UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: Proposed New Use for Flazasulfuron on Tree Nuts 

FROM: Andrew Shelby, Physical 

Stephen Carey, Biologis~t .-::., ... .,. 

Environmental Fate and Effe 

THRU: Mark Corbin, Branch Chief 

Environmental Fate arid Effects Division/ERB6·(7507P) 

TO: Emily Hartman, Risk Manager Reviewer (RM 25) 

Kable Davis, Product Manager Team 25 

Herbicide Branch/Registration Division (7505P) 

OFFICE OF 

CHEMICAL SAFETY AND 

PC Code: 119011 

DP Barcode: 415691 

DATE: 3112/2014 

The Environmental Fate and Effects Division has reviewed the submission by ISK Biosciences 

requesting the addition of a tree nut treatment use for their Flazasulfuron 25WG product (EPA ·'· 

Reg. No.71512-12). ISK Biosciences previously submitted a request for this product to be used 

on citrus, grapes, sugarcane and for industrial vegetation management, for which a first food use 

ecological risk assessment was performed (0372894, May 4, 2011). 

The maximum application rate considered in the previous ecological risk assessment is the same 

as the maximum application rate for the proposed new use on tree nuts (0.045 lb a.i./A) but the 

maximum number of applications is reduced from three to two for the requested tree nut new 

use. Further, the tree nut treatment application 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 with what is 

available for this new use on tree nuts. Finally, 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 represent EECs for treatment on tree nuts. However, 

for characterization specific to this new use on tree nuts, the California Almond scenario is used 

in the Surface Water Concentration Calculator (SWCC), a newly released interface for the use of 
the PRZMJEXAMS. Chemical 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 industrial vegetation management. The 

following table and figure summarize EECs from this scenario: 

Table 1. Estimated Environmental Concentrations (ppb) for Flazasulfuron. 

Peak (1-in-1 0 yr) 0.418 

4-day A vg (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 

Flazasulfuron. CAalmond_WirrigSTD, Pond 

......... 

..c 

0.8 

a. 

.._... a. 

c 0.6 0 

e 

c 

Q) 0.4 

0 

c 

0 

u 

0.2 

0 

0 5 10 15 

Year 

20 

- W2ter~ loJnn 

Ber.thic 

25 30 

Consistent with the previous assessment, the LOC is exceeded for non-listed terrestrial and 

aquatic vascular plants. The endangered species LOC is exceeded for direct effects to aquatic 

and terrestrial plants. In addition, there is potential for indirect effects to all animal taxa that 

depend on plants for survival, growth, or reproduction, which are presumably all animal taxa at 

the screening 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 designated critical habitats, where such 

designations have been made. However, at this time, it is premature to make effects 

determinations until further refinements are conducted. In order to make species-specific effects 
determinations, 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 of potential areas of effects and listed 

species/designated critical habitat of concern. 

The risk conclusions above are based on modeling which assumes that 100% of an agricultural 

field would be treated with flazasulfuron through broadcast spraying using ground equipment 

with a maximum number of applications (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.