UNITED S TATES EN V IRONMENT A L PROTECTION AGENCY WASHI N GTON D .C ., 20 4 60

POL L UT I ON P R EVEN TI ON

MEMORANDUM

SUBJECT: Proposed New Use for Flazasulfuron on Tree Nuts FROM: Andrew Shelby, Physical S tephen Ca re y,**Bi ologis** **~t**.-::., ....,. Environmental Fate and Effe THRU: Mark Corbin, Branch Chief Environmental Fa te arid Effects Division/ERB6 · (7507P) TO: Emily Hartman, Risk Manager Reviewer (RM 25) Kable Davis, Product Manager Team 25 Herbicide Branch/Registration Division (7505P) OF F ICE O F CHEM I CAL SA FE TY AND
PC Code : 119011 DP Barcode: 415691 DATE: 3112/201 4

The Environmental Fate and Effects Division has rev ie wed the submission by ISK Biosciences requesting the addi ti on o f a tree nut tr ea tment use for the ir Flazasulfuron 25WG product (EPA · ' · Reg. No.71512- 12)
. ISK Biosciences pre v iousl y submitted a request for this product to be used on citrus, grap es, sugarcane and for industrial vegetatio n management, for which a first food use ecological ri sk assessment was performed (0372894, May 4, 2011). The maximum app lication rate considered in the previous ecological risk assessment is the same as the maximum app li cation rate for the proposed new use on tree nuts (0.045 lb a.i./A) but the maximum number of appl ications is reduced from three to two for the requested tree nut new use. Further, the tree nut treatment app licatio n method for agricultural uses (ground broadcast) was also considered in the previous assessment. Because application rates are the same as in the previous assessment, terrestrial dietary-based EECs also represent EECs for treatment on tree nuts. In addition, no new ecological or fate studies have been submitted, and the data used for the ecological risk assessment on citrus, sugarcane, and grapes are consistent w ith what i s available for this new use on tree nuts. F inally, the PRZM/EXAMS scenarios used to represent citrus, grapes, and sugarcane in the previous assessment are also representative of tree nuts. Those scenarios included California grape, Florida citrus, Florida sugarcane, and Louisiana sugarcane. For these reasons, estimated environmental concentrations (EECs) from the previous ecological risk assessment may be used to represe nt EECs for treatment on tree nuts. However, for chara cterization specific to thi s new use on tree nuts , the Ca liforni a Almond scenario is used in the Surface Water Concentration Calcul ator (SWCC), a newly released interface for the use ofthe PRZMJEXAMS. Chem ical inputs are consistent with previous assessments and two 

### applications at 0.045 lb a.i. are applied 14 days apart beginning at crop emergence. EECs for this California Almond scenario fall within the range of EECs reported in the new use assessment for citrus, grapes, sugarcane and for indu strial vegetation management. The fo llowing tabl e and figure summarize EECs from this scenario: 

### Tab le 1. Estimated Environmental Concentrations (ppb) for Flazasu lfuron
. Peak (1-in

- 1 0 yr) 0.418 4-day Avg (1-in-1 0 yr) 0.0266

. 21-day Avg ( 1 -in-10 yr) 0.0257

60-day Avg (1-in-10 yr) 0.0235 365 -day Avg (1-in-10 yr) 0.0121 Entire Simulation Mean 0.00549 

### Figure 1. Yearly Peak Concentrations Fl azasulfuron

. CAa l mond_W i rri gSTD, Pond

......... ..c 0
. 8 a. a. .._... c 0
. 6 0 

# e c 0.4 Q) 0 c 0 u 0.2 0 0 5 10 15 Year 20 -**W2ter~ loJnn**  Be

r.thic

25 30

Consistent with the previous assessment, the LOC is exceeded for non - listed terrestrial and aquatic vascular plants. The endangered species LOC i s exceeded for direct effects to aquatic and terrestrial plants. In addition , there is potential for indirect effects to a ll animal taxa that depend on p l ants for survival, growt h , or reproduction , which are presumably all animal taxa at the screenin g level. Therefore , listed species from ali taxonomic groups are potentially at risk from flazasulfuron uses. The listed species identified in the previous assessment based on a search ofthe LOCATES database remain unchanged; however, potential direct effects on**~hese** endangered and threatened species from the use of flazasulfuron nationwide may be associated with modification of primary constituent elements of des ignated critical habitats, where such designations have been made. However, at this time, it is premature to make effect s determinations until further refinements are conducted. In order to make species-specific effectsdeterminations, useful refinements include the use of more detailed 1) species-specific ecological and biological data; 2) information on use patterns for flazasulfuron; and 3) sub-county level spatial proximity analyses for the co - occurrence ofpotential areas of effects and listed species/designated critica l habitat of concern. The risk conclusions above are based on modeling which assumes that 100% of an agricultura l field would be treated with flazasulfuron through broadcast spray ing using ground equipment with a maximum numb er of app lica tions (two) and a retreatment interval of 14 days. If the application rate were to be mitigated and reduced, exceedances may be reduced below the LOC for some or all taxa
.