MEMORANDUM DATED 10-4-2012

From: Steve Funk, HED/RAB3

 To: Barbara Madden, MUT/RD

Subject: Justification of the Cucurbit Group Tolerance (Inclusive of Cucumber Greenhouse Use) 

 Flonicamid

Barbara and Sidney,

The rationale for increasing the cucurbit group tolerance to encompass cucumber from greenhouses as 

opposed to creating a separate tolerance for cucumber is summarized on page 24 of Appendix II of the 

Summary Document of 10/02/2012 (D396902.me1).

"The existing tolerance for cucurbit vegetables is 0.4 ppm. This is based on the evaluation 

of crop field trial data for summer squash, cantaloupe, and cucumber (D290386, A. 

Acierto, 04/22/2005). The highest residues were 0.17 ppm on squash, 0.34 ppm on 

cucumber, and 0.25 ppm on cantaloupe. The recommended tolerance of 1.5 ppm for 

cucurbit vegetables is appropriate for the representative commodities."

Here is a detailed explanation:

At the time that the original group tolerance of 0.4 ppm was established, no statistical procedure for 

estimation was used. It was common practice to estimate the tolerance slightly above the highest field 

trial result. Thus, estimates would have been 0.2 ppm (based on squash), 0.4 ppm (based on cucumber), 

and 0.3 ppm (based on cantaloupe). The highest value (0.4 ppm) is adopted. The guidance is that the 

lowest estimate and the highest estimate should not differ by more than a factor of 5X, , 0.4 / 0.2 = 2 X in 

this case.

The estimate for cucumber from the greenhouse cucumber trials is 1.5 ppm. 1.5 / 0.2 = 7.5, which is in 

excess of the 5X allowed. The apparent conclusion would be that a group tolerance is not appropriate. 

However, the new cucumber value is based on the use of the Organization of Economic Cooperation and 

Development (OECD) calculation procedure. In order to make an appropriate comparison, the field trial 

data reviewed in 2005 (D290386, 04/22/2005; MRID 45854808) were re-evaluated with the OECD 

calculator. The findings are as follows: 

Flonicamid Cucurbit Field Trials Tolerance Estimates Based on OECD Procedure (2005 Data)

Flonicamid

Cucumber

MRID 45854808

0.3 lb ai/A, 0 d PHI

Total number of data (n) 6

Percentage of censored data 0%

Number of non-censored data 6

Lowest residue 0.138

Highest residue 0.324

Median residue 0.220

Mean 0.216
Standard deviation (SD) 0.067

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.324

- Mean + 4 SD 0.484

- CF x 3 Mean 0.649

Unrounded MRL 0.649

Rounded MRL 0.7

High uncertainty of MRL estimate.

[Small dataset]

Residues (mg/kg) n

0.138 1

0.153 1

0.216 1

0.224 1

0.242 1

0.324 1

Flonicamid

Cantaloupe

MRID 45854808

0.3 lb ai/A, 0 d PHI

Total number of data (n) 6

Percentage of censored data 0%

Number of non-censored data 6

Lowest residue 0.138

Highest residue 0.324

Median residue 0.227

Mean 0.219

Standard deviation (SD) 0.068

Correction factor for censoring (CF) 1.000

Proposed MRL estimate
- Highest residue 0.324

- Mean + 4 SD 0.489

- CF x 3 Mean 0.656

Unrounded MRL 0.656

Rounded MRL 0.7

High uncertainty of MRL estimate.

[Small dataset]

Residues (mg/kg) n

0.138 1

0.153 1

0.216 1

0.238 1

0.242 1

0.324 1

Flonicamid

Summer Squash

MRID 4584808

0.3 lb ai/A, 0 d PHI

Total number of data (n) 5

Percentage of censored data 20%

Number of non-censored data 4

Lowest residue 0.040

Highest residue 0.164

Median residue 0.142

Mean 0.123

Standard deviation (SD) 0.048

Correction factor for censoring (CF) 0.867

Proposed MRL estimate
- Highest residue 0.164

- Mean + 4 SD 0.317

- CF x 3 Mean 0.321

Unrounded MRL 0.321

Rounded MRL 0.4

High uncertainty of MRL estimate.

[Small dataset]

Residues (mg/kg) n

< 0.04 1

0.128 1

0.142 1

0.143 1

0.164 1

The tolerance estimate values are 0.7 (based on cucumber), 0.7 (based on cantaloupe), and 0.4 ppm 

(based on summer squash). The estimate for greenhouse cucumber is 1.5 ppm. The difference between 

the highest and lowest estimates (1.5 /0.4 = 3.8X) is <5X. Therefore, a cucurbit group tolerance of 1.5 

ppm is possible.

Steve Funk

OPP/HED/RAB3, S-10318

tele: 1-703-305-5430

cell: 1-240-374-8439

fax: 1-703-305-0871