J anuary 20 , 2016 to discuss their response

. The following is a list of BASF’s comments organized by topic with EFED ’s

response following each of BASF ’s comments.

1). Spray Drift Buffer Modeling

BASF submitted a report entitled “ Determination of Spray Drift Buffers for Protection of

Terrestrial Non

- Target Areas for Bentazon Herbicides” (MRID 49821201), which used the AgDRIFT model to calculate spray drift buffers for both aerial and ground applications.

EFED Response: EFED has reviewed the non

- GLP AgDRIFT modeling report (MRID 49821201). EFED concurs with the modeling results for the spray drift buffer zones based on the input parameters modeled , especially the droplet volume median diameter (VMD) for ground (≥340 μm) and aerial (≥940 μm) spray. EFED reco mmends that labels include enforceable label2

language to mandate use of these spray droplet sizes , as relevant, for both ground and aerial applications.

2). Proposed Spray Drift Language

BASF proposed specific label statements pertaining to spray drift. Only those statements that

EFED believes should be modified are presented below

. For ground applications:

BASF Statement: Apply this product using nozzles which deliver fine

- to

- medium/coar se spray droplets as defined by ASAE standard S

- 572 and as shown in nozzle manufacturer’s catalogs.

EFED Response: T he label should not focus on the type of nozzles, but rather on the droplet size. The following label language is suggested:

Use spray equipment producing spray droplets with a volume median diameter (VMD) of 340 μm or greater.

BASF Statement: Avoid potential adverse effects to non

- target areas by maintaining a

10

- foot buffer between the application area and the closest downwind edge of s ensitive terrestrial habitats (such as grasslands, forested areas, shelter belts, woodlots, hedgerows, riparian areas, and shrub lands).

EFED Response: Note that this statement is acceptable only if spray droplet size language similar to that recommended a bove is adopted. Based on AgDRIFT modeling

, the 10

- ft buffer is adequate only for ground applications using spray droplets with VMD ≥340 μm.

For aerial applications:

BASF Statement : Use low

- drift straight

- stream nozzles (D

- 6 or larger).

EFED Response: Aga in, the label should not focus on the type of nozzles, but rather on the droplet size. The following label language is suggested:

Use spray equipment producing spray droplets with a volume median diameter (VMD) of 940 μm or greater.

BASF Statement : Avoid potential adverse effects to non

- target areas by maintaining a

20

- foot buffer between the point of direct application and the closest downwind edge of sensitive terrestrial habitats (such as grasslands, forested areas, shelter belts, woodlots, hedger ows, riparian areas, and shrub lands).

EFED Response: Again this statement is acceptable only if spray droplet size language similar to that recommended above is adopted. Based on AgDRIFT modeling

, the 20

- ft buffer is sufficient only for aerial applicatio ns using spray droplets with VMD ≥940 μm

.

3). Minimum Retreatment Interval Change

BASF Comment: BASF proposes to change the minimum retreatment interval on b entazon product labels from 5 days (current minimum) to 7 days.

EFED Response: EFED concurs the changes, but reiterates that t he proposed retreatment3

interval extension alone does not change the bentazon risk picture for birds and mammals based

on the current default foliar half

- life assumption of 35 days. (Please see the response under “ 5 ). Foliar Dissipation Data ” section below for additional information needed to potentially modify

the 35

- day foliar half

- life assumption.)

4). Water Holding Time Requirement for Rice

BASF Comment: BASF proposes the following agronomic precautionary statement be included

in the b entazon product labels that contain a rice use section:

“Avoid releasing tailwater immediately after BASAGRAN application.”

EFED Response: To reduce the risk to aquatic plants from use on rice, EFED suggests the following enforceable label language for the label:

“ Do not release tailwater until it has been held for at least 4 days after the last bentazon application. ”

5 ). Foliar Dissipation Data

BASF submitted a report entitled “ Calculation of DT50 dissipation times for BAS 351 H

– Bentazone in wheat and pea plants from field trials in the Northern and Southern Zones of Europe” ( MRID 49821202 ), which summarizes the DT50 dissipation times obtained from these

field trials , but does not provide a full description of the materials and methods used to conduct

the field trials

. EFED Response : The full studies are needed in order to evaluate their usefulness for risk

assessment

. In other words, t he original studies should be submitted with a full description of the materials and methods (especially the precipitation data, sampling interval s , sample storage stability, sample recovery, analytical procedures

, and quality assurance procedures ). The submitted summary results (MRID 49821202) for the foliar dissipation half

- life may be

considered if the original studies are classified upon review as acceptable or otherwise useful for

risk assessment

.

References

Jackson, S.H. 2016. Determination of Spray Drift Buffers for Protection of Terrestrial Non

Target Areas for Bentazon Herbicide

. MRID 49821201

. 18pp

Miles, B. 2016. Calculation of DT50 Dissipation Times for BAS 351 H

- Bentazone in Wheat

and Pea Plants from Field Trials Conducted in the No rthern and Southern Zones of Europe . MRID 49821202. 86 pp

USEPA. 2014

. Registration Review Ecological Risk Assessment and Effects Determination for Sodium Bentazon. DP Barcode 417314. 140pp