UNITED ST ATES ENVIRONMENT AL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

MAY 0 4 20J5 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Response to the Dow AgroSciences Comments on Rice Production 

Practices and Use of Cyhalofop-butyl for Weed Control in Rice Production 

(DP # 424433) 

FROM: Su

Biological 

nil Ratna

A

yake, 

nalysis 

PhD

Br

, 

a

Biologist 

nch ~ 

~Nl ,. "-JV - k~~ ' \ 

Biological and Economic Analysis Division (7503P) 

THRU: Arnet Jones, Chief 

Biological Analysis Branc 

Biological and Economic Analysis Di n (7503P) 

TO: Jolene Trujillo, Chemical Review Manager 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel Date: March 3 2015 

INTRODUCTION 

The Office of Pesticide Programs (OPP) received comments from Dow AgroSciences (DAS), the 

registrant of cyhalofop-butyl, on the Biological and Economic Analysis Division's memo 

describing rice production practices and the use of cyhalofop-butyl in rice production 

(Ratnayake, 2014). This BEAD memo provided needed infonnation on rice production for the 

registration review of cyhalofop-butyl herbicide. The information provided to EFED included 

information on drill (dry) seeded and water (wet) seeded rice production, use of cyhalofop for 

weed control in these production systems, and duration of holding water following the 

applications of cyhalofop in these rice production systems. 

BEAD is thankful for the comments provided by DAS and BEAD·s responses for the DAS 

comments are given below. As a result of these comments, BEAD is revising the assessment, 

whi ch will be made available in the docket. 

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BEAD's statement on page 3 of 15: 

"After the emergence of seedlings, fields are maintained with a low level of water (shallow 

flooding). " · 

DAS Comment No. 1 

The statement should be corrected to read: in water-seeded rice, after the emergence of the rice 

seedlings, fields are maintained with a low level of water (shallow flood) until the permanent 

flood is established. In drill-seeded rice, after the emergence of rice seedlings, fields are 

maintained at a moist to wet condition by rainfall or quick irrigation (flushing) of water across 

the fields. The fields are not flooded until after the rice tillers, which can be 4-6 weeks after 

planting depending on the time of year and weather conditions. 

BEAD's Response: 

The DAS comment is referring to a statement in the first paragraph on page 3 of the BEAD 

assessment under the heading of drill seeding. This statement is accurate. For the rest of the DAS 

comment under the comment number 1, please check the BEAD's response for DAS comment 

number 2. 

BEAD's statement on page 3 of 15: 

"Three to four weeks after planting, the permanent flooding is established with 6-12 inches of 

water and post-flood herbicide treatments are applied to control existing weeds. " 

DAS Comment No. 2. 

The statement should be corrected to read: Four to six weeks after planting, the permanent flood 

is established in drill-seeded rice with 4-10 inches of water and post-flood herbicide treatments 

are applied to control existing weeds. 

BEAD's Response: 

This statement will be revised as the permanent flood is established when the seedlings have 4 to 

5 leaves or at the development of 2nd tiller. Most rice varieties achieve this stage within 4 to 6 

weeks after planting. This timing may vary depending on the location, type of the planted rice 

variety, (late or early), soil moisture, soil fertility, and weather conditions. At the establishment 

of permanent flood, rice fields are flooded to a depth of 4 to 10 inches of water. However, depth 

of water depends on seedling height of the planted rice variety. Seedlings should not be 

submerged and maintaining a water level about 1/3 to 1/2 of seedling height is important. 

BEAD's statement on page 4 of 15: 

"Mostly, pre-emergence herbicides are applied in the field before planting rice seeds. " 

DAS Comment No. 3. 

The statement should be corrected to read: Mostly, pre-emergence herbicides are applied in the 

field before planting rice seeds. 

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Agency's Response: The Agency does not find a difference between the DAS comment and the 

Agency's statement. Therefore, no change of the Agency's statement is needed. 

BEAD's statement on page 4 of 15: 

"Herbicides such as pendimethalin, molinale, thiobencarb, quinclorac are some of the preemergence herbicides used in rice production. " Dow AgroSciences, LLC Report JD: 

NTB 112414 Page 9 of 10 

DAS Comment No. 4. 

The request to cancel molinate pesticide registrations voluntarily was published in the Federal 

Register on 9/17/2003. The product cancellation order and amendment to terminate uses became 

effective 7/30/2008. As a consequence, the active should not be included in this listing. The 

statement should be corrected so that it reads: Herbicides such as pendimethalin, clomazone, 

thiobencarb and quinclorac are some of the pre-emergence herbicides used in rice production. 

BEAD's Response: The Agency agrees that the inclusion of molinate is an error. The reference 

to molinate will be deleted. Clomazone will be added to the list of pre-emergence herbicides. 

BEAD 's statement on page 8 of 15: 

A summmy of the estimated duration of water holding following herbicide applications in AR, 

LA, MS is presented. 

DAS Comment No. 5. 

DAS disagrees with the assumptions supporting the calculations in this section. The calculations 

assume that the water is held in the field after the pre-flood application. However, when a preflood application is made, the field is not flooded and it may be 2-3 weeks before the permanent 

flood is put on the rice field . Post-flood in drill seeded rice can be established from 4-6 weeks 

after planting versus 3-4 weeks. Drill seeded rice is not ready for pennanent flood in 3 weeks. 

The rice has to be tillered before the permanent flood is established. 

Agency's Response: The Agency disagrees that assumptions on calculations are wrong. The 

Agency did not assume that pre-flood applications are made after the establishment of permanent 

flood. In drill seeding, pre-flood applications are made before the establishment of pem1anent 

flood and after the pre-flood applications, a shallow level of water is maintained to have good 

soil moisture level for seedling growth. On the timing of establishment of permanent flood, 

please refer to the Agency's response for DAS comment number 2. 

BEAD's statement on page 9 of 15: 

A summmy of the cyhalofop applications in water seeded rice production is presented. 

DAS Comment No. 6. 

The instructions described in this section do not apply to granular formulations. This statement 

should be updated so that it reads: A summary of cyhalofop applications in water seeded (wet 

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seeded) rice production is presented for liquid formulations. 

BEAD's Response: The statement will be updated as suggested. 

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