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I. CONCLUSIONS

Deficiencies from D372901 (N. Dodd, 2/16/11) concerning multiresidue methods, storage 

stability, and rotational crop data are revised as follows. Refer to D372901 for other 

deficiencies.

860.1360 Multiresidue Methods

The ChemSAC determined on 10/19/11 that the requirement for multiresidue methods for 

flazasulfuron can be waived because the current (PAM) multiresidue methods are gas 

chromatographic methods that do not determine sulfonylureas.

860.1380 Storage Stability Data

Based on the submitted dates of spiking and extraction, grape storage stability samples in 

MRID 47939903 were stable in frozen storage at -20°C for at least one year. No 

additional information is required.

860.1850/860.1900 Confined/Field Accumulation in Rotational Crops

A confined rotational crop study will not be required to support the use on sugarcane 

provided that the 12-month plant-back interval (PBI) is retained on the label. This 

conclusion is based on low residues in metabolism studies, no detectable residues in field 

studies, and limited sugarcane acreage. If additional rotatable crops are registered in the 

future or if the petitioner wants to shorten the PBI, the confined rotational crop study will 

be required; depending on the results, a study to determine field accumulation in 

rotational crops may be required.

II. ACTION REQUESTED

HED has been asked to reconsider the following data requirements which were identified as 

deficiencies in D372901 (N. Dodd, 2/16/11):

860.1360 Multiresidue Methods

The petitioner is required to submit multiresidue methods data since tolerances will be 

established. 
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860.1380 Storage Stability Data

For MRID 47939903 (Howald, M., Ullrich-Mitzel, A. (1997) Storage Stability of SL-160 

Residues in Grapes. Document Number: 634713), the petitioner must provide dates of 

sample spiking and analysis to verify reported storage intervals.

860.1850/860.1900 Confined/Field Accumulation in Rotational Crops

A confined rotational crop study is required to support permanent registration of 

sugarcane. Depending on the results, a study to determine field accumulation in 

rotational crops may be required.

III. BACKGROUND

ISK Biosciences Corporation proposed tolerances for the herbicide flazasulfuron (N-[[(4,6-

dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(trifluoromethyl)-2-pyridinesulfonamide) on citrus, 

grapes, and sugarcane. A residue chemistry review was completed (D372901, N. Dodd, 

2/16/11). Additional information was submitted by the company. 

IV. RESULTS/DISCUSSION

Multiresidue Methods

In MRID 47939909, the petitioner requested a waiver of the multiresidue method (MRM) data 

requirement based on the absence of detectable residues (<0.003 ppm) in field trial residue 

samples of sugarcane, citrus, and grapes and the expected lack of residues in processed 

commodities reflecting treatment at 1x. HED determined that a waiver could not be granted 

based on the absence of detectable residues since a tolerance was to be established. As stated in 

an e-mail from Richard Loranger to Paula Deschamp on 9/16/11, “the absence of residues in the 

primary crop is not grounds to waive the MRM data. The MRM data are required so FDA can 

know whether or not their MRMs are capable of measuring the residue of concern if it were 

found in food/feed, especially at levels above the tolerance. The level of residues expected in 

legally treated crops is not relevant.”

ISK Biosciences Corporation submitted additional information (MRIDs 48623100 and 

48623101) in response to HED’s request for multiresidue methods for flazasulfuron. Citing two 

literature references, the company indicated that the Pesticide Analytical Methods (PAM) 

multiresidue methodology, which uses gas chromatography, cannot analyze sulfonylureas, 

including flazasulfuron. The company submitted a multiresidue method by Klein and Alder 

which determined flazasulfuron using liquid chromatography with tandem mass spectrometry 

(LC-MS/MS).

The ChemSAC determined on 10/19/11 that the requirement for multiresidue methods for 

flazasulfuron can be waived because the current (PAM) multiresidue methods are gas 

chromatographic methods that do not determine sulfonylureas.
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Storage Stability Data

Dates of spiking and extraction for grapes were submitted via an e-mail from Mark Gelin to 

Hope Johnson on 9/29/11 (Attachment 1). In MRID 47939903, storage time was considered 

from the date of sample fortification to the date of extraction. HED concludes that the storage 

stability study (MRID 47939903), together with the spiking and extraction dates, indicates that 

the residues of flazasulfuron (parent) are stable for intervals of at least 12 months in grapes at -

20°C. In MRID 47939903 (page 8), the petitioner indicated that experiments were started on 

9/2/96 and completed on 9/3/97. Although analysis times were not reported, no additional 

information is requred for this action since all grape residue samples (including the raw 

agricultural commodity and processed commodities) were stored less than 12 months.

Rotational Crop Data Requirements

The ChemSAC discussed rotational crop data requirements for flazasulfuron on sugarcane in 

connection with the review of flazasulfuron on citrus, grapes, and sugarcane (D372901, N. Dodd, 

2/16/11). Sugarcane is the only crop which is rotated. The proposed label requires a 12-month 

interval between the last application and the planting of a rotational crop. In D372901 (N. Dodd, 

2/16/11), HED requested a confined rotational crop study as a condition of registration.

The ChemSAC determined on 10/5/11 that a confined rotational crop study will not be required 

to support the use on sugarcane provided that the 12-month PBI is retained on the label. This 

conclusion is based on low residues in metabolism studies, no detectable residues in field studies, 

and limited sugarcane acreage. If additional rotatable crops are registered in the future or if the 

petitioner wants to shorten the PBI, the confined rotational crop study will be required.
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Attachment 1